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2020.0341.PR0011 Preliminary Drainage Report
Mountain Meadows Yelm, Washington Stormwater Site Plan Report November 5, 2020 Prepared by: PO Box 12690 Olympia, WA 98508 360.705.2474 www.olyeng.com I STORMWATER SITE PLAN REPORT MOUNTAIN MEADOWS Yelm, Washington November 5, 2020 Project Information Prepared for: Henrietta Morey Contact: Henrietta Morey PO Box 202 Kapowsin, WA 98344 Reviewing Agency Jurisdiction: City of Yelm Project Number: ___________________ Project Contact: Tami Merriman, Associate Planner References WSDOE Stormwater Management Manual for Western Washington, 2014 ed. (Stormwater Manual) Project Engineer Prepared by: Olympic Engineering, Inc. 11/5/2020 PO Box 12690 Olympia, WA 98508 (360) 705-2474 www.olyeng.com Contact: Chris Merritt, PE OE Project: 20047 File Number: 20047_pdr.doc II Table of Contents STORMWATER SITE PLAN REPORT ........................................................ I TABLE OF CONTENTS ................................................................................. II PART 1 – PROJECT OVERVIEW ................................................................. 1 PART 2 – EXISTING CONDITONS SUMMARY ......................................... 1 PART 3 – OFF-SITE ANAYLSIS .................................................................... 2 PART 4 – PERMANENT STORMWATER CONTROL PLAN ................... 2 Applicable Minimum Requirements .................................................................. 2 PART 5 – SPECIAL REPORTS AND STUDIES ......................................... 6 PART 6 – OTHER PERMITS ......................................................................... 6 PART 7 – OPERATION AND MAINTENANCE MANUAL ........................ 6 APPENDICES Appendix 1 – Preliminary Drainage Plans Appendix 2 – Preliminary Drainage Calculations Appendix 3 - Soils Report ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 1 PART 1 – PROJECT OVERVIEW Site Address: 8818 Burnett Rd. SE Yelm, WA 98597 Parcel Number: 21713310400 & 21713310402 Total Proposed Lease Area: ±4.389 Acres Zoning: R-6 Section, Township, Range: Section 13 Township 17 North Range 1 East, W.M. Proposed Improvements The proposed project will include subdividing two parcels totaling 4.389-acres into 22 single-family residential lots with associated roadway, frontage, water, sanitary sewer, storm drainage, landscaping, and private/public utility improvements. PART 2 – EXISTING CONDITONS SUMMARY The site contains an existing barn that will be demolished and removed. Topography is gently sloping down from east to west at an average slope of approximately 2-3%. Site vegetation consists mainly of pasture grasses and scotch bloom with a few conifer trees located mainly in the southwestern portion of the site. The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston County classifies the on-site and surrounding area soils as Spanaway Gravelly Sandy Loam (HSG A). A Soils Report was prepared by Parnell Engineering, dated September 18, 2020 and the soils encountered were consistent with the Spanaway classification. Two test pits were dug to a depth of 168” below-grade and no groundwater, or indications of, were encountered. See Soils Report in Appendix. Per FEMA FIRM Map Panel #53045C0335E, the project site and surrounding areas are within Zone X. The Zone X designation signifies areas that are outside of the 0.2% annual chance floodplain. There are no known critical areas (wetlands, streams, steep slopes, etc.) located on or within the immediate vicinity of the project site. The site and surrounding area are located in a Category I Critical Aquifer Recharge Area (CARA). All stormwater management BMP’s will meet or exceed DDECM requirements. ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 2 PART 3 – OFF-SITE ANAYLSIS The project site is bounded by Burnett Rd. SE to the west; by undeveloped parcels to the east and north; and by developed residential parcels to the south. There are no apparent indications of stormwater runoff entering the project site from surrounding properties and there does not appear to be any noticeable stormwater runoff from the subject parcel onto adjacent parcels. Stormwater runoff from the Burnett Rd. frontage currently sheet flows to a roadside ditch. There is no known ultimate outfall point other than infiltration within the ditch. All stormwater runoff generated by the proposed improvements will be dispersed and/or infiltrated on-site; therefore, a quantitative off-site analysis and/or mitigation is not warranted. PART 4 – PERMANENT STORMWATER CONTROL PLAN Applicable Minimum Requirements The minimum requirements for stormwater development and redevelopment sites are listed in Section I-2.4 of Volume I of the Stormwater Manual. Based on the thresholds given in this section, the proposed project must address or comment on Minimum Requirements #1 through #9. These requirements have been addressed as follows: Minimum Requirement #1 – Preparation of Stormwater Site Plans: A Stormwater Site Plan has been prepared (see Site Plan). Minimum Requirement #2 – Construction Stormwater Pollution Prevention Plan (SWPPP): A SWPPP meeting city requirements will be provided with the final Stormwater Site Plan Report. Minimum Requirement #3 – Source Control of Pollution: A Pollution Source Control Program will be prepared and provided prior to final project approval, if required. Minimum Requirement #4 – Preservation of Natural Drainage Systems and Outfalls: There are no known natural drainage systems or outfalls located on or immediately adjacent to the proposed lease area. ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 3 Minimum Requirement #5 – On-Site Stormwater Management: This project will meet the LID Performance Standard. The proposed stormwater Best Management Practices (BMP’s) are as follows: Lawn and Landscape Areas: • All disturbed areas, including the roadside planter areas and future individual lot lawn/landscape areas, will contain soils meeting the Post- Construction Soil Quality and Depth (BMP T5.13) requirements. Roof Areas: • It is anticipated that Stormwater runoff from the future individual lot roof areas will be tightlined to individual lot downspout infiltration trenches (BMP T5.10A) for detention and 100% infiltration of stormwater runoff from the roof areas. See Minimum Requirement #7 below for additional information. Other Hard Surface Areas: • Stormwater runoff from east half of the Burnett Rd. frontage and the on- site roadway will be collected and conveyed to a Type 2 catch basin containing Baysaver Bayfilter™ cartridges for treatment. Treated stormwater will be conveyed to a below-grade Infiltration Trench (BMP T7.20) consisting of StormTech chambers for storage and 100% infiltration. See Minimum Requirement #6 and #7 below for additional information. • Stormwater runoff from the improved portion of 89th Way will sheet flow to the existing storm drainage system located along 89th Ave. and ultimately be conveyed through a bioswale and into a detention pond located in Burnett Estates. There is only 2,462 sf of net new hard surface area associated with the 89th Way improvements and the existing Burnett Estates stormwater system has capacity to accommodate this additional runoff. • It is anticipated that stormwater runoff from the future individual lot driveway, walkway, and patio areas will be sheet flow dispersed (BMP T5.12) onto adjacent lawn/landscape areas. Soils within the dispersion areas will meet the Post-Construction Soil Quality and Depth (BMP T5.13) requirements. Modeling Narrative • Stormwater runoff from all proposed hard surface areas are being infiltrated and are considered “non-effective”; therefore, they can be excluded from the hard surface area threshold determination of Minimum Requirement #7. • In order to help meet the flow control requirement, stormwater runoff from the individual lot lawn/landscape and dispersed driveway/walkway/patio areas have been routed to a Compost Amended Vegetated Filter Strip (CAVFS) in WWHM. See Minimum Requirement #7 below for additional information. ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 4 • All lawn/landscape areas will meet the Post-Construction Soil Quality and Depth (BMP T5.13) requirements and have been modeled as “pasture” in WWHM. • The roof areas have been excluded from WWHM as they are not being routed to the main stormwater facility and they will be sized per prescriptive sizing standards for 100% infiltration. • The pre-developed land coverage has been modeled as “pasture”. • The project has a single Threshold Discharge Area (TDA). • Parnell Engineering recommended a 20”/hr design infiltration rate for the below-grade infiltration facility; however, a 15”/hr rate was used in WWHM to be conservative. Parcel Area: 4.389 acres Off-Site Area: 0.101 acres (East half of Burnett Rd.) Off-Site Area: 0.202 acres (89th Way SE) Total Project Area: 4.692 acres Project Areas Pre-Developed (Acres) Sub-Basin #1 Sub-Basin #2 Total Roadway 0.054 0.114 0.168 Roof 0.039 0.039 Pasture/Brush 4.397 4.397 Lawn/Landscape 0.088 0.088 Total 4.490 0.202 4.692 Project Areas Post-Developed (Acres) Sub-Basin #1 Sub-Basin #2 Total Roadway 0.6451 0.1271 0.772 Sidewalks 0.0861 0.0231 0.109 Roof (assumed on lots) 1.0101,2,3 1.010 Driveways (w/in R/W) 0.0611 0.061 Driveway (assumed on lots) 0.2533 0.253 Misc. (Walkway/ Patio) (assumed on lots) 0.5053 0.505 Lawn/Landscape (assumed on lots) 1.7363 1.736 Lawn/Landscape (w/in R/W) 0.1941 0.0521 0.246 Total 4.490 0.202 4.692 ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 5 1 “Non-effective” hard surface areas as these areas are being infiltrated. 2 Infiltrated hard surfaces (roof areas) not being routed to the main stormwater facility have been excluded from the post-developed scenario in WWHM. 3 It has been assumed that each lot will have a total of 3,500 sf of hard surface coverage (2,000 sf roof, 500 sf driveway, 1,000 sf walkway/patios) and the remaining lot area will consist of lawn/landscape. Minimum Requirement #6 – Runoff Treatment: This project will create more than 5,000 square-feet of new total pollution- generating hard surface (PGHS) area; therefore, a Runoff Treatment facility is required. Two Baysaver Bayfilter™ cartridges (BFC 30 gpm) will provide treatment of stormwater runoff from all pollution generating hard surface (PGHS) areas (parking lot and sidewalks contributing to the parking lot). Per WWHM modeling results, this project is required to treat a 15-minute water quality flow rate of 0.1051 cfs. 0.1223 cfs / 0.067 cfs/cartridge = 1.83 (Use two 30 gpm cartridges) The Washington State Department of Ecology issued a “General Use Level Designation for Basic Treatment” for this filter when using a 30 gpm/cartridge design flow rate (see Appendix). Minimum Requirement #7 – Flow Control: This project will create less than 10,000 square-feet of “effective” hard surface area, there will be less than a 0.15-cfs increase in the 100-year recurrence interval flow frequency from the pre- to post-developed condition, and less than 2.5-acres of native vegetation will be converted to pasture; however, more than ¾-acre of vegetation will be converted to lawn/landscape; therefore, Flow Control is applicable. See Minimum Requirement #5 above for a detailed description of the proposed Stormwater Management BMP’s. Per WWHM, the project meets the LID Performance Standard. In order to reduce the effective hard surface area and to help meet the flow control requirement, stormwater runoff from the individual lot lawn/landscape and dispersed driveway/walkway/patio areas have been routed to a Compost Amended Vegetated Filter Strip (CAVFS) in WWHM. Per the WWHM user’s manual, “The CAVFS surface area automatically receives rainfall and produces evapotranspiration. Due to this model input the CAVFS surface area should be excluded from the basin element’s total surface area.” Since the entire lawn/landscape area essentially is a CAVFS, the basin element area would become zero. However, to be conservative, the total proposed lawn/landscape surface area has been routed to the CAVFS. Furthermore, only the lawn/landscape area adjacent to the driveways along with the down-slope yard areas have been utilized as a CAVFS. In this situation, the CAVFS is intended to be a flow control facility with infiltration to the underlying soils. A 3”/hr infiltration rate of the underlying soils was used in WWHM (A 4”/hr rate for the surface soils was recommended in the Soils Report prepared by Parnell Engineering and a 3”/hr rate is typical for amended soils). ____________________________________________________________________________________ November 2020 Stormwater Site Plan Report 6 The 4’ high infiltration trench will provide for 1.6’ of freeboard. At a maximum ponding depth of 2.4’, the facility will draw down in 1.9 hours (2.4’x12”)/15”/hr = 1.9 hours). Minimum Requirement #8 – Wetlands Protection: There are no known wetlands on or immediately adjacent to the project site; therefore, this Minimum Requirement is not applicable. Minimum Requirement #9 – Operation and Maintenance: An operation and maintenance manual will be prepared prior to final project approval. The owner will be responsible for maintaining all stormwater facilities located on-site. PART 5 – SPECIAL REPORTS AND STUDIES A Soils Report for Evaluating Site Feasibility of Stormwater Infiltration, dated September 18, 2020 has been prepared by Parnell Engineering (see Appendix). PART 6 – OTHER PERMITS Right-of-way encroachment and grading permits will be required prior to construction start. A stormwater permit will be obtained from Ecology. PART 7 – OPERATION AND MAINTENANCE MANUAL An operation and maintenance manual will be provided prior to final project approval. The owner will be responsible for maintaining all stormwater facilities located on-site. Appendix 1 Preliminary Drainage Plans PO Box 12690Olympia, WA 98508360.705.2474Www.olyeng.com CHRIM.MERSTR ITHOT EP R PO Box 12690Olympia, WA 98508360.705.2474Www.olyeng.com CHRIM.MERSTR ITHOT EP R· · · · · · · · · · · · · · · · · · · · TYPE 2 CATCH BASIN (CB#10) BOTTOM ELEV. = 319.00 8' (2.4 m) MAX 18" (450 mm) MIN* MATERIAL LOCATION DESCRIPTION AASHTO MATERIAL CLASSIFICATIONS COMPACTION / DENSITY REQUIREMENT D FINAL FILL: FILL MATERIAL FOR LAYER 'D' STARTS FROM THE TOP OF THE 'C' LAYER TO THE BOTTOM OF FLEXIBLE PAVEMENT OR UNPAVED FINISHED GRADE ABOVE. NOTE THAT PAVEMENT SUBBASE MAY BE PART OF THE 'D' LAYER ANY SOIL/ROCK MATERIALS, NATIVE SOILS, OR PER ENGINEER'S PLANS. CHECK PLANS FOR PAVEMENT SUBGRADE REQUIREMENTS. N/A PREPARE PER SITE DESIGN ENGINEER'S PLANS. PAVED INSTALLATIONS MAY HAVE STRINGENT MATERIAL AND PREPARATION REQUIREMENTS. C INITIAL FILL: FILL MATERIAL FOR LAYER 'C' STARTS FROM THE TOP OF THE EMBEDMENT STONE ('B' LAYER) TO 18" (450 mm) ABOVE THE TOP OF THE CHAMBER. NOTE THAT PAVEMENT SUBBASE MAY BE A PART OF THE 'C' LAYER. GRANULAR WELL-GRADED SOIL/AGGREGATE MIXTURES, <35% FINES OR PROCESSED AGGREGATE. MOST PAVEMENT SUBBASE MATERIALS CAN BE USED IN LIEU OF THIS LAYER. AASHTO M145¹ A-1, A-2-4, A-3 OR AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57, 6, 67, 68, 7, 78, 8, 89, 9, 10 BEGIN COMPACTIONS AFTER 12" (300 mm) OF MATERIAL OVER THE CHAMBERS IS REACHED. COMPACT ADDITIONAL LAYERS IN 6" (150 mm) MAX LIFTS TO A MIN. 95% PROCTOR DENSITY FOR WELL GRADED MATERIAL AND 95% RELATIVE DENSITY FOR PROCESSED AGGREGATE MATERIALS. ROLLER GROSS VEHICLE WEIGHT NOT TO EXCEED 12,000 lbs (53 kN). DYNAMIC FORCE NOT TO EXCEED 20,000 lbs (89 kN). B EMBEDMENT STONE: FILL SURROUNDING THE CHAMBERS FROM THE FOUNDATION STONE ('A' LAYER) TO THE 'C' LAYER ABOVE. CLEAN, CRUSHED, ANGULAR STONE, NOMINAL SIZE DISTRIBUTION BETWEEN 3/4-2 INCH (20-50 mm) AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57 NO COMPACTION REQUIRED. A FOUNDATION STONE: FILL BELOW CHAMBERS FROM THE SUBGRADE UP TO THE FOOT (BOTTOM) OF THE CHAMBER. CLEAN, CRUSHED, ANGULAR STONE, NOMINAL SIZE DISTRIBUTION BETWEEN 3/4-2 INCH (20-50 mm) AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57 PLATE COMPACT OR ROLL TO ACHIEVE A FLAT SURFACE. ² ³ PLEASE NOTE: 1. THE LISTED AASHTO DESIGNATIONS ARE FOR GRADATIONS ONLY. THE STONE MUST ALSO BE CLEAN, CRUSHED, ANGULAR. FOR EXAMPLE, A SPECIFICATION FOR #4 STONE WOULD STATE: "CLEAN, CRUSHED, ANGULAR NO. 4 (AASHTO M43) STONE". 2. STORMTECH COMPACTION REQUIREMENTS ARE MET FOR 'A' LOCATION MATERIALS WHEN PLACED AND COMPACTED IN 6" (150 mm) (MAX) LIFTS USING TWO FULL COVERAGES WITH A VIBRATORY COMPACTOR. 3. WHERE INFILTRATION SURFACES MAY BE COMPROMISED BY COMPACTION, FOR STANDARD DESIGN LOAD CONDITIONS, A FLAT SURFACE MAY BE ACHIEVED BY RAKING OR DRAGGING WITHOUT COMPACTION EQUIPMENT. FOR SPECIAL LOAD DESIGNS, CONTACT STORMTECH FOR COMPACTION REQUIREMENTS.PO Box 12690Olympia, WA 98508360.705.2474Www.olyeng.com CHRIM.MERSTR ITHOT EP RNOTES: 1. SC-740 CHAMBERS SHALL CONFORM TO THE REQUIREMENTS OF ASTM F2418 "STANDARD SPECIFICATION FOR POLYPROPYLENE (PP) CORRUGATED WALL STORMWATER COLLECTION CHAMBERS", OR ASTM F2922 "STANDARD SPECIFICATION FOR POLYETHYLENE (PE) CORRUGATED WALL STORMWATER COLLECTION CHAMBERS". 2. SC-740 CHAMBERS SHALL BE DESIGNED IN ACCORDANCE WITH ASTM F2787 "STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC CORRUGATED WALL STORMWATER COLLECTION CHAMBERS". 3. "ACCEPTABLE FILL MATERIALS" TABLE ABOVE PROVIDES MATERIAL LOCATIONS, DESCRIPTIONS, GRADATIONS, AND COMPACTION REQUIREMENTS FOR FOUNDATION, EMBEDMENT, AND FILL MATERIALS. 4. THE SITE DESIGN ENGINEER IS RESPONSIBLE FOR ASSESSING THE BEARING RESISTANCE (ALLOWABLE BEARING CAPACITY) OF THE SUBGRADE SOILS AND THE DEPTH OF FOUNDATION STONE WITH CONSIDERATION FOR THE RANGE OF EXPECTED SOIL MOISTURE CONDITIONS. 5. PERIMETER STONE MUST BE EXTENDED HORIZONTALLY TO THE EXCAVATION WALL FOR BOTH VERTICAL AND SLOPED EXCAVATION WALLS. 6. ONCE LAYER 'C' IS PLACED, ANY SOIL/MATERIAL CAN BE PLACED IN LAYER 'D' UP TO THE FINISHED GRADE. MOST PAVEMENT SUBBASE SOILS CAN BE USED TO REPLACE THE MATERIAL REQUIREMENTS OF LAYER 'C' OR 'D' AT THE SITE DESIGN ENGINEER'S DISCRETION. INSPECTION PORT 12" X 12" ADS N-12 MANIFOLD PLACE MINIMUM 12.5' OF ADS GEOSYNTHETICS 315WTK WOVEN GEOTEXTILE OVER BEDDING STONE AND UNDERNEATH CHAMBER FEET FOR SCOUR PROTECTION AT ALL CHAMBER INLET ROWS EXCAVATION WALL (CAN BE SLOPED OR VERTICAL) SUBGRADE SOILS (SEE NOTE 5) ADS GEOSYNTHETICS 601T NON-WOVEN GEOTEXTILE ALL AROUND CLEAN, CRUSHED, ANGULAR STONE IN A & B LAYERS 12" (300 mm) MIN PERIMETER STONE (SEE NOTE 6) SC-740 END CAP *TO BOTTOM OF FLEXIBLE PAVEMENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR, INCREASE COVER TO 24" (600 mm). 51" (1295 mm)6" (150 mm) MIN A B C D 30" (760 mm) 12" 12" (300 mm) TYP 6" (150 mm) MIN PAVEMENT LAYER (DESIGNED BY SITE DESIGN ENGINEER) ACCEPTABLE FILL MATERIALS: STORMTECH SC-740 CHAMBER SYSTEMS SECTION A-A A A BAYSAVER - BAYFILTER DETAIL (CB#9) NTS 12"Ø PIPE - INLET - 324.70 36" FRAME AND COVER (MARKED "STORM" PER WSDOT STANDARD PLAN B-30.70-03 12"Ø INLET TREATED SEDIMENT CAPACITY # BAYFILTER CARTRIDGES CARTRIDGE DESIGN FLOW RATE DRAINAGE AREA WATER QUALITY FLOW BAYFILTER 60-2 MANHOLE LOCATION PROJECT 36" FRAME & COVER 2 MOUNTAIN MEADOWS CB#10 30 GPM 0.1051 CFS 12"Ø PIPE - OUTLET - 322.03 OVERFLOW ELEV.=168.20 COVERED BYPASS 12"Ø OUTLET RIM - ±173.00 NOTE: SEE WSDOT STANDARD PLANS B-10.20-01 B-30.90-01 FOR ACCESS AND STEP/LADDER LOCATION/ ORIENTATION AND DETAILS. Appendix 2 Preliminary Drainage Calculations Project: Chamber Model - SC-740 Units -Imperial Number of chambers -21 Voids in the stone (porosity) - 40 % Base of Stone Elevation -0.00 ft Amount of Stone Above Chambers - 6 in Amount of Stone Below Chambers -12 in Area of system -895 sf Min. Area - Height of System Incremental Single Chamber Incremental Total Chamber Incremental Stone Incremental Ch & St Cumulative Chamber Elevation (inches)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(feet) 48 0.00 0.00 29.83 29.83 2010.98 4.00 47 0.00 0.00 29.83 29.83 1981.15 3.92 46 0.00 0.00 29.83 29.83 1951.31 3.83 45 0.00 0.00 29.83 29.83 1921.48 3.75 44 0.00 0.00 29.83 29.83 1891.65 3.67 43 0.00 0.00 29.83 29.83 1861.81 3.58 42 0.05 1.15 29.37 30.53 1831.98 3.50 41 0.16 3.42 28.46 31.89 1801.45 3.42 40 0.28 5.92 27.47 33.39 1769.57 3.33 39 0.60 12.68 24.76 37.44 1736.18 3.25 38 0.80 16.84 23.10 39.93 1698.74 3.17 37 0.95 19.96 21.85 41.81 1658.80 3.08 36 1.07 22.56 20.81 43.37 1616.99 3.00 35 1.18 24.79 19.92 44.71 1573.62 2.92 34 1.27 26.58 19.20 45.78 1528.91 2.83 33 1.36 28.46 18.45 46.91 1483.13 2.75 32 1.45 30.54 17.62 48.15 1436.23 2.67 31 1.52 32.02 17.03 49.04 1388.07 2.58 30 1.58 33.23 16.54 49.77 1339.03 2.50 29 1.64 34.49 16.04 50.53 1289.26 2.42 28 1.70 35.69 15.56 51.25 1238.73 2.33 27 1.75 36.81 15.11 51.92 1187.48 2.25 26 1.80 37.86 14.69 52.55 1135.56 2.17 25 1.85 38.95 14.25 53.21 1083.01 2.08 24 1.89 39.75 13.93 53.69 1029.81 2.00 23 1.93 40.61 13.59 54.20 976.12 1.92 22 1.97 41.47 13.24 54.72 921.92 1.83 21 2.01 42.21 12.95 55.16 867.20 1.75 20 2.04 42.94 12.66 55.60 812.04 1.67 19 2.07 43.57 12.40 55.98 756.44 1.58 18 2.10 44.20 12.15 56.36 700.46 1.50 17 2.13 44.77 11.93 56.69 644.11 1.42 16 2.15 45.23 11.74 56.97 587.41 1.33 15 2.18 45.72 11.55 57.26 530.44 1.25 14 2.20 46.17 11.37 57.53 473.18 1.17 13 2.21 46.35 11.29 57.65 415.65 1.08 StormTech SC-740 Cumulative Storage Volumes Mountain Meadows 710 sf min. area Include Perimeter Stone in Calculations 12 0.00 0.00 29.83 29.83 358.00 1.00 11 0.00 0.00 29.83 29.83 328.17 0.92 10 0.00 0.00 29.83 29.83 298.33 0.83 9 0.00 0.00 29.83 29.83 268.50 0.75 8 0.00 0.00 29.83 29.83 238.67 0.67 7 0.00 0.00 29.83 29.83 208.83 0.58 6 0.00 0.00 29.83 29.83 179.00 0.50 5 0.00 0.00 29.83 29.83 149.17 0.42 4 0.00 0.00 29.83 29.83 119.33 0.33 3 0.00 0.00 29.83 29.83 89.50 0.25 2 0.00 0.00 29.83 29.83 59.67 0.17 1 0.00 0.00 29.83 29.83 29.83 0.08 WWHM2012 PROJECT REPORT 20047_101920 11/4/2020 2:10:51 PM Page 2 General Model Information Project Name:20047_101920 Site Name:Mountain Meadows Site Address:8818 Burnett Rd City:Yelm Report Date:11/4/2020 Gage:Eaton Creek Data Start:1955/10/01 Data End:2011/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC3:50 Percent of the 2 Year High Flow Threshold for POC3:50 Year 20047_101920 11/4/2020 2:10:51 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 4.436 Pervious Total 4.436 Impervious Land Use acre ROADS FLAT 0.054 Impervious Total 0.054 Basin Total 4.49 Element Flows To: Surface Interflow Groundwater 20047_101920 11/4/2020 2:10:51 PM Page 4 Water Quality Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.194 Pervious Total 0.194 Impervious Land Use acre ROADS FLAT 0.645 DRIVEWAYS FLAT 0.061 SIDEWALKS FLAT 0.086 Impervious Total 0.792 Basin Total 0.986 Element Flows To: Surface Interflow Groundwater 20047_101920 11/4/2020 2:10:51 PM Page 5 Mitigated Land Use Basin 1 - Roads Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.194 Pervious Total 0.194 Impervious Land Use acre ROADS FLAT 0.645 DRIVEWAYS FLAT 0.061 SIDEWALKS FLAT 0.086 Impervious Total 0.792 Basin Total 0.986 Element Flows To: Surface Interflow Groundwater SSD Table 1 SSD Table 1 20047_101920 11/4/2020 2:10:51 PM Page 6 Water Quality Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.194 Pervious Total 0.194 Impervious Land Use acre ROADS FLAT 0.645 DRIVEWAYS FLAT 0.061 SIDEWALKS FLAT 0.086 Impervious Total 0.792 Basin Total 0.986 Element Flows To: Surface Interflow Groundwater 20047_101920 11/4/2020 2:10:51 PM Page 7 Basin 1 - Lots Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 1.736 Pervious Total 1.736 Impervious Land Use acre DRIVEWAYS FLAT 0.253 SIDEWALKS FLAT 0.505 Impervious Total 0.758 Basin Total 2.494 Element Flows To: Surface Interflow Groundwater CAVFS 1 Surface 1 CAVFS 1 Surface 1 20047_101920 11/4/2020 2:10:51 PM Page 8 Routing Elements Predeveloped Routing 20047_101920 11/4/2020 2:10:51 PM Page 9 Mitigated Routing SSD Table 1 Depth:4 ft. Discharge Structure: 1 Riser Height:3 ft. Riser Diameter:8 in. Element Flows To: Outlet 1 Outlet 2 SSD Table Hydraulic Table Stage Area Volume Outlet Infilt (feet) (ac.) (ac-ft.) Struct (cfs) NotUsed NotUsed NotUsed 0.000 0.021 0.000 0.000 0.311 0.000 0.000 0.000 0.083 0.021 0.001 0.000 0.311 0.000 0.000 0.000 0.167 0.021 0.001 0.000 0.311 0.000 0.000 0.000 0.250 0.021 0.002 0.000 0.311 0.000 0.000 0.000 0.333 0.021 0.003 0.000 0.311 0.000 0.000 0.000 0.417 0.021 0.003 0.000 0.311 0.000 0.000 0.000 0.500 0.021 0.004 0.000 0.311 0.000 0.000 0.000 0.583 0.021 0.005 0.000 0.311 0.000 0.000 0.000 0.667 0.021 0.005 0.000 0.311 0.000 0.000 0.000 0.750 0.021 0.006 0.000 0.311 0.000 0.000 0.000 0.833 0.021 0.007 0.000 0.311 0.000 0.000 0.000 0.917 0.021 0.008 0.000 0.311 0.000 0.000 0.000 1.000 0.021 0.008 0.000 0.311 0.000 0.000 0.000 1.083 0.021 0.010 0.000 0.311 0.000 0.000 0.000 1.167 0.021 0.011 0.000 0.311 0.000 0.000 0.000 1.250 0.021 0.012 0.000 0.311 0.000 0.000 0.000 1.333 0.021 0.013 0.000 0.311 0.000 0.000 0.000 1.417 0.021 0.015 0.000 0.311 0.000 0.000 0.000 1.500 0.021 0.016 0.000 0.311 0.000 0.000 0.000 1.583 0.021 0.017 0.000 0.311 0.000 0.000 0.000 1.667 0.021 0.019 0.000 0.311 0.000 0.000 0.000 1.750 0.021 0.020 0.000 0.311 0.000 0.000 0.000 1.833 0.021 0.021 0.000 0.311 0.000 0.000 0.000 1.917 0.021 0.022 0.000 0.311 0.000 0.000 0.000 2.000 0.021 0.024 0.000 0.311 0.000 0.000 0.000 2.083 0.021 0.025 0.000 0.311 0.000 0.000 0.000 2.167 0.021 0.026 0.000 0.311 0.000 0.000 0.000 2.250 0.021 0.027 0.000 0.311 0.000 0.000 0.000 2.333 0.021 0.028 0.000 0.311 0.000 0.000 0.000 2.417 0.021 0.030 0.000 0.311 0.000 0.000 0.000 2.500 0.021 0.031 0.000 0.311 0.000 0.000 0.000 2.583 0.021 0.032 0.000 0.311 0.000 0.000 0.000 2.667 0.021 0.033 0.000 0.311 0.000 0.000 0.000 2.750 0.021 0.034 0.000 0.311 0.000 0.000 0.000 2.833 0.021 0.035 0.000 0.311 0.000 0.000 0.000 2.917 0.021 0.036 0.000 0.311 0.000 0.000 0.000 3.000 0.021 0.037 0.000 0.311 0.000 0.000 0.000 3.083 0.021 0.038 0.168 0.311 0.000 0.000 0.000 3.167 0.021 0.039 0.442 0.311 0.000 0.000 0.000 3.250 0.021 0.040 0.678 0.311 0.000 0.000 0.000 3.333 0.021 0.041 0.800 0.311 0.000 0.000 0.000 3.417 0.021 0.041 0.904 0.311 0.000 0.000 0.000 20047_101920 11/4/2020 2:10:51 PM Page 10 3.500 0.021 0.042 0.990 0.311 0.000 0.000 0.000 3.583 0.021 0.043 1.069 0.311 0.000 0.000 0.000 3.667 0.021 0.043 1.143 0.311 0.000 0.000 0.000 3.750 0.021 0.044 1.212 0.311 0.000 0.000 0.000 3.833 0.021 0.045 1.278 0.311 0.000 0.000 0.000 3.917 0.021 0.045 1.340 0.311 0.000 0.000 0.000 4.000 0.021 0.046 1.400 0.311 0.000 0.000 0.000 20047_101920 11/4/2020 2:10:51 PM Page 11 CAVFS 1 CAVFS Length: 1276.00 ft. CAVFS Width:10.00 ft. Gravel thickness: 1 ft. Material thickness of CAVFS layer: 0.75 ft. Slope of CAVFS layer: 0.075 ft. Infiltration On Infiltration rate:3 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):119.871 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):119.879 Percent Infiltrated:99.99 Total Precip Applied to Facility:3.809 Total Evap From Facility:2.485 Outlet Control Overflow Height: 0.5 ft. Overflow width: 638 in. Element Flows To: Outlet 1 Outlet 2 CAVFS Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.0220 0.0000 0.0000 0.0000 0.1286 0.0220 0.0012 0.0000 0.0000 0.2571 0.0220 0.0023 0.0000 0.0000 0.3857 0.0220 0.0035 0.0000 0.0000 0.5143 0.0220 0.0047 0.0000 0.0000 0.6429 0.0220 0.0059 0.0000 0.0000 0.7714 0.0220 0.0070 0.0000 0.0000 0.9000 0.0220 0.0082 0.0000 0.0000 1.0286 0.0220 0.0095 0.0000 0.0000 1.1571 0.0220 0.0108 0.0001 0.9747 1.2857 0.0220 0.0121 0.0001 0.9747 1.4143 0.0220 0.0134 0.0002 0.9747 1.5429 0.0220 0.0147 0.0002 0.9747 1.6714 0.0220 0.0160 0.0003 0.9747 1.8000 0.0220 0.0172 0.0004 0.9747 1.9286 0.0220 0.0185 0.0006 0.9747 2.0571 0.0220 0.0198 0.0007 0.9747 2.1857 0.0220 0.0211 0.0008 0.9747 2.3143 0.0220 0.0224 0.0010 0.9747 2.4429 0.0220 0.0237 0.0012 0.9747 2.5714 0.0220 0.0250 0.0014 0.9747 2.7000 0.0220 0.0263 0.0017 0.9747 2.8286 0.0220 0.0276 0.0020 0.9747 2.9571 0.0220 0.0289 0.0023 0.9747 3.0857 0.0220 0.0302 0.0026 0.9747 3.2143 0.0220 0.0315 0.0029 0.9747 3.3429 0.0220 0.0327 0.0033 0.9747 3.4714 0.0220 0.0340 0.0037 0.9747 3.6000 0.0220 0.0353 0.0041 0.9747 3.7286 0.0220 0.0366 0.0045 0.9747 3.8571 0.0220 0.0379 0.0050 0.9747 3.9857 0.0220 0.0392 0.0055 0.9747 20047_101920 11/4/2020 2:10:51 PM Page 12 4.1143 0.0220 0.0405 0.0061 0.9747 4.2429 0.0220 0.0418 0.0066 0.9747 4.3714 0.0220 0.0431 0.0072 0.9747 4.5000 0.0220 0.0444 0.0079 0.9747 4.6286 0.0220 0.0457 0.0085 0.9747 4.7571 0.0220 0.0470 0.0092 0.9747 4.8857 0.0220 0.0482 0.0099 0.9747 5.0143 0.0220 0.0495 0.0107 0.9747 5.1429 0.0220 0.0508 0.0115 0.9747 5.2714 0.0220 0.0521 0.0123 0.9747 5.4000 0.0220 0.0534 0.0132 0.9747 5.5286 0.0220 0.0547 0.0141 0.9747 5.6571 0.0220 0.0560 0.0150 0.9747 5.7857 0.0220 0.0573 0.0160 0.9747 5.9143 0.0220 0.0586 0.0170 0.9747 6.0429 0.0220 0.0599 0.0180 0.9747 6.1714 0.0220 0.0612 0.0191 0.9747 6.3000 0.0220 0.0625 0.0202 0.9747 6.4286 0.0220 0.0637 0.0214 0.9747 6.5571 0.0220 0.0650 0.0226 0.9747 6.6857 0.0220 0.0663 0.0238 0.9747 6.8143 0.0220 0.0676 0.0251 0.9747 6.9429 0.0220 0.0689 0.0264 0.9747 7.0714 0.0220 0.0702 0.0278 0.9747 7.2000 0.0220 0.0715 0.0292 0.9747 7.3286 0.0220 0.0728 0.0306 0.9747 7.4571 0.0220 0.0741 0.0321 0.9747 7.5857 0.0220 0.0754 0.0336 0.9747 7.7143 0.0220 0.0767 0.0352 0.9747 7.8429 0.0220 0.0780 0.0368 0.9747 7.9714 0.0220 0.0793 0.0385 0.9747 8.1000 0.0220 0.0805 0.0402 0.9747 8.2286 0.0220 0.0818 0.0419 0.9747 8.3571 0.0220 0.0831 0.0437 0.9747 8.4857 0.0220 0.0844 0.0455 0.9747 8.6143 0.0220 0.0857 0.0474 0.9747 8.7429 0.0220 0.0870 0.0493 0.9747 8.8714 0.0220 0.0883 0.0513 0.9747 9.0000 0.0220 0.0896 0.0533 0.9747 9.1286 0.0220 0.0909 0.0554 0.9747 9.2571 0.0220 0.0922 0.0575 0.9747 9.3857 0.0220 0.0935 0.0596 0.9747 9.5143 0.0220 0.0948 0.0618 0.9747 9.6429 0.0220 0.0960 0.0641 0.9747 9.7714 0.0220 0.0973 0.0664 0.9747 9.9000 0.0220 0.0986 0.0687 0.9747 10.029 0.0220 0.0999 0.0711 0.9747 10.157 0.0220 0.1012 0.0736 0.9747 10.286 0.0220 0.1025 0.0760 0.9747 10.414 0.0220 0.1038 0.0786 0.9747 10.543 0.0220 0.1051 0.0811 0.9747 10.671 0.0220 0.1064 0.1445 0.9747 10.800 0.0220 0.1077 0.1445 0.9747 10.929 0.0220 0.1090 0.1445 0.9747 11.000 0.0220 0.1097 0.1445 0.9747 CAVFS Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 20047_101920 11/4/2020 2:10:51 PM Page 13 11.000 0.0220 0.1097 0.0000 1.1193 0.0000 11.129 0.0220 0.1125 0.0000 1.1193 0.0000 11.257 0.0220 0.1153 0.0000 1.1193 0.0000 11.386 0.0220 0.1182 0.0000 1.1193 0.0000 11.514 0.0220 0.1210 0.0000 1.1193 0.0000 11.643 0.0220 0.1238 0.0000 1.1193 0.0000 11.700 0.0220 0.1251 0.0000 1.1193 0.0000 20047_101920 11/4/2020 2:10:51 PM Page 14 CAVFS 1 Surface 1 Element Flows To: Outlet 1 Outlet 2 CAVFS 1 20047_101920 11/4/2020 2:10:51 PM Page 15 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:4.436 Total Impervious Area:0.054 Mitigated Landuse Totals for POC #1 Total Pervious Area:1.93 Total Impervious Area:1.55 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.022097 5 year 0.035407 10 year 0.047212 25 year 0.066301 50 year 0.084098 100 year 0.105474 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.000018 5 year 0.000025 10 year 0.00003 25 year 0.000038 50 year 0.000045 100 year 0.000052 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.062 0.000 1957 0.027 0.000 1958 0.016 0.000 1959 0.018 0.000 1960 0.021 0.000 1961 0.029 0.000 1962 0.022 0.000 1963 0.042 0.000 1964 0.019 0.000 1965 0.022 0.000 20047_101920 11/4/2020 2:11:18 PM Page 16 1966 0.014 0.000 1967 0.027 0.000 1968 0.016 0.000 1969 0.013 0.000 1970 0.015 0.000 1971 0.062 0.000 1972 0.185 0.000 1973 0.019 0.000 1974 0.027 0.000 1975 0.017 0.000 1976 0.018 0.000 1977 0.026 0.000 1978 0.024 0.000 1979 0.025 0.000 1980 0.017 0.000 1981 0.035 0.000 1982 0.034 0.000 1983 0.034 0.000 1984 0.021 0.000 1985 0.018 0.000 1986 0.019 0.000 1987 0.029 0.000 1988 0.014 0.000 1989 0.035 0.000 1990 0.018 0.000 1991 0.107 0.000 1992 0.021 0.000 1993 0.042 0.000 1994 0.021 0.000 1995 0.031 0.000 1996 0.045 0.000 1997 0.016 0.000 1998 0.028 0.000 1999 0.019 0.000 2000 0.016 0.000 2001 0.015 0.000 2002 0.011 0.000 2003 0.024 0.000 2004 0.024 0.000 2005 0.015 0.000 2006 0.014 0.000 2007 0.023 0.000 2008 0.014 0.000 2009 0.017 0.000 2010 0.029 0.000 2011 0.014 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1847 0.0001 2 0.1070 0.0000 3 0.0624 0.0000 4 0.0623 0.0000 5 0.0446 0.0000 6 0.0424 0.0000 7 0.0418 0.0000 8 0.0352 0.0000 20047_101920 11/4/2020 2:11:18 PM Page 17 9 0.0351 0.0000 10 0.0341 0.0000 11 0.0340 0.0000 12 0.0306 0.0000 13 0.0293 0.0000 14 0.0293 0.0000 15 0.0290 0.0000 16 0.0279 0.0000 17 0.0271 0.0000 18 0.0269 0.0000 19 0.0267 0.0000 20 0.0256 0.0000 21 0.0246 0.0000 22 0.0241 0.0000 23 0.0241 0.0000 24 0.0239 0.0000 25 0.0229 0.0000 26 0.0223 0.0000 27 0.0216 0.0000 28 0.0213 0.0000 29 0.0212 0.0000 30 0.0210 0.0000 31 0.0210 0.0000 32 0.0194 0.0000 33 0.0193 0.0000 34 0.0192 0.0000 35 0.0192 0.0000 36 0.0185 0.0000 37 0.0182 0.0000 38 0.0178 0.0000 39 0.0177 0.0000 40 0.0174 0.0000 41 0.0170 0.0000 42 0.0166 0.0000 43 0.0165 0.0000 44 0.0163 0.0000 45 0.0159 0.0000 46 0.0159 0.0000 47 0.0150 0.0000 48 0.0150 0.0000 49 0.0149 0.0000 50 0.0145 0.0000 51 0.0143 0.0000 52 0.0139 0.0000 53 0.0136 0.0000 54 0.0135 0.0000 55 0.0132 0.0000 56 0.0110 0.0000 20047_101920 11/4/2020 2:11:18 PM Page 18 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0110 1737 0 0 Pass 0.0118 1337 0 0 Pass 0.0125 1081 0 0 Pass 0.0133 843 0 0 Pass 0.0140 659 0 0 Pass 0.0147 527 0 0 Pass 0.0155 416 0 0 Pass 0.0162 355 0 0 Pass 0.0170 305 0 0 Pass 0.0177 262 0 0 Pass 0.0184 219 0 0 Pass 0.0192 185 0 0 Pass 0.0199 157 0 0 Pass 0.0206 143 0 0 Pass 0.0214 122 0 0 Pass 0.0221 109 0 0 Pass 0.0229 82 0 0 Pass 0.0236 70 0 0 Pass 0.0243 62 0 0 Pass 0.0251 53 0 0 Pass 0.0258 49 0 0 Pass 0.0265 47 0 0 Pass 0.0273 42 0 0 Pass 0.0280 36 0 0 Pass 0.0288 34 0 0 Pass 0.0295 29 0 0 Pass 0.0302 28 0 0 Pass 0.0310 26 0 0 Pass 0.0317 26 0 0 Pass 0.0324 24 0 0 Pass 0.0332 22 0 0 Pass 0.0339 22 0 0 Pass 0.0347 19 0 0 Pass 0.0354 15 0 0 Pass 0.0361 15 0 0 Pass 0.0369 15 0 0 Pass 0.0376 13 0 0 Pass 0.0383 12 0 0 Pass 0.0391 11 0 0 Pass 0.0398 11 0 0 Pass 0.0406 11 0 0 Pass 0.0413 10 0 0 Pass 0.0420 9 0 0 Pass 0.0428 8 0 0 Pass 0.0435 8 0 0 Pass 0.0443 8 0 0 Pass 0.0450 6 0 0 Pass 0.0457 6 0 0 Pass 0.0465 6 0 0 Pass 0.0472 6 0 0 Pass 0.0479 6 0 0 Pass 0.0487 6 0 0 Pass 0.0494 6 0 0 Pass 20047_101920 11/4/2020 2:11:18 PM Page 19 0.0502 6 0 0 Pass 0.0509 6 0 0 Pass 0.0516 6 0 0 Pass 0.0524 5 0 0 Pass 0.0531 5 0 0 Pass 0.0538 5 0 0 Pass 0.0546 5 0 0 Pass 0.0553 5 0 0 Pass 0.0561 4 0 0 Pass 0.0568 4 0 0 Pass 0.0575 4 0 0 Pass 0.0583 4 0 0 Pass 0.0590 4 0 0 Pass 0.0597 4 0 0 Pass 0.0605 4 0 0 Pass 0.0612 4 0 0 Pass 0.0620 4 0 0 Pass 0.0627 2 0 0 Pass 0.0634 2 0 0 Pass 0.0642 2 0 0 Pass 0.0649 2 0 0 Pass 0.0657 2 0 0 Pass 0.0664 2 0 0 Pass 0.0671 2 0 0 Pass 0.0679 2 0 0 Pass 0.0686 2 0 0 Pass 0.0693 2 0 0 Pass 0.0701 2 0 0 Pass 0.0708 2 0 0 Pass 0.0716 2 0 0 Pass 0.0723 2 0 0 Pass 0.0730 2 0 0 Pass 0.0738 2 0 0 Pass 0.0745 2 0 0 Pass 0.0752 2 0 0 Pass 0.0760 2 0 0 Pass 0.0767 2 0 0 Pass 0.0775 2 0 0 Pass 0.0782 2 0 0 Pass 0.0789 2 0 0 Pass 0.0797 2 0 0 Pass 0.0804 2 0 0 Pass 0.0811 2 0 0 Pass 0.0819 2 0 0 Pass 0.0826 2 0 0 Pass 0.0834 2 0 0 Pass 0.0841 2 0 0 Pass 20047_101920 11/4/2020 2:11:18 PM Page 20 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 20047_101920 11/4/2020 2:11:18 PM Page 21 LID Report 20047_101920 11/4/2020 2:11:22 PM Page 22 POC 2 POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run. 20047_101920 11/4/2020 2:11:22 PM Page 23 POC 3 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #3 Total Pervious Area:0.194 Total Impervious Area:0.792 Mitigated Landuse Totals for POC #3 Total Pervious Area:0.194 Total Impervious Area:0.792 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #3 Return Period Flow(cfs) 2 year 0.276182 5 year 0.373147 10 year 0.441074 25 year 0.531254 50 year 0.601654 100 year 0.674863 Flow Frequency Return Periods for Mitigated. POC #3 Return Period Flow(cfs) 2 year 0.276182 5 year 0.373147 10 year 0.441074 25 year 0.531254 50 year 0.601654 100 year 0.674863 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #3 Year Predeveloped Mitigated 1956 0.221 0.221 1957 0.391 0.391 1958 0.199 0.199 1959 0.265 0.265 1960 0.311 0.311 1961 0.241 0.241 1962 0.326 0.326 1963 0.449 0.449 1964 0.278 0.278 1965 0.261 0.261 1966 0.199 0.199 20047_101920 11/4/2020 2:11:48 PM Page 24 1967 0.225 0.225 1968 0.217 0.217 1969 0.194 0.194 1970 0.209 0.209 1971 0.215 0.215 1972 0.346 0.346 1973 0.243 0.243 1974 0.350 0.350 1975 0.247 0.247 1976 0.258 0.258 1977 0.374 0.374 1978 0.318 0.318 1979 0.360 0.360 1980 0.242 0.242 1981 0.504 0.504 1982 0.499 0.499 1983 0.498 0.498 1984 0.302 0.302 1985 0.233 0.233 1986 0.269 0.269 1987 0.292 0.292 1988 0.154 0.154 1989 0.514 0.514 1990 0.236 0.236 1991 0.616 0.616 1992 0.304 0.304 1993 0.622 0.622 1994 0.305 0.305 1995 0.407 0.407 1996 0.321 0.321 1997 0.191 0.191 1998 0.408 0.408 1999 0.258 0.258 2000 0.192 0.192 2001 0.190 0.190 2002 0.149 0.149 2003 0.309 0.309 2004 0.346 0.346 2005 0.215 0.215 2006 0.162 0.162 2007 0.306 0.306 2008 0.191 0.191 2009 0.224 0.224 2010 0.375 0.375 2011 0.183 0.183 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #3 Rank Predeveloped Mitigated 1 0.6216 0.6216 2 0.6161 0.6161 3 0.5140 0.5140 4 0.5038 0.5038 5 0.4986 0.4986 6 0.4981 0.4981 7 0.4491 0.4491 8 0.4083 0.4083 9 0.4073 0.4073 20047_101920 11/4/2020 2:11:48 PM Page 25 10 0.3906 0.3906 11 0.3749 0.3749 12 0.3743 0.3743 13 0.3604 0.3604 14 0.3502 0.3502 15 0.3462 0.3462 16 0.3459 0.3459 17 0.3264 0.3264 18 0.3212 0.3212 19 0.3176 0.3176 20 0.3113 0.3113 21 0.3094 0.3094 22 0.3061 0.3061 23 0.3054 0.3054 24 0.3036 0.3036 25 0.3018 0.3018 26 0.2922 0.2922 27 0.2782 0.2782 28 0.2694 0.2694 29 0.2653 0.2653 30 0.2606 0.2606 31 0.2584 0.2584 32 0.2579 0.2579 33 0.2475 0.2475 34 0.2425 0.2425 35 0.2423 0.2423 36 0.2414 0.2414 37 0.2362 0.2362 38 0.2326 0.2326 39 0.2251 0.2251 40 0.2244 0.2244 41 0.2213 0.2213 42 0.2170 0.2170 43 0.2149 0.2149 44 0.2148 0.2148 45 0.2089 0.2089 46 0.1990 0.1990 47 0.1990 0.1990 48 0.1935 0.1935 49 0.1919 0.1919 50 0.1913 0.1913 51 0.1913 0.1913 52 0.1899 0.1899 53 0.1835 0.1835 54 0.1624 0.1624 55 0.1540 0.1540 56 0.1493 0.1493 20047_101920 11/4/2020 2:11:48 PM Page 26 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.1381 2189 2189 100 Pass 0.1428 1960 1960 100 Pass 0.1475 1720 1720 100 Pass 0.1521 1510 1510 100 Pass 0.1568 1368 1368 100 Pass 0.1615 1195 1195 100 Pass 0.1662 1047 1047 100 Pass 0.1709 954 954 100 Pass 0.1756 856 856 100 Pass 0.1802 760 760 100 Pass 0.1849 688 688 100 Pass 0.1896 611 611 100 Pass 0.1943 551 551 100 Pass 0.1990 517 517 100 Pass 0.2036 467 467 100 Pass 0.2083 412 412 100 Pass 0.2130 361 361 100 Pass 0.2177 326 326 100 Pass 0.2224 301 301 100 Pass 0.2271 280 280 100 Pass 0.2317 264 264 100 Pass 0.2364 239 239 100 Pass 0.2411 219 219 100 Pass 0.2458 207 207 100 Pass 0.2505 193 193 100 Pass 0.2552 181 181 100 Pass 0.2598 168 168 100 Pass 0.2645 155 155 100 Pass 0.2692 144 144 100 Pass 0.2739 129 129 100 Pass 0.2786 116 116 100 Pass 0.2832 104 104 100 Pass 0.2879 99 99 100 Pass 0.2926 90 90 100 Pass 0.2973 79 79 100 Pass 0.3020 73 73 100 Pass 0.3067 67 67 100 Pass 0.3113 62 62 100 Pass 0.3160 58 58 100 Pass 0.3207 55 55 100 Pass 0.3254 50 50 100 Pass 0.3301 47 47 100 Pass 0.3348 43 43 100 Pass 0.3394 39 39 100 Pass 0.3441 36 36 100 Pass 0.3488 33 33 100 Pass 0.3535 31 31 100 Pass 0.3582 30 30 100 Pass 0.3628 28 28 100 Pass 0.3675 26 26 100 Pass 0.3722 25 25 100 Pass 0.3769 23 23 100 Pass 0.3816 21 21 100 Pass 20047_101920 11/4/2020 2:11:48 PM Page 27 0.3863 21 21 100 Pass 0.3909 21 21 100 Pass 0.3956 20 20 100 Pass 0.4003 19 19 100 Pass 0.4050 18 18 100 Pass 0.4097 16 16 100 Pass 0.4144 16 16 100 Pass 0.4190 15 15 100 Pass 0.4237 15 15 100 Pass 0.4284 14 14 100 Pass 0.4331 14 14 100 Pass 0.4378 14 14 100 Pass 0.4425 14 14 100 Pass 0.4471 14 14 100 Pass 0.4518 13 13 100 Pass 0.4565 13 13 100 Pass 0.4612 13 13 100 Pass 0.4659 13 13 100 Pass 0.4705 13 13 100 Pass 0.4752 13 13 100 Pass 0.4799 12 12 100 Pass 0.4846 11 11 100 Pass 0.4893 11 11 100 Pass 0.4940 11 11 100 Pass 0.4986 11 11 100 Pass 0.5033 9 9 100 Pass 0.5080 8 8 100 Pass 0.5127 8 8 100 Pass 0.5174 6 6 100 Pass 0.5221 6 6 100 Pass 0.5267 6 6 100 Pass 0.5314 6 6 100 Pass 0.5361 6 6 100 Pass 0.5408 6 6 100 Pass 0.5455 6 6 100 Pass 0.5501 5 5 100 Pass 0.5548 5 5 100 Pass 0.5595 4 4 100 Pass 0.5642 4 4 100 Pass 0.5689 3 3 100 Pass 0.5736 3 3 100 Pass 0.5782 3 3 100 Pass 0.5829 3 3 100 Pass 0.5876 3 3 100 Pass 0.5923 3 3 100 Pass 0.5970 2 2 100 Pass 0.6017 2 2 100 Pass 20047_101920 11/4/2020 2:11:48 PM Page 28 Water Quality Water Quality BMP Flow and Volume for POC #3 On-line facility volume:0.1051 acre-feet On-line facility target flow:0.1223 cfs. Adjusted for 15 min:0.1223 cfs. Off-line facility target flow:0.0695 cfs. Adjusted for 15 min:0.0695 cfs. 20047_101920 11/4/2020 2:11:48 PM Page 29 LID Report 20047_101920 11/4/2020 2:11:48 PM Page 30 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 20047_101920 11/4/2020 2:11:48 PM Page 31 Appendix Predeveloped Schematic 20047_101920 11/4/2020 2:11:50 PM Page 32 Mitigated Schematic Appendix 3 Soils Report Mountain Meadows Soils Report For Evaluating Site Feasibility of Stormwater Infiltration BMP’s Associated with Roof, Driveway and Road Runoff. Site Address: 8818 Burnett Road SE, Yelm WA 98597 TPN: 21713310400 Prepared For: Henrietta Morey PO Box 202 Kapowsin, WA 98344 Contact: Henrietta Morey (253) 377-8400 moreyrealestate@gmail.com Prepared By: Parnell Engineering, LLC 10623 Hunters Lane S.E. Olympia, WA 98513 Contact: William Parnell, P.E. (360) 491-3243 parnelleng@hotmail.com PE PARNELL ENGINEERING, LLC SOIL EVALUATION REPORT FORM l: GENERAL SITE INFORMATION PROJECTTITLE:MountainMeadows SHEET:1OFl ` PEPROJEC丁NO∴20125 DATE:9/18/2020 PREPAREDBY:W冊amPa「neIi,P.E. 1.SiTEADDRESS:8818BumettRoadSE,YelmWA98597 TPN:21713310400 2.PROJECTDESCRIPTION:ProposedpIat. 3.SiTEDESCRIPTION:The2.89ac「eir「egula「shapedp「ojectsiteiscu「「entlyuno∞uPiedbyanybuiiding St「uCtu「eS.Site「eliefisgentIysIopingf「omeasttowest,Va「γingineIevationf「om340ft.atthenortheast P「OPe「tyCOme「tO328ft.aiongthewestp「opertyline.Sitevegetationconsistsofpastureg「assesandscotch bloomwithafewconifert「eesatthesouthwestp「opertyco「ne「.Theprojectsiteisboundedtothewestby Bu「nettRoadSEandresidentialp「opertytothenorth,eaStandsouth.Theon-Sitesoilsaremappedbythe Natu「alResourceConservationService(NRCS)asaweil-d「ainedSpanawayg「aveiIysandyloam(110) fo「medinvoicanicashovergrave=youtwash. 4.SUMMARYOFSOILSWORKPERFORMED:Twotestpitswe「eexcavatedbytrackhoetoamaximum depthof168’’beiowtheexistinggrade.Soilswe「einspectedbyente「ingandvisuallyloggingeachtestpitto adepthoffou「feet.SoiIsbeyondfourfeetwereinspectedbyexaminingbackhoetailings.Soiisampieswe「e takenfromtestpit#1and#2atlO8’’beIowtheexistinggrade.G「ainsizeanaIysismethodwasusedto dete「minethesuitab=ityofthe「ep「esentativesoiIhorizonsforstormwaterin凧t「ationfac冊es.Aninitial Satu「atedhyd「auIicconductivity(Ksat)wascaicuiatedandthenreducedbyco「「ectionfactors(CFT)to PrOduceanadjusteddesigninf冊「ation「ateKsatdesignforfac冊ysizingpu「poses.Testpitso旧ogdatasheets andg「ainsizeanaIysisdatawithKsatcaIculationsa「eincIudedinthis「eport. 5.ADDITIONALSOiLSWORKRECOMMENDED:Additionaisoilswo「kshouidnotbenecessa「y, 6.FINDiNGS:Theon-SitesoilsaremappedbyNRCSasaSpanawaygrave=ysandyloam(110).Testpits 「eveaIedsoiisconsistentofaSpanawayse「ieswithst「atumsoiisp「o輔ngave「yg「ave=yandcobbledfine SandyIoamove「lyinganext「emelygraveIiyandcobbledloamycoa「se高nesand.Winterwate「tabIewasnot PreSentandpossibIeindicatorswe「enotobvious.ThesoiIgrainsizeanaiysismethod「esuitedinadjusted KsatdesignvaluesforthefoiIowingsampIes:Testpit#1atlO8’’belowtheexistingg「ade-38.27in/hr,teStPit #2atlO8’’beIowtheexistinggrade-55.4in/hr. 7.RECOMMENDATIONS:TheSpanawayseriessoiisaresomewhatexcessivelydrainedsoiIsfoundon OutwaShpIainsfo「medinvoIcanicashoverg「ave=youtwash,in輔「ation「atesa「egeneraily「apidinthe SubstratumsoiIs.GrainsizeanaIysismethodresultedinadjustedKsatdesignvaiues>20in/h「.Fo「thetargeted Cho「izonsoiIs言tis「ecommendedKsatdesign(F)vaIuesdonotexceed20inlhr.Please「efe「totheattached SOiig「adationtest「esuItswithKsatdesigncaicuiations,aSSOCiatedindividualsoi=ogdatasheetsandtestpit/so旧og Iocationmap. Du「ingconst「uction,CaremuStbetakentop「eventthee「osionofexposedsoiIs.Sto「mwaterd「ainagefacility in輔「ationsu「facesmustbeproperIyprotectedfromcontaminationbythe血e-graineduppe「ho「izonsoiIs andfromcompactionbyconst「uctionsiteactivities.SoiIsnotp「operiyprotectedmaycausestormwate「 d「ainageinfilt「ationfac冊estonotperformasintended. Ihe「ebycertifythatIprepa「edthisreport,andconductedorsupervisedtheperfo「manceofreIatedwo「k"I 一 醗 雷 の 態繭 〇〇〇葛"葛「-○○ SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Mountain Meadows SHEET: 1 OF 2 PROJECT NO.: 20125 DATE: 9/16/2020 PREPARED BY: William Parnell, PE SOIL LOG: #1 LOCATION: 40 ft. north and 20 ft. east of the southwest property corner. (see attached site plan map) 1. TYPES OF TEST DONE: Grain size analysis 2. NRCS SOILS SERIES: Spanaway gravelly sandy loam (110) 3. LAND FORM: Outwash plain 4. DEPOSITION HISTORY: Volcanic ash over gravelly sand 5. HYDROLOGIC SOIL GROUP: A 6. DEPTH OF SEASONAL HW: Unknown 7. CURRENT WATER DEPTH: Greater than bottom of hole 8. DEPTH TO RESTRICTIVE HORIZONS: Greater than bottom of hole 9. MISCELLANEOUS: Gently sloping 10. POTENTIAL FOR: EROSION RUNOFF PONDING Slight Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: Roots were present to 60”. Use a design infiltration rate < 20 in/hr in the C horizon soils. Soils Strata Description Soil Log #1 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0”- 14” 10YR3/2 VGrCob SaLm some stones <15 <12 <45 1SBK - - - ff 2-6 4 Bw 14”- 18” 10YR3/4 VGrCob SaLm some stones <12 <8 <45 SG - - - ff 2-6 6 C1 18”- 60” 10YR5/4 ExGrCobC- FSa some stones <2 - <85 SG - - - ff >20 <20 C2 60”- 85” 10YR5/2 ExGrCobC- FSa some stones <2 - <85 SG - - - - >20 <20 C3 85”-168” 10YR5/2 ExGrcobM- FSa some stones <2 - <85 SG - - - - >20 <20 SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Mountain Meadows SHEET: 2 OF 2 PROJECT NO.: 20125 DATE: 9/16/2020 PREPARED BY: William Parnell, PE SOIL LOG: #2 LOCATION: 40 ft. north and 80 ft. east of the southwest property corner. (see attached site plan map) 1. TYPES OF TEST DONE: Grain size analysis 2. NRCS SOILS SERIES: Spanaway gravelly sandy loam (110) 3. LAND FORM: Outwash plain 4. DEPOSITION HISTORY: Volcanic ash over gravelly sand 5. HYDROLOGIC SOIL GROUP: A 6. DEPTH OF SEASONAL HW: Unknown 7. CURRENT WATER DEPTH: Greater than bottom of hole 8. DEPTH TO RESTRICTIVE HORIZONS: Greater than bottom of hole 9. MISCELLANEOUS: Gently sloping 10. POTENTIAL FOR: EROSION RUNOFF PONDING Slight Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: Roots were present to 28”. Use a design infiltration rate < 20 in/hr in the C horizon soils. Soils Strata Description Soil Log #2 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0”- 20” 10YR3/2 VGrCob SaLm some stones <15 <12 <40 1SBK - - - ff 2-6 4 Bw 20”- 28” 10YR3/4 VGrCob SaLm some stones <12 <8 <50 SG - - - ff 2-6 6 C1 28”- 68” 10YR5/4 ExGrCobM- FSa some stones <2 - <85 SG - - - ff >20 <20 C2 68”-168” 10YR5/2 ExGrCobM- FSa some stones <2 - <85 SG - - - - >20 <20 Abbreviations Textural Class (Texture) Structure (STR) Grades of Structure Cobbled - Cob Granular - Gr Strong - 3 Stoney - St Blocky - Blky Moderate - 2 Gravelly - Gr Platy - Pl Weak - 1 Sandy - Sa Massive - Mas Loamy - Lm Single Grained - SG Silty - Si Sub-Angular Blocky - SBK Clayey - Cl Coarse - C Very - V Extremely - Ex Fine - F Medium - M Induration & 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 Many - m Coarse - c <X> - Generalized range of infiltration rates from NRCS soil survey (<X>) FSP - Estimated Design Field Saturated Percolation rate based on horizon specific factors and specific test results. MountainMeadows 1 90 80 くの ∽ の ∈70 」 ○ 言60 掌 主50 D ⊂ 紛40 く○ ○. 宣30 の し20 10 0 C 」 i i l i I I 0.001 N i i I ) l i TestPit♯1atlO8’. \ i ● Sampiel i i l i l 100 10 1Samplel O.1 0.01 i obb i GバブVel 上辺nd i 鋤 ′ Coo糖e ん花柄朋 i 筋e Ksat Ca!culations Test pit#1 - SamPle #1 taken at lO8’’beiowthe existing grade Soil G「adation丁est Resuits: DlO = 0.31 D60 = 8.5 D90 =19.0 簡nesこ 0.0117 loglO (Ksat) = -1.57 + 1.90 (DlO) + 0.015 (D60)一0.013 (D90)- 2.08 (怖nes) IoglO(K艶t)=-1.57十1.90(0.31)十0.015 (8.5)-0.013 (19.0主2.08(0.0117)=-1.1248 Ksat = 0.0750 cmIs Ksat= 0.0750 cm/s xO.3937 in/cm x60 s/min x60 min/h「 Ksat= 106.32 inIhr Final Desi0n Infi!tration Rate CalcuIation : Ksat desian Ksat design = Ksat initfal X CFT Ksa白nitiai = 106.32 in/h「 CFT (Total Co汀eCtion Facto「- July 2016 SWMM) = CFvx CFtx CFm CFv = 1.0 (two tests pits, nO SOil variabiiity〉 CFt = 0.4 (g「ain size method) CFm = 0.9 (S航ation & biofouling) CF丁=1.OxO.4xO.9 Ksat desisn = Ksat initfai X CFT Ksatdesisn = 106.32 in仙「x l.OxO.4xO.9 Ksatdesisn = 38.27 in/h「 For stormwate「 fac冊y design purposes, uSe a Ksat design㈲三20 in/h「 MountainMeadows 3I4 3I8 4∴∴∴∴10 20 40 60 100 200 100 90 80 ∽ の くo E70 ○ 言60 筆 舌50 の ⊂ 総40 (o ⊂し 宣30 α) 直20 10 0“ C \ i l )i i i l i 0.001 " " 曇 ト l 1 l ) i ll l !TestPit#2atlO8.一 \ l・Samp-e2 " " " m m ○ 葛 S 喜 " 置 暮 菓 " m " S 喜 ○ " " " ○ 暮 ! I 100 10 1Sample2 0.1 - 0・01 bb G月ovel 上か〃d l s′〃 ′ Coa鵬e ん花dllm 」照ne Ksat Ca看cu看ations Test pit#2 - SamPIe #2 taken at lO8一一below the existing g「ade Soil G「adation丁est ResuIts: DlO = 0.35 D60 = 7.4 D90 =11.2 怖nes= 0.0128 loglO (Ksat) =一1.57 + 1.90 (DlO) + 0.015 (D60) - 0.013 (D90) -2.08 (ffines) iog「O (庵at)こ-1.57十1.90 (0.35)十0.015 (7.4)一0・013 (11・2) -2・08 (0・0128)こ-0・9662 Ksat= 0.1081 cm/s Ksat= 0.1081 cm/s x O.3937 in/cm x60 s/min x 60 min仙「 Ksat= 153.19 in/hr E吐宣IPesian In冊t「ation Rate Caicuiation : K8at desicIn Ksat design = Ksat initial X CFT KsatinitiaI = 153.19 in/hr CFT (Total Correction Factor - Juiy 2016 SWMM) = CFvx CFtxCFm CFv = 1.0 (two tests pits, nO SO= variabiirty) CFt = 0.4 (grain size method) CFm = 0.9 (S冊ation & biofouIing) CFT=1.OxO.4×0.9 Ksat design = Ksat initiaI X CFT Ksatdesign = 153.19 in川「× 1.O x O.4 xO.9 Ksatdesisn = 55.4 in仙r Fo「 stormwate「 fac岬y design purposes, uSe a Ksat desisn(F) ≦ 20 in仙 星星星星星星 ∀M M「]人 :曲塵皿瞭Idd- 一存灰汁7T￣ :Ⅱ∀0 帖 ▲害すo齢▼○○劃す動きH ⊥Y「d▲日▼NI動1「さすd 日量州か鳩舶陸棚1鴫格l蝿噌寝的 ￣剥調 蜘 強調りn櫨I蝕100櫨館腰山勘Ⅳ .飢7こ.し:「∀〇S :人80う納0ヨHO :人らiNM∀的 NV「d∃OYNIV曽q音o軸▼ S」議〇回V∃動軸i▼⊥Nno軸 ▲⊥i「i⊥∩ 大鶴V軸iいi〃「ささd NolSいう轡 〕⊥∀0 ●ON 画 国書臆園田 \ そ〕 \ uつ //