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Home My WebLink AboutSWP272862(1) N � r g0 N y �\4�W I L q � a Z o — z J � ' * 1908 South 180th Street Grade Separation Final Technical Information Report Submitted to City of Tukwila Public Works Department ' Tukwila, Washington ' RECEIVED Submitted by APR 2 3 2'"1 BERGER/ABAM ENGINEERS I NC. CITY OF REW 04 UTILITY SYS T Ft,iS Job No. A00084 Updated April 2001 26 <=z r r FINAL TECHNICAL INFORMATION REPORT 1 South 180th Street Grade Separation rSubmitted to City of Tukwila Public Works Department Tukwila,Washington 1 April 2001 r 1 ,r Submitted by BERGER/ABAM Engineers Inc. 33301 Ninth Avenue South, Suite 300 Federal Way,Washington 98003-2600 Job No.A00084 r FINAL TECHNICAL INFORMATION REPORT SOUTH 180TH STREET GRADE SEPARATION iTABLE OF CONTENTS SECTION PAGE 1.0 Project Overview ............................................................................................................. 1 2.0 Preliminary Conditions Summary and Off-Site Analysis ...................................... 6 3.0 Flow Control and Water Quality Facility Analysis and Design ........................... 10 4.0 Conveyance System Analysis and Design ................................................................. 16 5.0 Special Reports and Studies ......................................................................................... 21 6.0 Basin and Community Plan Areas .............................................................................. 22 7.0 Other Permits ................................................................................................................... 23 8.0 Erosion/Sedimentation Control Design ..................................................................... 24 9.0 Bond Quantities Worksheet, Retention/Detention Facility Summary Sheet, and Declaration of Covenant ........................................................................................ 25 10. Maintenance and Operations Manual ........................................................................ 26 j Final Technical Information Report A00084 South 180th Street Grade Separation ii April 2001 1.0 PROJECT OVERVIEW South 180th Street, an east-west principal arterial located in the Tukwila, Renton, and Kent areas of the Green River Valley, will be reconstructed to provide a grade separation between vehicular traffic and railroad tracks. The proposed roadway with four lanes, Class III bicycle route, curb and gutter, and sidewalks will pass under the existing railroad tracks and Interurban Trail. The project location and project limits are shown on the vicinity map in Figure 1. A system of catch basins and closed lines is proposed to collect and convey runoff. The runoff collected from the depressed roadway will be pumped to a new stormwater facility. The project will add approximately 0.377 acres (16,422 square feet) of new impervious surface to the site. Following is the summary of the surface areas of the project. Existing Proposed Net (increase) Impervious area (sidewalk+wall) 0.122 acres 0.458 acres 0.336 acres Impervious area (roadway) 1.294 acres 1.335 acres 0.041 acres Total impervious area 1.416 acres 1.793 acres 0.377 acres Pervious area 0.502 acres 0.125 acres Total project area 1.918 acres 1.918 acres Water quality and water quantity controls are required for this project. Final Technical Information Report A00084 South 180th Street Grade Separation 1 April 2001 WAY \ 2y0 Sw a 405 J INTERURBAN `� J AVE S SW 16TH ST sUl ! �� 1 ti 167 w r 21STCL o ST 0 w o cr_ ti { STRANDER 1 SW 27TH ST BLVD PROJECT Uj LIMITS co r_ V � � h N W Q > �O w SW 34TH ST Ln W TUKWILLA o z N J Q O � p w 181 SW 41ST ST O S RENTON PAP IBOTH --r` — SE 43RD ST PR RD SE ST OP j (5 160TH ST) 5 S 82n S ' �p Ln > Ln Q Z � } ti + ] > } a ! o � a co J a KENT 1 Source: _._. Vicinity Map BERGER/ARAM Engineers,Inc. 1999 Figure 1 South 180th Street Grade Separation King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGINEER DESCRIPTION Project Owner Project Name City of Tukwilla Dept. of Public Works_ South 180th Street Grade Separation Address Location 6300 Southcenter Blvd, Suite 100 Township 23N Tukwilla, WA 98118 Range 4E Phone 206 433-0179 Section 36 Project Engineer Chris Walcott Company BERGER/ABAM Engineers Inc. Address/Phone 206 431-2300 Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS APPLICATION 1 ❑ Subdivison ❑ DFW HPA Vshoreline Management ❑ Short Subdivision COE 404 ❑ Rockery Grading ❑ DOE Dam Safety IJ Structural Vaults ❑ Commercial ❑ FEMA Floodplain ❑ Other Other JARPA ❑ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community N/A Drainage Basin Springbrook Creek Part 6 SITE CHARACTERISTICS ❑ River ❑ Flood lain FEMA see Fig. 2 P g ❑ Stream Springbrook Creek, and Mill Creek ❑ Wetlands See Wetlands Study Critical Stream Reach ❑ Seeps/Springs ❑ Depressions/Swales ❑ High Groundwater Table ❑ Lake ❑ Groundwater Recharge ❑ Steep Slopes ❑ Other Final Technical Information Report A00084 South 180th Street Grade Separation 3 April 2001 Part 7 SOILS ISoil Type Slopes Erosion Potential Erosive Velcoties Woodinville Silt Loan 0—3% moderate_ Puyallup Fine Sandy Loam 0—3% moderate_ Urban Land 0—3% moderate ❑ Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT ❑ Ch. 4— Downstream Analysis ❑ ❑ ❑❑ Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION Sedimentation Facilities ❑ Stabilize Exposed Surface ❑ Stabilized Construction Entrance ❑ Remove and Restore Temporary ESC Facilities ❑ Perimeter Runoff Control ❑ Clean and Remove All Silt and Debris ❑ Clearing and Grading Restrictions ❑ Ensure Operation of Permanent Facilities ❑ Cover Practices ❑ Flag Limits of SAO and open space ElConstruction Sequence preservation areas ❑ Other ❑ Other Final Technical Information Report A00084 South 180th Street Grade Separation 4 April 2001 Part 10 SURFACE WATER SYSTEM Method of Analysis ❑ Grass Lined ❑ Tank ❑ Infiltration Y Channel SBUH. RATIONAL_ ,�-,/ ❑ Vault ❑ Depression l� Pipe System ❑ EnergyDissa ator ❑ Flow Dispersal Compensation/ P P Mitigation of ❑ Open Channel Wetland u n Waiver Eliminated Site ❑-,/ Dry Pond [� Stream El Regional Regional g L]� Wet Pond Detention Brief Description of System Operation Catch basins and closed lines collect and convey runoff to pump station. Runoff is lifted to pond for WQ and flow control Facility Related Site Limitations Reference Facility Limitation Part 11 'STRUCTURAL ANALYSIS ` Part 12 EASEMENTS/TRACTS ❑ Cast in Place Vault ❑ Drainage Easement Retaining Wall Access Easement Rockery> 4' High ❑ Native Growth Protection Easement Structural on Steep Slope ❑ Tract ❑ Other ❑ Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. 4/Z 'hZ,aw SignedDate Final Technical Information Report A00084 South 180th Street Grade Separation 5 April 2001 2.0 PRELIMINARY CONDITIONS SUMMARY AND OFF-SITE ANALYSIS The existing drainage system consists of two separate closed pipe systems, one on either side of the tracks. On the west side, the runoff collected along South 180th Street is conveyed to the system on 72nd Avenue South. East of the tracks, all runoff is collected and eventually discharged to Springbrook Creek via a 36-inch outlet. There are no water quality or water quantity controls for the roadway runoff. The portion of the project adjacent to Springbrook Creek is in a FEMA floodplain. See Figure 2, ' FEMA Floodplain. The entire project lies within a watershed defined by the City of Kent as Springbrook, Mill, and Garrison Creek Watershed. See Figure 3 for the watershed boundary. Springbrook Creek crosses South 108th Street via a 12-foot by 19-foot elliptical metal culvert located about 500 feet east of the tracks. The subbasins and drainage systems are described in more details in the following sections. Schematics of existing and proposed subbasins boundary are shown on Figure 4. Subbasin West 72nd Avenue South (Station 11+20)to Railroad Tracks(Station 16+10) Runoff from the roadway and few adjacent properties is collected along South 180th Street and conveyed to a 12-inch trunk line on 72nd Avenue South. This system flows south to South 182nd Street, then east under the railroad, and finally discharges to Mill Creek, a tributary to Springbrook Creek. Subbasin East Railroad Tracks(Station 16+10) to End of Project(Station 22+40) Roadway runoff from this section is collected by a system of catch basins and conveyed to a deep system of 36-inch RCP located on the north side of the road. The 36-inch RCP system also drains the off-site areas adjacent to South 180th Street. Flow from the 36-inch RCP system discharges to Springbrook Creek at a location about 30 feet north of South 180th Street. Final Technical Information Report A00084 South 180th Street Grade Separation 6 April 2001 i AIW N soulily Esr cz 39TH STREET \ LL - RM337 BOULEVARD soy», cPrtef ZONE AE o cz Pump Station Q cz l CITY OF TUKWILA Wcz 530091 CITY OF RENTON u- U) 530088 cz ZONE X '/� ZONE AE 0 J( U aR ) 00 o A� � +——+ — , Abandoned Railroad BRIDGE 0 �.. Q � 30UTHWLST 41S7 I STREET 18 $ 5 y i{ ZONE X NW z BROCY+ a z 3" YRtIyC' t Bike Trail 'i � 1 �_ 'a ,Badge i f1�Q�✓► � .� o 00 AM 27 43RD ^ STREET RM339 SOUTH sw CITY 0 TUKWILA _ [BOTH CITY OF RENTON } 9 oa CITY OF KENT U j �RM347 CITY OF KENT STREV P y �y = V zm a t$ STREET STREET ZONE AE �� c� f uj F y Foo&dgeLu Q `� }' ZONE AE ! � Lu Kent Bike T.ii! 36 a 3 � '`""• „ 'O SOUTH 182NO STREET 3I ' B CITY OF KENT --ZONE X 530080 ZONE AHD VE r xe (El. 17) S A0 t q FLOODING EFFECTS FROIN o�i ZONE X ,Mill Creek � ZONE X *� ZONE AE �� SPRING9ROOK CREEK c�a- ta: r { ZONE AE '' ZONE AE Hwy ZONE AE i EL 23 �n c>O 3 1.4 , K —. _ 47°Lb'It)" rn t JOINS P.�atvEt_ 0986 122°13'07" U Q 7 O W (n LL Im an OW,, m " m Im An In Im 4 m im 'M y igt'i.n,o+�k `��,\. �{? t.�:�,+ ! • ',,-%_" ,a, ! s � `.� •1 / -i ii :I: PYk - ��_I}.J IL:L..•. 'I:- ... ir.l _ �" .iid. _ .`f u. 7• i �,�I h n :` - • �\hop, - 1". /� ,J✓� ��,1. �: 1 i , 13 Pse. � •.� s . •� :•i t...• -' �� .� +kr 4' r 37 kkt�,. 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'..ry L. 1 31� 111 ------------ 1• `` Tnau•s 33 34 North 43 rd. �I• -. .... `1 �' _ an Source: Springbrook Creek Watershed Boundary Harza Northwest Inc. 1994 Figure 3 South 180th Street Grade Separation w gee G Existing Subbasins too` V) ai Q dischorges to creek O 0 O S. 180th St • = cn U 2'x19 o + culvert o, CN' o Q C N > w N a. o a c — c N N 2 C O O O s (n a] (/) W u asin West Subbasin East drain south then east to Mill Creek ee* G� oo Proposed Subbasins SQ�\�oo� / � > WQ & Flow control discharges o to creek o Pump o S. 180th St r } = O a N 12'x19' T N O + culvert 00 + cn N j + N + N O O Q W N N W ai > C O .O C O O Q O.� 3 a) N N (n w (AM Subbasin Subbasin East West ` drain south then east to Mill Creek ® Contributing area Flow line i Source: Subbasins BERGER/ARAM Engineers,Inc. 1999 Figure 4 South 180th Street Grade Separation 3.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Flow Control Two methods were used to analyze and design for the detention facility, the Santa Barbara Urban Hydrograph (SBUB) and the King County Runoff Time Series (KCRTS). KCRTS software was used to design a detention facility to meet level 1 flow control standards as specified in the King County Surface Water Design Manual (KCSWDM), 1998. The detention pond was sized to detain the proposed peak discharge rates to the limit of the existing discharge rates for the 2-year, and 10-year storms. Hydrologic models were developed using the SBUH method with 24-hour storm events, and Type la Hyetograph as implemented by the WaterWorks computer program. The detention pond was sized to detain the proposed peak discharge rates to the limit of the existing discharge rates for the 2-year, 10-year, and 100-year storms. The SBUH method was selected over the KCRTS method because the SBUH design is a better fit to the site topography, and provided a larger detention volume and less overflow rates, which are critical to the proposed mitigated wetland located downstream of the new detention pond. Table 1 shows the peak flow rates for the existing and proposed condition of roadway in Subbasin East and the required detention volume. WaterWorks outputs are attached at the end of the section. Table 1. Subbasin East Peak Flows Existing Proposed Pond Limits of drain area Station 16+10 to 22+40 Station 12+24 to 22+40 Pervious area 0.502 acre 0.000 acre Impervious area (roadway) 0.909 acre 1.516 acres Impervious area (offsite) 0.280 acres Two-year flow 0.44 cfs 0.84 cfs 0.44 cfs Ten-year flow 0.71 cfs 1.26 cfs 0.71 cfs 100-year flow 1.05 cfs 1.75 cfs 0.96 cfs Detention volume 2374 cf Right-of-way required 0.5 acres Water Quality Water quality facility was designed to treat the runoff from the total roadway surface area using the method listed in the KCSWDM for basic wetpond. Computations for the required volume are attached at the end of this section. Combined Detention and Wetpond The new pond was designed using the guidelines listed in the KCSWDM for combined detention and wetpond with 3H:1V interior slopes, 2H:1V exterior slope, 1 foot of freeboard, and a volume safety factor of 20%. A permanent pool of water at the bottom of the pond will provide water quality treatment while a live storage at the upper level provides detention capacity. An emergency overflow was provided to discharge 100-year flow for developed condition. An access ramp of 12 feet wide was provided to the wetpool cell at a maximum grade of 15 percent. Final Technical Information Report A00084 South 180th Street Grade Separation 10 April 2001 SOUTH 180TH STREET GRADE SEPARATION DETENTION POND DESIGN (65-FOOT ROADWAY SECTION) SBUH METHOD -WATERWORKS OUTPUTS PROJECT PRECIPS [2 yr] 2.00 in [10 yr] 2.90 in [100 yr] 4.00 in BasinID Peak Q Peak T Peak Vol Area Method Raintype Event ---- -- (cfs) (hrs) (ac-ft) ac /Loss Existing 0.44 7.83 0.1563 1.41 SBUH/SCS TYPElA 2 yr Existing 0.71 7.83 0.2489 1.41 SBUH/SCS TYPEIA 10 yr Existing 1.05 7.83 0.3674 1.41 SBUH/SCS TYPEIA 100 yr Proposed 0.84 7.83 0.2662 1.80 SBUH/SCS TYPElA 2 yr Proposed 1.26 7.83 0.4004 1.80 SBUH/SCS TYPElA 10 yr Proposed 1.75 -7o 7.83 0.5649 1.80 SBUH/SCS TYPElA 100 yr Drainage Area:Existing Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur 24.00 firs Area CN TC Pervious 0.5020 ac 79.00 ` 0.11 hrs Impervious 0.9090 ac 98.00 0.06 hrs Total 1.4110 ac Pervious TC Data: 1 Flow Type: Description: Length: Slope: Coeff: Travel Time Sheet 20.00 ft 2.00% 0.1500 3.42 min Shallow 370.00 ft 2.00% 27.0000 1.61 min Channel 200.00 ft 0.50% 42.0000 1.12 min Channel 100.00 ft 2.00% 42.0000 0.28 min Impervious TC Data: Flow Type: Description: Length: Slope: Coeff: Travel Time Sheet 32.00 ft 2.00% 0.0110 0.62 min Shallow 370.00 ft 2.00% 27.0000 1.61 min Channel 200.00 ft 0.50% 42.0000 1.12 min Channel 100.00 ft 2.00% 42.0000 0.28 min TC of 3.63 min<5 min,program will use a tc of 5 min in computations. 100 yr Flow Time Volume Summary: 1.0530 cfs 7.83 hrs 16003.29 cf- 0.3674 acft Drainage Area: Proposed Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur 24.00 hrs Area CN TC Pervious 0.0000 ac 0.00 0.00 hrs Impervious 1.8000 ac 98.00 0.04 hrs Total 1.8000 ac Final Technical Information Report A00084 South 180th Street Grade Separation 11 April 2001 iImpervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet 32.00 ft 2.00% 0.0110 0.62 min Shallow 260.00 ft 5.00% 27.0000 0.72 min Channel 180.00 ft 3.00% 42.0000 0.41 min Channel 150.00 ft 0.50% 42.0000 0.84 min TC of 2.59 min < 5 min, program will use a tc of 5 min in computations. 6-month Flow Time Volume Summary: 0.5033 cfs 8.00 hrs 7249.07 cf- 0.1664 acft HydID Peak Q Peak T Peak Vol Cont Area (cfs) (hrs) (ac-ft) (ac) out-2yr 0.44 8.17 0.2661 1.8000 out-10yr 0.71 8.17 0.4004 1.8000 out-100yr 0.96 8.17 0.5648 1.8000 NODE ID: POND1 Desc: DETENTION POND - DOE Start El: 23.0000 ft Max El: 50.0000 ft Contrib Basin: Contrib Hyd: Length ssl ss2 Width ss3 ss4 70.0000 ft 3.00h:1y 3.00h:1y 34.0000 ft 3.00h:1y 3.00h:1y CONTROL STRUCTURE ID: D-001 -MULTIPLE ORIFICE STRUCTURE Descrip: POND1 MULT. ORIFICE Start El Max El Increment 22.9000 ft 50.0000 ft 0.10 Orif Coeff: 0.62 Lowest orifice: 5.0 in IE 20.90 out to 2nd: 0.44 ft Second orifice: 3.0 in IE 23.34 2nd to 3rd: 0.20 ft Third orifice: 2.5 in IE 23.54 Oulet elevation 22.90 Top of 12" Dia. Riser elev 24.0 RLPCOMPUTE [POND1-RLP] SUMMARY 2 yr Match Q: 0.44 cfs Peak Out Q: 0.44 cfs - Peak Stg: 23.33 ft-Active Vol: 820.01 cf 10 yr Match Q: 0.71 cfs Peak Out Q: 0.71 cfs - Peak Stg: 23.58 ft-Active Vol: 1489.54 cf 100 yr Match Q: 1.05 cfs Peak Out Q: 0.96 cfs - Peak Stg: 23.89 ft-Active Vol: 2374.47 cf �r Final Technical Information Report A00084 South 180th Street Grade Separation 12 April 2001 SOUTH 180TH STREET GRADE SEPARATION DETENTION POND DESIGN (65-FOOT ROADWAY SECTION) KCRTS METHOD Basin: existing Impervious area=0.909 acres Till grass area = 0.502 acres Flow Frequency Analysis Time Series File:existing.tsf Project Location:Se a-Tac Scale factor: 1 Time step: Hourly Data type: Reduce Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak Peaks - Rank Return Prob (CFS) (CFS) Period 0.266 6 2/09/01 2:00 0.538 1 100.00 0.990 0.218 8 1/05/0216:00 0.343 2 25.00 0.960 0.320 3 2/27/03 7:00 0.320 3 10.00 0.900 0.236 7 8/26/04 2:00 0.284 4 5.00 0.800 0.284 4 10/28/0416:00 0.283 5 3.00 0.667 0.283 5 1/18/0616:00 0.266 6 2.00 0.500 0.343 2 10/26/06 0:00 0.236 7 1.30 0.231 0.538 1 1/09/08 6:00 0.218 8 1.10 0.091 Computed Peaks 0.473 50.00 0.980 Basin: proposed Impervious area= 1.796 acres Till grass area =0.0 acres Flow Frequency Analysis Time Series File:proposed.tsf 2 Project Location: Sea-Tac Scale factor: 1 Time step: Hourly Data type: Reduce Annual Peak Flow Rates--- ------Flow Frequency Analysis------- FlowRate Rank Time of Peak Peaks - Rank Return Prob (CFS) (CFS) Period 0.435 7 2/09/01 2:00 0.849 1 100.00 0.990 0.383 8 1/05/0216:00 0.652 2 25.00 0.960 0.532 3 12/08/0218:00 0.532 3 10.00 0.900 --- 0.447 6 8/26/04 2:00 0.531 4 5.00 0.800 0.531 4 10/28/0416:00 0.466 5 3.00 0.667 0.466 5 1/18/06 16:00 0.447 6 2.00 0.500 - 0.652 2 10/26/06 0:00 0.435 7 1.30 0.231 0.849 1 1/09/08 6:00 0.383 8 1.10 0.091 Computed Peaks 0.783 50.00 0.980 Final Technical Information Report A00084 South 180th Street Grade Separation 13 April 2001 Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 3.00 H:1V Pond Bottom Length: 136.00 ft Pond Bottom Width: 33.00 ft Pond Bottom Area: 4488. sq. ft Top Area at 1 ft. FB: 6660. sq. ft 0.153 acres Effective Storage Depth: 1.00 ft Stage 0 Elevation: 100.00 ft Storage Volume: 5007. cu. ft 0.115 ac-ft Riser Head: 1.00 ft Riser Diameter: 12.00 inches Number of orifices: 2 Full Head Pipe Orifice# Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 3.35 0.304 2 0.75 1.55 0.033 4.0 Top Notch Weir: None Outflow Rating Curve: None Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.85 ******* 0.77 1.12 101.12 5666. 0.130 2 0.47 ******* 0.33 0.97 100.97 4825. 0.111 3 0.46 0.32 0.32 0.94 100.94 4655. 0.107 4 0.52 ******* 0.31 0.86 100.86 4253. 0.098 5 0.44 ******* 0.28 0.81 100.81 3958. 0.091 6 0.53 0.27 0.27 0.76 100.76 3716. 0.085 7 0.38 ******* 0.20 0.44 100.44 2072. 0.048 8 0.45 ******* 0.20 0.43 100.43 2012. 0.046 Route Time Series through Facility Inflow Time Series File:proposed.tsf Outflow Time Series File:pondout Flow Frequency Analysis Time Series File:pondout.tsf Project Location:Se a-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.281 5 2/09/01 7:00 0.768 1.12 1 100.00 0.990 0.201 7 1/05/0217:00 0.329 0.97 2 25.00 0.960 0.305 4 2/27/03 9:00 0.322 0.94 3 10.00 0.900 0.198 8 8/23/0419:00 0.305 0.86 4 5.00 0.800 0.266 6 10/28/0419:00 0.281 0.81 5 3.00 0.667 0.329 2 1/18/0617:00 0.266 0.76 6 2.00 0.500 0.322 3 11/24/06 5:00 0.201 0.44 7 1.30 0.231 0.768 1 1/09/08 8:00 0.198 0.43 8 1.10 0.091 Computed Peaks 0.622 1.09 50.00 0.980 Final Technical Information Report A00084 South 180th Street Grade Separation 14 April 2001 Project 190 IW S7— Sheet of Job Number BERGER/ABAM Subject U?AT F _G UA L I T Y Designer M D E N G I N E E R S I N C. Date 2 2 0/01 RE F, Kc- Sw -DM �,4, >,►, l3AsI C- LO TI�o1J b Ai = 59 , 170 SF PKOPOSED POADI- AV A�, - t� = Ao = O P _ 0, 47 _ 0, V/,I = 0. ( 59 , 170) x 4 = � , OS I CCF ►.21 Vb _ x V, 3 X -Z, 051 = 3 , VOLUY14E FACT-OK _ G, 15 3 Gi= FOR 6s1 SI C- PO J r7 FPCf' ,! POfJ D GALC�UCAT IO�J A-Nb RCAF MF� emu, E Nr�IVT VJ 6 , l S 1?1 L F > V6 0 k-- L-[- SL-CJPE S Final Technical Information Report A00084 South 180th Street Grade Separation 15 April 2001 e I d Staff gage and Ground Water Well o ions C .... 3 F SN 1 th St 167 ,S 19th � r > SW 21 st St C a t CU o o '2 (GW SW 23rd t 16. St 15. G 1 't ` cr> 11.(GW-9) 10) 600 0 600 Cv Scale in Feet CD SW' 7th St SW 27th St '3.(GW-4) •W_6�/76. W-6) W-8'.. 05. (GW-L., -- i SW2thS ^, 9 .4. W-5) C SW 30th St110. = I. .9. (GW-8) �8. (GW-7) . 7 G 6) � J 167 �' SW k4th St - ------- Alien Quynn - Springbrook pump,etc. Page 1 From: "Sharon L. Wright-SEA" <sharonw@1405.wsdot.wa.gov> To: "Allen Quynn" <aquynn@ci.renton.wa.us> Date: 4/5/2005 12:53:19 PM Subject: Springbrook pump,etc. Hi Allen, The below responses are just a piece of all of the discussions that have been occurring on this matter, but wanted to give you what we have written. I think we have some good ideas on making gravity work if we can workout the details. Plan on the Thursday meeting at 11:30--I'm waiting to hear from Mike, but I think we can do it. Thanks. Sharon -----Original Message----- From: Peterson, Beth C. [mailto:Beth.Peterson@hdrinc.com] Sent: Tuesday, April 05, 2005 9:23 AM To: Sharon L. Wright- SEA Subject: RE: Springbrook Geotech Work Sharon- Here are my responses to Ron's e-mail: - Flow from pond: The flow from the pond is anticipated to be 4.2 cfs, which is the capacity of the existing Tukwila pump station pumping to the pond. -Topography and alignment: The first page of the sketches we gave to the City show the proposed alignment. We assumed the easiest/best place for the pipe alignment would be along the roadway. This can be revised. The topography was actual survey completed by Huitt-Zollars in December 2004-January 2005. -Pipe material and cover over pipe: If the City would accept ductile iron pipe and only one foot of cover of the pipe that would be fine with us. Keep in mind the first 3 sketches involved us modifying the existing outlet manhole at the Tukwila pond to ensure that the water will be diverted into our site. The existing outlet elevation is 22.9. Ideally we would like our pipe to be completely below that elevation, so that all the water will be diverted into our site, and in the case of more extreme events it would still discharge through the existing outlet into Springbrook Creek. This would make our invert elevation of the pipe 21.4 (shown in the last 2 sketches). I think it is worth discussing what site regrading we could do to help make a gravity outlet work. Let me know if you have any questions. Beth ��,► ,� t�s. burl/ he rl"el ,nJc�l -fv S/� �i3 rum :�.v-� / Allen Quynn -Springbrook pump,etc. This e-mail and any files transmitted with it are confidential and are intended solely for the use of the individual or entity to whom they are addressed. If you are NOT the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, forwarding, printing, or copying of this e-mail is strictly prohibited. Allen Quynn - Re: Springbrook Geotech Work Page 1 From: Ronald Straka To: Sharon L. Wright- SEA Date: 3/31/2005 8:10-42 AM Subject: Re: Springbrook Geotech Work I received the sketches late yesterday and gave them to Allen to review. Based upon my review, it is my opinion that a gravity system is feasible. The gravity system is preferred by City of Renton due to maintenance reasons, and cost. I think that the BOC would prefer a gravity system vs a mechanical system, which requires energy that has environmental impacts to produce. we did our own analysis to see if we could drain water to the Site D wetland from the Tukwila pond and it looked like we had 2-3 feet of fall and it could be done, same as your plans. We should be getting the As-built drawings of the Tukwila S. 180th underpass that we could use to further refine the analysis. Do you have the flow that we were anticipating from the pond? I though Mat had done the research as to how much is pumped into the pond (average pump discharge), but I couldn't find any record of what that flow was, so we couldn't determine the size of pipe needed. The plans show a 15" pipe, but I cannot tell if the pipe size needs to be that large, since I do not know the design flow. Was the topography on the maps actual field data or was it the City topography? If there is concern about the lack of cover(1-foot would be acceptable to the City with Ductile Iron Pipe), could we consider doing excavation between the 19 and 21 contours to create more open water to gain a lower invert elevation and reduce the length of pipe. I think we may want to look to see if there are better alignments for the pipe, but this is a good start and I feel the gravity system is feasible. What does WSDOT think. The following are my comments regarding the Geotechnical Analysis draft of scope: 1. 1 have asked Allen Quynn to review all of the existing groundwater monitoring wells in the area and to determine which ones are functional or not. We should be able to provide you with a listing of groundwater monitoring wells that are functional so you shouldn't need the consultant to do that for you. We will provide you a listing and map of all ground water wells in the area along with which ones we have data on and the period for which we collected the data. 2. Allen indicated that he has already provided you (Mat)with our data regarding our ground monitoring that had done in the past. I asked him to review what we have already provided to you to verify that you have all of the information. 3. The City Wetland Mitigation Bank Program included geotechnical work on sites E and the eastern portion of Site C. You should already have the geotechnical reports for this work, which included test pits, soil characterization and ground water information. If not contact Allen Quynn to get the data. 4. Allen will be going through the files of other project in the area (City and Development)to get their Geotechnical reports that could be reviewed for useful information these projects included the following: SW 27th Street Culvert Replacement Oakesdale Ave SW Phase 1 &2 Transportation Project SW 27th/Strander Blvd Transportation Project Oakesdale Business Center Project(by Site D) Oakesdale Commerce Center Development Project(south of Site B) Other Development project near the sties. If you don't think this is useful, let Allen Quynn know as soon as possible, so he doesn't waste time gathering the information. In addition in the next 2 months we will be doing some geotechncial boring at SW 34 Culvert crossing of Springbrook Creek as part of our CIP project to replace the culverts with a box culvert in 2006 or 2007, depending on permits. We are in the process of signing a pre-design contract with RW Beck for this project within the next two weeks. AIIen Quynn - Re: Springbrook Geotech Work Page 2� >>> "Sharon L. Wright- SEA" <sharonw(aD1405.wsdot.wa.gov> 03/29/2005 4:53:38 PM >>> Ron--we are going to be looking for someone to do the following work at Springbrook. Let me know if you see an opportunity for shortcuts/cost savings or any other task you think of. Did you receive the pipe sketches? Thanks. Sharon review of plans review of existing data determine if existing wells are functional recommend additional wells and test pits as necessary excavate test pits perform laboratory to determine soil properties assess groundwater levels install piezometers/monitoring wells analysis of subsurface conditions estimate water retention Sharon L. Wright, AICP 1-405 Project Team Direct: 425.456.8572 Alternate: 425.450.6264 sharon.wright(a)1405.wsdot.wa.gov 600-108th Ave. NE Suite 405 Bellevue, WA 98004 This e-mail and any files transmitted with it are confidential and are intended solely for the use of the individual or entity to whom they are addressed. If you are NOT the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, forwarding, printing, or copying of this e-mail is strictly prohibited. CC: Allen Quynn 6.15 X 6.15 7.52 7.29 1010 X X 6.15 X 7.32 X X 7.29 0.30 6.15 X X 6.15 7.52 X6.15 X6.11 X7.32 6.15 7.29 X 10.10 X 1 7.42 X X X 6.15 6.15 X 6.15 ?; j 7.6f 10.30 X 6.15 X 1, r 6.11 X }1,n tc3 Lt X / X 10.10 X 7.81 6.11 X 6.11 X 6.15 X i $1 10.30 X X },, y, • ,, 6.15 i ✓ i 10.13 f:' X 6.11 6.11 6.11 X X X f X 10.33 �j X6.15 6.11 8. 3 v ✓ ' 6.11 f! 6.11 X X8.20.. 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X �2.0 - 90,vs- �.�►S Il 6.11 \ \ x x 6.11 X 10.26 X x 6.31 8 20 .......7.65 X X / X �Swpc = 1, _ a U o Z 3 10.20 i �> 7.62 x x -6.8Q X ._ X7.32 < I 7.78 7.32x X 66.44 LdPIO , ! x X 0.33 x 6.74 5 Nii X 81�4 (� X7 X6 \13 :-' . 0.17 X6.9O X7 2 6.64 1 7.32 i!I X 6 9.0 X X 23 X x 7 l 6.70 '' / 7.06 , .2�3 X x \ X 1 5 10 6 8 x6.83 .. x ,' X 6.90 �h.52 X 7.29 6.87 X 1 as X X X 10. 7 6.87 17.46 6.96 X X x 6:44 x / :.. .„......... 7.32 10 3 x 10. X 7.16 ` �� 7:52 6.54 X 6.44 x i x iid �I X 7.32 10. 0 ?� 7. 2 6.74 10 0 x 7.29 X 6.70 X 7.23.. X X 7.32 x 10. 9 6.74 �n is 71n Allen Quynn-RE: S 180th St Grade Separation As Builts Page 1 From: "Chris Walcott" <Walcott@abam.com> To: <Aquynn@ci.renton.wa.us> Date: 3/16/2005 10:01:53 AM Subject: RE: S 180th St Grade Separation As-Builts Allen: I'm not quite sure what elevation you're looking for, so here are all the one's I can think of. The pond has an outflow pipe with an IE of 22.0. This pipe has an IE into the flow control structure of 23.0 feet. The flow control structure has a 5"orifice at 20.90, a 3" orifice at 23.34 and a 2.5" orifice at 23.54. The riser overflow is 12" at 24.0. The flow control structure outlet IE is 22.9. The bottom of the first pond cell is 19.0 and the second cell is 20.0. The top of the divider is 22.0. The rim of the pond is 26.0 or more, except for 2y an overflow into the wetland at 25.0. I hope this gives you what you need. If not, let me know. -----Original Message----- From: Bob Giberson [mailto:bgiberson@ci.tukwila.wa.us] Sent: Wednesday, March 16, 2005 9:39 AM To: Walcott@abam.com Cc: Aquynn@ci.renton.wa.us Subject: S 180th St Grade Separation As-Builts Chris: Do you have an ETA on the final reproducibles for the As-Builts? Tukwila previously agreed to provide copies of the As-Builts to each of Renton's divisions (Water, Sewer, Surface Water and Transportation). Is this something that you can do within your current scope and budget, or should we plan on handling that through our printer? Also, Allen Quynn is looking for an immediate elevation at the water quality pond that dumps into Springbrook Creek(Allen is cc'd on this e-mail), if you could contact him directly, I'd appreciate it. Thanks, Bob CC: "Bob Giberson" <bgiberson@ci.tukwila.wa.us> r // SDMH RIM=25.81 IE 12"ABS W=21.91 IE 12"ABS S` 21.91 VT 2 SDMH RIM=26.52 IE 12"ABS NW--23.12 +• /E 890IP E=22.92 N Y NVJ fn mo+a v� L4 � zy� / \ \ ry�� I vn Co 4d,• X % isj / O +\`• z4�4 • \ ca W W4 41 If TOP L As a OF POND t�.. t � � �ti� • y i n � � ma z i' '= g0 ' P -v, Profile Window Alt.1 — 15" pipe at 0.5% 30 vvt IW.22.8 0 20 Y-1 'w. 10 e ++ + + + Stoon + + + + UNE SURFACE OFFSET Spdngbrook 0.00 Scal ed 5.0000 TimesTimesVer. S. ed 1.0000 Times Ho, Profile Window Alt. 2 Dicharging at Station 2+50 21" pipe atO.12% 30 "o INV.22.8 20 INV.22.0 10 + + r Q St*n + + LINE SURFACE OFFSET Spdngbrook 0.00 SmW 5.0000 Times Yff. SmIed 1.0000 Times 11or. Profile Window Alt. 3 Discharging at Station 0+00 15" pipe atO.42% k- 30 INV.22.8 20 \1,0 -,kj-j o 10 per + Stao?n + 4 + CW XKC LINE SURFACE OFFSET Sp(ingbrwk 0.00 Scaled 5.0000 Times Ver. Scaled 1.0000 rime.H.(. Profile Window Alt.4 No modification to existing pond outlet 18" pipe atO.27% 30 INV. 21.4 20 INV.19.0 10 + + + + + St*n + + + + 04 LINE SURFACE OFFSET SpHngbrook 0.00 Sco ed 5.0000 Times Ver. Styled 1.6000 Times How. Profile Window A Alt. 5 No modification to existing pond outlet 30' pipe @ 0% 30 I V. 21.4 20 10 + St*n + + + 11100 4.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN General The proposed conveyance system was analyzed and designed in accordance with the current guidelines listed in the KCSWDM. The Rational Method was used to compute the 25-year peak discharges for all pipelines, and the 100-year peak flow for the pump capacity. Table 2 shows the precipitation coefficients and calculated peak flows. Gutter flows and inlet spacing were determined by using the method listed in the Washington State Department of Transportation(WSDOT) Hydraulics Manual. The Backwater Analysis method was used to analyze the new system to verify adequate capacity. Computations are attached at the end of this section. Table 2. Precipitation Intensity Coefficients for Rational Method Recurrence Interval 24-Hr Precipitation aR bR Flow 25-Year 3.4 inches 2.66 0.65 4.183 cfs 100-Year 4.0 inches 2.61 0.63 5.012 cfs Source: King County Surface Water Design Manual Runoff from South 180th Street will be collected by catch basins along the gutter on both sides of the roadway. No modifications are proposed for the off-site lines. Subbasin West 72nd Avenue South(Station 11+20)to Station 12+25 No modifications are proposed to the existing system west of 72nd Avenue South. The existing roadway storm sewer system east of the intersection must be removed. New catch basins and 12- inch pipe will collect and convey runoff from Station 12+25 to the west. This system will be tied to the existing system on 72nd Avenue South. Subbasin East Station 12+25 to Springbrook Creek Culvert (Station 21+84) Runoff will be collected by catch basins along the gutter on both sides of the roadway. The mainline of 12-inch pipe will convey the flow to the pump station located on the north side of the road, approximately at Station 18+00. The station will have two pumps that alternate pumping the runoff. This allows for even wear on both pumps and provides for a backup pump during the maintenance or replacement of one pump. The runoff then will be pumped to the new stormwater facility located 50 feet north of South 180th Street and east of the tracks for water quality and water quantity control. Flows from the new facility will be conveyed via 12-inch pipe to the existing 36-inch RCP system and discharge to Springbrook Creek at the original outfall. Springbrook Creek Culvert (Station 21+84)to End of Project (Station 22+40) No major modifications are proposed to the existing system. Final Technical Information Report A00084 South 180th Street Grade Separation 16 April 2001 Project S 196 TH Sheet _ of Job Number A 00 4 4 BERGER/ABAM Subject PEAK F L.O 0 Designer M b E N G I N E E R S I N C. FOR Co M EyA tJC.E. Date KLSW DM l �l� FATIO>JAL ME rHob T = L/(Go V-, L _ 4�20 _ GL6R KR = AO R/(T) S A - I,7 Ac, A G o, q0 T = 4.G0 t(60 X 2 0 x VO, n�� = 1, 97 MIN, LET T = 6 , 3 M „V, r P- 3,4 lNcft 7�3 4 X , 73.4 7 = 4. 19 3 CPS o,C> 12- 0 , 8S19 P- 4,0INCH Z = 4 , 0 x 0, 9,Io = 3,27& O. = 0. 90 X 3, 7C, x i, 7 = 5 , OIZ Cr=S = z, 50 (:rPNI Final Technical Information Report A00084 South 180th Street Grade Separation 17 April 2001 Project Sheet of Job Number BERGER/ABAM Subject t>P A Designer �D E N G I N E E R S I N C. 7T• _ %.,C'►.t Date RsF{KF0CF 4=. SrC?T ��Y7 �°.F' �.•' L ETL i 1i 1! TKA6'F' ,'. iy st!Jr J �f � U -o /O i _ q. 5 x �� CJ� / q d d x s. e, ►g ._x 5,:� C. it GL C i. 0. 1`I R Final Technical Information Report A00084 South 180th Street Grade Separation 18 April 2001 HIGHWAY DRAINAGE(English Units) T= 5 Project Name: S. 180th St. Grade Separation m= 6.89 Project Number: A00084 n = 0.539 S.R.: NA C= 0.9 Designed By: MD I = 2.89384 (25-yr 24-hour storm) Date: 1/5/2001 GW= 1.67 Width= 32.5 (1/2 of roadway width+sidewalk) dmax= 0.19' (depth of flow at face of curb) Zmax= 9.5 (from curb to 1/2 of lane) Sta. Width Distance I Delta Q1 Sum Q1 Sloe IsuperIG.W.1 d I Zd I V I Q bp 1 12+15.00 ---- ------- ---- ---- ---- ---- --- --- --- --- ---- ------------ 14+11.00 32.5 196.00 0.381 0.381 6.00% 0.02 1.67 0.07 3.51 3.50 0.068 15+70.00 32.5 159.00 0.309 0.377 3.50% 0.02 1.67 0.08 3.87 2.89 0.084 16+60.00 32.5 90.00 0.175 0.259 1.00% 0.02 1.67 0.09 4.25 1.67 0.068 16+90.00 32.5 30.00 0.058 0.127 0.10% 0.02 1.67 0.10 5.01 0.60 0.043 22+80.00 ---- ------- ---- ---- ---- ---- --- -- 20+50.00 32.5 230.00 0.447 0.447 3.75% 0.02 1.67 0.08 4.07 3.12 0.109 18+07.00 32.5 243.00 0.472 0.582 3.50% 0.02 1.67 0.09 4.56 3.30 0.172 17+20.00 32.5 87.00 0.169 0.341 0.75% 0.02 1.67 0.10 4.98 1.64 0.115 16+90.00 32.5 30.00 0.058 0.173 0.10% 0.02 1.67 0.11 5.63 0.66 0.068 Reference: WSDOT Hydraulics Manual 5.4,5.5 i 1 1 Final Technical Information Report AOOO84 South 180th Street Grade Separation 19 April 2001 o � R w � � (D o � � w K - m m a �o n � w w a c, m �o M 't7 w � � b w o R. z o �* 0 -- - .. 1 -_ T. _._- - i A0008 t - South 180th Street Grad BARREL Separation� e e I I 1 , � 1- 1-- � I 3ackwater Calculation zs-yr 24-hrs Storm L L ENTR ENTR EXIT OUTLET INLET APPR BEND JUNC DESIGN'--- - VEL ROM TTO' 02 01 03 SIZE!LENGTH' SLOPE C _ EL. El. HEAD (cir) EL LOSS EL. LOSS LOSS CNTRL 1 CNTRL VEL HEAD HEAD HW RIM FREE- , r I ( ) ( ) ( I 1 ( ), O O �- -O O O -(] �L- O_-r ,-ELEV. _HEAD,� LOSS LOSS. EL EL BOARD (cfs cfs) (cfs In tt)I (fVtt) ft)_ (tt) '_(It) ! (tVs tt tt tt ft tt HEAD ! 1 i Kf OUT IN AREA VEL i d� (D+d�)/2 TW FRICT. LAT.' PIPE PIPE. PIPE n Ke Kb z tt tt tt 4 ELEV. _:_-(tt) (ft) (tt) (tt) (tt) , HGL HEAD i _ 0 01 0 00 1.3-0, 1.50 0.79 5 27 0 43 0.85 0.93 2.50 0 171 2.67 1 0.22 0.43 3.32 _3 20 0.139 0.00 0.00 3 18 9.03 5.85 � P.S. 15 4.140 - 4.140 0.00� 12 -�, 15 001 0.013 0 012;0 5 I _. 0.010 10.0121 0.5 0 0/ !0 00 1.60 2 50 0.79 2.99 0.14 0.64 0.82 2A2 0.319 2.74 , 0.07 0.14 2.95 3.45 0.139 0.00 0 00 3.31 ' 7.18 3.87 I 12 07 00'� I '0.00' � _. � '. 15 13 2.350 2.350 0 00 0.82 3 42 0 110 3.53 0.07 0.14- 3 74 3,95 J 0.026 0.00 0.00 3.92 705 313 13 11 2.350 2.350 0.00 12 30.00 0.013 0.012 0 5 0 01 ,0 00 2.60 3 00 0 79 2.99 0 14 0.64 0.010 `0 012,0 5 i 0 01 0 00'! 3.60 3 90 0.79 1.29 0.03 0.42 0.71_ 4.31 0.020 4 33 0.01 0 03_ 4 37 4 50 0.042 _0.00 0.00 446 7.18 2.72 O 19 7 0.960 0.960 0.00 12 90.p0 0.010 0.012 0 5,0 0110 00 4.00 5 70 0.79 1.22; 0 02 0.41 0.71 14 71 0.055 4 76 0.01 0 02 y_4 80 6 30 0.016 0.00 0.00 6.28 9.16 2.88 i _ 12 010 010 - 12 159.001 0.051 0.0121 0 5 0.01 0.00 1 5.80 13.90 0.79 1 1.02, 0.02 0.38 0.69 6.49 0 068 6.56 0.01 0.02 7_6.58_ 14.50 0.042 0.00 0.00 14.46 17.61 3.15 5 3 0.500 10.289 0.00! 12 B5.001` 0.059 1 0.012'_0 5 0.07 it 0 00 15.00 20 00 0.79}1.64{ 0.04 r 0.48 0.74 1 15,74 0.094+_15,83 -0.02 0.04 15.90 120 50 t-0.000 0.00 000 20 50 2.11 15 16 1.000 1.000 0 00 12 50.301 0.010 0.012 0 5 0 01 0 00 4.50 5 00*0.79 1.27 I obi` 0.42 _ 0 71_ r 2.50 i_0 033_IT_2 53 4 0_01 0.03� 2.57_7__5 50 0.076 T 0.00� 0.00 5.48 129.03' 3.55 16 18� c800 0.8001 0.00_- 12 I. 141.00� 0,057 '0.012 i 0.5 0.01�0 00!5.10,13.10 0.79 1.02 j 0 02_' 0.38 1 _0.69 5.79 .0 060_t 5 85 _0.01 _02 _5 87_ -_13 60 t0002 0,00 �0.00 r 13 60) 16.23� 2.63 _ }0.20 _. ! - _ ---. 0.79 t 0.38 11 0.00 0.23 4 0_62__f 14.421.0.006 1 14_42 0.o0 0.00 '_1 2_y_16.80T_0.000� 0,00- 0_00_11680{ 20.9 2.10 t- r -- i i - -1 0 5 0 0 0 42 13 80�18 30 - -- --- - - - ----- - -t- 4 1 B 20, 0 500 ,0.300 _12 --102 OOI 0.044 0 012� � _ - -. - r -� -_ -- � ----- _ ..�- -.. - --- .. .. ... . ... References. Kin Coun Surtace Water Des n Manua! and WSDOT Hydraulics Manual a LV O O O O 00 5.0 SPECIAL REPORTS AND STUDIES Because there are no new roadway developments proposed within the floodplain, a flood hazard study is not needed for this project. However, the project will impact the wetlands located within the project site thus impacting their flood storage capacity. The impacts to these wetlands will be analyzed in the following sections. See South 180th Street, Grade Separation Wetlands Study, (BERGER/ABAM Engineers Inc., 1999) for detailed descriptions of the wetlands. The project proposes to fill part of the wetlands located between the existing tracks to construct the shooflies for the railroad tracks. Approximately 1.09 acres of Wetland B, which is located north of South 180th Street, will be filled. Assuming that the displaced volume of 170,000 cubic feet of water in this impacted area is added to the remaining of 24.5 acres of Wetland B and the connecting wetlands, the water level would be raised by 1.9 inches. This small change in water elevation will not create or aggravate any existing drainage problem in the Springbrook Creek floodplain. Wetland C, which is located between the existing tracks and south of South 180th Street will be completely filled. Because Wetland C is less than 0.1 acre in size, and its flood storage capacity is low, impacts to downstream flooding is minimal. ' A wetland mitigation plan was developed for the project to compensate for impacts on Wetland B and Wetland C at a ratio of 1.5 to 1 (area created to area impacted). The impacted flood storage capacity is thus compensated. Other Studies A geotechnical engineering report, studies of wetlands, streams, and wildlife were completed for this project. r i Final Technical Information Report A00084 South 180th Street Grade Separation 21 April 2001 6.0 BASIN AND COMMUNITY PLAN AREAS Not applicable for this project. Final Technical Information Report A00084 South 180th Street Grade Separation 22 April 2001 ' 7.0 OTHER PERMITS ' The required permits needed for this project are listed below. Grading DFW HPA ' COE 404 JARPA i i 1 1 1 i 1 1 i Final Technical Information Report A00084 South 180th Street Grade Separation 23 April 2001 ' 8.0 EROSION/SEDIMENTATION CONTROL DESIGN A Temporary Erosion and Sediment Control Plan will be submitted with the final construction plans to the City of Tukwila for approval with the construction permit application. Construction phasing will minimize the extent and duration of areas exposed. Mulching and seeding disturbed areas will be done as soon as grading is completed. Filter fabric fences will be installed downslope of all construction areas and sediment traps will be used to protect new and existing catch basins. Runoff from the construction site will be conveyed to the sediment pond for settling before discharge to the existing outfall. Final Technical Information Report A00084 ' South 180th Street Grade Separation 24 April 2001 ' 9.0 BOND QUANTITIES WORKSHEET, RETENTION/DETENTION FACILITY SUMMARY SHEET AND DECLARATION OF COVENANT 1 Bond Quantities Worksheet The stormwater facilities will be bonded per the requirements of the City of Tukwila. 1 1 i 1 1 1 1 Final Technical Information Report A00084 South 180th Street Grade Separation 25 April 2001 ' 10.0 MAINTENANCE AND OPERATIONS MANUAL A Maintenance and Operations Manual will be prepared for the stormwater facilities as outlined the KCSWDM. The Maintenance and Operations Manual for the pump station will be prepared according to the manufacturer requirements. 1 Final Technical Information Report A00084 ' South 180th Street Grade Separation 26 April 2001