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Preliminary Drainage
~~~ r ~e Estates Yelm, WA Preliminary Drainage Report August 2005 Prepared by: Olympic Engineering 1252 Devon Loop NE Olympia WA 98506 360.870.2561 360.705.9361 fax merritt@olyes.com PRELIMINARY DRAINAGE REPORT Yelm, Washington August 2005 Project Information (~e/,f ~w.it~ 1~.'ts.r Project: ire Estates Prepared for: Rainier General Development Contact: Doug Bloom P.O. Box 627 Rainier, WA 98576 (360) 446-3083 Reviewing Agency Jurisdiction: Project Number: Project Contact Project Engineer Prepared by: Contact: OE Project No. File Name: t~o~ W A r~,~~P w ~ ~ ~ _ 374H _ E~~ RES ~i/t~ 5! 0 7 !~ City of Yelm Tami Merriman (360) 458-8496 Olympic Engineering 1252 Devon Loop NE Olympia, WA 98506 (360) 870-2561 Chris M. Merritt, P.E. 05023 05023_pdr.doc FAX (360) 705-9361 PROJECT ENGINEERS CERTIFICATION: I hereby certify that this Preliminary Drainage Report for the Longmire Estates Plat in the City of Yelm, Washington has been prepared by me or under my supervision and meets the intent of the WSDOE 1992 Stormwater Management Manual, unless noted otherwise, and normal standards of engineering practice. I understand that the jurisdiction does not and will not assume liability. for the sufficiency, suitability, or performance of drainage facilities designed for this development. 1 Table of Contents .APPENDICES PART I STORM DRAINAGE REPORT ........................................................ 2 Appendix 1-Preliminary Drainage Calculations SECTION 1 -PROPOSED PROJECT DESCRIPTION ............................... 2 Appendix 2- Vicinity Map SECTION 2 -EXISTING CONDITIONS ..................................................... 3 Appendix 3 -Drainage Basin Map Appendix 4 -Soils Report SECTION 3 -INFILTRATION RATES /SOILS REPORT .......................... 3 SECTION 4 - WELLS AND SEPTIC SYSTEMS ......................................... 4 SECTION 5 -FUEL TANKS ........................................................................ 4 SECTION 6 -SUB-BASIN DESCRIPTION ................................................. 4 SECTION 7 -ANALYSIS OF 100-YEAR FLOOD ....................................... 4 SECTION 8 -AESTHETIC CONSIDERATIONS FOR FACILITIES......... 4 SECTION 9 - DOWNSTREAM ANALYSIS ................................................. 4 SECTION 10 -COVENANTS, DEDICATIONS, EASEMENTS ................... 5 SECTION 11 -ARTICLES OF INCORPORATION ....................................... 5 PART II EROSION CONTROL REPORT ....................................................6 SECTION 1 -CONSTRUCTION SEQUENCE AND PROCEDURE .......... 6 SECTION 2 -TRAPPING SEDIMENT ........................................................6 SECTION 3 -PERMANENT EROSION CONTROL ................................... 7 SECTION 4 - GEOTECHNICAL ANALYSIS AND REPORT ..................... 7 SECTION 5 -INSPECTION SEQUENCE ................................................... 7 SECTION 6 - CONTROL OF POLLUTANTS ..............................................8 PART III MAINTENANCE PLAN ................................................................9 SECTION 1 -REQUIRED MAINTENANCE ............................................... 9 SECTION 2 -RESPONSIBLE ORGANIZATION ...................................... 18 SECTION 3 -VEGETATION MANAGEMENT PLAN .............................. 18 SECTION 4 - SOURCE CONTROL ............................................................ 18 ii PART I STORM DRAINAGE REPORT SECTION 1 -PROPOSED PROJECT DESCRIPTION Prepared for: Rainier General Development Contact: Doug Bloom P.O. Box 627 Rainier, WA 98576 (360) 446-3083 Parcel Number: Total Site Area: Zoned: Site Address: Required Permits: Section, Township, Range: 21724420700 2.16 Acres R-4 1528 Longmire St SE Yelm, WA 98597 Grading, Utility, Building, etc. Section 24 Township 17 North Range 1 East, W.M. Project Overview The project site is located adjacent to Longmire St. SE in Yelm. The applicant proposes to construct a new public roadway through the parcel connecting to Longmire St. and to install utility services to serve 10 single family lots. Access to the proposed lots will be from the new public roadway. Longmire Street frontage improvements including roadway widening, sidewalks, storm drainage, water, and sanitary sewer will be designed and installed by others as part of a master planned community project to the west. The development will be constructed in one phase. Construction will include clearing and grading of the site, storm drainage improvements, underground utilities, and paving. City of Yelm sanitary sewer and water mains will be extended into the site to provide services to the residential lots. Stormwater facilities will be constructed that consist of a proposed biofiltration swale for storm water treatment along with an infiltration pond for retention and infiltration of stormwater runoff created by the new development. For stormwater design purposes, the proposed development has been subdivided into one drainage sub-basin (see preliminary calculations in Appendix). Stormwater Treatment: All stormwater runoff from the new roadway will be collected in a series of catch basins and conveyed to a biofiltration swale for treatment. The proposed biofiltration swale exceeds the minimum WSDOE requirements. See Preliminary Drainage Calculations in Appendix. Stormwater Storage: Discharge from the biofiltration swale will flow into an infiltration pond for stormwater retention and infiltration to groundwater. The proposed stormwater pond exceeds the minimum storage requirements per the WSDOE. Runoff from the Longmire St. frontage will be collected by a series of catch basins and discharged to the proposed master planned community to the west. See Preliminary Drainage Calculations in Appendix. Roof Runoff: Roof runoff from each residential home will be tightlined to individual lot infiltration drainrock drywells. The drywells shall be sized to accommodate 125 cf of storage volume per 1,000 sf of roof area. SECTION 2 -EXISTING CONDITIONS The project site contains a single family residence with a barn and both will be demolished. Site relief is nearly level, sloping away from the center of the property to the north, east, and south at a gradient of 3% or less. There are no site distinguishing features other than an existing domestic well. Site vegetation consists of uncropped field grasses, maintained grass lawn, and landscaping adjacent to the existing house. The project site is bounded by residential property to the north, northeast, and west, and by Longmire Street SE to the south and southeast. See Section 6 for description of off-site drainage to the property, if any. The project site is located in an aquifer sensitive area based on review of Thurston County Comprehensive Plan Map M-8. This project will comply with the stormwater treatment requirements of the DOE Manual. SECTION 3 -INFILTRATION RATES /SOILS REPORT The Soil Conservation Service (SCS) soil survey of Thurston County classifies the on-site soils as Spanaway Gravelly Sandy Loam (Hydrologic Group A). Soil testing by Parnell Engineering confirmed the Spanaway series classification. One test pit was excavated by backhoe to a depth of 156" below the existing grade and one double ring infiltration test was completed. Test pit soil log data sheets and infiltration test results are included in the Appendix of this report. SECTION 4 -WELLS AND SEPTIC SYSTEMS Two wells were located within 200-feet of this project, however, their respective 100' protective radii's fall outside this projects boundary. An existing on-site well will be decommissioned prior to final project approval. Water and sanitary sewer services for the proposed project will be provided by the City of Yelm. A septic system currently serves the existing home. This will be abandoned per Department of Health standards during development. SECTION 5 -FUEL TANKS No fuel tanks were located during our site inspection or soils work. The latest "LUST" list (Leaking Underground Storage Tank) was reviewed and no listing for the subject site was found. SECTION 6 -SUB-BASIN DESCRIPTION The project site is located within the Nisqually River Drainage Basin per the Thurston County Geodata Center. From our site visit there were no signs of existing drainage swales or channels on the proposed property. There did not appear to be a significant amount of off-site runoff onto the site from the adjacent properties. Hazardous material handling or transportation is not expected in the area tributary to the on-site detention facility. SECTION 7 -ANALYSIS OF 100-YEAR FLOOD This site does not appear to be located within a flood plain. SECTION 8 -AESTHETIC CONSIDERATIONS FOR FACILITIES All disturbed pervious areas including the storm drainage area and open space tract will be vegetated and landscaped. SECTION 9 -DOWNSTREAM ANALYSIS Preliminary calculations for the project stormwater treatment and storage systems are included in the Appendix of this report. All stormwater runoff generated by site development will be treated, stored, and infiltrated on-site. In the event of a failure, storm water will overflow through the catch basin rims and temporarily back onto the public roadway. Adjacent properties should not be affected due to failure of the proposed stormwater system. SECTION 10 -COVENANTS, DEDICATIONS, EASEMENTS On-site drainage facilities will require routine maintenance. A maintenance agreement will be prepared and finalized prior to final project approval. SECTION 11 -PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION In light of the residential nature of this project, special covenants covering landscape, maintenance, signage, stormwater and site maintenance may be put in place at the time of final platting. The Owner's and/or their representatives will perform maintenance of these private storm drainage facilities. PART II EROSION CONTROL REPORT SECTION 1 -CONSTRUCTION SEQUENCE AND PROCEDURE Proposed development of the residential property will include site grading and erosion control measures designed to contain silt and soil within the project boundaries during construction until permanent erosion control is in place. Erosion/sedimentation control will be achieved by a combination of structuraUvegetative cover measures and construction practices tailored to fit the site. Best Construction Management Practices (BMP's) will be employed to properly clear and grade the site and to schedule construction activities. Before any construction begins on-site, erosion control facilities shall first be installed. The planned construction sequence is as follows: 1. Install rock construction entrance. Use 4" to 8" diameter spalls with 12" minimum depth. 2. Install filter fabric fencing, where appropriate. 3. Construct temporary sedimentation basins, if necessary. 4. Clear site (grubbing and rough grading). 5. During November 1 through March 31, all disturbed areas greater than 5,000 sf that are to be left un-worked for more than twelve (12) hours, shall be stabilized by one of the following: mulch, sodding, or plastic covering. 6. Install underground utilities (cable, telephone, power, etc.). 7. If applicable, provide catch basin protection by installing filter fabric and hay bales around all inlets to drainage system. 8. After paving is complete, install landscape, sod and/or seed, and mulch all disturbed areas. • 9. Maintain all erosion control facilities until the entire site is stabilized and silt runoff ceases. 10. Designate an area for washing of equipment and concrete trucks to control the runoff and eliminate entry into storm drainage systems. SECTION 2 -TRAPPING SEDIMENT A stabilized construction entrance shall be installed at the entrance to the proposed plat to prevent vehicles from tracking soil away from the disturbed areas. If sediment is tracked onto public roadways, sediment shall, on a daily basis, be swept or shoveled from paved surfaces and not washed down into the roadside storm drainage system. The contractor shall not be allowed to leave disturbed areas greater than 5,000 sf that are to be left un-worked for more than twelve (12) hours uncovered during the rainy season from November 1 through March 31. Mulch, sodding or plastic covering will be used to prevent erosion in these areas. During construction, the contractor will also be required to install filter fabric fencing as needed, per the erosion control plan and as directed by the engineer, or City Inspector SECTION 3 -PERMANENT EROSION CONTROL & SITE RESTORATION All disturbed areas will be paved, covered with a building or landscaped with grass, shrubbery or trees. SECTION 4 -GEOTECHNICAL ANALYSIS AND REPORT There are no slopes exceeding 15% on-site, therefore, a geotechnical analysis was deemed unnecessary. SECTION 5 -INSPECTION SEQUENCE In addition to the normal City inspections, the Project Engineer shall inspect the facilities related to storm water treatment, erosion control, storage and conveyance during construction. At a minimum, the following items shall be inspected at the time specified: 1. The erosion control facilities shall be inspected before the start of clearing and grading to ensure the following structures are in place: a. Construction Entrance b. Filter Fabric Fences 2. The conveyance systems will be inspected after construction of the facility, but before the project is completed to ensure the following are in working order: a. Road Drainage Conveyance System b. Biofiltration Swale c. Infiltration Pond 3. The permanent site restoration measures should be inspected after landscaping is completed. A final inspection shall be performed to verify final grades, settings of structures and all necessary information to complete Engineer's Construction Inspection Report Form and Residential Agreement to maintain stormwater facilities. These forms must be completed prior to final public works construction approval. SECTION 6 -CONTROL OF POLLUTANTS OTHER THAN SEDIMENTS Washout from a concrete truck shall not be dumped into the storm drain, or onto soil or pavement, which carries stormwater runoff. It can be dumped into a designated area to be later backfilled or hardened and broken up for disposal into a dumpster. The Contractor will be required to designate a wash down area for equipment and concrete trucks. PART III MAINTENANCE PLAN SECTION 1 -REQUIRED MAINTENANCE The following pages contain maintenance needs for most of the components that are part of your drainage system, as well as for some components that you may not have. Let us know if there are any components that are missing from these pages. Ignore the requirements that do not apply to your system. You should plan to complete a checklist for all system components on the following schedule: 1.Monthly from November through April. 2.Once in late summer (preferably September). 3.After any major storm (use 1" in 24 hours as a guideline) items marked "S" only. Using photocopies of these pages, check off the problems you looked for each time you did an inspection. Add comments on problems found and actions taken. Keep these "Checked" sheets in your files, as they will be used to write your annual report (due in May). Some items do not need to be looked at every time an inspection is done. Use the suggest frequency at the left of each item as a guideline for your inspection. You may call the jurisdiction for technical assistance. Please do not hesitate to call, especially if you are unsure whether a situation you have discovered may be a problem. ATTACHMENT `A' Inspection Period: MAINTENANCE PROGRAM COVER SHEET Number of Sheets Attached: Date Inspected: Inspector's Signature: ATTACHMENT "A": MAINTENANCE PROGRAM Maintenance Checklist for Conveyance Systems (Pipes, Ditches and Swales) Frequency Drainage ~ Req'd Problem Conditions To Check For Conditions That Should Exist System Feature M.S. Pipes ~ Sediment & Accumulated sediment that Pipe cleaned of all sediment and debris exceeds 20% of the diameter debris. of the pipe. M ~ Vegetation Vegetation that reduces free All vegetation removed so water movement of water through flows freely- pipes. A ~ Damaged Protective coating is Pipe repaired or replaced. (rusted, bent damaged, rust is causing or crushed) more than 50% deterioration to any part of pipe. M ~ Any dent that significantly Pipe repaired or replaced. impedes flow (i.e., decreases the cross section area of pipe by more then 20%). M ~ Pipe has major cracks or Pipe repaired or replaced. tears allowing groundwater leakage. M.S. Swales ~ Trash & Dumping of yard wastes such Remove trash and debris and debris as grass clippings and dispose as prescribed by County branches into Swale. Waste Management Section_ Unsightly accumulation of non-degradable materials such as glass, plastic, metal, foam and coated paper. M ~ Sediment Accumulated sediment that Swale cleaned of all sediment and buildup exceeds 20% of the design debris so that it matches design. depth. M ~ Vegetation Grass cover is sparse and Aerate soils and reseed and mulch not growing weedy or areas are bare areas. Maintain grass height or over-grown overgrown with woody at a minimum of 6" for best vegetation. stormwater treatment. Remove woody growth, recontour and reseed as necessary. M ~ Conversion Swale has been filled in or If possible, speak with homeowner by home- blocked by shed, woodpile, and request that Swale area be owner to shrubbery, etc. restored. Contact County to incompatible report problem if not rectified use voluntarily. A ~ Swale does Water stands in Swale or A survey may be needed to check not drain flow velocity is very slow. grades. Grades need to be in 1% Stagnation occurs. range if possible. If grade is less than 1%, under drains may need to be installed. If you are unsure whether a problem exists, please contact the Jurisdiction and ask for technical assistance. ATTACHMENT "A" (CONTINUED) Maintenance Checklist for Catch Basins and Inlets Frequency Drainage J Req'd Problem Conditions To Check For Conditions That Should Exist System Feature M,S General J Trash, Trash or debris in front of the No trash or debris located debris, and catch basin opening is blocking immediately in front of catch sediment capacity by more than 10%. basin opening. Grate is kept in or on clean and allows water to basin enter. M J Sediment or debris (in the No sediment or debris in the basin) that exceeds 1/3 the catch basin. Catch basin is depth from the bottom of basin dug out and clean. to invert of the lowest pipe into or out of the basin. M,S J Trash or debris in any inlet or Inlet and outlet pipes free of pipe blocking more than 1/3 of trash or debris. its height. M J Structural Corner of frame extends more Frame is even with curb. damage to than 3/4 inch past curb face frame into the street (if applicable). and/or top slab M J Top slab has holes larger than 2 Top slab is free of holes and square inches or cracks wider cracks. than 1/4 inch (intent is to make sure all material is running into the basin). M J Frame not sitting flush on top Frame is sitting flush on top slab, i.e., separation of more slab. than 3/4 inch of the frame from the top slab. A J Cracks in Cracks wider than 1/2 inch and Basin replaced or repaired to basin longer than 3 feet, any evidence design standards. Contact a walls/ of soil particles entering catch professional engineer for bottom basin through cracks, or evaluation. maintenance person judges that structure is unsound. A J Cracks wider than 1/2 inch and No cracks more than 1/4 inch longer than 1 foot at the joint of wide at the joint of inlet/outlet any inlet/outlet pipe or any pipe. evidence of soil particles entering catch basin through cracks. A J Settlement Basin has settled more than 1 Basin replaced or repaired to /misalign- inch or has rotated more than 2 design standards. Contact a ment inches out of alignment. professional engineer for evaluation. Frequency Drainage System Feature J Req'd Problem Conditions To Check For Conditions That Should Exist M,S J Fire hazard Presence of chemicals such No color, odor, or sludge. Basin is or other as natural gas, oil, and dug out and clean. pollution gasoline. Obnoxious color, odor, or sludge noted. M,S J Outlet pipe is Vegetation or roots growing No vegetation or root growth clogged with in inlet/outlet pipe joints present. vegetation that is more than six inches tall and less than six inches apart. If you are unsure whether a problem exists, please contact the Jurisdiction and ask for technical assistance. Comments: Kev A =Annual (March or April preferred) M =Monthly (see schedule) S =After major storms ATTACHMENT "A" (CONTINUED) Maintenance Checklist for Grounds (Landscaping) Frequency Drainage ~ Problem Conditions to Check For Conditions That Should Exist System Feature M General ~ Weeds Weeds growing in more than Weeds present in less than 5% of (nonpoisonous) 20% of the landscaped azea the landscaped area. (trees and shrubs only). M ~ Safety hazard Any presence of poison ivy or No poisonous vegetation or other poisonous vegetation or insect nests present in insect nests. landscaped area. M,S ~ Trash or litter See Ponds Checklist. See Ponds Checklist. M,S ~ Erosion of Noticeable rills are seen in Causes of erosion are identified Ground Surface landscaped areas. and steps taken to slow down/spread out the water. Eroded areas are filled, contoured, and seeded. A Trees and ~ Damage Limbs or parts of trees or Trim trees/shrubs to restore shrubs shrubs that are split or shape. Replace trees/shrubs broken which affect more with severe damage. than 25% of the total foliage of the tree or shrub. M ~ Trees or shrubs that have Replant tree, inspecting for been blown down or knocked injury to stem or mots. Replace over. if severely damaged. A ~ Trees or shrubs which are Place stakes and rubber-coated not adequately supported or ties around young trees/shrubs are leaning over, causing for support. exposure of the roots. If you are unsure whether a problem exists, please contact the Jurisdiction and ask for technical assistance. Comments: Kev A =Annual (March or April preferred) M =Monthly (see schedule) S =After major storms ATTACHMENT "A" (CONTINUED) Maintenance Checklist for Energy Dissipaters Freq. Drainage ~ Problem Conditions to Check For Conditions That Should Exist System Feature A Rock Pad ~ Missing or Only one layer of rock exists Replace rocks to design moved rock above native soil in area 5 standard. square feet or larger, or any exposure of native soil. A Rock-filled Missing or Trench is not full of rock. Add large rock (f301b. each) so trench for moved rock that rock is visible above edge discharge from of trench. pond M Dispersion Pipe plugged Accumulated sediment that Pipe Cleaned/flushed. trench with sediment exceeds 20% of the design depth. M Perforations Over 1 /2 of perforations in Clean or replace perforated pipe. plugged pipe are plugged with debris and sediment. M,S Not discharging Visual evidence of water Trench must be redesigned or water properly discharging at concentrated rebuilt to standard. Elevation of points along trench (normal lip of trench should be the same condition is a "sheetflow" of (flat) at all points. water along trench). Intent is to prevent erosion damage. M,S Water flows out Maintenance person Facility must be rebuilt or top of observes water flowing out redesigned to standards. Pipe is "distributor" during any storm less than probably plugged or damaged catch basin the design storm or its and needs replacement. causing or appears likely to cause damage. M,S Receiving area Water in receiving area is Stabilize slope with grass or over-saturated causing or has potential of other vegetation, or rock if causing landslide. condition is severe. If you are unsure whether a problem exists, please contact the Jurisdiction and ask for technical assistance. Comments: Key: A =Annual (March or April preferred) M =Monthly (see schedule) S =After major storms ATTACHMENT "A" (CONTINUED) Maintenance Checklist for Ponds Freq. Drainage ~ Problem Conditions to Check For Conditions That Should Exist System Feature M.S. General ~ Trash & debris Dumping of yard wastes Remove trash and debris and buildup in pond such as grass clippings and dispose as prescribed by County branches into basin. Waste Management Section Unsightly accumulation of non-degradable materials such as glass, plastic, metal, foam, and coated paper. M.S. ~ Trash rack Bar screen over outlet more Replace screen. Remove trash plugged or than 25% covered by debris and debris and dispose as missing or missing. prescribed by County Waste Management Section. M ~I Poisonous Any poisonous vegetation Remove poisonous vegetation. vegetation which may constitute a Do not spray chemicals on hazard to the public. vegetation without obtaining Examples of poisonous guidance from the Cooperative vegetation include: tansy Extension Service and approval ragwort, poison oak, from the County. stinging nettles, devilsclub M.S. ~ Fire hazard or Presence of chemicals such Find sources of pollution and pollution as natural gas, oil, and eliminate them. Water is free gasoline, obnoxious color, from noticeable color, odor, or odor, or sludge noted. contamination. M ~ Vegetation not For grassy ponds, grass For grassy ponds, selectively growing or is cover is sparse and weedy thatch, aerate, and reseed ponds. overgrown or is overgrown. For Grass cutting unnecessary unless wetland ponds, plants are dictated by aesthetics. For sparse or invasive species wetland ponds, hand-plant are present. nursery-grown wetland plants in bare areas. Contact the Cooperative Extension Service for direction in invasive species such as purple looseime and reed canary grass. Pond bottoms should have uniform dense coverage of desired plant species. M ~ Rodent holes Any evidence of rodent Rodents destroyed and dam or holes if facility is acting as berm repaired. Contact the ~ a dam or berm, or any Thurston County Health Dept. evidence of water piping for guidance. through dam or berm via rodent holes. M Insects When insects such as wasps Insects destroyed or removed and hornets interfere with from site. Contact Cooperative maintenance activities, or Extension Service for guidance. when mosquitoes become a nuisance. A ~ Tree Growth Tree growth does not allow Trees do not hinder maintenance maintenance access or activities. Selectively cultivate interferes with maintenance trees such as alders for firewood. activity (i.e., slope mowing, silt removal, ore ui ment Freq. Drainage ~ Problem Conditions to Check For Conditions That Should Exist System Feature movements). If trees are not interfering with access, leave trees alone. M Side slopes of ~ Erosion on Check around inlets and Find causes of erosion and pond berms or at outlets for signs of erosion. eliminate them. Then slopes entrance/ Check berms for signs of should be stabilized by using exit sliding or settling. Action appropriate erosion control is needed where eroded measure(s); e.g., rock damage over 2 inches deep reinforcement, planting of grass, and where there is potential compaction. for continued erosion. M Storage area ~ Sediment Accumulated sediment that Sediment cleaned out to designed buildup in pond exceeds 10% of the pond shape and depth; pond designed pond depth. reseeded if necessary to control Buried or partially buried erosion. outlet structure probably indicates significant sediment deposits. A Pond dikes .~ Settlements Any part of dike which has Dike should be built back to the settled 4 inches lower than design elevation. the design elevation. A Emer-gency ~ Rock missing Only one layer of rock Replace rocks to design overflow/ exists above native soil in standards. spillway area 5 square feet or larger, or any exposure of native soil. One time Emer-gency ~ Overflow Side of pond has no area Contact County for guidance. overflow/ missing with large rocks to handle spillway emergency overflows. If you are unsure whether a problem exists, please contact the Jurisdiction and ask for technical assistance. Comments: Key: A =Annual (March or April preferred) M =Monthly (see schedule) S =After major storms SECTION 2 -RESPONSIBLE ORGANIZATION The Homeowner's Association shall be responsible for the operation and maintenance of all on-site drainage facilities. SECTION 3 -VEGETATION MANAGEMENT PLAN All disturbed pervious areas within the site will be landscaped to provide an aesthetically pleasing environment. SECTION 4 -SOURCE CONTROL Warning signs (e.g., "Dump No Waste -Drains to Groundwater") will be embossed or painted on or adjacent to all storm drain inlets and will be repainted periodically as necessary. Appendix I Preliminary Drainage Calculations PRELIMINARY DRAINAGE CALCULATIONS The following calculations were based on the requirements contained in the WSDOE Stormwater Management Manual, 1992 edition. DESIGN AND BASIN INFORMATION SUMMARY: Post llevelopment Basin Urea Summary (Acres} s -= ~~. Sub-Basin A Total Impervious Roadway 0.29 0.29 Concrete Sidewalk 0.04 0.04 Impervious Driveway 0.14 0.14 Impervious Roof Area 0.46 0.46 Disturbed Pervious 0.65 0.65 Non-Tributary 0.58 0.58 Total 2.16 2.16 Roof Area: 2,000 sf/lot Driveway Area: 600 sf/lot Soil Classification: SCS Soil Classification: Spanaway Gravelly Sandy Loam Hydrologic Group: A Design Infiltration Rate: 20"/hr SUB-BASIN `A' WATER QUALITY CALCULATIONS Minimum Stormwater Treatment Area Required: Formula 6-9 from page III-6-14: b = Qn - Zy 1.486 yi.ss~ so.5 Qsmo = 0.13 cfs (see attached StormShed output) b = 0.62' (see attached FlowMaster output) 0.62' x 200' long swale = 124 sf min. Stormwater Treatment Area Provided: 124 sf / 2' wide =min. 62' long Total Treatment Area Provided: 2' wide x 150' long = 300 sf > 124 sf .: OK Check Velocity: V = 0.70 cfs < 1.5 cfs .: OK (see attached FlowMaster output) SUB BASIN `A' WATER QUANTITY CALCULATIONS *See attached StormShed software output Stage Elevation Pond Bottom Peak Stage* lft Freeboard Total Storage Volume Provided 48 Hour Drawdown: 346.0 346.49 347.0 348.0 Live Storage Volume 0 cf 1,007 cf 2,074 cf 4,867 cf = 2,074 cf > 1,007 cf .: OK (1,739 sf)(20 in/hr)(1'/12")(48 hours) = 139,120 cf ROOF RUNOFF Roof runoff from each residential home will be tightlined to individual lot infiltration drainrock drywells. The drywells shall be sized to accommodate 125 cf of storage volume per 1,000 sf of roof area. Olympic Engineering Longmire Estates #05023 Sub-Basin A Water Quality Basin A 6-mo Event Summary: BasinlD PeakQ Peak T Peak Vol Area Event ------- (cfs) (hrs) (ac-ft) ac Basin A 6-mo 0.13 8.00 0.0414 0.47 Drainage Area: Basin A 6-mo Hyd Method: SCS Unit Hyd Peak Factor: 484.00 Storm Dur 24.00 hrs Area CN Pervious 0.0000 ac 77.00 Impervious 0.4700 ac 98.00 Total 0.4700 ac Supporting Data: Impervious CN Data: Roadway 98.00 Driveways 98.00 Sidewalks 98.00 Pervious TC Data: Flow type: Description: Fixed None Entered Impervious TC Data: Flow type: Description: Shallow Impervious Sub-Basin A Water Quantity StormShed 8/10!2005 Method Raintype /Loss SCS/SCS TYPE1A 6 mo Loss Method: SCS CN Number SCS Abs: 0.20 TC 0.00 hrs 0.06 hrs 0.2900 ac 0.1400 ac 0.0400 ac Length: Slope: 0.00 ft 0.00% Length: Slope: 290.00 ft 0.50% Coeff: Travel Time 0.0000 0.00 min Coeff: Travel Time 27.0000 3.36 min RLPCOMPUTE [Pond Level Pool] SUMMARY 100 yr MatchQ=PeakQ= 0.6082 cfs Peak Out Q: 0.3935 cfs -Peak Stg: 346.49 ft - Active Vol: 1007.41 cf Summary Report of all RLPooI Data Project Precips [2 yr] 2.00 in [5 yr] 2.50 in [10 yr] 3.00 in [25 yr] 3.00 in [100 yr] 4.00 in [6 mo] 1.28 in BASLIST2 [Basin A] Using [TYPE1A] As [100 yr] LSTEND BasinlD PeakQ Peak T Peak Vol Area Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /Loss Basin A 0.6082 8.00 0.2484 1.12 SCS/SCS TYPEIA 100 yr 1 of 3 Olympic Engineering Longmire Estates StormShed #05023 8/10/2005 BASLIST (TYPE1A] AS [100 yr] DETAILED [Basin A] LSTEND Drainage Area: Basin A Hyd Method: SCS Unit Hyd Peak Factor: 484.00 Storm Dur 24.00 hrs Area Pervious 0.6500 ac Impervious 0.4700 ac Total 1.1200 ac Supporting Data: Pervious CN Data: Landscaping Impervious CN Data: Roadway Sidewalks Driveways Pervious TC Data: Flow type: Description: Sheet Landscaping Impervious TC Data: Flow type: Description: Shallow Roadway HYDLIST SUMMARY [Basin A 100-yr out] LSTEND HydID Peak Q Peak T ------- (cfs) (hrs) Basin A 100-yr out 0.39 8.50 STORLIST (Infiltration Pond] LSTEND Node ID: Infiltration Pond Desc: Infiltration Pond Start EI: 346.0000 ft Contrib Basin: Stage Input Volume 346.00 0.00 cf 0.00 cf 347.00 2074.00 cf 2074.00 cf 348.00 4867.00 cf 4867.00 cf DISCHLIST [Infiltration Pond] LSTEND Loss Method: SCS CN Number SCS Abs: 0.20 CN TC 78.00 0.47 hrs 98.00 0.06 hrs 78.00 0.6500 ac 98.00 0.2900 ac 98.00 0.0400 ac 98.00 0.1400 ac Length: Slope: 200.00 ft 1.00% Length: Slope: 290.00 ft 0.50% Coeff: Travel Time 0.1500 28.47 min Coeff: Travel Time 27.0000 3.36 min Peak Vol Cont Area (ac-ft) (ac) 0.2481 1.1200 Max EI: 348.0000 ft Contrib Hyd: Volume 0.0000 acft 0.0476 acft 0.1117 acft Control Structure ID: Infiltration Pond -Stage Discharge rating curve Descrip: Infiltration Pond 2 of 3 Olympic Engineering Longmire Estates StormShed #05023 8/10/2005 Start EI 346.0000 ft Stage 346.0000 ft 347.0000 ft 348.0000 ft Max EI 348.0000 ft Increment 0.10 Discharge 0.0000 cfs 0.8100 cfs 0.8100 cfs 3of3 Biofiltration Swale Worksheet for Trapezoidal Channel Project Description Worksheet Biofiltration Swale Flow Element Trapezoidal Channel Method Manning's Formula Solve For Bottom Width Input Data Mannings 0.070 Coefficient Channel Slope 0.020 ft/ft 000 Depth 0.17 ft Left Side Slope 3.00 H V Right Side 3.00 H Slope V Discharge 0.13 cfs Results Bottom Width 0.62 ft Flow Area 0.2 ft2 Wetted 1.67 ft Perimeter Top Width 1.62 ft Critical Depth 0.09 ft Critical Slope 0.177700 ft/ft Velocity 0.70 ft/s Velocity 0.01 ft Head Specific 0.17 ft Energy Froude 0.36 Number Flow Type Subcritical Project Engineer: Chris c:\...\05023 - longmire estates\drainage\05023.fm2 FlowMaster v7.0 [7.0005] 8/10/2005 9:13:51 AM ©Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 Appendix II Vicinity Map W ~ T _~ LL. w ~ g mr~ ~~ ~ N Z Q ~ O ~ ~ z ~ z U m o Q o ~ 0 N a ~ a a ~ y ~ W H W Z ~ V t9 ~ O J x z~ `~.° a o ~ t0 J O1 lA M N 01 C Q O ~/1 ~ ~i 1~ O y ~ W n 0 • d N M M N T .... .... .--I Appendix III Drainage Basin Map 0 0 N I- W W L~ O O .~ ~ II o W O Q ~ U O ~ ~ ~ ~ \ ~ I `~ ~ ~ ~ ~ I ~ ~ ~\ ~\` \ i '~ \ .~ ~ `1. ~i•<~, ~ i ~ ~ _ ~ ~~ i \~ 9. \ 7~ / ~ ~ ``i ~ / F ~ ~ m --- _ __--__ ~ ~ cn ~ ~ ~, ~ f .- 7 _ _...._ ._ r- -~ -- - - - -- -- a - _ _ ~ i ti ` ~ % ~x ~ o I ~' . a ~ i 5 ~ o ~ i 6ri H I ' i I I 1 ' I ~ I W ~ N w w ~ ~ Q ~ N Z ~ Z ~ Z z m0 O ~ Q ~ ~ m 0 Q W Z a N N m W ~ ~ a c~ Z Z a O O W ~ Z ~p w d O ~ ~ J 01 lA M N O ~ C Q O lA ~j 1~ O N ~ GO f~ 0 •n N M M N ? ... u .-1 Appendix IV Soils Report SOIL EVALUATION REPORT FORM 1: GENERAL SITE INFORMATION PROJECT TITLE: Longmire Estates SHEET: 1 OF 1 PROJECT NO. :05129 DATE: 8/8/05 PREPARED BY :William Parnell, P.E. 1. SITE ADDRESS: 15218 Longmire Street Yelm, Wa. 98597 TAX PARCEL NUMBER: 21724420700 2. PROJECT DESCRIPTION: Create a 10 lot residential subdivision. 3. SITE DESCRIPTION: The 2.18 acre project site is currently occupied by a single residential dwelling and an outbuilding. Site relief is nearly level, sloping away from the center of the property to the north, east and south at a gradient of 3% or less. There are no site distinguishing features other than an existing domestic well. Site vegetation consists of uncropped field grasses, maintained grass lawn and landscaping adjacent to the existing house. The project site is bounded by residential property to the north, northeast and west,- and by Longmire Street SE to the south and southeast. On-site soils are awell-drained Spanaway series formed in glacial outwash. 4. SUMMARY OF SOILS WORK PERFORMED: One test pit was excavated by backhoe to a depth of 156" below the existing grade. Soils were inspected by entering and visually logging each test pit to a depth of four feet. Soils. beyond four feet were inspected by examining backhoe tailings. One double ring infiltration test was completed. A test pit soil log data sheet and a double ring infiltration test result are included in this report. 5. ADDITIONAL SOILS WORK RECOMMENDED: Additional soils work should not be necessary unless drainage infiltration facilities are located outside the general area encompassed by the soil test pits. 6. FINDINGS: The Natural Resource Conservation Service soil survey for Thurston County mapped the on-site soils as a Spanaway Gravelly Sandy Loam (110). The completed test pit confirmed the Spanaway designation generally profiling a gravelly fine sandy loam surface soil overlying an extremely gravelly & cobbley coarse-medium sand substratum. The substratum gravels and sands were moderately loose. Winter water table was not present and indicators were not visible. A double ring infiltration test completed at 80" below the existing grade revealed an infiltration rate of 75.8 in/hr. 7. RECOMMENDATIONS: The Spanaway soil series is a somewhat excessively drained soil that formed in gravelly glacial outwash. Infiltration rates are generally rapid in the substratum soils. The specified substratum C-horizon soils should be targeted for all drainage infiltration facilities as noted in the attached soil log data sheets. A design infiltration rate of 20 in/hr or less would be appropriate for these targeted soils. During construction, care must be taken to prevent the erosion of exposed soils. Drainage facility infiltration surfaces must be .properly protected from contamination by the fine-grained upper horizon soils and from compaction by construction site activities. Soils not properly protected will cause drainage infiltration facilities to prematurely fail. I hereby certify that I prepared this report, and conducted or supervised the performance of related work. I certify that I am qualified to do this work. I represent my work to be complete an accurate within the bounds of uncertainty inherent to the practice of soils science, and to be suitable for its intended use. 1 t~i ~,~ ` SIGNED: DATE: ~ ~l~l~ ~° i-. - SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Longmire Estates SHEET: 1 OF 1 PROJECT NO. :05129 DATE: 7/21/05 PREPARED BY :William Parnell, P.E. SOIL LOG: #1 LOCATION: 30 ft. east and 20 ft. north of the southwest property comer. 1. TYPES OF TEST DONE: 2. SCS SOILS SERIES: 3. LAND FORM: Double Ring Infiltration Spanaway (1.10) Terrace 4. DEPOSITION HISTORY: 5. HYDROLOGIC SOIL 6. DEPTH OF SEASONAL HW: GROUP: Glacial Outwash A/B Unknown 7. CURRENT WATER 8. DEPTH TO IMPERVIOUS 9. MISCELLANEOUS: DEPTH: LAYER: Greater than bottom of hole Greater than bottom of hole Nearly Level 10. POTENTIAL FOR: EROSION RUNOFF PONDING Minimal Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: A double ring infiltration test completed at 80" below the existing grade revealed an infiltration rate of 75.8 in/hr. Use a design infiltration rate of 20 in/hr or less for drainage infiltration facilities located in the C2, C3 and C4 horizon soils. Soils Strata Description Soil Log #1 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0"- 16" 10YR2/1 GrFSaLm <20 <5 <15 1 SBK - - - ff 2-6 2 Bw 16"- 24" 10YR3/4 ExGrCSaLm <15 - <85 SG - - ff 2-6 6 C1 24"- 48" 10YR3/6 ExGrM-FSa <3 - <70 SG - - - - >20 30 C2 48"- 67" t0YR5/1 Gravel <1 - <100 SG - - - - >20 >40 C3 67"-114" 10YR3/4 ExGrMSa <1 - <80 SG - - - - >20 75.8 C4 114"-156" 10YR5/1 ExGrCSa <1 - <98 SG - - - - >20 >40 Abbreviations Textural- Class (Texture) Structure (STR) Grades of Structure Cobbley -Cob Granular - Gr Strong - 3 Stone - St Block - Blk Moderate - 2 Gravelly - Gr Platy - PI Weak - 1 Sandy - Sa Massive - Mas Loam - Lm Sin le Grained - SG Silty - Si Sub-Angular Blocky - SBK Clayey - CI Coarse - C Very - V Extreme) - Ex Fine - F Medium - M Induration 8~ Cementation (IND) (CEM) Weak - Wk Moderate -Mod Strong - Str Mottles (MOT) 1 Letter Abundance 1st Number Size 2nd Letter Contrast Few - F Fine - 1 Faint - F Common - C Medium - 2 Distinct - D Many - M Coarse - 3 Prominent - P Roots (ROO) 1st Letter Abundance 2nd Letter Size Few - f Fine - f Common - c Medium - m Man - m Coarse - c <X> -Generalized range of infiltration rates from SCS soil survey (<X>) DOUBLE RING INFILTRATION TEST LONGMIRE ESTATES Test Date : 7/21 /2005 Completed By : William Parnell. PE DOUBLE RING INFILTRATION TEST RESULTS Test Hole # 1 ( Test run @ 80" below existing ground surtace ) Start Sto Ela sed Time Total Dro Infiltration Rate ( Min } (Min) (Min) (Inches) (In/Hr ) 0 45" 45" 6" 45" 1' 30" 45" 6" 1' 30" 3' 30" 2' 00" 6" . 3' 30" 6' 00" 2' 30" 6" 6' 00" 9' 00" 3' 00" 6" 9' 00" 12' 15" 3' 15" 6" 12' 15" 15' 45" 3' 30" 6" 15' 45" 19' 15" 3' 30" 6" 19' 15" 22' 45" 3' 30" 6" 22' 45" 27' 00" 4' 15" 6" 27' 00" 31' 15" 4' 15" 6" 31' 15" 36' 00" 4' 45" 6" 36' 00" 40' 00" 4' 00" 6" 40' 00" 44' 30" 4' 30" 6" 44' 30" 49' 15" 4' 45" 6" 49' 15" 54' 00" 4' 45" 6" 75.8 54' 00" 59' 30" 4' 30" 6" 59' 30" 1: 03' 00" 4' 30" 6"