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04 - 06141-Erosion Report, 2024.11.21CONSTRUCTION STORMWATER POLLUTION PREVEIITION PLAN FOR Carter Loop SE City of Yelmo Washington November 2024 Prepared for: Projects West, Inc. $ Prepared by: Matthew Seawright, B.I.T., Project Designer Approved By: Daniel Smith, P.8., Senior Project Manager RBPORT #0614I "I hereby state that this Drainage and Erosion/Sediment Control Plan for the Carter Loop SE project has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community of professional engineers. I understand that City of Yelm does not and will not assume liability for the sufficiency, suitability or performance of drainage facilities prepared by me." This analysis is based on data and records either supplied to, or obtained by, C.E.S. NW, Inc. These documents are referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. TABLE OF CONTENTS PAGE CONSTRUCTION STORMWATER POLLUTION PREVENTION .................................................................... 1 1. PROPOSED PROJECT DESCRIPTION ...................................................................................................................... 1 2. EXISTING SITE CONDITIONS ............................................................................................................................... 2 3. ADJACENT AREAS .............................................................................................................................................. 2 4. CRITICAL AREAS ................................................................................................................................................ 2 5. SOIL .................................................................................................................................................................... 2 6. POTENTIAL EROSION PROBLEM AREAS .............................................................................................................. 2 7. CONSTRUCTION PHASING ................................................................................................................................... 3 8. CONSTRUCTION SCHEDULE ................................................................................................................................ 4 9. THIRTEEN ELEMENTS ......................................................................................................................................... 4 10. FINANCIAL/OWNERSHIP RESPONSIBILITIES ....................................................................................................... 6 11. ENGINEERING CALCULATIONS ........................................................................................................................... 6 Appendix A Maps Vicinity Map .........................................................................................................................A-1 Soils Map and Descriptions ..................................................................................................A-2 FIRM Panel 53067C0365F ...................................................................................................A-3 Appendix B Construction Best Management Practices (BMPs) ..........................................................B-1 Appendix C Geotechnical Engineer’s Report ........................................................................................C-1 1 CONSTRUCTION STORMWATER POLLUTION PREVENTION 1. Proposed Project Description This report accompanies the Carter Loop SE short plat as submitted to the City of Yelm for site plan review. Pursuant to City of Yelm Municipal Code (YMC) 13.16.060 the methodology and design criteria for the project are established by the Department of Ecology’s 2019 Stormwater Management Manual for Western Washington (Manual). The Carter Loop SE project proposes a six (6) lot short plat on parcel #52920000003 with an area totaling 0.92 acres. The site is accessed from Carter Loop SE. A Vicinity Map can be found in Appendix “A” of this report. A project summary is as follows: Land Use Application – Final Short Plat Address – 15106 Carter Loop SE, Yelm, WA 98597 Parcel Number – 52920000003 Zoning – R-6 (Mod. Density Residential) Legal description – Tract D of Plat of Hawks Landing as Recorded March 13, 2003 Under Auditor's File No. 3511261; In Thurston County, Washington. The property is Tract D of Hawks Landing. The existing site coverage includes a single-family residence, concrete sidewalk, and landscaping that is typically found in single-family developments. The property has frontage along State Route 507, however access is only proposed from Carter Loop SE. The project proposes to remove the existing site improvements and subdivide the parcel into six (6) lots. Additionally, each proposed lot will allow for up to 4,500 sq.ft. of rooftops and up to 500 sq.ft. of driveway. Runoff from the future rooftops and driveways will be infiltrated with infiltration trenches (BMP T7.20). All disturbed areas which are not converted to impervious surfaces will have their soils amended per BMP T5.13). 2 2. Existing Site Conditions The current site coverage includes a single-family residence, concrete sidewalk, and typical residential landscaping. The site slopes from southwest to northeast with an elevation change of approximately 4 feet from the southwestern edge of the property. There is a stockpile of soils on the proposed lot 5 that doesn’t affect overall stormwater runoff direction and will be removed as part of the project. Stormwater runoff from this site is currently sheet flows to the northeast. The entire City of Yelm and its urban growth area is identified as a highly susceptible critical aquifer recharge area. The parcel and all the proposed improvements are located within Zone X, which is considered outside of the 100-year floodplain, per FEMA Map #53067C0365F. A copy of the FIRM Panel map can be found in Appendix “B” of this report. 3. Adjacent Areas The site is located within the Hawk’s Landing plat. Generally, the project site is surrounded by single family residences. The site is bordered by SR 507 to the northeast and undeveloped land to the east. Adjacent areas are protected from sediment with the erosion control BMPs shown on the approved plans and described within this report. 4. Critical Areas The entire City of Yelm and its urban growth area is identified as a highly susceptible critical aquifer recharge area. However, less than 5,000 sq.ft. of pollution generating impervious surfaces are proposed; therefore treatment is not required. 5. Soil Half of the onsite soils are identified as Everett very gravelly sandy loam and half Spanaway gravelly sandy loam (32 and 110) determined by the USDA SCS maps of Thurston County, Washington. These soils are classified as Type A soils and have low erosion potential. A description of these soils and a copy of the soil map for this portion of Thurston County have been included in Appendix “A” of this report. These findings are supported by the geotechnical report prepared by Golder Associates Inc. dated March 29, 2007, which indicates the site is comprised of fine to coarse gravel with some cobbles under a layer of topsoil. A copy of the study is included in Appendix “C” of this report. 3 6. Potential Erosion Problem Areas There are no steep slopes on site. The project will not experience problems with erosion if the BMPs described within this report and on the approved plans are implemented. 7. Construction Phasing The proposed improvements include an erosion/sedimentation control plan designed to prevent sediment-laden runoff from leaving the project site during construction. The design specifies a combination of structural measures, cover measures and construction practices that are to be implemented to maintain erosion control. Prior to the start of any clearing and grading of the site, all erosion control measures should be constructed. A general outline of the proposed construction sequence has been included. The contractor will employ the best construction practices to properly clear and grade the site. The planned construction sequence is as follows: Construction Sequence: 1. Arrange and attend pre-construction conference with the City of Yelm. 2. Stake clearing and grubbing limits. 3. Install filter fabric fence and construction entrance. 4. Flag infiltration area limit compaction and sediment laden runoff from this area. 5. Install/implement erosion control features. 6. Clear and grub site as necessary to install site improvements. During wet season, do not clear any more area than can be stabilized, per the grading and erosion control plan, in a given workday. Do not compact infiltration areas. 7. Grade site per grading plan. 8. Extend 2" force main in carter loop and stub water and cover. 9. Construct fire hydrants and restore right-of-way. 10. Stabilize unpaved areas of the site by hydro-seeding or other appropriate methods per the erosion control notes. 11. Construct sidewalk and walkways per approved plans. 12. Once the site has been fully stabilized, place infiltration facilities online. 4 13. Remove all temporary erosion control facilities after site has been permanently stabilized and approved by the city. 14. Clean storm drainage system piping and catch basins. 15. Call for final inspection(s). 8. Construction Schedule Construction that exposes soils should be limited during the wet season (October 1 to April 30). During this time erosion control BMPs should be checked regularly (once a week) and after each major storm event. Generally, grading, utility installation, and paving should be completed prior to the wet season. 9. Thirteen Elements 9.1 Mark Clearing Limits The project proposes to clear areas onsite. Clearing limits are to be staked by a professional land surveyor as shown on the approved plans. Clearing shall remain within these limits. 9.2 Establish Construction Access A stabilized construction entrance (BMP C105) is proposed to protect Carter Loop SE from sediment. Adjacent paved surfaces must be cleaned daily, or if deemed necessary, more frequently. 9.3 Control Flow Rates The project will clear approximately 0.95 acres to construct the site improvements. The project will mitigate runoff with cover measures (BMP C120 and C121), and silt fences (BMP C233). 9.4 Install Sediment Controls The project proposes silt fences (BMP C233) around the perimeter of the site to trap sediment onsite. 9.5 Stabilize Soils The project will stabilize exposed soils with the use of cover measures. These cover measures are mulching, temporary seeding, and plastic sheeting (BMP C120, C121, C123). 5 9.6 Protect Slopes Just like stabilizing the exposed soils the project’s exposed slopes will be controlled with the same covering measures (BMP C120, C121, and BMP C123). 9.7 Protect Drain Inlets Existing offsite drain inlets and proposed drain inlets will be protected from sediment with the use of bag filters (BMP C220). 9.8 Stabilize Channels and Outlets The project does not construct or modify channel and outlets therefore this element does not apply to this project. 9.9 Control Pollutants The project will require earth moving equipment. When vehicles are stored onsite care needs to be taken to make sure that any fluid leaks are contained with drip pans and the fluids are disposed of properly. All spills need to be cleaned up immediately as per the Department of Ecology (ECY) and City of Yelm’s Standards. 9.10 Control Dewatering This project proposal does not include dewatering. Runoff and seepage should be collected and conveyed to catch basin after runoff has been appropriately filtered onsite. 9.11 Maintain BMPs The proposed BMPs need to be maintained as per the approved plans notes and specifications. In general, when sediment accumulation has reached 1/3 of the treatment device or one (1) foot of depth it should be removed. Also, if there is a major storm event then the proposed BMPs should be check and cleaned appropriately. If the sediment removed from these devices is approved by a geotechnical engineer, they can be stabilized onsite. If not, they must be removed as per the ECY and the City of Yelm’s requirements. 9.12 Manage the Project A construction sequence is provided on the plans. This construction sequence needs to be followed to ensure that sediment is not deposited downstream. The City and the Project Engineer 6 needs to inspect the erosion control BMPs after installation and during construction. The contractor is to employ a Certified Erosion and Sediment Control Lead (CESL, BMP C160) as described by the State to help manage and inspect the erosion control devices. Detailed descriptions of each BMP listed above can be found in Appendix “B” of this report. 9.13 Protect Low Impact Development BMPs. The project proposes infiltration trenches to control its runoff. Care should be taken to prevent sediment laden runoff from entering the trench or the surrounding soils during construction. Construction equipment and staging should be limited where the trenches are proposed onsite. 10. Financial/Ownership Responsibilities The owner and responsible party for the initiation of financial securities is C & E Developments, LLC. Their contact information is as follows: Projects West, Inc 2014 Meridian St S Puyallup, WA 98371 11. Engineering Calculations The project proposes BMPs that do not require supporting engineering calculations. 7 APPENDIX A MAPS Vicinity Map A-1 Soils Map and Descriptions A-2 FIRM Panel 53067C0365F A-3 Sw Berry Valley Rd 24 ?-28 TF-9—e Nisqually Ov va/ley Goff Course PI M (D CO - - -------- ---------- -- -- - - ------------------------- School 107th Lp Se S-28 Ca g 25 Fox H-111 Rd q,- �vv SITE TI 7N N w LO LSD S VICINITY MAP NTS Soil Map—Thurston County Area, Washington (Carter Loop SE) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/12/2024 Page 1 of 3 51 9 7 8 9 0 51 9 7 9 0 0 51 9 7 9 1 0 51 9 7 9 2 0 51 9 7 9 3 0 51 9 7 9 4 0 51 9 7 9 5 0 51 9 7 9 6 0 51 9 7 9 7 0 51 9 7 9 8 0 51 9 7 9 9 0 51 9 8 0 0 0 51 9 8 0 1 0 51 9 8 0 2 0 51 9 8 0 3 0 51 9 8 0 4 0 51 9 7 8 9 0 51 9 7 9 0 0 51 9 7 9 1 0 51 9 7 9 2 0 51 9 7 9 3 0 51 9 7 9 4 0 51 9 7 9 5 0 51 9 7 9 6 0 51 9 7 9 7 0 51 9 7 9 8 0 51 9 7 9 9 0 51 9 8 0 0 0 51 9 8 0 1 0 51 9 8 0 2 0 51 9 8 0 3 0 51 9 8 0 4 0 528900 528910 528920 528930 528940 528950 528960 528970 528980 528990 529000 529010 528900 528910 528920 528930 528940 528950 528960 528970 528980 528990 529000 529010 46° 56' 6'' N 12 2 ° 3 7 ' 1 3 ' ' W 46° 56' 6'' N 12 2 ° 3 7 ' 7 ' ' W 46° 56' 1'' N 12 2 ° 3 7 ' 1 3 ' ' W 46° 56' 1'' N 12 2 ° 3 7 ' 7 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 35 70 140 210 Feet 0 10 20 40 60 Meters Map Scale: 1:754 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Thurston County Area, Washington Survey Area Data: Version 17, Aug 29, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: May 26, 2023—Aug 14, 2023 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Thurston County Area, Washington (Carter Loop SE) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/12/2024 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 32 Everett very gravelly sandy loam, 0 to 8 percent slopes 0.5 48.9% 110 Spanaway gravelly sandy loam, 0 to 3 percent slopes 0.5 51.1% Totals for Area of Interest 1.0 100.0% Soil Map—Thurston County Area, Washington Carter Loop SE Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/12/2024 Page 3 of 3 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 3/12/2024 at 12:30 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 122°37'29"W 46°56'17"N 122°36'52"W 46°55'53"N Basemap Imagery Source: USGS National Map 2023 8 APPENDIX B Construction Best Management Practices (BMPs) B-1 Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and  visibility restored. BMP C105: Stabilized Construction Access Purpose Stabilized construction accesses are established to reduce the amount of sediment transported onto  paved roads outside the project site by vehicles or equipment. This is done by constructing a sta- bilized pad of quarry spalls at entrances and exits for project sites. Conditions of Use Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction  site if paved roads or other paved areas are within 1,000 feet of the site. For residential subdivision construction sites, provide a stabilized construction access for each res- idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient  length/width to provide vehicle access/parking, based on lot size and configuration. On large commercial, highway, and road projects, the designer should include enough extra mater- ials in the contract to allow for additional stabilized accesses not shown in the initial Construction  SWPPP. It is difficult to determine exactly where access to these projects will take place; additional  materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the  access shall be reduced to the maximum practicable size when the size or configuration of the site  does not allow  the full length (100’). Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls,  a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con- crete, cement, or calcium chloride for construction access stabilization because these products raise  pH levels in stormwater and concrete discharge to waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up  into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con- struction Access Geotextile Standards. Geotextile Property Required Value Grab Tensile  Strength (ASTM D4751)200  psi min. Table II-3.2: Stabilized Construction Access Geotextile Standards 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 275 Geotextile Property Required Value Grab Tensile  Elongation (ASTM D4632)30%  max. Mullen Burst  Strength (ASTM D3786-80a)400  psi min. AOS (ASTM D4751)20-45  (U.S. standard sieve size) Table II-3.2: Stabilized Construction Access Geotextile Standards (continued)  l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used  as a stabilized access. Also consider the installation of excess concrete as a stabilized access.  During large concrete pours, excess concrete is often available for this purpose.  l Fencing (see BMP C103:  High-Visibility Fence) shall be installed as necessary to restrict  traffic to the construction access.  l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can  substantially increase the effectiveness of the pad and reduce the need for maintenance.  l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at  all possible. If a construction access must cross a sidewalk or back of walk drain, the full length  of the sidewalk and back of walk drain must be covered and protected from sediment leaving  the site. Alternative Material Specification WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes  that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then  released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock  while continuously verifying that the Stabilized Construction Access remains effective. To remain  effective, the BMP must prevent sediment from migrating off site. To date, there has been no per- formance testing to verify operation of this new  specification. Jurisdictions may use the alternative  specification, but must perform increased off-site inspection if they use, or allow others to use, it. Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand- ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016)  for ballast except for the following special requirements. The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access  Alternative Material Requirements. Sieve Size Percent Passing 2½″99-100 Table II-3.3: Stabilized Construction Access Alternative Material Requirements 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 276 Sieve Size Percent Passing 2″65-100 ¾″40-80 No. 4 5 max. No. 100 0-2 % Fracture 75 min. Table II-3.3: Stabilized Construction Access Alternative Material Requirements (continued)  l All percentages are by weight.  l The sand equivalent value and dust ratio requirements do not apply.  l The fracture requirement shall be at least one fractured face and will apply the combined  aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the specifications.  l If the access is not preventing sediment from being tracked onto pavement, then alternative  measures to keep the streets free of sediment shall be used. This may include replace- ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of  the access, or the installation of BMP C106: Wheel Wash.  l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep- ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement  shall not be cleaned by washing down the street, except when high efficiency sweeping is inef- fective and there is a threat to public safety. If it is necessary to wash the streets, the con- struction of a small sump to contain the wash water shall be considered. The sediment would  then be washed into the sump where it can be controlled.  l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi- ciency mechanical sweeper because this creates dust and throws soils into storm systems or  conveyance ditches.  l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be  removed immediately.  l If vehicles are entering or exiting the site at points other than the construction access(es),  BMP C103:  High-Visibility Fence shall be installed to control traffic. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 277  l Upon project completion and site stabilization, all construction accesses intended as per- manent access for maintenance shall be permanently stabilized. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 278 Figure II-3.1: Stabilized Construction Access 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 279 Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by washing dirt from  the wheels of motor vehicles prior to the motor vehicles leaving the construction site. Conditions of Use  l Use a wheel wash when BMP C105:  Stabilized Construction Access is not preventing sed- iment from being tracked off site.  l Wheel washing is generally an effective BMP when installed with careful attention to topo- graphy. For example, a wheel wash can be detrimental if installed at the top of a slope abut- ting a right-of-way where the water from the dripping truck can run unimpeded into the street.  l Pressure washing combined with an adequately sized and surfaced pad with direct drainage  to a large 10-foot x 10-foot sump can be very effective.  l Wheel wash wastewater is not stormwater. It is commonly called process water, and must be  discharged to a separate on-site treatment system that prevents discharge to waters of the  State, or to the sanitary sewer with local sewer district approval.  l Wheel washes may use closed-loop recirculation systems to conserve water use.  l Wheel wash wastewater shall not include wastewater from concrete washout areas.  l When practical, the wheel wash should be placed in sequence with BMP C105:  Stabilized  Construction Access. Locate the wheel wash such that vehicles exiting the wheel wash will  enter directly onto BMP C105:  Stabilized Construction Access. In order to achieve this, BMP  C105:  Stabilized Construction Access may need to be extended beyond the standard install- ation to meet the exit of the wheel wash. Design and Installation Specifications Suggested details are shown in Figure II-3.2: Wheel Wash. The Local Permitting Authority may  allow  other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base mater- ial or 8 inches over a good subgrade is recommended to pave the wheel wash. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 280 Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and  to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre-construction condition or better to pre- vent future erosion. Perform street cleaning at the end of each day or more often if necessary. BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of  the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will  remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September  1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket  until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of  September. Otherwise, vegetation will not establish itself enough to provide more than average pro- tection. Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and  transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding.  See BMP C121: Mulching for specifications. Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta- bilization means the completion of all soil disturbing activities at the site and the establishment of a  permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement,  riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil  Quality and Depth. Design and Installation Specifications General  l Install channels intended for vegetation before starting major earthwork and hydroseed with a  Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control  blankets over the top of hydroseed. Before allowing water to flow in vegetated channels,  establish 75 percent vegetation cover. If vegetated channels cannot be established by seed  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 284 before water flow; install sod in the channel bottom — over top of hydromulch and erosion con- trol blankets.  l Confirm the installation of all required surface water control measures to prevent seed from  washing away.  l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per- cent tackifier. See BMP C121: Mulching for specifications.  l Areas that will have seeding only and not landscaping may need compost or meal-based  mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on  the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality  and Depth.  l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up  in contact with the soil surface. This reduces the ability to establish a good stand of grass  quickly. To overcome this, consider increasing seed quantities by up to 50 percent.  l Enhance vegetation establishment by dividing the hydromulch operation into two phases:  o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in  the first lift.  o Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by:  o Installing the mulch, seed, fertilizer, and tackifier in one lift.  o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per  acre.  o Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance  vegetative establishment. The increased cost may be offset by the reduced need for:  o Irrigation.  o Reapplication of mulch.  o Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon- ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre  minimum).  l Seed may be installed by hand if:  o Temporary and covered by straw, mulch, or topsoil.  o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or  erosion blankets.  l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 285 recommended mixes for both temporary and permanent seeding.  l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per  acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply  the wet area seed mix at a rate of 60 pounds per acre.  l Consult the local suppliers or the local conservation district for their recommendations. The  appropriate mix depends on a variety of factors, including location, exposure, soil type, slope,  and expected foot traffic. Alternative seed mixes approved by the local authority may be used,  depending on the soil type and hydrology of the area. Common Name Latin Name % Weight % Purity % Germination Temporary Erosion Control Seed Mix A standard mix for areas requiring a temporary vegetative cover. Chewings or   annual blue grass Festuca rubra var. commutata or Poa anna 40 98 90 Perennial rye  Lolium perenne 50 98 90 Redtop or colonial  bentgrass  Agrostis alba or  Agrostis tenuis 5 92 85 White dutch clover Trifolium repens 5 98 90 Landscaping Seed Mix A recommended mix for landscaping seed. Perennial rye blend Lolium perenne 70 98 90 Chewings and red  fescue blend Festuca rubra var. commutata or Fes- tuca rubra 30 98 90 Low-Growing Turf Seed Mix A turf seed mix for dry situations where there is no need for watering. This mix requires very little main- tenance. Dwarf tall fescue  (several  varieties) Festuca arundin- acea var. 45 98 90 Dwarf perennial  rye (Barclay) Lolium perenne var. barclay 30 98 90 Red fescue Festuca rubra 20 98 90 Colonial bentgrass Agrostis tenuis 5 98 90 Bioswale Seed Mix A seed mix for bioswales and other intermittently wet areas. Tall or meadow fes-Festuca arundin-75-80 98 90 Table II-3.4: Temporary and Permanent Seed Mixes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 286 Common Name Latin Name % Weight % Purity % Germination cue acea or   Festuca elatior Seaside/Creeping  bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or  Agrostis gigantea 5-10 90 80 Wet Area Seed Mix A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet- lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Tall or meadow fes- cue Festuca arundin- acea or Festuca elatior 60-70 98 90 Seaside/Creeping  bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus praten- sis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 Meadow Seed Mix A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col- onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed- ing should take place in September or very early October in order to obtain adequate establishment prior to  the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending  the soil can reduce the need for clover. Redtop or Oregon  bentgrass Agrostis alba or  Agrostis ore- gonensis 20 92 85 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 Table II-3.4: Temporary and Permanent Seed Mixes (continued) Roughening and Rototilling  l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk  slopes before seeding if engineering purposes require compaction. Backblading or smoothing  of slopes greater than 4H:1V is not allowed if they are to be seeded.  l Restoration-based landscape practices require deeper incorporation than that provided by a  simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to  improve long-term permeability, infiltration, and water inflow qualities. At a minimum,  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 287 permanent areas shall use soil amendments to achieve organic matter and permeability per- formance defined in engineered soil/landscape systems. For systems that are deeper than 8  inches complete the rototilling process in multiple lifts, or prepare the engineered soil system  per specifications and place to achieve the specified depth. Fertilizers  l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended.  This will prevent the over-application of fertilizer.  l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ- ing nitrogen, phosphorus, and potassium) in the least water-soluble form.  l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90  pounds per acre. Always use slow-release fertilizers because they are more efficient and  have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit- ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating.  l There are numerous products available that take the place of chemical fertilizers. These  include several with seaweed extracts that are beneficial to soil microbes and organisms. If  100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be  necessary. Cottonseed meal provides a good source of long-term, slow-release, available  nitrogen. Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix  l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix  (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre  with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during  application. Numerous products are available commercially. Most products require 24-36  hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally,  products come in 40-50 pound bags and include all necessary ingredients except for seed and  fertilizer.  l Install products per manufacturer's instructions.  l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation  establishment. Advantages over blankets include:  o BFM and MBFMs do not require surface preparation.  o Helicopters can assist in installing BFM and MBFMs in remote areas.  o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses  for safety.  o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 288 Maintenance Standards Reseed any seeded areas that fail to establish at least 75 percent cover (100 percent cover for areas  that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such  as sodding, mulching, nets, or blankets.  l Reseed and protect by mulch any areas that experience erosion after achieving adequate  cover. Reseed and protect by mulch any eroded area.  l Supply seeded areas with adequate moisture, but do not water to the extent that it causes run- off. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant  establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating  soil temperatures. There are a variety of mulches that can be used. This section discusses only the  most common types of mulch. Conditions of Use As a temporary cover measure, mulch should be used:  l For less than 30 days on disturbed areas that require cover.  l At all times for seeded areas, especially during the wet season and during the hot summer  months.  l During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief. Mulch may be applied at any time of the year and must be refreshed periodically. For seeded areas, mulch may be made up of 100 percent:   l cottonseed meal;   l fibers made of wood, recycled cellulose, hemp, or kenaf;  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 289  l compost;   l or blends of these. Tackifier shall be plant-based, such as guar or alpha plantago, or chemical-based such as poly- acrylamide or polymers.  Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Recycled cellulose may contain polychlorinated biphenyl (PCBs). Ecology recommends that  products should be evaluated for PCBs prior to use. Refer to BMP C126:  Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM  shall not be directly applied to water or allowed to enter a water body. Any mulch or tackifier product used shall be installed per the manufacturer’s instructions. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table II-3.6: Mulch Standards and  Guidelines. Consult with the local supplier or the local conservation district for their recom- mendations. Increase the application rate until the ground is 95% covered (i.e. not visible under the  mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or  other areas highly susceptible to erosion. Where the option of “Compost” is selected, it should be a coarse compost that meets the size grad- ations listed in Table II-3.5: Size Gradations of Compost as Mulch Material when tested in accord- ance with Test Method 02.02-B found in Test Methods for the Examination of Composting and Compost (Thompson, 2001). Sieve Size Percent Passing 3"100% 1"90% - 100% 3/4"70% - 100% 1/4"40% - 100% Table II-3.5: Size Gradations of Compost as Mulch Material Mulch used within the ordinary high-water mark of surface waters should be selected to minimize  potential flotation of organic matter. Composted organic materials have higher specific gravities  (densities) than straw, wood, or chipped material. Consult the Hydraulic Permit Authority (HPA) for  mulch mixes if applicable. Maintenance Standards The thickness of the mulch cover must be maintained. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the  erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 290 Mulch Mater- ial Guideline Description Straw Quality Standards Air-dried; free from undesirable seed and coarse material. Application Rates 2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre Remarks Cost-effective protection when applied with adequate thickness. Hand- application generally requires greater thickness than blown straw. The  thickness of straw may be reduced by half when used in conjunction with  seeding. In windy areas straw must be held in place by crimping, using a  tackifier, or covering with netting. Blown straw always has to be held in  place with a tackifier as even light winds will blow it away. Straw, however,  has several deficiencies that should be considered when selecting mulch  materials. It often introduces and/or encourages the propagation of weed  species and it has no significant long-term benefits It should also not be  used within the ordinary high-water elevation of surface waters (due to flot- ation). Hydromulch Quality Standards No growth inhibiting factors. Application Rates Approx. 35-45 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre Remarks Shall be applied with hydromulcher. Shall not be used without seed and  tackifier unless the application rate is at least doubled. Fibers longer than  about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less  than 3/4 inch. Compost Quality Standards No visible water or dust during handling. Must be produced per WAC 173- 350, Solid Waste Handling Standards, but may have up to 35% biosolids. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs per cubic yard) Remarks More effective control can be obtained by increasing thickness to 3". Excel- lent mulch for protecting final grades until landscaping because it can be dir- ectly seeded or tilled into soil as an amendment. Compost used for mulch  has a coarser size gradation than compost used for BMP C125: Topsoiling  / Composting or BMP T5.13: Post-Construction Soil Quality and Depth. It  is more stable and practical to use in wet areas and during rainy weather  conditions. Do not use near wetlands or near phosphorous impaired water  bodies. Chipped Site Veget- ation Quality Standards Gradations from fines to 6 inches in length for texture, variation, and inter- locking properties. Include a mix of various sizes so that the average size  is between 2- and 4- inches. Application Rates 2" thick min.; Table II-3.6: Mulch Standards and Guidelines 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 291 Mulch Mater- ial Guideline Description Remarks This is a cost-effective way to dispose of debris from clearing and grub- bing, and it eliminates the problems associated with burning. Generally, it  should not be used on slopes above approx. 10% because of its tendency  to be transported by runoff. It is not recommended within 200 feet of sur- face waters. If permanent seeding or planting is expected shortly after  mulch, the decomposition of the chipped vegetation may tie up nutrients  important to grass establishment.  Note: thick application of this material over existing grass, herbaceous spe- cies, and some groundcovers could smother and kill vegetation. Wood- Based Mulch Quality Standards No visible water or dust during handling. Must be purchased from a supplier  with a Solid Waste Handling Permit or one exempt from solid waste reg- ulations. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs. per cubic yard) Remarks This material is often called "wood straw" or "hog fuel". The use of mulch  ultimately improves the organic matter in the soil. Special caution is  advised regarding the source and composition of wood-based mulches. Its  preparation typically does not provide any weed seed control, so evidence  of residual vegetation in its composition or known inclusion of weed plants  or seeds should be monitored and prevented (or minimized). Wood Strand Mulch Quality Standards A blend of loose, long, thin wood pieces derived from native conifer or  deciduous trees with high length-to-width ratio. Application Rates 2" thick min. Remarks Cost-effective protection when applied with adequate thickness. A min- imum of 95-percent of the wood strand shall have lengths between 2 and  10-inches, with a width and thickness between 1/16 and 1/2-inches. The  mulch shall not contain resin, tannin, or other compounds in quantities that  would be detrimental to plant life. Sawdust or wood shavings shall not be  used as mulch. [Specification 9-14.4(4) from the Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT, 2016) Table II-3.6: Mulch Standards and Guidelines (continued) BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place  on steep slopes and in channels so that vegetation can become well established. In addition, some  nets and blankets can be used to permanently reinforce turf to protect drainage ways during high  flows.  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 292 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days,  except as stated below.  l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel- atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications  greater than six months.  l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that  might be adversely impacted by concentrated runoff. Such areas include steep and/or  unstable slopes.  l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on- site measures to counteract the increases. Creating a trough with wattles or other material  can convey clean water away from these areas.  l To prevent undercutting, trench and backfill rolled plastic covering products.  l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance,  removal, and disposal add to the total costs of this BMP.  l Whenever plastic is used to protect slopes, install water collection measures at the base of the  slope. These measures include plastic-covered berms, channels, and pipes used to convey  clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a  plastic covered slope with dirty runoff from a project.  l Other uses for plastic include:  o Temporary ditch liner.  o Pond liner in temporary sediment pond.  o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel  being stored.  o Emergency slope protection during heavy rains.  o Temporary drainpipe (“elephant trunk”) used to direct water. Design and Installation Specifications  l Plastic slope cover must be installed as follows:  1. Run plastic up and down the slope, not across the slope.  2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 298  3. Provide a minimum of 8-inch overlap at the seams.  4. On long or wide slopes, or slopes subject to wind, tape all seams.  5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope  and backfill with soil to keep water from flowing underneath.  6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them  together with twine to hold them in place.  7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This  prevents high velocity runoff from contacting bare soil, which causes extreme erosion.  8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be  staked in place.  l Plastic sheeting shall have a minimum thickness of 0.06 millimeters.  l If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall  be installed at the toe of the slope in order to reduce the velocity of runoff. Maintenance Standards  l Torn sheets must be replaced and open seams repaired.  l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi- ation.  l Completely remove plastic when no longer needed.  l Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C124: Sodding Purpose The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage  paths where concentrated overland flow will occur. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 299 BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of  erosion and sediment control (ESC), and water quality protection. The designated person shall be  responsible for ensuring compliance with all local, state, and federal erosion and sediment control  and water quality requirements. Construction sites one acre or larger that discharge to waters of the  State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible  representative. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur- face waters of the state. Sites less than one acre may have a person without CESCL certification  conduct inspections. The CESCL shall:  l Have a current certificate proving attendance in an erosion and sediment control training  course that meets the minimum ESC training and certification requirements established by  Ecology. Ecology has provided the minimum requirements for CESCL course training, as well as a list  of ESC training and certification providers at:  https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed- iment-control  OR  l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform- ation go to:  http://www.envirocertintl.org/cpesc/ Specifications  l CESCL certification shall remain valid for three years.  l The CESCL shall have authority to act on behalf of the contractor or project proponent and  shall be available, or on-call, 24 hours per day throughout the period of construction.  l The Construction SWPPP shall include the name, telephone number, fax number, and  address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention  Plans (Construction SWPPPs).  l A CESCL may provide inspection and compliance services for multiple construction projects  in the same geographic region, but must be on site whenever earthwork activities are  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 327 occurring that could generate release of turbid water.  l Duties and responsibilities of the CESCL shall include, but are not limited to the following:  o Maintaining a permit file on site at all times which includes the Construction SWPPP  and any associated permits and plans.  o Directing BMP installation, inspection, maintenance, modification, and removal.  o Updating all project drawings and the Construction SWPPP with changes made.  o Completing any sampling requirements including reporting results using electronic Dis- charge Monitoring Reports (WebDMR).  o Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner.  o Keeping daily logs, and inspection reports. Inspection reports should include:  n Inspection date/time.  n Weather information; general conditions during inspection and approximate  amount of precipitation since the last inspection.  n Visual monitoring results, including a description of discharged stormwater. The  presence of suspended sediment, turbid water, discoloration, and oil sheen shall  be noted, as applicable.  n Any water quality monitoring performed during inspection.  n General comments and notes, including a brief description of any BMP repairs,  maintenance or installations made as a result of the inspection.  n A summary or list of all BMPs implemented, including observations of all  erosion/sediment control structures or practices. The following shall be noted:  1. Locations of BMPs inspected.  2. Locations of BMPs that need maintenance.  3. Locations of BMPs that failed to operate as designed or intended.  4. Locations of where additional or different BMPs are required. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by  wind, rain, runoff, and vehicle tracking. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 328 thickness is 2 feet.  o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an  engineered energy dissipator.  o Filter fabric or erosion control blankets should always be used under riprap to prevent  scour and channel erosion. See BMP C122:  Nets and Blankets.  l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas.  This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart- ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals. Maintenance Standards  l Inspect and repair as needed.  l Add rock as needed to maintain the intended function.  l Clean energy dissipator if sediment builds up. BMP C220: Inlet Protection Purpose Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta- bilization of the disturbed area. Conditions of Use Use inlet protection at inlets that are operational before permanent stabilization of the disturbed  areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and  within 500 feet of a disturbed or construction area, unless  those inlets are preceded by a sediment  trapping BMP. Also consider inlet protection for lawn and yard drains on new home construction. These small and  numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof  drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap  these drains to prevent sediment from entering the system until completion of landscaping. Provide  18-inches of sod around each finished lawn and yard drain. Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods  for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain- age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with  additional end-of-pipe treatment where stormwater ponding would cause a hazard. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 356 Type of Inlet Pro- tection Emergency Overflow Applicable for Paved/ Earthen Sur- faces Conditions of Use Drop Inlet Protection Excavated  drop  inlet protection Yes, temporary  flooding may   occur Earthen Applicable for heavy flows. Easy   to maintain. Large area requirement:   30'x30'/acre Block  and gravel  drop inlet pro- tection Yes Paved or Earthen Applicable for heavy  concentrated flows.  Will not pond. Gravel and wire  drop inlet pro- tection No Paved or Earthen Applicable for  heavy concentrated flows.  Will pond. Can withstand traffic. Catch  basin filters Yes Paved or Earthen Frequent maintenance  required. Curb Inlet Protection Curb  inlet pro- tection with  wooden weir Small capacity  overflow Paved Used for sturdy, more compact  install- ation. Block and gravel  curb inlet pro- tection Yes Paved Sturdy, but  limited filtration. Culvert Inlet Protection Culvert  inlet sed- iment trap N/A N/A 18 month expected life. Table II-3.10: Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet.  Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include:  l Provide a depth of 1-2 ft as measured from the crest of the inlet structure.  l Slope sides of excavation should be no steeper than 2H:1V.  l Minimum volume of excavation is 35 cubic yards.  l Shape the excavation to fit the site, with the longest dimension oriented toward the longest  inflow area.  l Install provisions for draining to prevent standing water.  l Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 357  l Grade the approach to the inlet uniformly.  l Drill weep holes into the side of the inlet.  l Protect weep holes with screen wire and washed aggregate.  l Seal weep holes when removing structure and stabilizing area.  l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass  flow. Block and Gravel Filter A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel.  See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil- ters include:  l Provide a height of 1 to 2 feet above the inlet.  l Recess the first row of blocks 2-inches into the ground for stability.  l Support subsequent courses by placing a pressure treated wood 2x4 through the block open- ing.  l Do not use mortar.  l Lay some blocks in the bottom row on their side to allow  for dewatering the pool.  l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings.  l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter.  l An alternative design is a gravel berm surrounding the inlet, as follows:  o Provide a slope of 3H:1V on the upstream side of the berm.  o Provide a slope of 2H:1V on the downstream side of the berm.  o Provide a 1-foot wide level stone area between the gravel berm and the inlet.  o Use stones 3 inches in diameter or larger on the upstream slope of the berm.  o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of  the berm. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 358 Figure II-3.17: Block and Gravel Filter   2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 359 Gravel and Wire Mesh Filter Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not  provide an overflow. Design and installation specifications for gravel and wire mesh filters include:  l Use a hardware cloth or comparable wire mesh with ½-inch openings.  o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey- ond each side of the inlet structure.  o Overlap the strips if more than one strip of mesh is necessary.  l Place coarse aggregate over the wire mesh.  o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at  least 18-inches on all sides. Catch Basin Filters Catch  basin filters are designed by manufacturers for construction sites. The limited sediment stor- age capacity increases the amount of inspection and maintenance required, which may be daily for  heavy sediment loads. To reduce maintenance requirements, combine a catch  basin filter with  another type of inlet protection. This type of inlet protection provides flow  bypass without overflow  and therefore may be a better method for inlets located along active rights-of-way. Design and install- ation specifications for catch basin filters include:  l Provides 5 cubic feet of storage.  l Requires dewatering provisions.  l Provides a high-flow bypass that will not clog under normal use at a construction site.  l Insert the catch  basin filter in the catch  basin just below the grating. Curb Inlet Protection with Wooden Weir Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb  inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection  with wooden weirs include:  l Use wire mesh with ½-inch openings.  l Use extra strength filter cloth.  l Construct a frame.  l Attach the wire and filter fabric to the frame.  l Pile coarse washed aggregate against the wire and fabric.  l Place weight on the frame anchors. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 360 Block and Gravel Curb Inlet Protection Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and  gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe- cifications for block and gravel curb inlet protection include:  l Use wire mesh with ½-inch openings.  l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening.  These are spacer blocks.  l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks.  l Place blocks on their sides across the front of the inlet and abutting the spacer blocks.  l Place wire mesh over the outside vertical face.  l Pile coarse aggregate against the wire to the top of the barrier. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 361 Figure II-3.18: Block and Gravel Curb Inlet Protection   2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 362 Curb and Gutter Sediment Barrier Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3  feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation  specifications for curb and gutter sediment barrier include:  l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high  and 3 feet wide, at least 2 feet from the inlet.  l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the  trap to sediment trap standards for protecting a culvert inlet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 363 Figure II-3.19: Curb and Gutter Barrier 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 364 Maintenance Standards  l Inspect all forms of inlet protection frequently, especially after storm events. Clean and  replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the  inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and  put fresh rock around the inlet.  l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly  over the surrounding land area or stockpile and stabilize as appropriate. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site  by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland  flow. Conditions of Use  l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre.  l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub- stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap- ping BMP. The only circumstance in which overland flow can be treated solely by a brush  barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is  small.  l Brush barriers should only be installed on contours. Design and Installation Specifications  l Height: 2 feet (minimum) to 5 feet (maximum).  l Width: 5 feet at base (minimum) to 15 feet (maximum).  l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability  of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 365 BMP C233: Silt Fence Purpose Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary  physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Silt fence may be used downslope of all disturbed areas.  l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the  top of the silt fence, but shall allow the water to pass through the fence.  l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial  amounts of overland flow. Convey any concentrated flows through the drainage system to a  sediment trapping BMP.  l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide  an adequate method of silt control for anything deeper than sheet or overland flow. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 370 Figure II-3.22: Silt Fence 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 371 Design and Installation Specifications  l Use in combination with other construction stormwater BMPs.  l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V.  l Maximum sheet or overland flow path length to the silt fence of 100 feet.  l Do not allow flows greater than 0.5 cfs.  l Use geotextile fabric that meets the following standards. All geotextile properties listed below  are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or  exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): Geotextile Property Minimum Average Roll Value Polymeric  Mesh AOS  (ASTM D4751) 0.60 mm maximum for slit film  woven (#30 sieve).  0.30 mm  maximum for all other geotextile types (#50 sieve).  0.15 mm minimum for all fabric  types (#100 sieve). Water  Permittivity  (ASTM D4491) 0.02 sec-1 minimum Grab  Tensile Strength  (ASTM D4632) 180 lbs. Minimum for extra  strength fabric.  100 lbs  minimum for standard strength fabric. Grab Tensile Strength  (ASTM D4632) 30% maximum Ultraviolet  Resistance  (ASTM D4355) 70%  minimum Table II-3.11: Geotextile Fabric Standards for Silt Fence  l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire,  safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are  available that have synthetic mesh backing attached.  l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum  of six months of expected usable construction life at a temperature range of 0°F to 120°F.  l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can  be left in place after the project is completed, if permitted by the local jurisdiction.  l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand- ard Notes for silt fence on construction plans and specifications:  1. The Contractor shall install and maintain temporary silt fences at the locations shown in  the Plans.  2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those  activities. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 372  3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original  ground surface.  4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric  lengths as required. Locate all sewn seams at support posts. Alternatively, two sections  of silt fence can be overlapped, provided  that the overlap is long enough and that the  adjacent silt fence sections are close enough together to prevent silt laden water from  escaping through the fence at the overlap.  5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples,  wire, or in accordance with the manufacturer's recommendations. Attach the geotextile  fabric to the posts in a manner that reduces the potential for tearing.  6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of  the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely  to the up-slope side of the posts with the geotextile fabric up-slope of the mesh.  7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2- inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh  shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh  must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it  supports.  8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill  and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can  pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up  support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches  min.  9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth  is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be  reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of  3H:1V or steeper and the slope is perpendicular to the fence. If required post depths  cannot be obtained, the posts shall be adequately secured by bracing or guying to pre- vent overturning of the fence due to sediment loading.  10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max- imum of 6-feet. Posts shall consist of either:  l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be  free of defects such as knots, splits, or gouges.  l No. 6 steel rebar or larger.  l ASTM A 120 steel pipe with a minimum diameter of 1-inch.  l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft.  l Other steel posts having equivalent strength and bending resistance to the post  sizes listed above.  11. Locate silt fences on contour as much as possible, except at the ends of the fence,  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 373 where the fence shall be turned uphill such that the silt fence captures the runoff water  and prevents water from flowing around the end of the fence.  12. If the fence must cross contours, with the exception of the ends of the fence, place  check dams perpendicular to the back of the fence to minimize concentrated flow and  erosion. The slope of the fence line where contours must be crossed shall not be  steeper than 3H:1V.  l Check dams shall be approximately 1-foot deep at the back of the fence. Check  dams shall be continued perpendicular to the fence at the same elevation until  the top of the check dam intercepts the ground surface behind the fence.  l Check dams shall consist of crushed surfacing base course, gravel backfill for  walls, or shoulder ballast. Check dams shall be located every 10 feet along the  fence where the fence must cross contours.  l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The  following are specifications for silt fence installation using the slicing method:  1. The base of both end posts must be at least 2- to 4-inches above the top of the geo- textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or  string level, if necessary, to mark base points before installation.  2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard  applications.  3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as  possible to the geotextile fabric, enabling posts to support the geotextile fabric from  upstream water pressure.  4. Install posts with the nipples facing away from the geotextile fabric.  5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8- inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each  puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post  nipple when tightening to prevent sagging.  6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure  with 3 ties.  7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level.  8. Compact the soil immediately next to the geotextile fabric with the front wheel of the  tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the  upstream side first and then each side twice for a total of four trips. Check and correct  the silt fence installation for any deviation before compaction. Use a flat-bladed shovel  to tuck the fabric deeper into the ground if necessary. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 374 Figure II-3.23: Silt Fence Installation by Slicing Method 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 375 Maintenance Standards  l Repair any damage immediately.  l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap- ping BMP.  l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to  flow  and then causing channelization of flows parallel to the fence. If this occurs, replace the  fence and remove the trapped sediment.  l Remove sediment deposits when the deposit reaches approximately one-third the height of  the silt fence, or install a second silt fence.  l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown. BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a  physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use  l Vegetated strips may be used downslope of all disturbed areas.  l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat  substantial amounts of overland flow. Any concentrated flows must be conveyed through the  drainage system to BMP C241:  Sediment Pond (Temporary) or other sediment trapping  BMP. The only circumstance in which overland flow  can be treated solely by a vegetated strip,  rather than by a sediment trapping BMP, is when the following criteria are met (see Table II- 3.12: Contributing Drainage Area for Vegetated Strips): Average Contributing Area Slope Average Contributing Area Per- cent Slope Max Contributing area Flowpath Length 1.5H : 1V or flatter 67% or flatter 100 feet 2H : 1V or  flatter 50% or flatter 115 feet 4H : 1V or  flatter 25% or flatter 150  feet 6H : 1V or  flatter 16.7% or flatter 200  feet 10H  : 1V or  flatter 10% or flatter 250  feet Table II-3.12: Contributing Drainage Area for Vegetated Strips 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 9 APPENDIX C Geotechnical Engineer’s Report C-1 Golder Associates Inc. 18300 NE Union Hill Road, Suite 200 Redmond, WA USA 98052-3333 Telephone (425) 883-0777 Fax (425) 882-5498 www.golder.com i older ociT%s REPORT ON GEOTECHNICAL INVESTIGATION YELM COMMERCIAL 15106 CARTER LOOP SOUTHEAST YELM, WASHINGTON Submitted to: Mr. Paul Edminster Projects West, LLC 2014 Meridian Street South Puyallup, Washington 98371-7510 Ms. Sarah Hales CES Northwest Inc., 5210 -12th Street East Fife, Washington 98424 Submitted by: Golder Associates Inc. 18300 Northeast Union Hill Road, Suite end, Washington 98052 Scott D. Dinkelman, LEG Senior Consultant Distribution: 2 Copies —Projects West, LLC 2 Copies — CES Northwest, Inc, March 29, 2007 Richard D. Luark, PE, LEG Associate and Senior Consultant 073-93048.000 032907sdd1_Yelm Commercial Geotech.doc OFFICES ACROSS AFRICA, ASIA, AUSTRAUA, EUROPE, NORTH AMERICA AND SOUTH AMERICA March 29, 2007 ES-1 073-93048.000 EXECUTIVE SUMMARY The purpose of this geotechnical investigation is to provide a description of the surface and subsurface conditions at the subject site and based on those conditions to provide geotechnical engineering recommendation for developing the site with the proposed commercial development. Our scope of services included a field investigation, geotechnical analysis, and preparation of this report. The proposed development is located at 15106 Carter Loop Southeast, in Yelm, Washington. Review of preliminary site development drawings prepared by CES Northwest, Inc. indicates it is planned to develop the approximately one acre site with a three -building commercial development. The proposed one story buildings will range in size from 500 square feet to 5,000 square feet. Based on the results of our investigation, the proposed site development is feasible from a geotechnical engineering standpoint. Support for the proposed buildings may be provided using conventional spread and continuous footing foundation systems bearing on competent native soils or on structural fill used to modify site grades. Slab on grade floors may be similarly supported. Stormwater from the development will be collected, treated, and infiltrated into the site soils using an underground infiltration gallery located below the paved parking and drive areas. Our scope of services included an evaluation of the feasibility of infiltrating stormwater. Based on in -situ infiltration tests and on textural analyses of the soils, in our opinion, infiltration of stormwater should be feasible. �L 032907sddi YelmCommercialGeotech.doc 1 - Golder Associates March 29, 2007 EXECUTIVE SUMMARY -i- TABLE OF CONTENTS 073-93048.000 ...................................................................................... ES-1 1.0 PURPOSE AND SCOPE ...................................................... 2.0 SITE AND PROJECT DESCRIPTION............................................................................2 3.0 FIELD INVESTIGATION.................................................................................................3 4.0 SUBSURFACE CONDITIONS........................................................................................4 4.1 Soil................................................................................................................................4 4.2 Groundwater..................................................................................................................4 5.'0 INFILTRATION ASSESSMENT.....................................................................................5 5.1 Infiltration Testing and Textural Analysis....................................................................5 5.2 Infiltration Conclusions................................................................................................6 6.0 ENGINEERING RECOMMENDATIONS ........... :........................................................... 7 6.1 General..........................................................................................................................7 6.2 Seismic Criteria.............................................................................................................7 6.2.1 Liquefaction Hazards.......................................................................................8 6.3 Foundations...................................................................................................................8 6.4 Slab -on -Grade Floors....................................................................................................9 6.5 Excavations and Slopes................................................................................................9 . 6.5.1 Temporary ..................................... Slopes.......................................................9 6.5.2 Permanent Slopes...........................................................................................10 6.6 Retaining Walls and Backfilled Walls....................................................................",..10 6.7 Permanent Drainage Provisions..................................................................................10 6.8 Suggested Minimum Pavement Sections....................................................................11 7.0 EARTHWORKS..............................................................................................................12 7.1 General.........................................................................................................................12 7.2 Construction Drainage................................................................................................12 7.3 - Erosion Control...........................................................................................................12 7.4 Site Preparation and Stripping....................................................................................12 7.4.1 Fill Materials and Placement.........................................................................13 7.4.2 Subgrade.........................................................................................................14 7.5 Utilities........................................................................................................................14 7.6 Construction Geotechnical Monitoring.......................................................................14 8.0 ADDITIONAL SERVICES.............................................................................................15 032907sdd1_Yelm Commercial Geotech.doc Golder Associates March 29, 2007 9.0 USE OF THIS REPORT .... 10.0 REFERENCES ................... -n- LIST OF TABLES Table 5-1 Infiltration Test and Textural Analysis Summary Table 6-1 Capillary Break Recommendations Table 6-2 Suggested Pavement Sections LIST OF FIGURES Figure 1 Vicinity Map Figure 2 Test Pit Location Plan LIST OF APPENDICES Appendix A Test Pit Logs Appendix B Laboratory Test Results 032907sdd1_YelmCommercial Geotechdoc Golder Associates T-1 March 29, 2007 -1- 073-93048.000 1.0 PURPOSE AND SCOPE iThe purpose of our geotechnical investigation is to provide a description of the surface and subsurface conditions at the site and based on those conditions to provide geotechnical recommendations for _ foundations, earthworks, drainage, infiltration, and retaining walls. Our scope of services consisted of a field investigation, laboratory testing, geotechnical analysis, and preparation of this report that includes the following: • Surface and subsurface soil and water conditions; • Site preparation, grading and earthwork procedures, including stripping depth recommendations, details of structural fill placement and. compaction; • Suitability of existing on -site materials for use as structural fill, and recommendations for imported fill materials; • Infiltration recommendations; • Short-term and long-term groundwater seepage and erosion control measures; • Foundation design recommendations, including bearing capacity and lateral pressures for structures and walls; • Estimates of potential total and differential settlement magnitudes; • Temporary and permanent slope recommendations; and • Suggested pavement sections. 032907sdd1 YelmCommercialGeotech.doc Golder Associates - , March 29, 2007 -2- 2.0 SITE AND PROJECT DESCRIPTION 073-93048.000 The subject site consists of an approximately one acre parcel located at 15106 Carter Loop Southeast in Yelm, Washington (Figure 1, Vicinity Map). The irregular -shaped property is bordered to the north by State Route 507, to the east by a stormwater quality pond, to the south by Carter Loop Road and residences, and to the west by residences (Figure 2, Test Pit Location Plan). Review of the preliminary site plan provided by the project civil engineer indicates it is planned to j develop the site with a three building commercial development along with associated asphalt paved drive and parking areas, underground utilities and a stormwater infiltration system. The majority of the site is relatively level with little discernible elevation change and contains a iJ vacant residence in the central portion of the site. The site is vegetated with scots broom and tall grass. The western portion of the site contains an approximately 10 foot high soil stockpile. We anticipate the proposed buildings will be single story structures .and of concrete masonry unit or wood -frame construction with slab -on -grade floors. Based on our experience with this type of construction, we anticipate perimeter wall loads will be approximately 3 to 4 kips per lineal foot and I interior columns will have loads of approximately 60 to 80 kips. We estimate slab -on -grade floor loads will be approximately 250 pounds per square foot (pso. I At the time of our investigation, the project was in the preliminary design phase and no grading plan was available. However, based on the relatively level condition of the site, we estimate cuts and fills will typically be in the range of five feet or less. It is planned to mass grade the site, with soil generated from cut areas used on -site as structural fill. We anticipate the stockpiled soil will be exported. Stormwater from the development will be collected, treated and infiltrated. The infiltration system will consist of a below grade infiltration gallery located beneath the parking lot in the west portion of the site. The conclusions and recommendations provided in this investigation are based on our understanding of the proposed development, which is in turn based on the preliminary drawings and design information provided us. If the above design information is incorrect or changes, Golder should be consulted to review the recommendations contained in this report. In any case, Golder should be retained to perform a review of the final design in order to confirm the geotechnical recommendations have been interpreted and implemented into the construction drawings. 032907sddl Yelm Commercial Geotech.doc Golder Associates March 29, 2007 -3- 073-93048.000 3.0 FIELD INVESTIGATION The field investigation was completed on February 26, 2007. The field investigation consisted of excavating 10 test pits (Test Pits TP-1 through TP-10) at the approximate locations shown on the Test Pit Location Plan, Figure 2. The locations shown on Figure 2 should be considered approximate as the locations were estimated by pacing from on -site features shown on the site plan provided by the project civil engineer. The test pit logs are included in Appendix A. r 4 The test pits were excavated using. a Case 580K rubber tired backhoe operated by Custom Backhoe j Service. The test pits were excavated to depths ranging from 10 to 12.5 feet below existing grade and were logged by an engineer from Golder. Pertinent information was recorded, including sample depths, soil contacts, depth to groundwater seepage, and soil engineering characteristics. I . :i The soil samples collected at the test pit locations were classified in accordance with Golder Technical Procedure TP-1.2-6, "Field Identification of Soil". The samples were collected and !, returned to our Redmond, Washington laboratory for further classification and testing. The stratification lines indicated on the test pit logs represent the approximate depth of transitions between soil units and depths to groundwater conditions. Actual transitions between soil units may be more gradual. In addition, the subsurface descriptions are based on the conditions encountered at the time of our exploration. Soil and groundwater conditions between our exploration locations may vary from those encountered and groundwater conditions may vary during certain times of the year. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations are encountered at the time of construction, Golder should be requested to reevaluate the recommendations of this report and to modify or verify them in writing prior to proceeding with the grading and construction. 032907sddl_Yelm Commemial Geotech.doc Golder Associates March 29, 2007 -4- 073-93048.000 1 4.0 SUBSURFACE CONDITIONS 4.1 Soil Subsurface soil and groundwater conditions at the site were assessed as described in the Field j Investigation section of this report. Based on subsurface conditions encountered at our exploration 1 locations, the site soils consist of localized areas of existing fill and native recessional outwash gravel. Please refer to the test pit logs contained in Appendix A for a detailed description of the subsurface conditions encountered at each exploration location. The following is a generalized summary of the soil conditions encountered. • Topsoil - At all of our test pit locations, a surficial layer of topsoil was encountered. The topsoil ranged from 6 to 12 inches thick and consisted of organic debris in a silty sand (Unified Soil Classification SM) matrix. The topsoil was characterized by its dark brown color and an abundance of organic debris and roots. • Fill — At the locations of Test Pits TP-1, TP-3, and TP-6, we encountered existing fill. The fill was comprised of fine to coarse gravel (GP) with some cobbles. The fill was characterized by its loose to compact condition and the presence of trace amounts of organic debris, its dark brown to black mottled color, and the presence of a buried topsoil horizon at the contact with the underlying native soils at the locations of Test Pits TP-1 and TP-3. • Recessional Outwash — Underlying the topsoil in Test Pits TP-2, TP-4, TP-5, and TP-7 through TP-10, we encountered recessional outwash consisting of loose to dense poorly and well graded gravel containing some cobbles, and trace amounts of silt and sand (GP). The out•,vash was typically loose at the ground surface, grading to dense with depth. The northeast portion of the site contains a stockpile of soils. Based on visual observation of the stockpile, it appears to consist of topsoil and vegetation that was stripped from the site. 4.2 Groundwater Light to moderate groundwater seepage was encountered in Test Pits TP-1, TP-3, TP-4, TP-7, and TP-8 at depths ranging from 10.5 to 12 feet below existing grade. Groundwater levels are not static; there will likely be fluctuations in the groundwater level depending on the season, amount of rainfall, and other factors. Generally, the water level is higher and seepage rates are greater in the wetter, winter months and early spring (typically October through May). 032907sdd1_YelmComma•cialGeotech.doc Golder Associates i_ ,I March 29, 2007 -5- 073-93048.000 5.0 INFILTRATION ASSESSMENT We understand it is planned to dispose of stormwater runoff from the proposed development using an infiltration gallery located below the asphalt paved parking and driveway areas. As part of our study, we conducted an infiltration evaluation to determine the feasibility of infiltrating stormwater at the site. Our infiltration evaluation consisted of the following: • Performing infiltration tests using the EPA Falling Head Infiltration Test Procedure in three of our test pits at 4.5 to 5 feet below grade; • Conducting textural analyses of representative soils . collected at various elevations in potential infiltration areas; and • Interpreting the field data and laboratory analyses to provide ultimate infiltration rates for the project civil engineer's design. 5.1 Infiltration Testing and Textural Analysis The City of Yelm uses the Washington Department of Ecology Stormwater Manual for Western Washington (Ecology 1998) for infiltration system design. In order to evaluate the infiltration capabilities of the site soils, we performed a textural analysis of the soils in general accordance with the United States Department of Agriculture (USDA) Natural Resource Conservation Service (MRCS) classification method and performed in -situ infiltration tests in Test Pits TP-7, TP-8, and TP-9. Table 5-1 provides a summary of our textural analyses and measured ultimate infiltration rates. The test results are attached as Appendix B. TABLE 5-1 Infiltration Test and Textural Analysis Summary Measured Location Depth USDA Texture USCS Soil Classification Infiltration Rate (below Classification (inches/hour) rade TP-7 3.0 Extremely gravelly loamy Well graded GRAVEL, -- coarse sand some sand TP-7 4.5 Extremely gravelly loamy Well graded GRAVEL, 27 coarse sand some sand. TP-8 8.0 Extremely gravelly coarse Poorly graded GRAVEL 473 sandy loam TP-9 4.5 Extremely gravelly coarse Poorly graded GRAVEL 183 sandy loam TP-9 8.0 Extremely gravelly coarse Poorly graded GRAVEL -- sandy loam TP-10 8.0 Extremely gravelly loamy Well graded GRAVEL; -- coarse sand some sand 032907sdd1 Yelm Commercial Geotech.doc Golder Associates March 29, 2007 -6- 073-93048.000 5.2 Infiltration Conclusions Based on the results of our field exploration, infiltration tests, and textural analyses, in our opinion, infiltration of stormwater should be feasible in the area of Test Pits TP-8 and TP-9. The site is underlain by extremely gravelly coarse sandy loam and loamy sand. The field measured infiltration rates in Test Pits TP-8 and TP-9 were 473 inches per hour and 183 inches per hour, respectively. In our opinion, the infiltration system, if located in the area of Test Pits TP-8 and TP-9 can be designed for an ultimate infiltration rate of 60 inches per hour. The infiltration rate should be reduced by a factor of safety of 2.0 to achieve a long-term infiltration rate of 30 inches per hour. The infiltration system should be located at least three feet above the seasonal high groundwater table or shallowest relatively impermeable soil layer. Groundwater seepage was encountered at 12 feet below grade in Test Pit TP-8, as such, we recommend using that depth as the seasonal high groundwater table in the area of the infiltration system. The infiltration capability of the natural deposits underlying the site will vary vertically and laterally. Due to this potential variability, a representative from Golder should observe the infiltration system excavation to verify the soil and groundwater conditions encountered in the infiltration system jexcavation are as anticipated. 032907sddl_Yelm Commercial Geotech.doc Golder Associates March 29, 2007 -7- 073-93048.000 6.0 ENGINEERING RECOMMENDATIONS This section of the report presents our recommendations based on subsurface exploration data, observed surface conditions at the time of our field exploration, and on geotechnical analyses completed for this study. The recommendations provided in this report are applicable to this site and are based on our understanding of the conceptual design parameters provided by the client at the time of this study. The recommendations contained in this report do not include an assessment of the presence or implication(s) of possible surface and/or subsurface contamination resulting from previous site activities and/or resulting from the introduction of materials from off site sources. Recommendations that pertain to environmental issues are outside the scope of services for this report and have not been investigated or addressed in this report. 6.1 General Based on the results of our investigation, the proposed site development is feasible from a geotechnical standpoint and can be completed using conventional construction practices. Support for the proposed buildings may be provided using conventional spread and continuous footing foundation systems bearing on competent native soil or on structural fill. If existing fill or loose native soil is encountered at construction subgrade elevations in structural areas, the fill should be overexcavated and replaced with structural fill. Unsuitable soils should be removed from structural areas to expose the compact to dense native soils that were generally encountered within several feet of existing grade. The site soils should be suitable for use as structural backfill, however, they may need to be moisture conditioned to achieve adequate compaction. Geotechnical recommendations that may be used for planning and preliminary design are discussed below. 6.2 Seismic Criteria The 2003 International Building Code (IBC) seismic design section provides a series of site classes that are used as a basis for seismic design of structures. Washington State adopted the International Building Code (IBC) on July 1, 2004. Based on the encountered soil conditions, Site Class D, Very Dense Soil and Soft Rock as identified in Table 1615.1.1 of the IBC should be used for design. This conclusion is based on an assumed average "N-value" of greater than or equal to 50 in the upper 100 feet of the site. The following design parameters are based on the peak ground acceleration (PGA), the 0.2 second spectral acceleration (SS), and the 1.0 second spectral acceleration (Si) for the project site latitude of North 46.934581, longitude West 122.619775. These parameters were taken from the United States Geological Survey website for the Earthquake Hazards Program Probabilistic Hazard Lookup by latitude and Iongitude (USGS 2002). The following (un-modified) interpolated probabilistic ground motion values (2 percent probability of exceedance in 50 years) can be used for seismic design: • PGA = 0.5Ig • 0.2 sec SA SS = 1.14g 032907sddl_Yelm Co=mial Geotech.doc Golder Associates March 29, 2007 -8- 073-93048.000 1 6.2.1 Liquefaction Hazards Liquefaction is a phenomenon in which soils lose all shear strength for short periods of time during an earthquake. Groundshaking of sufficient duration results in the loss of grain -to -grain contact and rapid increase in pore water pressure, causing the soil to behave as a fluid. To have a potential for liquefaction, a soil must be cohesionless with a grain size distribution of a specified range (generally sand and silt); it must be loose; it must be below the groundwater table; and it must be subject to sufficient magnitude and duration of groundshaking. The effects of liquefaction may be large total and/or differential settlement for structures founded in the liquefying soils. In our opinion, the predominantly gravel soils underlying the site have a low susceptibility toward liquefaction. 6.3 Foundations Based on the results of our study, the proposed development is feasible from a geotechnical engineering standpoint, provided the recommendations contained in this report are incorporated into the project design. Support for the proposed buildings may be provided using conventional spread and continuous footing foundation systems bearing on competent native soil or on newly placed structural fill as described in the Earthworks section of this report. If very loose to loose native soil is encountered at construction subgrade elevations they should either be compacted in -place to the requirements of structural fill or they should be overexcavated and replaced with structural fill. If existing fill is encountered at construction subgrade elevations the fill should be overexcavated and replaced with structural fill. Alternatively, the footings may be extended through the loose fill or native soils to the underlying compact to very dense native soils. Foundations should be designed based on the following parameters: Maximum Allowable Bearing Pressures: Compact structural fill Native soils (compact to dense) 2,500 psf 2,500 psf The bearing capacity values may be increased by 1/3 for short-term wind or seismic loading. Passive Pressure: (equivalent fluid density) 350 pcf Coefficient of Friction: 0.30 (includes Factor of Safety of 1.5) Minimum Embedment for Frost Protection: Perimeter footings 18 inches Interior footings (below exterior grades) 12 inches Minimum Footing Widths: Perimeter footings 18 inches Interior isolated footings 18 inches 032907sddl Yelm Commercial Geotech.doc ,_ ; - Golder Associates March 29, 2007 -9- 073-93048.000 Based on the anticipated loading, we estimate settlement due to dead and live loads could be about 1 inch with differential settlement of about 1/2 inch. Most of this settlement will be realized during construction, as the dead loads are applied. The foundation bearing soils should be observed by a representative from Golder prior to placing forms or rebar to verify the bearing soil conditions are as anticipated. 6.4 Slab -on -Grade Floors Conventional slab -on -grade floors can be supported on compact to very dense native soils or on structural fill placed and compacted as noted in the Earthworks section of this report. Slab -on -grade. floors should not be founded on organic soils, loose native soils, or on uncompacted or uncontrolled fills. Slabs should be underlain by a capillary break material, consisting of at least four inches of clean, free draining sand and gravel or crushed rock that contains less than 3 percent fines passing the US No. 200 sieve (based on the minus US No. 4 sieve fraction) and meets the following specification: TABLE 6-1 Capillary Break Gradation Sieve Size Percent Passing 1-inch 100 US No. 4 0 - 20 US No. 200 0-3 Vapor transmission through floor slabs is an important consideration in the performance of floor coverings and controlling moisture in structures. Floor slab vapor transmission can be reduced through the use of suitable vapor retarders such as plastic sheeting placed between the capillary break and the floor slab, and/or specially formulated concrete mixes. Framed floors should also include vapor protection over any areas of bare soils and adequate crawl space ventilation and drainage should be provided. The identification of alternatives to prevent vapor transmission is outside of our expertise. A qualified architect or building envelope consultant can make recommendations for reducing vapor transmission through the slab. 6.5 Excavations and Slopes 6.5.1 Temporarppes The inclination of temporary slopes is dependent on several variables, including the height of the cut, the soil type and density, the presence of groundwater seepage, construction timing, weather, and surcharge loads from adjacent structures, roads and equipment. In no case should excavation slopes be greater than the limits specified in local, state (WISHA), and federal (OSHA) safety regulations. Safe temporary slopes are the responsibility of the contractor and should comply with all applicable OSHA and WISHA standards. Golder should observe temporary slope excavations during construction to verify soil and groundwater conditions. If temporary slopes cannot be constructed in accordance with OSHA/WISHA guidelines, temporary shoring may be necessary. Shoring will help protect against slope or excavation collapse and iwill provide protection to workers in the excavation. 032907sdd1 Yelm Commercial Geotechdoc L` Golder Associates March 29, 2007 -10- 073-93048.000 If groundwater seepage is encountered in site excavations, the excavation should be sloped to an inclination of 2H:1V or flatter to reduce caving or sloughing of the excavation face or sidewalls. In addition, the contractor may need to install temporary drainage measures to protect the cut face and to prevent degradation of the excavation area until permanent drainage measures can be installed. 6.5.2 Permanent Slopes Permanent cut and fill slopes should be inclined no steeper than 2H:1V. Cut slopes should be observed by Golder during excavation to. verify that conditions are as anticipated. Supplementary recommendations can then be developed, if needed, to improve stability, including flattening of slopes or installation of surface or subsurface drains. In our experience, 2H:lV and steeper slopes will likely experience erosion or sloughing during the first winter season, until vegetation is well established. Aggressive erosion control measures, including utilization of plastic sheeting can be used to reduce erosion and sloughing and surficial slope damage. Permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. 6.6 Retaining Walls and Backfilled Walls If the proposed site development is to include retaining walls, the walls should be designed to resist the lateral loads imposed by the retained soils and applicable surcharge loads. The following equivalent earth pressures may be used for design of retaining walls in conjunction with the foundation recommendations given in Section 6.3, and the drainage recommendations given in Section 6.8. Earth Pressures for retaining structures or backfilled walls: Restrained Walls (Equivalent Fluid Weight) 55 pcf Cantilevered Walls (Equivalent Fluid Weight) 35 pcf Passive Earth Pressure 350 pcf The earth pressure values provided in this section are based on the assumption the retaining walls will have a flat backslope, the backfill will be horizontal, and will be fully drained. Surcharges due to backfill slopes, hydrostatic pressures, traffic, structural loads, or other surcharge loads should be added to the above design lateral pressure. A uniform seismic surcharge pressure equal to 8H in psf, where H equals the height of the wall in feet, is recommended. 6.7 Permanent Drainage Provisions Permanent control of surface water should be incorporated in the final grading design. It is important to separate all surface water drainage including roof downspouts from building underdrain system such as footing drains. The water collected from roof downspout and footing drains should be separately tightlined to an appropriate discharge point. Cleanouts should be installed at strategic locations to allow for periodic maintenance of the footing drain and downspout tightline systems. Subsurface drainage measures may include: 032907sddl Yelm Commercial Geotech.doc L I - v^^older Associates r- March 29,-2007 -11- 073-93048.000 i • WALL DRAINS: To reduce the potential for hydrostatic pressures to develop behind retaining walls, the retaining wall backfill should consist of a free -draining material that extends at least 18 inches behind the wall. The free draining backfill should consist of either pea gravel or washed rock. A rigid, 4 inch diameter, schedule 40, perforated PVC drain pipe should be placed at the base of the wall and should be surrounded by at least !, I six inches of drainage gravel with a minimum of two inches below the invert. The remainder of the backfill should consist of structural fill. The pipe should be placed with the perforations in the down position. Alternatively, a geocomposite drainage board can be used in place of the free draining backfill. The geocomposite should be connected to drain into the PVC drain. A relatively fine grained soil should be placed within a foot of the ground surface and the slope behind the wall should be graded to drain away from the wall. • FOOTING DRAINS: Footing drains should be installed around the perimeter of each of the buildings, at or just below the invert of the footings, with a gradient sufficient to initiate flow. A footing drain should consist of a rigid, 4 inch diameter, schedule 40, perforated PVC drain pipe that is placed with the perforations in the down position. The footing drains should be surrounded by a minimum of six inches of drainage gravel with a minimum of two inches below the pipe invert. In no case should roof downspouts be connected to the footing drain system. 6.8 Suggested Minimum Pavement Sections The recommended minimum pavement structure thicknesses for the future collector roadways are shown in Table 6.2. These sections are based on our experience with similar soils under similar anticipated traffic conditions. TABLE 6-2 Suggested Minimum Pavement Structure Designs Asphalt Concrete Asphalt Treated Crushed Aggregate Alternative (Class B) Thickness Base Thickness Base Thickness inches inches inches I 3 N/A 6 II 2 4 N/A Regardless, of the section used, the pavement materials should conform to the Pierce County requirements. The adequacy of site pavements is related in part to the condition of the underlying subgrade. To provide a proper subgrade for pavements, the subgrade should be treated and prepared as described in the Earthworks section of this report. 032907sdd1 Yelm Commercial Geotmh.doc - Golder Associates March 29, 2007 -12- 073-93048.000 7.0 EARTHWORKS 7.1 General Excavating and compacting fill on the site will require careful site preparation, surface drainage control, soil handling procedures, dust control, and sequencing on the part of the earthworks contractor. These issues are described in the following sections of this report. 7.2 Construction Drainage Surface water and shallow groundwater should be collected and tightlined to an appropriate surface water collection system. Surface water drainage from the site must be controlled during and after construction to avoid erosion and uncontrolled runoff. 7.3 Erosion Control Erosion control for the site should include best management practices incorporated in the civil design drawings and may contain the following recommendations: • Complete the primary site grading during the summer months; • Limit exposed cut slopes; • Route surface water through temporary drainage channels around and away from exposed slopes; • Use silt fences, straw bales, and temporary sedimentation ponds to collect and hold eroded material on the site; • Seed or plant vegetation on exposed areas where work is completed and no buildings are proposed; and • Retain existing vegetation to the greatest possible extent. We recommend the grading contractor sequence excavations so as to provide constant positive surface drainage for rainwater and groundwater seepage that may be encountered. This will require grading slopes, constructing temporary ditches, sumps and/or berms. Permanent slopes shall not be graded steeper than 2H:1V and, until vegetation is established, should be protected with plastic sheeting during adverse weather conditions. 7.4 Site Preparation and Stripping At the time of this report a grading plan was not available, so the extent of cuts and fills across the site was not known. We anticipate site earthwork will include cuts and fills in the proposed improvement area, preparation of the footing subgrades, backfilling foundation walls, and installing utilities. The building and pavement areas and areas where structural fill are to be placed should be stripped and cleared of surface vegetation, organic matter, and other deleterious material. Based on the thickness of the topsoil and vegetation cover encountered at our exploration locations, we estimate a typical stripping depth of approximately six to twelve inches with localized areas that may need to extend deeper. 032907sdd1 YelmCo==ialGeotech.doc Golder Associates March 29, 2007 -13- 073-93048.000 Root balls from vines, brush, and trees should be grubbed out to remove roots greater than approximately 1-inch in diameter. The excavation to remove root balls could exceed a depth of 2 feet below the existing ground surface. Depending on the grubbing methods used, disturbance and loosening of the subgrade could occur. Soil disturbed during grubbing operations should be compacted to the requirements of structural fill. Stripped materials should not be mixed with materials to be used as structural fill. The stripped soil materials may be utilized on site in non-structural landscaping areas or they should be exported. Excavations should be sequenced to limit the amount of exposed subgrade, particularly if the grading is conducted during the rainy season. The granular soils encountered at our test pit locations should generally hold up during wet weather, but may become unworkable if they are over their optimum moisture content. Conversely, if the site soils become too dry, dust problems may arise. 7.4.1 Fill Materials and Placement Structural fill should be free of organic and inorganic debris, be near the optimum moisture content, and capable of being compacted to the required specifications listed below. If the required compaction criteria cannot be achieved using the on -site soils, then an imported structural fill material may be needed. Structural till imported for use during wet weather should consist of a well graded soil free of organic material, with less than 5 percent fines (that portion of the soil that passes the U.S. No. 200 sieve). Other fill materials may be used with approval of the geotechnical engineer. Maximum Lift Thickness: • On -site native soils or imported Qranular materials - 12 inches loose. Minimum Compaction Requirements: • Beneath Building Foundations - The structural fill should be compacted to at least 95 percent of the ASTM D 1557 maximum dry density value (modified Proctor value) for the material. The structural fill beneath footings should at a minimum extend laterally at a 1H:1V slope projected down and away from the bottom footing edge. • Beneath Roadways, Slabs and Pavements — Three feet below final grade, structural fill should be compacted to at least 90 percent of the ASTM D 1557 maximum dry density value for the material. Within about three feet of subgrade elevation, the fill should be compacted to at least 95 percent of the ASTM D 1557 maximum dry density value for the material. • Utility Trench Backfill - The fill should generally be compacted to at least 90 percent of the ASTM D 1557 maximum dry density value for the material, except within three feet of subgrade elevation, where the fill should be compacted to at least 95 percent of the ASTM D 1557 maximum dry density value for the material. • Non-structural/Landscaped Areas - Firmly compact the soil to prevent excessive settlement and sloughing. Topsoil generated during stripping of the site would likely be suitable for these areas. Structural fill should be compacted with equipment suitable to achieve proper compaction. If density tests taken in the fill indicate that compaction is not being achieved due to high moisture content, then the fill should be scarified, moisture -conditioned, and recompacted. If the required compaction 032907sdd1_Yelm Commemial Geotech.doc Golder Associates March 29, 2007 -14- 073-93048.000 cannot be achieved then the material should be overexcavated and replaced with a suitable material or a soil admixture used to dry the soil. 7.4.2 Sub rg ade The subgrade soils should be prepared in accordance with the recommendations in this section to achieve a. firm and unyielding condition. Prior to paving, the subgrade should be observed by a Golder representative during a "proof roll" completed by a fully loaded dump truck. Soft or l excessively yielding areas should be remediated or overexcavated and replaced prior to construction of paving. The site soils will be sensitive to disturbance from construction activities and rainfall. Pavement and foundation subgrades should be maintained in a well compacted state and protected from degradation prior to paving or concrete placement. Disturbed or wet areas should be remediated by a method determined suitable, based on the observed field conditions. The options may include excavation and replacement of the disturbed soil, placement of a geotextile separation fabric (such as Mirafi 600x or equivalent), .chemical stabilization, and/or installation of drainage improvements. Protection measures may include restricted traffic, perimeter drain ditches, or placement of a protective gravel layer on the subgrade. 7.5 Utilities Maintaining safe utility excavations is the responsibility of the utility contractor. The soil and groundwater conditions in the utility excavations will vary across the site. The loose to compact gravelly soil underlying the site will be susceptible to raveling and caving when excavated. As appropriate, trench shoring should be used by the utility contractor. Existing underground utilities to be abandoned should be plugged or removed so they do not provide a conduit for water and cause soil saturation and instability problems. Utility trench backfill is a concern in preventing settlement along utility alignments, particularly in pavement areas. It is important that each section of utility line be adequately supported in the bedding material. Fill should be carefully placed and hand tamped to about 12 inches above the crown of the pipe . before any heavy compaction equipment is brought into use. The remainder of the trench backfill should be placed in lifts having a loose thickness of 12 inches. 7.6 Construction Geotechnical Monitoring Critical aspects of the foundation and earthwork should be observed and tested by Golder. Construction observation and testing services may include but not be limited to dewatering, foundation subgrade verification, installation of underdrains, pavement subgrade verification, and placement and compaction of structural fills. i 032907sddi_Yelm Commercial Geotech.doe i Golder Associates i ,I 1 March 29, 2007 -15- 073-93048.000 8.0 ADDITIONAL SERVICES As the geotechnical engineer of record, Golder should be retained to provide a review of the draft plans and specifications. The purpose of our review will be to verify the recommendations presented in this report have been properly interpreted and implemented "in the construction drawings and specifications. In addition, the review will allow a discussion of possible changes prior to finalization of the drawings. Golder should also be retained to observe the geotechnical aspects of the project during construction. The purpose of construction observation services is to verify that the actual conditions encountered during construction are consistent with the conditions encountered at our exploration locations. Our construction observation services will also allow us to facilitate changes in the design in the event subsurface conditions differ from those anticipated prior to the start of construction. 032907sdd] Yelm Commercial Geotech.doc Golder Associates March 29, 2007 -16- 073-93048.000 1 9.0 USE OF THIS REPORT This report has been prepared exclusively for the use of Projects West, LLC and CES Northwest, Inc. We encourage review of this report by bidders and/or contractors as it relates to factual data only (logs of test pits, conclusions, etc.). The conclusions and recommendations presented in this report are based on the explorations and observations completed for this study and conversations regarding the proposed site develop, and are not intended, nor should they be construed to represent a warranty regarding the proposed development, but are forwarded to assist in the planning and design process. Judgment has been applied in interpreting and presenting the results. Variations in subsurface conditions outside the actual exploration locations are common in glacial environments such as those encountered in the Puget Sound area. Actual conditions encountered during construction may be different from those observed in the test pits. The test pits were excavated in general accordance with locally accepted geotechnical engineering practice, subject to the time limits and financial and physical constraints applicable to the services for this project, to provide information for the areas explored. There are possible variations in the subsurface conditions between the test locations and variations over time. . 032907sddl Yelm Commercial Geotech.doc Golder Associates March 29, 2007 -17- 073-93048.000 10.0 REFERENCES ') IBC (2003). International Building Code. International Code Council, Country Club Hills, Illinois. l Washington Department of Ecology (1998) Surface Water Design Manual for Western Washington, Olympia, Washington. 032907sdd1_YelmCommercial Geotech.doc Golder Associates FIGURES Golder Associates Crystct! Spring 7 �� MobBe- 1 Yel f Flume -- - _.-_ Hare Pak 1 i V 6-12 LN ! ,, +1 �` . � E �9 It" .` ;:vx -330 ' • :\ I + /'" \i-' ''co_S• AthAll 90 lei( r-- • • � i • � 0\1 1 Imo• �\ `.�� ��•-^^�: _ +�'� meld � i sss :.:� \, •� t'\\ e 2 0 � o , I ell o � �7ti � - � ` �- by '" -mom A •\: I ) ( (tl 'o �\,r\fir l `\? \ o \ � �� • , I �J11 Ii .%Towe !1 ' s �• . r /fir ) ./ • .rr.n...' ` \ V '�' Y 'v 4 ,S -s =op Golf Course Cr 50 iv 20'�� - }• 3 •—� 3�5� �5 `j�� ��• 3F r,` • 3p I .•Corners' \\.� ,(%1 1- 11 -.- ,\.. .;CRlIUDF �. ROAD•'; ....-- .:\ / / � „ � / if 11 •' - ' ee�-_. � ---, ado` o l�� t 00 �'\ '•.ter" '`�\,t/�- ` \ :(/ �.. -� � `�.� 10 36 3n V I �L�� • -!40e l•Lp.• 1 �J "-�i I�.jc.i--'/ ...� �,\.. _jam t„�;,, � /: r � V 0 2000 SCALE IN FEET N FIGURE Source: USGS 7.5 Minute Topographic Quadrangle Map, VICINITY MAP Tenalquot Prairie, WA, 1990, McKenna, WA, 1990 CES NW/YELM COMMERCIAL GEOTECHMA 07393048000fig01.fh11 I Mod:03/13/07 1 AMP Golder Associates 0031500002000fig01.fh11 I Mod:MM/DD/YY I XXX Golder Associates APPENDIX A TEST PIT LOGS Golder Associates Golder LOG OF TEST PIT TP-1 Associates Temp 50 OF Weather_ partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE, Yelm, WA I 2 12 16 �iii'iii'i i iii'i'►i'ii'i'ii'ii'ii���'i'i•♦ 0000�'O�O'000�0►OODOOOOOOOOO��DO000�0 'i'ii'iiiii'ii'i0•►•i'i'i'i'iiii'i'iiii!i'i'ii'i•�• •iii'i'ii'ii'ii'i'i�►•iiii'iii'i'i'iiii!�•iii'ii� •i'ii'i'i'i'iiiiii•►'iiii'i'i'i'i'i'ii'iii'iii'ii• •i'i'iii'iii'iiii�►'i'i'iiii'iii'i'ii'ii'i'iiii� 4:!:!:!:!RN 'i`i`�'i`i`i`i`i`i`i`iD`►`i`i`i`i`i`i`�`i`i`i`i`�`i'i`iD`�'i`i` 'ii'iiiiiiiii0�►•i'i'i'i'ii'ii'ii'iiiiii'i'i'�• .'.O•O.•.'O�❖�•O.O�►•�•O.❖.O•O.•00.'Di�Oii00•i� 'i'ii'�'i'iiii'iii•►•i'i'i'i'ii'ii'i'i'i'i'ii'ii'i'i'i• iiiiiiii'ii'iii�►•i'i'i'iii'ii'i'ii'i'i!iii'i'i'i� .•�'i'i'iii0❖.•O.O!►•�•�•�•O�O'•O•••�00'i!O.•.00•�! .'.•O.❖.•.00•i•�•i'i!►❖.❖.❖.•.00❖.❖.000❖.•.� ❖00�•.'.O'0.00'�•►•.'.•.'O.'.•000OOOi�ii0❖.•�•SUM LITHOLOGIC DESCRIPTIONS AND EXCAVATION NOTES A 0.0 - 0.3 ft: Loose to compact, black, decayed organics and roots in a silty fine to medium SAND matrix, little to some coarse gravel, little fine gravel, trace to little cobbles, little rootlets, damp (SM) (TOPSOIL) B 0.3 - 7.0 ft: Compact, dark brown, fine to coarse GRAVEL, some cobbles, little fine to coarse sand, trace silt, moist (GP) (FILL) C 7.0 - 7.5 ft: Compact, black, silty fine to medium SAND, some fine to coarse gravel, little cobbles, trace rootlets, moist (SM) (BURIED TOPSOIL HORIZON) D 7.5 -11.0 ft: Dense, grayish -brown, fine to coarse GRAVEL, some cobbles, little fine gravel, little fine to coarse sand, occasional boulders, moist to wet (GP) (RECESSIONAL OUTWASH) SAMPLES NO. DEPTH (ft) MOISTURE (off) 1 0.3 4.5 2 2.5 3 7.5 4 11.0 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) 09:30 10.7 SPECIAL NOTES: Minor caving from 0-7 feet (cobble and gravel fallout/spreading) rXGolder LOG.OF TEST PIT TP-2 ssociate§ Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator _Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE, Yelm, WA 2 6 12 16 r'.� i'•� r: is •� is L•i. '�Ijis •� i:� is r: �'i:�: .1 `LLo d 1 0 0 I-0'0"0 a lzz:��o Qolz 0030 'Z o QD°O° o QD° QD°O° o O00 o oa0000aooao0oo 01000 °& a°Qo ooeo o°Qo o°Qo 00. 30 o DOo D�o Oo DOo D o D� 0 0 �DO° 0 0 �B�DO° l 01 0 DOo OOo00o00oJOo00 D oO° 0000 QD�°°QD°O°°o QD°O°o 00000000000000 �°°QD�° 0 O00 ° o o° o o° o° o o° o ° o o D o D o 00000000000000 o D o D o D DO00 ° 30.30 3 �303 ° Qo go Bottom of Test Pit at 10.0 ft A 0.0 - 0.8 ft: Loose, black, decayed organics and roots in a COBBLE and coarse GRAVEL matrix, little fine to medium sand, little fine gravel, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 0.8 -10.0 ft: Compact, medium brown, fine to coarse GRAVEL, some cobbles, little fine gravel, little fine to coarse sand, moist (GP) (RECESSIONAL OUTWASH) -- becomes compact to dense, grayish brown at 8 feet SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 0.5 2 2.5 3 1 8.5 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) SPECIAL NOTES: Minor to moderate caving from 0-10 feet (cobble and gravel fallout/spreading); Groundwater not observed. r Golder LOG OF TEST PIT TP-3 - Associates Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE Yelm WA 3E 2 'iii'iii�i'ii.•'iiiiiii'i'i!ii'i'�i•.'i� �i'00�'0000�'�'00:►0�•O�•�000000'O��i'�'O�'�'�': - �i•O�•�•00�•00�00•:►��i00•�O'00�0000�:•�•�•�•�•�•: 'i'i'i'iii'i'i'ii'ii•:►i'iii'iiii'ii'i'ii�:'ii'iii•: 'iiiiii'iiiiii•:►i'iii'ii'ii'ii'i'ii�:'iiii'i•: :❖:❖:❖:❖:❖:❖i':❖:❖:❖:❖:❖:❖:':❖:❖:❖: iiii'i'i'i'iiii0'i�►'i'ii'iiiiiiiiii!i'i'ii'ii� A 0.0 - 0.5 ft: Loose to compact, black, decayed organics and roots in a COBBLE matrix, some coarse gravel, little fine gravel, little fine to medium sand, trace silt, trace rootlets, trace scrap wood, trace glass, moist (GP) (TOPSOIL) B 0.5 - 5.0 ft: Compact to dense, light brown to orangish-brown, COBBLES and coarse GRAVEL, little fine to coarse sand, little fine gravel, trace silt, trace rootlets, moist (GP) (FILL) C 5.0 - 5.5 ft: Loose, black to brown, silty fine to medium SAND, little to some fine to coarse gravel, trace rootlets, moist (SM) (BURIED TOPSOIL HORIZON) D 5.5 - 11.0 ft: Compact to dense, medium brown, medium to coarse sandy fine to coarse GRAVEL, little cobbles, trace fine sand, moist (GP) (RECESSIONAL OUTWASH) SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 1.0 2 4.0 3 7.0 4 11.0 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) 10:30 10.5 SPECIAL NOTES: Minor caving from 6-8.5 ft (cobble and gravel fallout/spreading); Some minor layering of cobbles/gravels/sands apparent from 6-11 ft. -Golder LOG OF TEST PIT TP-4 Associates Temp 50 T Weather_ partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE, Yelm, WA 6 12 16 —. —.A::—.:—:—_. .. .. B I► .. .. do. .•. ►'. •. ►•. . . .• .'•:.'•�. :.'•:.'• .'•:. AK-0 &W ate! AL. AAK Bottom of Test Pit at 12.6 It A 0.0 -1.0 ft: Loose, black, decayed organics and roots in a COBBLE and coarse GRAVEL matrix, some fine to medium SAND, little fine gravel, trace silt, trace rootlets, damp (GP) (TOPSOIL) B 1.0 - 12.5 ft: Compact to dense, orangish-brown, coarse GRAVEL, little cobbles, little fine gravel, little fine to coarse sand, trace silt, damp (GW) (RECESSIONAL OUTWASH) -- becomes grayish brown at 5 feet SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 4.0 2 10.0 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) 11:20 12.0 SPECIAL NOTES: Minor caving from 2.5-8 ft (cobble and gravel fallout/spreading). %_ =Gok%r LOG OF TEST PIT TP-5 Associates Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE Yelm WA 2 6 12 16 v 0 ° 0 00 0 00 °0 0 bO o 0 OO OOO 00000000000000 O'O� 000 p'bO pDOo O" QD 1DO° O O O O O O pDO �DOo 0O bDO �D bDO° 0.0 O0- 0� QC) 00 000 DoDoO � D 0O'o 1z 00000000000000 000 Qo oo& °o 'No o°Qo oo& -& 00 O O O 00000000000000 O O O DO00 °Do °Doo o °Do °D 1 0 °Do° Oo000000000000 DO00 Bottom of Test Pit at 11.0 ft LITHOLOGIC DESCRIPTIONS AND EXCAVATION NOTES A 0.0 - 0.5 ft: Loose, black, decayed organic matter and roots in a COBBLE and coarse GRAVEL matrix, some fine to medium SAND, little fine gravel, trace silt, trace rootlets, damp (GP) (TOPSOIL) B 0.5 -11.0 ft: Compact to dense, orangish-brown, fine to coarse GRAVEL, some cobbles, little fine to coarse sand, trace rootlets, damp (GP) (RECESSIONAL OUTWASH) -- becomes grayish brown at 4 feet -- sand becomes medium to coarse at 4 feet SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 3.0 2 10.0 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) SPECIAL NOTES: Moderate caving from 1-8 ft (cobble and gravel fallout/spreading); Groundwater not observed. (V,,GolderLOG OF TEST PIT TP-6 ssociates Temp_OF Weather Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date - Elevation Datum MSL Job 073-93048 Location Yelm 2 6 12 16 �i'�'�'�'�'DO.00�i�i�i►��i�i'�'�'Oi�i�i�i'�'�O�:�i�i�i'�'��i �i�i'Oi'�'�'Oi'�'�'�'��i►i�i�i�i�i�i'�O�i�i�i�i'i�:0'��i�i'�'i �000•'•�OOOOOOOi►O• �i�i�i'��i�i00�i�i'��i�i►i�i �iO�i�i�i�i�i�i�i�i'Oi'i►i�i'�O�ii'��i'�O�i�i�:�i'��i'��i�i �i�i�i�i'��i�i�iO�i�i�i�i►'��i�i'��'��i�i00�i�i�i�i�i�i�i'i c�►i0000000•�:�OOOOOi i'��i�i'�'�'��:�i�i�i'�'�'i i'i'i'i'i'i i'i'i i'i i i'i'i-- '��i�i'�'�'�'��i'�'�'i►i�i�i�i'�'Oi'�'�O�i�i'��:0'��i�i'�'i --'i ME L L, Bottomlaw A 0.0 - 0.5 ft: Loose, black, decayed organic matter and roots in a GRAVEL and COBBLE matrix, little to some fine to medium sand, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 0.5 - 5.0 ft: Loose to compact, coarse GRAVEL, little to some coarse sand, little fine gravel, little cobbles, trace silt, moist (GW) (FILL) C 5.0 - 7.5 ft: Loose, coarse, black, fine to coarse GRAVEL, some fine to medium sand, little to some cobles, trace silt, trace rootlets, moist (GP) (RECESSIONAL OUTWASH) D 7.5 -11.5 ft: Compact to dense, medium brown to grayish -brown, coarse GRAVEL, little to some cobbles, little to some fine to coarse sand, little fine gravel, trace silt, moist (GW) (RECESSIONAL OUTWASH) SAMPLES NO. DEPTH MOISTURE (ft) (%) TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) SPECIAL NOTES: Minor to moderate caving from 1 - 9 feet (cobble and gravel fallout/spreading). Groundwater not observed. 9mrssociates Golder LOG OF TEST PIT TP-7 Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE Yelm WA i r 2 M 12 16 �III� W. �'7M'! '•�. Bottom of Test Pit at 11.5 ft A 0.0 - 0.5 ft: Loose to compact, black, decayed organic matter and roots in a coarse GRAVEL matrix, some fine to medium SAND, little to some cobbles, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 0.5 - 11.5 ft: Compact to dense, grayish -brown, medium to coarse GRAVEL, some cobbles, little to some fine to coarse sand, trace silt, moist (GW) (RECESSIONAL OUTWASH) SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 4.0 2 6.0 3 8.0 6.6 4 10.5 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) 14:10 11.0 SPECIAL NOTES: Minor to moderate caving from 0-11.5 ft (cobble and gravel fallout/spreading); Infiltration test performed at 4 ft. Golder LOG OF TEST PIT TP-8 Associates Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 41OG Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE Yelm WA I �--12 6 12 16 oao o�� oo ti� o71 �p00 QD°Ooo o QD°O° o QD° �C" o 00000000000000 Iz 000 O b°OO p°OO O0 & 00 O° ° bo 0, OD OD O OD OD OD �p0 bbOo 0 ' 3� QD< 00000'o0000000 :'0 0,( 0Q°O°o& Oo ^°^rY Qab° Obo 00 o D o D o 00000000000000 B D o D o D 10oo 0 & 00 & 00 0o & 00 & 0 & 00 O O O 00.0000000000Q O O O OQ0 0 0 00 0 00 �O0Oo 00 0 00 0 O 00 o OQo0o000 0 6 0 o0Qo'3 o DO O00 O Q°OO o°OO OO Q°OO Q° 030 00 OD OD O OD OD OD Bottom of Test Pit at 12.0 ft LITHOLOGIC DESCRIPTIONS AND EXCAVATION NOTES A 0.0 - 0.5 ft: Loose, black, decayed organics and roots in a COBBLE and coarse GRAVEL matrix, little fine to medium sand, little fine gravel, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 0.5 -12.0 ft: Loose to compact, orangish-brown, fine to coarse GRAVEL, some cobbles, little to some fine to coarse sand, trace silt, trace rootlets, moist (GP) (RECESSIONAL OUTWASH) -- becomes compact to dense, grayish -brown at 5 feet SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 5.0 5.5 2 8.0 3 10.0 TIME DEPTH OF HOLE (ftj DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) 15:20 12.0 SPECIAL NOTES: Minor to moderate caving from 0-1Ift (cobble and gravel fallout/spreading); Infiltration test performed at 4 ft. Golder LOG OF TEST PIT TP-9 Associates Temp 50 OF Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 410G Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location 15106 Carter Loop SE, Yelm, WA 12 16 0 o 00 30 00 00 0 00 o 0 1 o 00 o DODOo o 0Qo0QoaQo4Qo0Q Oo 1) O 000 O �oOO QoOO OO Q1'OO b0 0 Q0OO QQo0Qo0oQo Q �Qo o 00 o 00 00o 00 D , OOC J. o0oOQoOQB`)QooQ ODODoDO OQo 0 o 00 0 OOeo CC& e0 0 10bo 0o o DOo OOo oQoo0oo0ooQooQ Oo DOo D o DO DOQo o DOo DOo Oo DOo D o DO �poo0)Qo000 DOQo 0 bo 00 0 00 00 b0 00 0 0 o 00 o DOo DOo Oo D�o D O02(2) 0 oOgoO 0 o D� 0 OQo Bottom of Test Pit at 11.0 ft A 0.0 -1.0 ft: Loose, black, decayed organics and roots in a COBBLE and coarse GRAVEL matrix, little to some fine to medium sand, little fine gravel, little boulders, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 1.0 - 11.0 ft: Compact to dense, orangish-brown, fine to coarse GRAVEL, some cobbles, little fine to coarse sand, trace silt, moist (GP) (RECESSIONAL OUTWASH) - becomes compact to dense, grayish brown at 5 feet SAMPLES NO. DEPTH (ft) MOISTURE (%) 1 4.5 4.5 2 7.0 3 8.5 4 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) SPECIAL NOTES: Minor to moderate caving from 0-11 ft (cobble and gravel fallout/spreading); Groundwater not observed; Some minor layering of cobbles/gravels/sands apparent from 5-11 ft; Infiltration test performed at 4 ft. I'MUGolder LOG OF TEST PIT TP-10 Associates Temp 50 °F Weather partly cloudy Engineer B. Mattson Operator Ryan Equipment John Deere 41 OG Contractor Custom Backhoe Date 2/26/2007 Elevation Datum MSL Job 073-93048 Location15106 Carter Loop SE, Yelm, WA %M 6 12 16 a r.'.� ii'•� s:� r: •� r: a•r: .. .: s•r: •� r:� r r: LJ �� o 0 0 00 0 00 0030 00 0 0° 00 o DOo DOo 0Oo00o00000000 Oo DOo D o DO OQo o ° r'<Z b°O° o ° ° ° O1< r° ° Q°O° (3 0 00 0000000000 O00 ° o °0 ° °° °0 ° o° ° �'Q� , 0 00 �< o D�o D�o OOo00o00o00000 OQo ° Qo 0 0 Qo 0 0 DOo B �o 0 0 Qo Co 0 Qo .0 o DOo a0oorl_0oa0000o00 DOo D o DO oQo < <D C3 O D ODODO 00O00O 00 00 OO 00 o ° °° ° °° 00 ° °0 ° O' O ' ° ° °° '< o DDo DOo O0a00a00o00000 OQo o Q°O° o Q°O° o Oo Q°O° o Q° C o Q°O° o Bottom of Test Pit at 12.0 ft LITHOLOGIC DESCRIPTIONS AND EXCAVATION NOTES A 0.0 - 1.0 ft: Loose, black, decayed organics and roots in a COBBLE and coarse GRAVEL matrix, little to some fine to medium sand, little fine gravel, trace silt, trace rootlets, moist (GP) (TOPSOIL) B 1.0 - 12.0 ft: Compact to dense, orangish-brown, fine to coarse GRAVEL, little to some cobbles, little to some fine to coarse sand, little fine gravel, trace silt, moist (GP) (RECESSIONAL OUTWASH) -- becomes brown at 5 feet -- becomes gray at 9 feet Z SAMPLES NO. DEPTH MOISTURE 1 3.0 2 7.0 3 10.0 TIME DEPTH OF HOLE (ft) DEPTH TO W/L (ft) DEPTH TO SEEPAGE (ft) SPECIAL NOTES: Minor to moderate caving from 0-12 ft (cobble and gravel fallout/spreading); Groundwater not observed. APPENDIX B LABORATORY TEST RESULTS Golder Associates k d \ u � %2 . o � $ o = m m E k � § / k0 ® .% % § d � k § c . Lu % \ U) 2w � �J,� R �k 05O %q w « � Z ® CO / co / 7� zi 2 \ / e f— /§ 2 a /m _— § k �§ & OL z /\ ® \ \ E � � � 7 R S C 2 2 ? R q 2 y iH S|]M kg SN|SSVd IN]0�1]d USDA SIEVE ANALYST RESULTS o 7_ \� uj U ) wcn— �� « 2_ � c 2 k / « / J— � �— }— G_ E k o u u o o \ 2 % < � 2 7 w co m 7 ƒ � � y 7 f En \ u 0 � § Q ) k ? u U _ E CL 0 O > co k % D R %� �> § % Q / ®x Lu mk �q D e w ww 3= \[ 2 R m E� FL \/ _ / $ R E 1H S|]M ­ *g S B 2 N|SSVd . ? 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