Loading...
HomeMy WebLinkAboutSWP272314(1) . r reinConsulting Engineers Drainage Report Hunter Douglas, Inc. Renton, WA .. SI�� 4) pp�11 N „ANAL EXPIRES 10/10 f $ Prepared For: Hunter Douglas, Inc. 7015 S. 212th St. Kent, WA 98032 (206) 8724109 Contact: Allen Tosch 206) 622-6322 F2x ["06: 622-3130 Seattle Portland San Francisco Los Angeles Phoenix San Diego SECTION I (Project Overview) KPFF Consulting Engineers 1 wAlcivil\hd.er\ann\word\drainrpt.doc General Project Description The subject property is located near the southwest corner of the intersection between Raymond Avenue SW and SW 19th Street in Renton, Washington. The site is bounded on the north by the unconstructed right-of-way for SW 19th Street, on the east by Springbrook Creek, on the south by the unconstructed right-of-way for SW 23rd Street, and on the west by private property owned by the Boeing Company (formerly Longacres Race Track). The subject property consists of 14.15 acres and is a part of the Renton valley. A Class III wetland (Wetland "B"), which encompasses approximately 4.2 acres, is located at the southern end of the site. The Sensitive Map Folio identifies Springbrook Creek as a Class 11 stream with salmonids. Due to building restrictions related to surface water, the actual buildable area is limited to areas north of the wetland and west of the creek. The existing site topography consists of relatively flat terrain that generally declines in elevation to the west. Moderate to steep slopes can be found along the banks of Springbrook Creek and also within areas in Wetland "B." The average slope throughout the proposed site (buildable area) is approximately 1 percent and has a maximum topographic rise of 3 feet. Presently, most of the on-site vegetation consists of sparse grass and bushes. The easternmost portion of the site (along the banks of Springbrook Creek) is lightly wooded with small alder trees. The geotechnical report provided by Earth Consultants has identified silty sand, peat and silt in their field observations. Based on the Soil Conservation Service mapping of the area (i.e., King County Soil Survey), the on-site soil consists of primarily Puyallup fine sandy loam (Hydrologic Soil Group B). However, there are smaller areas along the western portion of the property where the soil composition consists of urban land soils (variable hydrologic soil type). The geotechnical report also indicated that the groundwater table is approximately 12 - 15 feet below existing surface elevations. The proposed Hunter Douglas development is a commercial project planned for warehouse, office and manufacturing use. The project area consists of roughly 7.4 acres. The development of the property will incorporate a I-story, 114,000-square foot building with dock high service. Associated paved parking areas and internal roadways will accommodate future service activities. The primary site access will be provided from Raymond Street. A concrete bridge crossing Springbrook Creek will be constructed to connect the site with its primary access road. In addition, an emergency vehicle access road will be constructed through the Boeing property and will enter the site along the west property line. The new facility is planned to be available for occupancy in the fall of 1997. KPFF Consulting Engineers 2 w:\lcivil\hd.er\ann\word\drainrpt.doc Based on the King County Surface Water Design Manual, the project site is located within the Black River subbasin of the Green River drainage basin. It is also a part of the Green River community planning area. Properties within these areas are not subject to any P-suffix development standards. Existing Drainage System Presently, stormwater runoff sheetflows overland towards the east. Due to the pervious nature of the on-site soils, it is assumed that some stormwater is directly infiltrated into the ground. The remaining surface water appears to either flow into the existing wetland or into Springbrook Creek. Wetland "B" forms an integral part of the property's natural drainage system, as it serves as the site's existing retention/detention and conveyance system. Wetland "B" has been classified as a Class III wetland. A 25-foot Native Growth Protection Easement (NGPE) will be provided to protect the existing habitat from the effects of the new development. The wetland will remain undeveloped. Presently, the wetland collects and conveys runoff (via an existing 36-inch pipe) to Springbrook Creek. Both on-site and off-site areas contribute flows to the wetland. Off-site runoff enters the subject property (via an existing 36-inch pipe) along its western boundary. Springbrook Creek basically forms the eastern boundary of the project site. It is a part of the East Side Green River Watershed Project (ESGRWP). The ESGRWP is a comprehensive public improvement project which will attempt to resolve existing flooding problems, prevent future flooding problems, and improve the environmental resources in the Renton valley area. The City of Renton is currently performing hydrologic studies of the watershed tributary to Springbrook Creek. Based on this analysis, the City will be able to accurately identify/predict existing and future creek flows. At the present time, a portion of the proposed site is within FEMA's 100-year floodplain (elevation = 19.6 feet) delineation for Springbrook Creek. According to our calculations, approximately 92,000 cubic feet of compensatory floodplain storage will have to be provided on-site. However, due to the City's future channel widening project, no compensatory storage will be provided by the proposed development. A City of Renton letter addressing this issue is enclosed in Section VIII of this report. KPFF Consulting Engineers 3 w:\lcivil\hd.er\ann\word\drainrpt.doc Proposed Drainage System The stormwater management plan for the proposed project consists of a 2-celled combination wet pond/detention pond and a conveyance system consisting of a series of underground pipes. The combination wet pond/detention pond will serve to provide both water quality treatment and streambank erosion control. The pond has been designed to provide 46,433 ft' of live storage and 23,560 ft; of dead storage. The design of all stormwater drainage facilities is based on standards outlined in the "Stormwater Management Manual for the Puget Sound Basin" (February 1992), prepared by the Department of Ecology. A more detailed description of the proposed drainage system is provided in subsequent sections. Downstream Basin Analysis The downstream drainage system for the subject property consists of Springbrook Creek. As previously mentioned, the City of Renton is performing hydrologic studies of the creek and, therefore, has indicated a downstream analysis of the creek is not required. Flows discharged from the proposed detention facility during post-developed conditions are limited to the peak rate of runoff during predeveloped site conditions and, consequently, is not expected to negatively impact the downstream drainage system. KPFF Consulting Engineers 4 w:\lcivil\hd.er\ann\word\drainrpt.doc SECTION II (Core and Special Requirements Summary) KPFF Consulting Engineers 5 w:\lcivil\hd.er\ann\word\drainrpt.doc Core and Special Requirements Summary The intent of this section is to address the core and special requirements set forth by the King County Surface Water Design Manual and the requirements of the most recent Sensitive Areas Ordinance (SAO) that pertain to the project. Each requirement will be listed with a brief statement explaining how the design addresses or conforms to the conditions. Core Requirements 1.2.1 Discharge at the Natural Location Presently, stormwater runoff from the site either flows to the east and outfalls into Springbrook Creek, or flows to the south and outfalls into the existing wetland. The proposed detention system will discharge developed flows at a controlled rate into Springbrook Creek to match existing runoff conditions. 1.2.2 Off-Site Analysis The City of Renton is currently analyzing existing and future flows within Springbrook Creek and has indicated a downstream analysis will not be required for this project. Flows discharged from the detention facility during post- developed conditions are limited to the peak rate of runoff during predeveloped site conditions and, therefore, will not negatively impact the downstream drainage system. 1.2.3 Runoff Control Developed flows from the detention facility will be discharged into Springbrook Creek. Although the site is located within Renton's city limits (which has adopted the King County Surface Water Design Manual for its drainage requirements and policies), the Department of Fisheries is the governing agency that has jurisdiction over discharge of developed runoff into any fish-bearing stream (i.e., Springbrook Creek). The Department of Fisheries has adopted the Washington State Department of Ecology's (DOE) Stormwater Management Manual (February 1992) for its drainage requirements and policies. Therefore, the detention system has been designed to adhere to the requirements outlined by the Department of Ecology. The detention requirements are as follows: a. Release 50 percent of the existing peak runoff rate or less during the 2-year, 24-hour design storm event. b. Release the existing peak rate runoff rate or less during the 10-year, 24-hour design storm event. KPFF Consulting Engineers 6 w:\lcivil\hd.er\ann\word\drainrpt.doc a c. Release the existing peak rate runoff rate or less during the 100-year, 24-hour design storm event. These requirements exceed those established by King County. 1.2.4 Conveyance System Closed pipe systems will be designed to convey and contain the peak runoff rate for the 25-year design storm. Structures for pipe systems will have a minimum of 0.5 feet of freeboard between the hydraulic grade line and the top of the structure for the 25-year peak rate of runoff. 1.2.5 Erosion/Sedimentation Control Plan Erosion control measures are outlined in Section VII. Special Requirements These "Special Requirements" are in addition to the seven core requirements and must be met when the threshold applies to this project. 1.3.1 Critical Drainage Areas The project site is not located within a critical drainage area. 1.3.2 Compliance with an Existing Master Drainage Plan There are no master drainage plans covering the project site. 1.3.3 Conditions Requiring a Master Drainage Plan This project does not require a master drainage plan. 1.3.4 Adopted Basin or Community Plans This project lies within the Green River community planning area and falls under the jurisdiction of the City of Renton. There is no adopted basin plan at this time. KPFF Consulting Engineers 7 w:\Icivil\hd.er\ann\word\drainrpt.doc 1.3.5 Special Water Quality Controls The project will increase impervious area subject to vehicular use by more than one acre and, therefore, a wet pond or water quality swale is required. The final design proposal for the site will include a wet pond designed to the Department of Ecology's standards. These standards will provide a facility that will at least double the King County volume requirements. This project has obtained a code alteration modification to receive credit for providing more wet pond volume than that required by King County. For this reason, the City of Renton has waived the requirement for a biofiltration swale pertaining to this project. 1.3.6 Coalescing Plate Oil/Water Separators The project will not increase impervious area subject to vehicular use (3.03 acres) by 5 acres or more within the drainage basin. Therefore, a coalescing oil/water separator is not required. 1.3.7 Closed Depressions The project is not tributary to any closed depressions. 1.3.8 Use of Lakes, Wetland, or Closed Depressions for Peak Runoff Control The project will not use a lake, wetland or closed depression for peak runoff control. 1.3.9 Delineation of 100-Year Floodplain See Appendix "D." 1.3.10 Flood Protection Facilities for Classes I and II Streams There are no existing or proposed flood protection facilities for Classes I or H streams within the project. 1.3.11 Geoetchnical Analysis and Report The geotechnical analysis and report for this project has been prepared by Earth Consultants ("Geotechnical Engineering Study," August 19, 1996). A copy of the report will be available upon request. KPFF Consulting Engineers 8 w:\lcivil\hd.er\ann\word\drainrpt.doc 1.3.12 Soils Analysis and Report The soils in the project area have been mapped and identified in the King County Soil Survey using SCS classifications. In addition, the geotechnical report prepared by Earth Consultants contains a detailed description and analysis of the on-site soils. KPFF Consulting Engineers 9 w:\lcivil\hd.er\ann\word\drainrpt.doc Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET OWNERPART 1 PROJECT AND PART 2 PROJECT LOCATION - . . . x Project Owner r I I Project Name Pyry4b.- vC,1cLS, Jr,[ Address 1015 S. 212."' S Q Location Phone (206) '572-4109 � Township 231� Proiect Engineer MarJL�. Vel dee, I Range ' Section 2 Company ILPFF Co Syl4i Project Size 7.4 AC Address Phone Cz06) b?2- 23� I Upstream Drainage Basin Size AC PART3 TYPE • • . �- • �• I � Subdivision DOF/G HPA Shoreline Management I Short Subdivision U COE 404 Rockery Grading 1-7 DOE Dam Safety a Structural Vaults Commercial i 17—. FEMA Floodplain Other Other �r,dVg•�•r,�) I � HPA COE rVeUands PART 5 SITE COMMUNITY AND DRAINAGE BASIN Community � �reer, TZ.IJer' I j Drainage Basin S r t n River Floodplain Stream 5pr-i!L-,A bnck= Cre-eV- Wetlands C IC SS Critical Stream Re ch 0 Seeps/Springs Cepressicns/Swales High Groundwater Table Lake Cj Groundwater Recharge Steep Slopes Other Lakeside/Erosion Hazard Soil lType lopes Erosion Potential Erosive Velocities urbQyl �Y1 � ��O I I u Additional Sheets Attatched 1/90 Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 MELOPMENT 1.11111111TATIONS REFERENCE LIMITATION/SITE CONSTRAINT Ch.4-Downstream Analysis L—: I Additional Sheets Attatched MINIMUM ESC REQUIREMENTS MINIMUM ESC REOUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION Sedimentation Facilities Stabilize Exposed Surface Stabiiized Construction Entrance Remove and Restore Temporary ESC Facilities Perimeter Runoff Control C:ean and Remove All Silt and Debris Cieanng and Grading Restrictions Ensure Ooeration of Permanent Facilities Cover Practices Flag Limits of NGPES LWI Construction Sequence Other Other SURFACEPART 10 E• SYSTEM I—J Grass Lined Channel Tank Infiltration Method of Analysis Pipe System Vault 7— Depression SCS Tyfle I A Open Channel Energy Dissapator Flow Dispersal Compensation/Mitigaticn X Dry Pond Wedand Waiver of Eliminated Site Storage Wet Pond Stream Regional Detention N OnQ. Brief Description of System Operation �.QI�hIr�Go✓1 We P�k 4 4(or1 Pare _UJI �Socla4-ed cr)n✓e�r ' Facility Related Site Limitations C Additional Sheets Attatched Reference Facility Limitation PART 11 STRUCTURAL ANALYSIS PART 12 EASENIENTS/TRACTS require special structural review) Drainage Easement Cast in Place Vault 0 Other 0 Access Easement Retaining Wall Native Growth Protection Easement I� Rockery>4'High Tract Structural on Steep Slope Other PART 14 SIGNATURE OF . • • I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attatchments. To the best of my knowledge the information provided here is accurate. sq,,.eo�• SECTION III (Retention/Detention Analysis and Design) KPFF Consulting Engineers 10 w:\lcivil\hd.er\ann\word\drainrpt.doc Procedure for Basin Runoff Analysis The following 'Basin Summary" section lists the specific design parameters and associated references to derive the stormwater runoff values for both the predeveloped and post-developed basin conditions. The computational steps outlined below have been applied to obtain the existing and developed basin runoff quantities for up to the 100- year, 24-hour design storm event: 1. Identify and delineate the overall drainage basin for each discharge point from the development site under existing conditions. • Identify existing land uses. • Identify existing soil types using SCS soil survey or on-site evaluation. • Identify existing drainage features (i.e., streams, depressions, etc.). 2. Select and delineate pertinent subbasins based on existing conditions. • Select separate subbasins for on-site and off-site drainage. • Select separate subbasins for major drainage features. 3. Determine runoff parameters for each subbasin under existing conditions. • Identify pervious and impervious areas. • Select CN values based on soil type and land use. • Compute the time of concentration for each basin analyzed. 4. Compute existing runoff hydrographs based on basin characteristics and appropriate design storms for each subbasin. 5. Repeat Steps 1 - 4 for the detained basin. Basin Summary The following pages give a point-by-point listing of the input parameters for the hydrologic analysis of the existing and developed runoff conditions to design the detention system. The SCS Hydrograph Method with Type IA rainfall distribution has been used in the analysis. The computer program "Waterworks 4.1 Id" has been used to develop and manipulate hydrographs. The supporting calculations are provided at the end of this section. KPFF Consulting Engineers ]1 w:\lcivil\hd.er\ann\word\drainrpt.doc Based on the King County Soil Survey, the on-site soils consists of a combination of Puyallup fine sandy loam and urban land soils. The Soil Conservation Service classifies Puyallup soils in the "B" hydrologic group and states that urban land soils have a variable hydrologic soil characteristic. Due to the hydrologic soil variability of urban land soils, a hydrologic soil group of "B" was assumed to perform the analysis for the proposed stormwater drainage system. KPFF Consulting Engineers 12 w:\lcivil\hd.er\ann\word\drainrpt.doc BASIN SUMMARY I. Existing Basin Conditions A. Total Basin Area= 7.36 acres 1. Pasture = 7.36 acres B. Soil Type 1. Puyallup Fine Sandy Loam: Hydrologic Soil Group "B" 2. Urban Land: Hydrologic Soil Group Variable Due to the hydrologic soil variability of urban land soils, a hydrologic soil group of "B" was assumed for the analysis. C. CN Values 1. Pasture: CN = 78 D. Time of Concentration Travel Path 1. Sheetflow: 300 LF (pasture) @ S = (20-18)/480 = 0.4% 2. Shallowflow: 210 LF (pasture) @ S = 0.4% E. Precipitation 1. 2-Year, 24-hour Design Storm = 2.0" 2. 10-Year, 24-hour Design Storm = 2.9" 3. 100-Year, 24-hour Design Storm = 3.9" II. Developed Basin Conditions A. Total Basin Area= 7.36 acres 1. Pervious Areas (i.e., lawn, landscaping, etc.) = 1.41 acres 2. Impervious Areas (i.e., parking, roadway, rooftops, etc.) = 5.95 acres KPFF Consulting Engineers 13 w:\lcivil\hd.er\ann\word\drainrpt.doc B. Soil Type 1. Puyallup Fine Sandy Loam: Hydrologic Soil Group "B" 2. Urban Land: Hydrologic Soil Group Variable Due to the hydrologic soil variability of urban land soils, a hydrologic soil group of "B" was assumed for the analysis. C. CN Values 1. Pervious Areas: CN = 80 2. Impervious Areas: CN = 98 D. Time of Concentration Travel Path 1. As a practical limit for developing hydrographs, a time of concentration of 5 minutes for pervious and impervious areas was assumed for the hydrologic basin analysis. E. Precipitation 1. 2-Year/24-Hour Design Storm= 2.0" 2. 10-Year/24-Hour Design Storm= 2.9" 3. 100-Year/24-Hour Design Storm= 3.9" Note: All areas shown in the Basin Summary have been obtained using the AutoCAD software program. KPFF Consulting Engineers 14 w:\lcivil\hd.er\ann\word\drainrpt.doc Detention Requirement Developed flows from the detention facility will be discharged into Springbrook Creek. Although the site is located within Renton's city limits (which has adopted the King County Surface Water Design Manual for its drainage requirements and policies), the Department of Fisheries is the governing agency that has jurisdiction over discharge of developed runoff into any fish-bearing stream (i.e., Springbrook Creek). The Department of Fisheries has adopted the Washington State Department of Ecology's (DOE) Stormwater Management Manual (February 1992) for its drainage requirements and policies. Therefore, the detention system has been designed to adhere to the requirements outlined by the Department of Ecology. The performance of the site's stormwater detention system must comply with the following requirements: a. Release 50 percent of the existing peak runoff rate or less during the 2-year, 24- hour design storm event. b. Release the existing peak runoff rate or less during the 10-year, 24-hour design storm event. c. Release the existing peak runoff rate or less during the 100-year, 24-hour design storm event. Detention System Analysis and Design The entire subject property will not be developed. Due to the existing wetland and stream, the project area will comprise of 7.36 acres of the northwest corner of the site. The effective existing drainage basin included in the hydrologic analysis only includes areas that will be altered by the proposed development. Based on the existing topographic survey information of the adjoining properties, there is no off-site runoff tributary to the proposed detention system. Under post-developed conditions, 1.41 acres of pervious and 5.95 acres of impervious area will contribute flows to the detention facility. Based on the site layout and grading, no areas will bypass the detention system. The stormwater runoff from the bridge crossing Springbrook Creek will be tributary to the detention/wet pond system for the Opus site (i.e., Springbrook Industrial Center which is located east of the subject property). The proposed bridge will slightly change the predeveloped conditions of this area and will not significantly impact the existing Opus system. The Opus stormwater management system was designed based on the requirements defined by the Department of Ecology, which is more stringent than that required by the City of Renton. To show that the additional runoff from the bridge can be adequately detained by the Opus pond, a basin runoff analysis of the bridge has been performed. The results of this analysis is compared (by flow rate) with the designed performance of the Opus detention system, which is shown in the following table: KPFF Consulting Engineers 15 w:\lcivil\hd.er\ann\word\drainrpt.doc Bridge Opus Det. Ratio of Opus Det. Renton Stormwater Inflow Col. 1/ Allowable Allowable Runoff Rate Rate (cfs) Col. 2 Release Rate - Release Rate (cfs) (%) DOE (cfs) (cfs) 2-year, 24-hour 0.05 2.05 2.44 0.16 0.31 Design Storm 10-year, 24-hour 0.08 3.08 2.60 0.89 0.89 Design Storm 100-year, 24-hour 0.10 4.22 2.37 1.68 No Detention Design Storm Requirement Based on the information presented in the preceding table, the inflow rates to the Opus detention system will increase by less than 3 percent for each storm event. The conservative design of the system during the 2-year and 100-year storm events will provide sufficient volume to accommodate the runoff increase and still exceed the City of Renton's stormwater management requirements. A combination wet pond/detention pond is proposed for the project. The developed runoff from the site will enter a 69.245 ft' (i.e., live storage = 46,433 ft' and dead storage = 23,560 ft') 2-celled system that is located between Wetland "B" and the southernmost end of the parking area. The on-site conveyance system will direct flows to the facility. The two cells of the detention system will perform in series and will be hydraulically controlled by a flow restrictor structure located near Detention Pond #1. In the event of an overflow condition, an emergency spillway for each pond cell has been designed to discharge into the wetland. The volume of storage in the combined detention system and the peak flows for the associated hydraulic design have been determined by using the SCS Hydrograph Method with Type IA rainfall distribution and level pool routing. The design volume of the detention facility complies with the DOE peak runoff rate control performance requirements. The results of the analysis are tabulated below: Existing Peak Dev. Peak Detention Required Runoff Rate Runoff Rate Release Rate Detention (cfs) (cfs) (cfs) Storage (ft') 2-year, 24-hour 0.28 2.67 0.14 31,818 Design Storm 10-year, 24-hour 0.86 4.13 0.65 35,636 Design Storm 100-year, 24-hour 1.69 5.78 1.36 38,160 Design Storm KPFF Consulting Engineers 16 w:\lcivil\hd.er\ann\word\drainrpt.doc Detention Pond Volume Results Provided Detention Volume =46,433 W/Required Detention Volume = 38,160 ft3 Detention Volume Ratio (Provided/Required) = 46,433/35,636 = 1.30 KPFF Consulting Engineers 17 w:\lcivil\hd.er\ann\word\drainrpt.doc 1/21/97 4 : 52 : 59 pm KPFF Inc. page 3 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION CALC. — DEPT. OF ECOLOGY STDS. --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id VOL (cf) ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- 2-YR RELEASE RATE ............ 0.14 2.67 1 3 16.04 10 31818.25 cf 10-YR RELEASE RATE ........... 0.65 4.13 1 3 16.30 11 35635.73 cf 100-YR RELEASE RATE .......... 1.36 5.78 1 3 16.48 12 38160.27 cf 1j21j97 4 : 52 :55 pm KPFF Inc. page 2 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527 . 1 DETENTION CALC. - DEPT. OF ECOLOGY STDS. --------------------------------------------------------------------- --------------------------------------------------------------------- HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres --------------------------------------------- --------------------------------------------- 1 0.284 590 12391 cf 7 .36 2 2 .673 500 39939 cf 7 .36 3 0 .862 560 27186 cf 7 .36 4 4. 130 490 61730 cf 7 . 36 5 1 . 686 560 46549 cf 7 . 36 6 5. 783 500 86521 cf 7 . 36 10 0 . 142 1460 19900 cf 7 . 36 11 0 . 645 910 40105 cf 7 . 36 12 1 . 355 640 64722 cf 7 . 36 1/21/97 4 : 54: 5 pm KPFF Inc. page 2 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 DETENTION CALL. - DEPT. OF ECOLOGY STDS . --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE STORAGE TABLE CUSTOM STORAGE ID No. 1 Description: DETENTION POND STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 13.00 0.0000 0.0000 14.10 9630 0.2211 15.20 22146 0.5084 16.30 35579 0.8168 13.10 849.20 0.0195 14.20 10768 0.2472 15.30 23283 0.5345 16.40 37023 0.8499 13.20 1698 0.0390 14.30 11905 0.2733 15.40 24421 0.5606 16.50 38467 0.8831 13.30 2548 0.0585 14.40 13043 0.2994 15.50 25559 0.5868 16.60 39910 0.9162 13.40 3397 0.0780 14.50 14181 0.3256 15.60 26697 0.6129 16.70 41354 0.9494 13.50 4246 0.0975 14.60 15319 0.3517 15.70 27835 0.6390 16.80 42798 0.9825 13.60 5095 0.1170 14.70 16457 0.3778 15.80 28972 0.6651 16.90 44241 1.0156 13.70 5944 0.1365 14.80 17594 0.4039 15.90 30110 0.6912 17.00 45685 1.0488 13.80 6794 0.1560 14.90 18732 0.4300 16.00 31248 0.7174 13.90 7643 0.1755 15.00 19870 0.4562 16.10 32692 0.7505 14.00 8492 0.1949 15.10 21008 0.4823 16.20 34135 0.7836 1/29/97 11 :23 : 22 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION CALL. - DEPT. OF ECOLOGY SIDS. --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE DISCHARGE TABLE MULTIPLE ORIFICE ID No. 1 Description: DETENTION POND CONTROL STRUC. Outlet Elev: 13 .00 Elev: 11 .00 ft Orifice Diameter: 1 . 7197 in. STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfs-- ------- (ft) ---cis-- ------- (ft.) ---cfs-- ------- (ft) ---cfs-- ------- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 13.00 0.0000 14.10 0.0842 15.20 0.1190 16.30 0.1458 13.10 0.0254 14.20 0.0879 15.30 0.1217 16.40 0.1480 13.20 0.0359 14.30 0.0915 15.40 0.1243 16.50 0.1501 13.30 0,0440 14.40 0.0950 15.50 0.1269 16.60 0.1523 13.40 0,0508 14.50 0.0983 15.60 0.1294 16.70 0.1544 13.50 0.0567 14.60 0.1015 15.70 0.1319 16.80 0.1564 13.60 0.0622 14.70 0.1046 15.80 0.1343 16.90 0.1585 13.70 0.0671 14.80 0.1077 15.90 0.1367 17.00 0.1605 13.80 0.0718 14.90 0.1106 16.00 0.1390 13.90 0.0761 15.00 0.1135 16.10 0.1413 14.00 0.0803 15.10 0.1163 16.20 0.1436 1/29/97 11 : 23: 28 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION CALC. - DEPT. OF ECOLOGY STDS . STAGE DISCHARGE TABLE NOTCH WEIR ID No. 2 Description: DETENTION POND CONTROL STRUC. Weir Length: 1 . 5700 ft. Weir height (p) : 3.0900 ft. Elevation 16.09 ft. Weir Increm: 0 . 10 STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cis-- ------- (ft) ---cis-- ------- (ft) ---cfs-- ------- i.ft) ---cis-- ------- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 16.09 0.0000 16.30 0.4848 16.60 1.7837 16.90 3.4641 16.10 0.0051 16.40 0.8616 16.70 2.3103 17.00 4.0820 16.20 0.1855 16.50 1.2981 16.80 2.8721 1/21/97 4:54: 6 pm KPFF Inc. page 5 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 DETENTION CALC. - DEPT. OF ECOLOGY STDS. STAGE DISCHARGE TABLE COMBINATION DISCHARGE ID No. 3 Description: ORIFICE & NOTCH WEIR DISCHARGE Structure: 1 Structure: Structure: 2 Structure: Structure: STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- -------------------------------------- 13.00 0.0000 14.10 0.0842 15.20 0.1190 16.30 0.6306 13.10 0.0254 14.20 0.0879 15.30 0.1217 16.40 1.0096 13.20 0.0359 14.30 0.0915 15.40 0.1243 16.50 1.4483 13.30 0.0440 14.40 0.0950 15.50 0.1269 16.60 1.9359 13.40 0.0508 14.50 0.0983 15.60 0.1294 16.70 2.4647 13.50 0.0567 14.60 0.1015 15.70 0.1319 16.80 3.0286 13.60 0.0622 14.70 0.1046 15.80 0.1343 16.90 3.6226 13.70 0.0671 14.80 0.1077 15.90 0.1367 17.00 4.2425 13.80 0.0718 14.90 0.1106 16.00 0.1390 13.90 0.0761 15.00 0.1135 16.10 0.1464 14.00 0.0803 15.10 0.1163 16.20 0.3290 1/21/97 4 : 52 : 55 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION CALC. - DEPT. OF ECOLOGY STDS . --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: 100EX NAME: 100-YR STORM, EXISTING COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7. 36 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 3 .90 inches AREA. . : 7 .36 Acres 0.00 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 78 . 00 0 . 00 TC. . . . : 88 .90 min 0 .00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 300. 00 ns:0 .2400 p2yr: 2 . 00 s: 0. 0040 TcReach - Shallow L: 210 .00 ks:9 .00 s:0 .0040 PEAK RATE: 1 . 69 cfs VOL: 1 .07 Ac-ft TIME: 560 min BASIN ID: 10EX NAME: 10-YR STORM, EXISTING COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7 . 36 Acres BASEFLOWS : 0. 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 .90 inches AREA. . : 7 . 36 Acres 0 .00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 78 .00 0 .00 TC. . . . : 88 .90 min 0 .00 min ABSTRACTION COEFF: 0. 20 TcReach - Sheet L: 300 . 00 ns:0.2400 p2yr: 2 .00 s:0 .0040 TcReach - Shallow L: 210 . 00 ks: 9 . 00 s: 0 .0040 PEAK RATE: 0 . 86 cfs VOL: 0 . 62 Ac-ft TIME: 560 min BASIN ID: 2EX NAME: 2-YR STORM, EXISTING COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7. 36 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 7 . 36 Acres 0 .00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 78 .00 0 . 00 TC. . . . . 88 .90 min 0. 00 min ABSTRACTION COEFF: 0. 20 TcReach - Sheet L: 300. 00 ns:0.2400 p2yr: 2 .00 s:0 .0040 TcReach - Shallow L: 210. 00 ks:9 . 00 s:0.0040 PEAK RATE: 0 . 28 cfs VOL: 0.28 Ac-ft TIME: 590 min 1/21/97 4 : 54:5 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION CALC. - DEPT. OF ECOLOGY STDS . --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: 100DEV NAME: 100-YR STORM, DEVELOPED COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7.36 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 1. 41 Acres 5 . 95 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 80. 00 98 .00 TC. . . . . 5 .00 min 5 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 5 . 78 cfs VOL: 1 .99 Ac-ft TIME: 500 min BASIN ID: 10DEV NAME: 10-YR STORM, DEVELOPED COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7 .36 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2 .90 inches AREA. . : 1 .41 Acres 5 .95 Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 80 . 00 98 . 00 TC. . . . . 5 . 00 min 5 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 4. 13 cfs VOL: 1 . 42 Ac-ft TIME: 490 min BASIN ID: 2DEV NAME : 2-YR STORM, DEVELOPED COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7 .36 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2 .00 inches AREA. . : 1 . 41 Acres 5 . 95 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 98 . 00 TC. . . . : 5. 00 min 5 .00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 2 . 67 cfs VOL: 0 .92 Ac-ft TIME: 500 min kOS 3/17/97 3 : 3 : 35 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527 . 1 DETENTION CALC. - DEPT . OF ECOLOGY STDS . BASIN SUMMARY BASIN ID: 100BRIDG NAME: 100-YR STRM, BRIDGE BASIN ANAL SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 12 Acres BASEFLOWS : 0. 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 3.90 inches AREA. . : 0.00 Acres 0 . 12 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 0.00 98 .00 TC. . . . : 0 .00 min 5 .00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 0 . 10 cfs VOL: 0 .04 Ac-ft TIME: 500 min BASIN ID: 10BRIDGE NAME: 10-YR STORM, BRIDGE BASIN ANAL SCS METHODOLOGY TOTAL AREA. . . . . . . : 0. 12 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 .90 inches AREA. . : 0 . 00 Acres 0 . 12 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 0 . 00 98 . 00 TC. . . . . 0.00 min 5 . 00 min ABSTRACTION COEFF: 0. 20 PEAK RATE: 0 . 08 cfs VOL: 0 . 03 Ac-ft TIME: 490 min BASIN ID: 2BRIDGE NAME: 2-YR STORM, BRIDGE BASIN ANAL SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 12 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 .00 inches AREA. . : 0 . 00 Acres 0. 12 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 0.00 98 . 00 TC. . . . : 0.00 min 5 . 00 min ABSTRACTION COEFF: 0. 20 PEAK RATE: 0 . 05 cfs VOL: 0 . 02 Ac-ft TIME: 500 min SECTION IV (Detention System Overflow Analysis) KPFF Consulting Engineers 18 w:\lcivil\hd.er\ann\word\drainrpt.doc Detention System Overflow Analysis In the following overflow analysis, the developed basin hydrograph during the 100-year, 24-hour design storm event is routed through the detention system using the level pool routing technique. For the purpose of the analysis, it is assumed that the 18-inch overflow riser and notch weir (flow restrictor) is the only means of release (i.e., plugged orifice conditions) from the detention facility. This hydraulic analysis will determine whether the overflow riser has sufficient capacity to convey the peak rate of runoff during the 100-year, 24-hour storm. The detention system and associated overflow riser has been designed to provide a maximum of 0.50 feet of headwater (overflow depth). The overflow water surface elevation will be determined to ensure that the maximum 0.50 feet of headwater is not exceeded. For the purpose of the analysis, it is assumed that the detention system is at its highest capacity. Known Design Parameters a. Water surface elevation = 17.00' b. Overflow riser elevation = 17.00' c. Allowable maximum water surface elevation (i.e., inside top of control structure) = 17.50' d. Tributary detained basin inflow to detention vault Q, ;,,, = 5.78 cfs Overflow Analysis Results a. Outflow from detention system Q w.u,; = 5.78 cfs b. Overflow water surface elevation = 17.15' The results of the analysis show that the 100-year, 24-hour overflow water surface elevation is below the maximum water surface elevation defined by the inside top of the control structure (refer to following pages for calculations). KPFF Consulting Engineers 19 w:\lcivil\hd.er\ann\word\drainrpt.doc Emergency Overflow Spillway Calculations The emergency overflow spillway will be designed to pass the 100-year, 24-hour storm event during developed runoff conditions. Known Parameters Q W-yr= 5.78 cfs Spillway side slopes = 3(H):1(H) H = height of water above the emergency spillway =0.35 feet Elevation of spillway bottom= 17.15 Elevation of spillway top = 18.00 Calculations L = bottom length of overflow spillway (6-foot minimum) _ [QI(X)YA3.21H3n)] - 2.414 _ [5.78/(3.21)(0.35)3'2] - (2.4)(0.35) = 7.86-foot Based on the above calculations, the emergency overflow spillway will be constructed with an 8-foot bottom length. KPFF Consulting Engineers 20 w:\lcivil\hd.er\ann\word\drainrpt.doc 2/13/97 3: 14:5 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 DETENTION OVERFLOW ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAR-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id VOL (cf) ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- 100-YR OVERFLOW .............. 5.78 5.78 1 3 17.15 10 2.98 cf 1/29/97 11 :0:30 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION OVERFLOW ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE STORAGE TABLE CUSTOM STORAGE ID No. 1 Description: DUMMY STG-STR: ASSUME NO STRG STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 17.00 0.0000 0.0000 17.20 4.0000 0.0001 17.40 8.0000 0.0002 17.50 10.000 0.0002 17.10 2.0000 0.0000 17.30 6.0000 0.0001 17.50 10.000 0.0002 2/13/97 3 : 14:39 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 DETENTION OVERFLOW ANALYSIS STAGE DISCHARGE TABLE NOTCH WEIR ID No. 1 Description: DETENTION POND CONTROL STRUC. Weir Length: 1 .5700 ft. Weir height (p) : 3.0900 ft. Elevation 16.09 ft. Weir Increm: 0. 10 STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- 16.09 0.0000 16.40 0.8616 16.80 2.8721 17.20 5.3814 16.10 0.0051 16.50 1.2981 16.90 3.4641 17.30 6.0568 16.20 0.1855 16.60 1.7837 17.00 4.0820 17.40 6.7456 16.30 0.4848 16 70 3 03 17 '0 7222 17 `0 4453 1 U.IV L.J1 1l.1 Y.ILLL 1/.J /.YY 2/13/97 3 :14:44 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 DETENTION OVERFLOW ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE DISCHARGE TABLE RISER DISCHARGE ID No. 2 Description: DETENTION POND CONTROL STRUC. Riser Diameter ( in) : 18.00 elev: 17 .00 ft Weir Coefficient. . . : 9 .739 height: 17.50 ft Orif Coefficient. . . : 3.782 increm: 0.10 ft STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 17.00 0.0000 17.10 0.4620 17.30 2.4004 17.50 5.1649 17.00 0.0000 17.20 1.3066 17.40 3.6957 2/13/97 3 : 14:50 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION OVERFLOW ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE DISCHARGE TABLE COMBINATION DISCHARGE ID No. 3 Description: RISER & NOTCH WEIR DISCHARGE Structure: 1 Structure: Structure: 2 Structure: Structure: STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- 16.09 0.0000 16.40 0.8616 16.80 2.8721 17.20 6.6881 16.10 0.0051 16.50 1.2981 16.90 3.4641 17.30 8.4572 16.20 0.1855 16.60 1.7837 17.00 4.0820 17.40 10.441 16.30 0.4848 16.70 2.3103 17.10 5.1841 17.50 12.610 1/29/97 10 : 56 :41 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 DETENTION OVERFLOW ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: 100DEV NAME: 100-YR STORM, DEVELOPED COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7. 36 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : TYPEIA DERV IMP PRECIPITATION. . . . : 3.90 inches AREA. . : 1.41 Acres 5.95 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 80 .00 98. 00 TC. . . . . 5. 00 min 5 .00 min ABSTRACTION COEFF: 0. 20 PEAK RATE: 5 .78 cfs VOL: 1.99 Ac-ft TIME: 500 min SECTION V (Conveyance System Analysis and Design) KPFF Consulting Engineers 21 w:\Icivil\hd.er\ann\word\drainrpt.doc Conveyance System Analysis and Design The proposed conveyance system has been analyzed for up to the 100-year, 24-hour design storm event using the Soil Conservation Service Unit Hydrograph Method with Type IA rainfall distribution. The computer program "Waterworks 4.11" has been used in the pipe sizing analysis. The pipe system has been designed (using both uniform and backwater flow conditions) to meet the standards established by the Department of Ecology. Calculations shown in the following pages include the analysis for the on-site conveyance system. KPFF Consulting Engineers 22 w:\lcivil\hd.er\ann\word\drainrpt.doc 2/14/97 2 :28 : 42 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY Hydraulic Gradeline for Reach HGL1 <-FROM-> <--TO--> <FLOV> floss Ent HGL EntLoss ExtLoss Outlet Inlet AppHead BndHead JunHead HeadWtr -cb/mh- -------- -------- cfs -loss- -Elev-- --loss- --loss- --Elev- --Elev- --loss- --loss- --loss- --Elev- --Rim-- --------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------- 17.00 CB1 2.65 0.05 17.05 0.01 0.04 17.09 13.16 0.02 0.03 0.00 17.10 18.65 CB2 CB1 2.21 0.06 17.16 0.00 0.02 17.19 13.63 0.01 0.00 0.00 17.18 18.70 CB3 CB2 1.67 0.03 17.22 0.00 0.01 17.23 13.91 0.04 0.06 0.01 17.26 19.10 CB4 CB3 1.33 0.24 17.49 0.01 0.04 17.55 15.39 0.00 0.00 0.00 17.25* 17.15 CB5 CB4 0.34 0.01 17.26 0.00 0.00 17.26 16.96 0.00 0.00 0.00 17.26 18.84 2/14/97 2 :28 : 51 pm KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVFYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY Hydraulic Gradeline for Reach HGL2 <-FROM-> <--TO--> <FLOW> floss Ent HGL EntLoss EatLoss OutLet Inlet AppRead BndHead JunHead HeadWtr -cb/mh- -------- -------- cfs -loss- -Elev-- --loss- --loss- --Elev- --Elev- --loss- --loss- --loss- --Elev- --Rim-- --------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------- 17.00 CB6 3.06 0.08 17.08 0.01 0.05 17.14 13.51 0.03 0.05 0.00 17.15 17.90 CB7 CB6 2.65 0.08 17.23 0.01 0.03 17.27 14.26 0.01 0.00 0.01 17.10* 17.00 CB8 CB7 1.70 0.05 17.15 0.00 0.01 17.16 14.76 0.01 0.02 0.01 17.10* 17.00 CB9 CB8 0.67 0.04 17.14 0.00 0.01 17.15 16.08 0.00 0.00 0.00 17.15 17.90 CB10 CB9 0.39 0.01 17.16 0.00 0.00 17.16 17.28 0.00 0.00 0.00 17.28 19.19 CB11 CB10 0.18 1.13 tw & do <dc: Inlet Ctrl Assumed 18.35 0.00 0.00 0.00 18.35 20.27 2/13/97 12 :20: 7 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY Network Reach LINE2 REACH <-AREA> <-DIA> LENGTH SLOPE < n > DSGN Q $ PIPE Ndepth %Depth Vact Vfull C Area ID (Ac) (ft) (ft) ft/ft ------ (cfs) ------ (ft) ------ (fps) (fps) ------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------- P1l 0.21 1.00 115.00 0.0098 0.0120 0.18 4.45 0.15 14.88 2.51 5.39 All P10 0.45 1.00 83.00 0.0149 0.0120 0.39 7.65 0.19 19.39 3.63 6.64 AlO P9 0.78 1.00 124.00 0.0073 0,0120 0.67 18.95 0.31 30.63 3.30 4.63 A9 P8 1.56 1.50 214.00 0.0026 0,0120 1.70 27.29 0.56 37.12 2.84 3.61 A8 P7 3.05 1.50 153.00 0.0050 0,0120 2.65 30.49 0.59 39.41 4.09 5.04 A7 P6 3.53 1.50 111.00 0.0049 0.0120 3.06 35.75 0.65 43.03 4.21 4.97 A6 2/13/97 12 : 19 : 14 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527 . 1 100-YR COVEYANCE ANALYSIS REACH SUMMARY Network Reach LINE1 REACH <-AREA> <-DIA> LENGTH SLOPE < n > DSGN Q % PIPE Ndepth %Depth Vact Vfull C Area ID (Ac) (ft) (ft) ft/ft ------ (cfs) ------ (ft) ------ (fps) (fps) P5 0.39 1.00 119.00 0.0144 0.0120 0.34 6.82 0.18 18.33 3.45 6.53 A5 P4 1.53 1.00 201.00 0.0050 0.0120 1.33 45.26 0.49 49.22 3.46 3.85 A4 P3 1.92 1.50 154.00 0.0020 0.0120 1.67 30.33 0.59 39.30 2.59 3.19 A3 P2 2.55 1.50 161.00 0.0030 0.0120 2.21 32.93 0.62 41.11 3.23 3.90 A2 Pl 3.06 1.50 92.00 0.0051 0.0120 2.65 30.26 0.59 39.25 4.12 5.09 Al 2/13/97 12 : 20:31 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS REACH SUMMARY PIPE REACH ID No. P1 From: To: Pipe Diameter: 1 .5000 ft n: 0. 0120 Pipe Length 92 . 0000 ft s: 0.0051 Up invert 12 .8500 ft down invert: 12. 3800 ft Collection Area: 3.0600 Ac. Design Flow 2 . 6547 cfs Dsgn Depth: 0.59 ft Pipe Capacity 8 . 7730 cfs Design Vel 4. 1249 fps Travel Time: 0. 37 min Pipe Full Vel 5.0949 fps PIPE REACH ID No. P10 From: To: Pipe Diameter: 1 . 0000 ft n: 0.0120 Pipe Length 83. 0000 ft s: 0 . 0149 Up invert 17 . 1400 ft down invert: 15 .9000 ft Collection Area: 0 . 4500 Ac. Design Flow 0 . 3885 cfs Dsgn Depth: 0 . 19 ft Pipe Capacity 5. 0817 cfs Design Vel 3 .6310 fps Travel Time: 0. 38 min Pipe Full Vel 6 . 6402 fps PIPE REACH ID No. P11 From: To: Pipe Diameter: 1 .0000 ft n: 0.0120 Pipe Length : 115 . 0000 ft s: 0.0098 Up invert 18 .2700 ft down invert: 17 . 1400 ft Collection Area: 0 . 2100 Ac. Design Flow 0 . 1834 cfs Dsgn Depth: 0. 15 ft Pipe Capacity 4 . 1267 cfs Design Vel 2 .5116 fps Travel Time: 0. 76 min Pipe Full Vel 5.3924 fps PIPE REACH ID No. P2 From: To: Pipe Diameter: 1 .5000 ft n: 0 .0120 Pipe Length 161 .0000 ft s: 0.0030 Up invert 13 .3400 ft down invert: 12.8570 ft Collection Area: 2 .5500 Ac. Design Flow 2 .2138 cfs Dsgn Depth: 0 . 62 ft Pipe Capacity 6.7228 cfs Design Vel 3.2336 fps Travel Time: 0.83 min Pipe Full Vel 3 .9043 fps 2/13/97 12:20: 31 am KPFF Inc. page 2 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527. 1 100-YR COVEYANCE ANALYSIS REACH SUMMARY PIPE REACH ID No. P3 From: To: Pipe Diameter: 1 . 5000 ft n: 0. 0120 Pipe Length 154 . 0000 ft s: 0.0020 Up invert 13 . 6500 ft down invert: 13 . 3409 ft Collection Area: 1 .9200 Ac. Design Flow 1 . 6680 cfs Dsgn Depth: 0. 59 ft Pipe Capacity 5 . 4992 cfs Design Vel 2 . 5873 fps Travel Time: 0 .99 min Pipe Full Vel 3. 1937 fps PIPE REACH ID No. P4 From: To: Pipe Diameter: 1 . 0000 ft n: 0. 0120 Pipe Length 201 . 0000 ft s: 0 . 0050 Up invert 15 . 1500 ft down invert: 14 . 1456 ft Collection Area: 1 . 5300 Ac. Design Flow 1 . 3319 cfs Dsgn Depth: 0 . 49 ft Pipe Capacity 2 .9428 cfs Design Vel 3 . 4601 fps Travel Time: 0 . 97 min Pipe Full Vel 3 . 8454 fps PIPE REACH ID No. P5 From: To: Pine Diameter: 1 .0000 ft n: 0. 0120 Pipe Length : 119 . 0000 ft s: 0. 0144 Up invert 16.8400 ft down invert: 15 . 1264 ft Collection Area: 0.3900 Ac. Design Flow 0. 3407 cfs Dsgn Depth: 0 . 18 ft Pipe Capacity 4 . 9957 cfs Design Vel 3 . 4523 fps Travel Time: 0. 57 min Pipe Full Vel 6 . 5279 fps PIPE REACH ID No. P6 From: To: Pipe Diameter: 1 .5000 ft n: 0. 0120 Pipe Length : 111 . 0000 ft s: 0.0049 Up invert 13 . 1800 ft down invert: 12 . 6400 ft Collection Area: 3. 5300 Ac. Design Flow 3 .0607 cfs Dsgn Depth: 0 . 65 ft Pipe Capacity 8 . 5611 cfs Design Vel 4 .2090 fps Travel Time: 0.44 min Pipe Full Vel 4.9719 fps 2/13/97 12 : 20: 31 am KPFF Inc. page 3 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527. 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY PIPE REACH ID No. P7 From: To: Pipe Diameter: 1 . 5000 ft n: 0.0120 Pipe Length 153 .0000 ft s: 0. 0050 Up invert 13 . 9500 ft down invert: 13 . 1800 ft Collection Area: 3 . 0500 Ac. Design Flow 2 . 6460 cfs Dsgn Depth: 0 . 59 ft Pipe Capacity 8 . 6791 cfs Design Vel 4 . 0890 fps Travel Time: 0 . 62 min Pipe Full Vel 5 . 0404 fps PIPE REACH ID No. P8 From: To: Pipe Diameter: 1 . 5000 ft n: 0.0120 Pipe Length 214 . 0000 ft s: 0. 0026 Up invert 14 . 5000 ft down invert: 13 . 9500 ft Collection Area: 1 . 9600 Ac. Design Flow 1 . 6984 cfs Dsgn Depth: 0 . 56 ft Pipe Capacity 6 .2225 cfs Design Vel 2 . 8446 fps Travel Time: 1 .25 min Pipe Full Vel 3 . 6138 fps PIPE REACH ID No. P9 From: To: Pipe Diameter: 1 . 0000 ft n: 0.0120 Pipe Length 124 . 0000 ft s: 0.0073 Up invert 15 . 9000 ft down invert: 15 .0000 ft Collection Area: 0 . 7800 Ac. Design Flow 0 . 6722 cfs Dsgn Depth: 0 . 31 ft Pipe Capacity 3 .5467 cfs Design Vel 3 .2952 fps Travel Time: 0 . 63 min Pipe Full Vel 4 . 6345 fps 2/13/97 12 : 22 : 10 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: Al NAME: AREA TRIB. TO CB #1 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0.51 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 01 Acres 0 . 50 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80. 00 98.00 TC. . . . . 5 .00 min 5.00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0.44 cfs VOL: 0 . 15 Ac-ft TIME: 500 min BASIN ID: A10 NAME: AREA TRIB. TO CB #10 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 24 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 01 Acres 0 . 23 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 .21 cfs VOL: 0 . 07 Ac-ft TIME: 500 min BASIN ID: All NAME: AREA TRIB. TO CB #11 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 21 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 00 Acres 0 . 21 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 0 .00 98.00 TC. . . . : 0 .00 min 5 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0. 18 cfs VOL: 0 .06 Ac-ft TIME: 500 min BASIN ID: A2 NAME: AREA TRIB. TO CB #2 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 63 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE . . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .01 Acres 0 . 62 Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 80 . 00 98. 00 TC. . . . : 5 . 00 min 5.00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 .55 cfs VOL: 0. 19 Ac-ft TIME: 500 min 2/1J, 97 12 : 22 : 10 am KPFF Inc. page 2 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A3 NAME: AREA TRIB. TO CB #3 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 39 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0.01 Acres 0 .38 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 .00 98. 00 TC. . . . : 5. 00 min 5 .00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 0. 34 cfs VOL: 0. 11 Ac-ft TIME: 500 min BASIN ID: A4 NAME: AREA TRIB. TO CB #4 SCS METHODOLOGY TOTAL AREA. . . . . . . : 1 . 14 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 01 Acres 1 . 13 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 98 . 00 TC. . . . : 5 . 00 min 5 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 . 99 cfs VOL: 0.34 Ac-ft TIME : 500 min BASIN ID: A5 NAME: AREA TRIB. TO CB #1 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 39 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . , . : 3 . 90 inches AREA. . : 0 . 00 Acres 0 . 39 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 0. 00 98 .00 TC. . . . : 0.00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0.34 cfs VOL: 0. 12 Ac-ft TIME: 500 min BASIN ID: A6 NAME: AREA TRIB. TO CB #6 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0 . 48 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 .90 inches AREA. . : 0 .01 Acres 0 . 47 Acr.- s TIME INTERVAL. . . . . 10 . 00 min CN. . . . : 80 . 00 98.00 TC. . . . : 5 .00 min 5 .00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 0 .41 cfs VOL: 0 . 14 Ac-ft TIME: 500 min 2/13/97 12 : 22 : 10 am KPFF Inc. page 3 HUNTER DOUGLAS, INC. KPFF PROJECT #96527 . 1 100-YR COVEYANCE ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A7 NAME: AREA TRIB. TO CB #7 SCS METHODOLOGY TOTAL AREA. . . . . . . : 1 . 09 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 .90 inches AREA. . : 0 . 01 Acres 1 . 08 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 98 . 00 TC. . . . . 5.00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 . 95 cfs VOL: 0 . 32 Ac-ft TIME: 500 min BASIN ID: A8 NAME: AREA TRIB. TO CB #8 SCS METHODOLOGY TOTAL AREA. . . . . . . : 1 . 18 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 01 Acres 1 . 17 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80. 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0. 20 PEAK RATE: 1 . 03 cfs VOL: 0 . 35 Ac-ft TIME: 500 min BASIN ID: A9 NAME: AREA TRIB. TO CB #9 SCS METHODOLOGY TOTAL AREA. . . . . . . : 0. 33 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 01 Acres 0 . 32 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 98. 00 TC. . . . . 5 .00 min 5 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 .28 cfs VOL: 0 . 10 Ac-ft TIME: 500 min SECTION VI (Water Quality Analysis and Design) KPFF Consulting Engineers 23 w:\lcivil\hd.er\ann\word\drainrpt.doc Water Quality Analysis and Design The project will increase impervious area subject to vehicular use by more than 1 acre; and, therefore, a wet pond or water quality swale is required. The final design proposal for the site will include a wet pond designed to the Department of Ecology's standards. As shown below, these standards will provide a facility that will at least double the King County volume requirements. Therefore, the City of Renton has agreed to grant a code alteration modification for this project to receive credit for providing more wet pond volume than that required by King County. Consequently, a biofiltration swale for this project is not required. 1. King County Wet Pond Storage Requirement = (0.23 acre-ft)(43,560 ft') _ 10,019 ft' (see calculations on following pages) 2. DOE Wet Pond Storage Requirement = (0.53 acre-ft)(43,560 ft') = 23,087 ft' (see calculations. on following pages) 3. Provided Wet Pond Storage Volume = 23,560 ft' 4. Provided Wet Pond Volume/King County Wet Pond Volume Requirement = 23,560/10,019 = 2.35 Wet Pond Water Surface Area Results 1. Required Surface Area (1 percent of total site impervious area) _ (0.01)(259,182 ft') = 2,592 ft' 2. Provided Surface Area (i.e., both cells) = 8,120 ft= 3. Surface Area Ratio (Provided/Required) = 8,120/2,592 = 3.13 KPFF Consulting Engineers 24 w:\lcivil\hd.er\ann\word\drainrpt.doc 1/29/97 11 : 20 : 26 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT ##96527 . 1 WETPOND VOL. - DEPT. OF ECOLOGY STDS . BASIN SUMMARY BASIN ID: PT-WQ NAME: 6-MONTH STORM, DEVELOPED COND. SCS METHODOLOGY TOTAL AREA. . . . . . . : 7. 36 Acres BASEFLOWS: 0 .00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 1. 28 inches AREA. . : 1. 41 Acres 5 .95 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 98 . 00 TC. . . . . 5.00 min 5.00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 1 .55 cfs VOL: 0 .53 Ac-ft TIME: 490 min kOS 5/9/97 10 : 53 :35 am KPFF Inc. page 1 HUNTER DOUGLAS, INC. KPFF PROJECT #96527. 1 WETPOND VOL. - KING COUNTY STDS. BASIN SUMMARY BASIN ID: PT-WQ NAME: WATER QUALITY STORM: ( 1/3 )P2 SCS METHODOLOGY TOTAL AREA. . . . . . . : 7. 36 Acres BASEFLOWS: 0. 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 0. 67 inches AREA. . : 1 . 41 Acres 5 .95 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80. 00 98 . 00 TC. . . . : 5 .00 min 5.00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0. 68 cfs VOL: 0.23 Ac-ft TIME: 490 min SECTION VII (Erosion/Sedimentation Control Design) KPFF Consulting Engineers 25 w:\lcivil\hd.er\ann\word\drainrpt.doc Sediment Trap Design A. Determine Pond Geometry 1. Design Flow (QZ) = 2.67 cfs (2-year, 24-hour design storm for developed site). 2. Determine the required surface area at the top of the riser. a. SA = (2)(Q2/0.00096) _ (2)(2.67/0.00096) = 5,563 ftz 3. The temporary sediment trap will remain in operation until the cleared portion of the site is permanently stabilized against erosion by vegetative cover or equivalent. The required sediment trap geometry is as follows: • Required surface area at top of riser= 5,563 ft'. • Provided surface area at top of riser = 5,600 ft'. • Maximum 2:1 interior and exterior side slopes (with fencing provided at or above the maximum water surface elevation). • One foot of freeboard between the top storage elevation (i.e., 17.00) and the crest of the emergency spillway. • Flat-bottomed. • Minimum 1 foot deep spillway. • Length to width ratio between 3:1 to 6:1. B. Depth Gauge 1. To aid in determining sediment depth, 1-foot intervals shall be prominently marked on the riser. KPFF Consulting Engineers 26 w:\lcivil\hd.er\ann\word\drainrpt.doc SECTION VIII (Special Reports and Studies) KPFF Consulting Engineers 27 w:\lcivil\hd.er\ann\word\drainrpt.doc Special Reports and Studies Contents of this section: a. Northwest Hydraulic Consultants, Inc.: HEC-2 Modeling of Proposed Springbrook Creek Road Crossing for Winmar Project (August 20, 1996). b. City of Renton: Raymond Center West Compensatory Floodplain Storage (October 23, 1996). KPFF Consulting Engineers 28 wAlcivil\hd.er\ann\word\drainrpt.doc northwest hydraulic consultants inc. sacramento 16300 Christensen road.suite 350 vancouver "`' VC. tukwila,wasnington 98188-3418 edmonton 'gyp`' " SET T i E (206)241-6000-phone (206)439-2420-fax seattle � August 20, 1996 r zs i I :D KPFF Consulting Engineers 1 Attn: Mr. Tom Jones _ y 1201 Third Avenue, Suite 900 Seattle, WA 98101 RE: HEC-2 modeling of proposed Springbrook Creek road crossing for Winmar project. Dear Mr. Jones: Northwest Hydraulic Consultants (NHC) has completed its hydraulic impact analysis of the proposed road crossing over Springbrook Creek for the Winmar development. You had retained us to determine, using the HEC-2 backwater model program, the potential water level increases due to constructing a bridge over Springbrook Creek. The proposed bridge site is in south Renton, Washington,just upstream of SW 19th Street (extended). We are pleased to summarize - herein our analysis and present our results. Baseline Modeling (no bridge) Using an existing HEC-2 model developed by NHC for the City of Renton, we ran the following baseline scenarios: • Existing channel topography, future land-use 100-yr discharge, and no Winmar bridge crossing; • Alternative 2 channel improvement proposed under the East Side Green River Watershed Project (ESGRWP), future land-use 100-yr discharge, and no Winmar bridge crossing" The proposed channel widening improvements under the ESGRWP extend from SW 16th Street to about SW 23rd Street, which includes the reach through the Winmar project. The existing condition HEC-2 model had already been modified by HNTB Corporation to reflect the Alternative 2 channel improvements. We utilized their baseline model to simulate this condition. The discharges used for the respective baseline model runs were taken from Table 1 of a letter dated February 2, 1996, from Scott Woodbury of the City of Renton to Tim Puryear of the Winmar Company. The following table presents these flows, extending from the Black River Pump Station (BRPS) upstream through the channel improvement reach (to SW 23rd). These RIVER ENGINEERING HYDRAULIC MODEL TESTING 11 HYDRAULIC ANALYSIS AND DESIGN COASTAL ENGINEERING HYDROLOGY I SEDIMENTATION ENGINEERING NUMERICAL MODELING APPLIED RESEAgCH FORENSIC ENGINEERING Tom Jones 2 August 20, 1996 flows represent the ESGRWP conveyance event, which assumes no pumping restrictions at the BRPS. The table also compares water surface elevations from the ESGRWP (using the FEQ unsteady model) to the water surface elevations we computed with the baseline HEC-2 models described above. The HEC-2 model results are shown to compare reasonably well to the FEQ results from the ESGRWP. Existing channel, future 100-yr Alt. 2 channel, future 100-yr flow: flow: ESGRWP HEC-2 ESGRWP HEC-2 Location/ Flow water water Flow water water description (cfs) level (ft) level (ft) (cfs) level (ft) level (ft) BRPS inflow 1223 4.7 4.7 1747 5.4 5.4 Grady Way u/s 1110 7.6 7.6 1498 8.8 8.7 SW 16th u/s 1106 8.2 8.0 1488 9.1 9.1 SW 19th extend 1088 11.6 11.9 1441 11.0 10.5 SW 23rd extend 989 12.6 li.3 1344 11.9T 11.7 The existing HEC-2 model, as well as the ESGRWP, reference elevations to the NGVD 1929 datum. Therefore, all results herein (including the above table) are referenced to this datum. To convert to the NAVD 1988 datum, one should add 3.57 feet to these elevations. With-bridge Modeling The baseline HEC-2 models were modified to reflect the proposed bridge crossing over Springbrook Creek, resulting in the following baseline scenarios: • Existing channel topography, future land-use 100-yr discharge, and Winmar bridge alternative 4 (from KPFF); • Alternative 2 channel improvement proposed under the East Side Green River Watershed Project, future land-use 100-yr discharge, and Winmar bridge alternative 4. The respective "with-bridge" models were run using the same discharges as used for the baseline conditions (see above table). Winmar bridge alternative 4a consists of a clear-span bridge, 72 ft long between abutments and 37 ft wide. The proposed bridge deck is 3 ft above the approximate water surface of the 100-yr storage event (assumes BRPS pumping restrictions), as per City of Renton clearance northwest hydraulic consultants inc. Tom Jones 3 August 20, 1996 requirements. For the 100-yr conveyance event, the abutments of the proposed structure may encroach somewhat into the channel. Please find attached a cross-section plot from the HEC-2 model, showing the Winmar bridge crossing over the proposed ESGRWP alternative 2 flood control channel. Results For each of the respective channel conditions (existing and ESGRWP improvement), the baseline results were compared to the results with the proposed Winmar bridge. We also investigated the potential further impacts due to shortening the bridge span by 6, 12, and 18 ft (i.e. moving the abutments in towards the channel). The following table summarizes the impacts due to the bridge, in terms of upstream water level increases (given in feet). Existing channel, future 100-yr Alt. 2 channel, future 100-yr flow: flow: Bridge alternative Just u/s of At u/s Winmar Just u/s of At u/s Winmar (span length) proposed bridge property line proposed bridge property line Bridge 4a (72 ft) 0.01 0.00 0.01 0.01 Bridge 4b (66 ft) 0.02 0.01 0.03 0.02 Bridge 4c (60 ft) 0.03 0.02 0.05 0.04 Bridge 4d (54 ft) 0.03 0.03 0.09 0.06 The results show that the primary bridge design (bridge alternative 4a) will have minimal impact on Springbrook Creek 100-yr conveyance event water levels. The computed results from HEC-2 indicate the water surface elevation just upstream of the bridge would increase from 12.26 ft to 12.27 ft (NGVD 1929), given the existing channel. At the upstream property line, there is no impact shown. For the proposed ESGRWP alternative 2 channel widening, the abutments cause a minor increase in water level, from 10.74 ft to 10.75 ft at the bridge. Shorter bridge lengths (bridges 4b through 4d) result in measurable, although still small, increases in water level. Conclusions The analysis described herein indicates the proposed Winmar bridge design(alternative 4a) would have negligible hydraulic impact on water levels in Springbrook Creek, given both the existing channel and the ESGRWP improved channel geometry. Furthermore, the proposed clear-span bridge design calls for no piers; therefore local pier scour does not need to be investigated. northwest hydraulic consultants inc. Tom Jones 4 August ?0, 1996 The input and output files for the HEC-2 models are included on the enclosed diskette. Please call me should you have any questions. I look forward to working with you again soon. Yours very truly, NORTHWEST HYDRAULIC CONSULTANTS g;z Robert C. Elliot, P.E. northwest hydraulic consultants inc. Springbrook Futr Brdge4a Cross -section 7755 . 000 30 N 25 L] z Bridge Deck •�= 20 0 � i----------------------------------15 > � I I w I I I � 10 I , i I 10.75 ' 5 Proposed ESGRWP Channel 0 400 420 440 460 480 500 520 540 560 Distance (feet) CITY OF RENTON .� Planning/Building/Public Works Department Gregg Zimmerman P.E.,Administrator Jesse Tanner,Mayor RECE! KPFF SEATTLE JIJ o �-- October 23, 1996 Mark Miller co - Mark Miller Consultants, Inc. I -j 10801 Main ST- STE 100 FILE i Bellevue,WA 98004 1 SUBJECT: RAYMOND CENTER WEST (CITY FILE NO. LUA-96-104,SA,SM,ECF) COMPENSATORY FLOODPLAIN STORAGE Dear Mr. Miller: I received the attached letter from Tom Jones of KPFF dated August 23, 1996, requesting that the City allow the Raymond Center West project to use the City's hydraulic model of Springbrook Creek for determining the volume of compensatory storage required, rather than the FEMA 100- year flood elevation. I am addressing my response directly to you in your capacity as agent for the owner of the project site so that you and the owner will have this letter prior to the site plan review hearing scheduled for October 29, 1996. Upon review of the request, I have decided not to allow use of the City's model for determining the compensatory storage requirement. It has been City policy to use FEMA floodplain elevations in determining compensatory storage. In fact, in just the past two years, several development projects were required to provide compensatory storage using FEMA elevations, such as the 16th Street Technical Center, Springbrook Industrial Center, and Allpak developments. According to calculations by KPFF using FEMA floodplain elevations, approximately 92,000 cubic feet of compensatory floodplain storage would have to be provided by the Raymond Center West project. From review of the preliminary site plans, it appears that this volume of flood storage could easily be excavated rvi`u.in the 50-foot setback area along the east boundary of the site without encroaching into the code required 25-foot stream buffer, which is measured from the ordinary high water mark of the creek. While the Raymond Center West project could construct its compensatory storage within the 50- foot setback, the City has plans, as you know, to acquire rights to use the 50-foot setback along Springbrook Creek for a future channel widening project. A draft environmental impact statement for the proposed channel widening project is scheduled for issuance next month for public comment under the title of the East Side Green River Watershed Project (City File LUA-95-205,ECF). Obtaining rights for the channel widening depends upon the granting of a drainage easement (or deed) over the 50-foot setback area from the owner of the Raymond Center West site. Mark Miller Mark Miller Consultants, Inc. Raymond Center West Compensatory Floodplain Storage Page 2 -� Because the City needs the drainage easement for the channel widening project and because widening of the channel would create a significant amount of Foodplain storage within the 50-foot setback area, I propose that the City agree to provide the compensatory storage for the Raymond Center West project in exchange for the granting of a drainage channel easement over the 50-foot setback area to the City. Such an agreement would of course require City Council approval. A draft drainage channel easement agreement is enclosed whereby the City would agree to provide the compensatory storage for the Raymond Center West project. The easement would benefit the City by enabling the channel to be widened. Construction of the channel widening is currently scheduled for the summer of 1998, depending upon whether funding for construction is available from the project's federal sponsor, the Natural Resources Conservation Service. The easement agreement would directly benefit the Raymond Center West project by transferring the compensatory storage responsibility to the City. Widening of the channel would also provide additional flood protection to the Raymond Center West site and reduce current flooding problems in the valley area streets that serve the project site. I would appreciate the owner's consideration of this proposal. If you have any questions, please contact me at(206) 277-6211. Sincerely, l Gregg Zimmerman, P.E.,Administrator Plana ng/Building/Public Works Department H:D0CS:96-715:SW:ps Attachment CC: Project File Ron Olsen Ron Straka Scott Woodbury Jennifer Henning Tom Jones/Mark Veldee,KPFF SECTION IX (Appendix) KPFF Consulting Engineers 29 w:\lcivil\hd.er\ann\word\drainrpt.doc 5T JCD� A; ST z L I Sr S• I M E M ST I z IT 4rH _�T ZA S 1?8TH ST MH I - tL'�TT RE AIRPORT P, oRT wy S 132ND St 1 1 1 LUL S IT NE MIC IT ST • S TOBtN rfUlcm, 300 QO 134 TH­ 7III)ST 1 tv 18 RENT HS a S , 2ND RIVER CEPIETERY PAW S 3W ST RENT S 4TH e t Ot Ate' & 6TH ST RI I fH I i=�' S I 7rW II TH CT 41 r PARK JI RICE ?ENM VILLAGE AMMO '4j, STCi CENTER Iti PARK III S R VILLAGE PL 3 1ITH ST AR o" imv XIIIAY S_ 15T 1 7 SW 16TH ST SW —w 16TH ST S 16TH ST S 4 Y-4 SE 19- S 18THrM 'yP ST .1. < ,4 1, SW 19tH ST 14 Iratit .S A", S 19fHis— LONGACRES L.Aj HILL 4 W, —t- PARK S %LT., RACE 'Un, TRACK _SW 21ST ST a__ ii„ PUGET S,21SI "to r. 39 E Ziff ST TH, SW 23RD T S 23R0 6i ST i KID z' S _I )62ND ZI Z: ST I— SEST ST IS 27M ,T SE 164TH110, I 20TN IWTII SE 29�'1 I 29—TH ST ST SE is".Sri It SrR 66rh Tr !9 SW 30TH 30 "O Il� C' - +JII , SY CT - 33RD ST 15 SE 169TH L E 11,9TH I max' SE _170TH I 16 FS �14 170THI Sw ;5 S7 TH - ST v I- ND ST I IT ]7'Rl)ST 7 7;1_1'� SE 4, SE 11M IT < r,, Ad 51 71K ST IT ' " I 1 Sr 2! 8TH Si ST 1 414 ST 174TH 5 IN FS SW ST .3 1 1 1 :r SE 17STH ati, SE 176T ST SW ST I 1 Si -F, Figure 1: Vicinity Map Scale: NTS KPFF Consulting Engineers 30 w:\lcivil\hd.er\ann\word\drainrpt.doc Armen :S 'Fie I" I i �� .i)• �; bsta'� BPW, C 900 BM j254 <<_� r• •• a• :w _1 BeFI. .1v • p own I � i a� to Oyp'�"�. ''s!''r'Gx°"gr�QE+.. � N•...,�_ .� s Y g q ''' •HIV - mow. r ::,r.\ ',• ; -lay .___ _ • , �. �,�, �,. _ Wo i Ur — --- — 13--- I I �� L, •: I i Pu Ur Y Py Ng' Be C' Go urse • Ur I p� ■ Wo I q m , pq •� ,h.. sp\I '0� •�. \ Sew ge 0 TH ��� • • �. %Dis al �I 2 I Ng Ur Ur .0 :129 • :Pr uc. �. •. ', 11 ,' ,16{ Longacred • \ i i �i ��, + �L III• • ,�• •I ,. S ' ^ « •'�I i i Rpa PY �r Q 3 K s►:- "e. -•„ eCAj T M Ur- iipl Ur ��� �•'d" 'a= '�"' 3 Itt O••,M• 1• I o Track ;, Ur i i Ng u I C R rvoir ��_ • C \` _ ..Py } + ■ I .. D W p•• Ifs•', i 2 1 r . TU Sp z y •'W 2 z w • O a Pu - m f Sk Tu 25 BM r v _• �y,� Sk Ur LIM r i�• 'V I ".... � } �, r •� fir. �� ,F � �,,� .�:.. Figure 2: Soils Map Scale: NTS KPFF Consulting Engineers 31 w:\Icivil\hd.er\ann\word\drainrpt.doc SOIL LEGEND The first capital letter is the initial one of the soil name. A•...,,,,.I caottot lever, A, B,C, D, E, or F, Indicates the class of slope. SYmbais—th.nu,slope letter are those of nearly level soils. SYMBOL NAME AgB Alderwood gravelly sandy loam,0 to 6 percent slopes AgC Alderwood gravelly sandy loom,6 to 15 percent slopes AgD Alderwood gravelly sandy loom, 15 to 30 percent slopes AkF Alderwood and Kitsap soils,very steep AmB Arents,Alderwood material,0 to 6 percent slopes• AMC Arents,Alderwood material,6 to 15 percent s lopes An Arents, Everett material"' BeC Beausite gravelly sandy loom,6 to 15 percent slopes BeD Becusite gravelly sandy loam, 15 to 30 percent slopes BaF Beausite gravelly sandy loam, 40•0 75 percent slopes Bh Bellingham silt loam Br Briscot silt loam Bu Buckley silt loam CIO Coastal Beaches Ea Earimont silt loam Ed Edgewick fine sandy loom EvB Everett gravelly sandy loam,0 to 5 percent slopes EvC Everett gravelly sandy loam,5 to 15 percent slopes EvD Everett gravelly sandy loam, 15 to 30 percent slopes EwC Everett-Alderwood gravelly sandy foams, 6 to 15 percent slopes InA Indianola loamy fine sand, 0 to 4 percent slopes InC tndianola ioamy fine sand,4 to 15 oercent slopes InD Indianola ioamy fine sand, 15 to 30 percent slopes KpB Kitsap silt loam,2 to 8 percent slopes KoC Kitsap silt loom,8 to 15 percent slopes KPD Kitsap silt loam, 15 to 30 percent slopes KsC Klaus gravelly loamy sand,6 to 15 percent slopes Ma Mixed alluvial land NeC Neilson very gravelly loamy sand,2 to 15 percent slopes Ng Newberg silt loam Nk Nooksack silt loom No Norma sandy loam Or Orcas peat Os Oridia silt loam OvC Ovall gravelly loam,0 to 15 percent slopes OvD Ovall gravelly loom, 15 to 25 percent slopes OvF Ovail gravelly loam,40 to 75 percent slopes Pc Pilchuck loamy fine sand Pk Pilchuck fine Bondy loam Pu Puget silty clay loom Py Puyallup fine sandy loam RaC Rognar fine sandy loam,6 to 15 percent slopes RoD Rognor fine sandy loom, 15 to 25 percent slopes RdC Rognar-Indianola association,sloping* RdE Rognar-Indianola association,moderately steep• Re Renton silt loom Rh Riverwash so Solal silt loam Sh Snmmomish silt loam Sk Seattle muck Sm sholcor muck Sn Si silt loam So Snohomish silt loom Sr Snohomish silt loam,thick surface variant Su Sultan silt loam Tu Tukwila muck Ur Urban land Wo Woodinville silt loom Figure 3: Soils Legend KPFF Consulting Engineers 32 w:\lcivil\hd.er\ann\word\drainrpt.doc �1t _ M .r .�...� 4 skinFA Opp at wo wpm WAA Ili DWAIRI;BUDWADFRI, R � . r M, Pit 111111 put ► ,, �� t. law 1� _�. •.:fit FA , �• M r�► PV .� -•�iI KING COUNTY, WASHINGTON, SURF .-\ CE WATER DESIGN MANUAL (2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20 CN points). However, high CN areas should not be combined with low CN areas (unless the low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be generated and summed to form one hydrograpn. FIGURE 3.5.'A HYDROLOGIC SOIL GROUP OF THE SOILS INKING COUNTY HYDROLOGIC HYDROLOGIC SOIL GROUP GROUP' SOIL GROUP GROUP' Alderwood C Orcas Peat 0 Arents. Alderwood Material C Oridia D Arents, Everett Material B Ovall C Beausite C Pilchuck C Bellingham 0 Puget 0 Briscct D Puyallup S f Buckley D Ragnar B I Coastal Beaches Variable Rentcn 0 arimont Silt Loam D Riverwash Variable Edgewick C Saial C Everett A/B 'Sammamish 0 Indianola A Seattle 0 Kitsap C Shacar 0 Klaus Si Silt C Mixed alluvial Land Variable Snohomish 0 Neiiton A Sultan C Newberg B Tukwila D Nooksack C Urban Variable Normal Sandy Loam D Woodinville I 0 HYDROLOGIC SOIL GROUP CLASSIFICATIONS A. (Low runoff potential). Soils having high infiltration rates, even when thoroughly wetted, and consisting chiefly of deep, well-to-excessively drained sands or gravels. These soils have a high rate of water transmission. B. (Moderately low runoff potential). Soils having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C. (Moderately high runoff potential). Soils having slow infiltration rates when thoroughly wetted, and consisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine textures. These soils have a slow rate of water transmission. 0. (High runoff potential). Soils having very slow infiltration rates when thoroughly wetted and consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a hardpan or clay layer at or near the surface, and shallow soils over nearly impervious material. These soils have a very slow rate of water transmission. From SCS, TR-55, Second Edition, June 19M, Exhibit A-t. Revisions made from SCS, Soil Interpretation Record, Form #5, September 1988. �� 3.5.3_2 11/92