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18-102329-SFREFZUBMITTED JUL 0 3 2018 MEMORANDUM 4701 SW Admiral Way, Ste 353 M Seattle, WA Date: May 24, 2018 To: City of Federal Way Public Works Department From: Anna Nguyen, P.E. Subject: Drainage Design Project Address: 27xx S 282nd Street, Lot CFTY OF FEDERAL WAY COMMUNFTY DEVELOPMENT www.ConceptBusinessGroup.com -Dwuftned by: LA-A4n r A4V.4 . pa363A2AA4134C0. Design Requirements The City of Federal Way utilizes the Addendum to the 2016 King County Surface Water Manual (KCSWM), dated January 8, 2017 for its drainage requirements. The project is subject to Drainage Requirements because the project is a "single family residential... project that results in >_2,000 sf of new plus replaced impervious surface..." Impervious Surfaces (SF) Proposed House (including overhang) 2,096 Proposed Driveway 376 Proposed Walkway 18 Total NEW Impervious Surface 2,490 Flow Control The project meets the Basic Exemption from Flow control in Core Requirement #2: Basic Exemption #1, because less than 5,000 SF of new plus replaced impervious surface and less than 3/ acres of new pervious surface is proposed for the development. Water Quality This project is exempt from Water Quality treatment as defined by Core Requirement #8 because it proposes less than the 5,000 SF threshold of pollution -generating impervious surface (PGIS). PGIS is defined as "an impervious surface considered to be a significant source of pollutants in surface and storm water runoff. Such surfaces include those subject to vehicular use or storage of erodible or leachable materials, wastes, or chemicals, and which receive direct rainfall or the run-on or blow-in of rainfall." Non-metal rooftops are not considered PGIS; therefore, are not included in the PGIS area calculations. Infiltration Test An infiltration test was conducted at this site on May 12, 2018. Per the Infiltration Memorandum, prepared by our company, dated May 22, 2018, measured infiltration rate is 1.5 inches/hour. A NEW DIMENSION OF DESIGN PERCEPTION Lot B - 27xx S 282"d Street Page 2 of 3 Small Lot Stormwater BMP Evaluation The project utilizes Better Site Design by generally matching existing grades where feasible. Existing trees and other vegetation around the site perimeter will be preserved where possible to help minimize disturbance to the hydrologic cycle. Native soils in all disturbed pervious areas will be amended with compost. Soil Management Plan Within the limits of site disturbance, duff and topsoil will be retained in an undisturbed state and stockpiled for later use to stabilize and amend soils throughout the Site. Postconstruction soil amendment will meet the requirements of Appendix C, Section C.2.13. BMP Feasibility and Applicability Discussion • Full dispersion, per Appendix C, Section C.2.1, of runoff from impervious surfaces is not feasible due to insufficient area on the site for dispersion flow paths. The site does not contain native vegetation; therefore, a native vegetative flow path of 100 ft is not feasible within the project limit. ■ Full infiltration, per Appendix C, Section C.2.2, is not feasible. As discussed in above, infiltration tests were conducted with measured rates of 1.5 inches/hour. Sites with measured infiltration rates less than 2 inches/hour contain soils equivalent to "fine sand" classification. Full infiltration is only feasible on sites with coarse or medium sand. ■ Limited Infiltration is feasible for this site. No other BMP's is required to be evaluated for roof stormwater management. • Permeable Pavement, per Appendix C, Section C.2.7 is not feasible for the driveway surface area because the slope of the driveway exceeds 10%. Stormwater from the roof and driveway surfaces will be mitigated using limited infiltration BMP's. Per the 2016 KCSWM Section C.2.2, infiltration trenches for projects with fine sand soils must be at least 21 feet in length per 1,000 square feet of new impervious roof surface based on a 2 feet wide bottom. Infiltration BMP Facility Design Impervious Surface Required Provided 2,096 SF (roof) + 376 SF (driveway) 52 LF x 2' W x 2' D = 104 SF x 2' D 35 LF x 3' W x 2' D = 105 SF x 2' D Erosion & Sediment Control Plan All erosion and sediment control (ESC) measures shall be governed by the requirements of the City of Federal Way. Erosion control measures have been included on the Site Plan to assist the contractor in complying with these requirements and designed to prevent sediment -laden run-off from leaving the site during construction. Mark Clearing Limits/Minimize Clearing Prior to beginning land disturbing activities, all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area and any existing or proposed LID facility THE CONCEPT GROUP Lot B - 27xx S 282"d Street Page 3 of 3 areas shall be clearly marked, both in the field and on the Simplified site CSWPP plan, to prevent damage and offsite impacts. Minimize Sediment Tracked Offsite Install a stabilized entrance for construction vehicle access to minimize the tracking of sediment onto public roads per TESC Plans. Trapping Sediment Erosion/ sedimentation control is achieved by a combination of structural measures, cover measures, and construction practices that are tailored to fit the specific site. ESC control measures will be used to reduce erosion and retain sediment on the construction site. The control measures will be selected to fit specific site and seasonal conditions. Refer to attached ESC details. The following items will be used to control erosion and sedimentation processes: ■ Filter fabric fences (silt fences) ■ Ground cover measures such as straw cover and/or hydroseeding • Dust control Construction Sequence and Procedure Prior to the start of any grading activity upon the site, all erosion control measures, including installation of a stabilized construction entrance, shall be installed in accordance with the construction documents. The best construction practice will be employed to properly clear and grade the site and to schedule construction activities. The planned construction sequence for the construction of the site is as foI lows: 1. Flag or fence clearing limits. 2. Install perimeter protection (silt fence, brush barrier, etc.). 3. Maintain and relocate erosion control measures or install new measures so that as site conditions change the erosion and sediment control is always in accordance with the 2016 King County Erosion and Sediment Control Standards. 4. Cover all areas that will be unworked for more than seven days during the dry season or two days during the wet season with straw, wood fiber mulch, compost, plastic sheeting or equivalent. 5. Upon completion of the project, all disturbed areas must be stabilized and BMPs removed as appropriate. THE CONCEPT GROUP ATTACHMENTS DRAINAGE & ESC PLANS I I I ! I I I I I I' I I I I ! os� 1 I DRALVRA[}E•: /LyfA1,LOWJJ0E 74Di FENCE _ "k W60CTS`D,P1Ny.�l i-00 I ` FOR TIME PNOTECg1 1 � [ 1 •' I CLEARBCC LIAR .I [ I6.TP2 SF�0.17 ACRE1 ' 1 mT+PGRARr srocllacE I COVER S I , PER WAX. im SHEET 1 I lI Elf. III SEWFJR EA$EMETRT JIBE I momwi11 INSTALL SRT MW PER OETNL THIS SHEE' I I I I PRDTALLCONsmucTweNTR HCE e � i f I i lam DEYAIL iHc+TvrcEr ME EA EMENTCE E T pE.0.'a �TOI IOtI751 A. Pr •��L ..�_ _ . = Ids + �.�:�.. Y,1.•. EART "IVtA.IM VCLWE GP I IIII ATES: LOCATION CUT (CY) F LL (Cl) SITE 6 FOUNDATION 130 40 IIDiUONTAL LRMNIC SCVE 10 6 0 s 10 LIL - 1 B REC WROED CONSTRUCTION BEOLENOE. MNITRACTOR TO PROTECT MUD FROM BED10 TRACKER] ONTO IHE IrNUIIC RAAD MIN. 1FLAG OR FENCE CLEARING LIMITS. 2. INSTALL CATCH BASIN PROTECTION IF REOUIRED. 3. GRADE AND INSTALL CONSTRUCTION ENTRANCE(S).4. INSTALL PERNETER PROTECTION (SILT FENCE, BRUSH BARRIER. ETC.). S.MAINTAIN EROSION CONTROL MEA3URES IN ACCORDANCE WffH lbft CITY OF FEDERAL WAY STANDARDS AND MANUFACTURERSEDGEOFE1fI RECOMMENDATIONS6.RELOCATE Pt EROSION CONTROL MEASURES OR INSTALLNEW MEASURESSO THATAS SITE CONDI IONS CHANGE THE EROSION AND SEDIMENT CONTROL IS ALWAYS IN ACCORDANCE WITH CITY OF INSTALL DRIVEWAY CULVERT �. PROVAEfiAf. TYPE REDMOND EROSION AND SEDIMENT CONTROL STANDARDS. IFTIEREISAR0AOr111E r 2,COVER ALL AREAS THAT WILL BE UNWORKED FOR MORE THAN DSRESSMORESSAREA PERKING COUNTY ROAD STANDARDSOIoffxtILR LMDEIBCRESEVENDAVS DURING THE DRY SEASON OR TWO DAYS DURING THE WETSEASON WITH STRAW, WOOD FIB ER MULCH, COMPOST, Nam& PUSTIO SHEETING OR EW NALENT. AS PER KMD toutaYROAD STMIOAHU$DRWEMAYS$HALL IRE PAVED TO THE EDGE OF B. STAS12E ALLAREAS THAT REACH FINAL GRADE WITHINSEVEN RGS HT -OF -WAY PRIOR TO YAUN110H0F THE 0DIMPRMIM ENTRANCE TO AVOID DAMAGING OF DAYS. THE ROADWAY. B. SEED OR SOD ANY AREAS TO REMAIN UNWORKED FOR MORE THAN AD IT IS RECOMMENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE ROM 30 DAYS 10. UPON COMPLETION OF THE PROJECT, ALL DISTURBED AREAS MUST CONSTRUCTM ENTRANCE DETAL BE STABRJZED AND SMPS REMOVED IF APPROPRIATE PER 2015 KCSWDM FIGURE C.3.1A SCALE NONE T X T X 14 GA WIRE OR OXW ALENT, 1l8YANOARD STREN0I.RTASRDCu6E0. FILTERFABRK: - � TIT xBEn I u T 'I BgIA� R� 11r--MV-11- C MYR — POST SPACMVIAY BE 1NC11EAM TO V IF WIRE BACKWO 5 USED LLOR 31RVRT1,q'%f'1N000 POBTS.STEEG$L tZgWAUEN,WASHED GRAVEL REDAR OR EOVNAIbT WASHED GRAVEL NOIED FILTER FABRIC FENCES SHALL BE INSTALLED ALONG CONTOUR WHENEVER P05561E SLT FENCE DETAL PER 2016 KCSWDM FIGURE CJDA SCALE NONE TOE IN SFIE"NB M MWn1UMsW TRENCH SANDBAGS. OR EGUNALENT MAYBE USED TO WEIGHT PLASTIC SEAMS BETWEEN SHEETS MUST OVERLAP A MINIMUM OF 12-AND BE WEIGHTED OR TAPED AT TOE WHEN NEEDED M AAE= COVEFM DETAL PER2016KCSM FIGUREC.3AA SCALE NONE t ALL WORK AND MATERIALS TO BE PER CRY OF FEDERAL WAY STANDARDS. 2. KEEP OFFSRE STREETS CLEAN AT ALL TIMES. FLUSHING STREfZS SHALL NOT BE ALLOWED. ALL STREETS SHOULD BE SWEPT. 3. ADDITIONAL EROSIONISEDMENT CONTROL MEASURES MAY BE REQUIRED BY CITY INSPECTOR A. WHEN WORK IS STOPPEDCOMPLETED WAN AREA, THE CITY WSPECTOR MAY REQUIRE POST -CONSTRUCTION EROSION CONTROL INCLUDING SEEDING OR OTHER MEASURES. 6. LOCATIONS SHOWN OF EXISTING UTILITIES ARE APPROXIMATE. IT SHALL BETHERESPCNSIBRITY OF THE CONTRACTOR TO VERIFY THE CORRECT LOCATIONS T AVOID DAMAGE OR F THE CONTRACTOR B. S SHALL. BE THE OTHERR RELATED PERM CONTACTORTO OBTAIN STREET USE AND OTHER RELATED PERMITS PRIOR TO ANY CONSTRUCTION. ALL COVER IS TO REMAIN UNDISTURBED OUTSIDE OF C S. THEINSPECTED. AND OPERATING ANY GRADING OR L BEEXTENSIVE INSTALLED, INSPECTED. AND OHESE BEFOREANY BEADINGGR SATISFACTORILY LAND AINEDUCLEARING. THESECONTROLSMUST N SCAPIN ARECO MAINTAINEDUNTIL CONSTRUCTION AND LANDSCAPING ARE COMPLETE B. TIEIMPERVIOUS SURFACES (ROOF,SSOONS, DRIVEWAYS, ETC.) TO COMPLETED DRAINAGE SYSTEM AS SOON AS POSSIBLE 10. AND ALL NBMUCPERMITS U MEETING WITH DBHE CONSTSUCTIONTARTO DIVISION AND ALL PERMITS MUSTBE COMPLETED BEFORE STARTOF CONSTRUCTION- 11. CLEARING LIMITSSHALLBE BE LOCATED BYA LICENSED CIVIL ENGINEER OR LAND9BNH10R. 12 APPROVAL OF THIS TEMPONARY EROSIONISE OVALOATION CONTROL ROAD(TESC)PLANDOESNOT CONSTITUTE AN APPROVAL OF PERMANENT ROAD OR DRAINAGE DESIGN, 13. THIS APPROVAL FOR TE30. IS VALID FOR CONSTRUCTION BETWEEN MAY L AND RAINY E SEASON (O0. THIS OBER 1 THROUGH FOR PRIL IS NOT VALID FOR THE RMNV SEASON (OCTOBER 1 THROUGH APRIL 30). I E<EM PROPERTY ME �� ADJACENT PROPERTY LINE _--- RIGHT OF WAY LINE IAP� VrIMh I18IOW. - — RIGHT OF WAY CENTERLINE CdllDeA7reyavdig. - — — — — — - IXEAgEvrNriWE LUND. I 1OF M y1 2 LuwC Co C.=PQ Q� Lb Z 0 N 3J 0XLu cl c'j Lu LL YfI�IFI �Ii �I �r ! 1 ! I i �kABE v4r� I REC.f Tgp20RJ0L1 i I ! ! ! yTT FILM VE ROOF DTi ROOF DDII'R SPOUT WRH WA%*DROCK314'• 11/2' OVERFLOW WYE AND �RKHD PERFORATED PIPE ®OD% SPLASH BLOCK E%WTu4D[.ROU40 ------- �-- --- ----- E--r- BOUD PIPE • alII FINE MESH EN� a I T ELEVATION VIEW NTS PROPOSED r PM1�J✓POS D 5FR i s OYCkR4NG F.XMIT hG GROUND [y.CKFILI -. 4-PERFORATED', lF �- TI FOOPE -ecnuc.wr r. TO DRAT (SLOPE TO DRAM) I r s c,uraE.urra fill - +A'(f11 FILTER FABRIG�(E'P�RELY I I ' IREORADE F•]C DIiCM^ ��{ x. ] �� CR161D PERFORATED PVC%PE 1T- I I AS pF�r P ^'y�f1 � '�4 WDLEVEL (fYP) WASHED ROCK 3!4'-1 12' (TYP) 1 YR�.'l40NP4YiMMY I —� C PVC DOWNSPOUT DRAIN LINE s T1Nl5f4DRADE �-- BACKFILL -PRq'IDDT 12' MN CAVERAGE OPDRAWWFIN CLEAN I wr.3A' WAS"DROCK FILI ER FABRIC �Y rAD 1100%OR EQUIVALENT) DiMEWAY N PERFORATED PVC FOOTING DRAIN LINE NOTES >5 r PSEEASEM6FT ROOF I FUDTHC7 RAILTRATION TRENCH DEL f 1 T2EC.�11W901001 SfXENONE DRAIN LINES TO BE SEPERATE AND TIGHT. PROVIDE CLEAN OUTS. ELBOWS _ AND OTHER FITTINGS AS NEEDED. '".'.__ SITE DATA DRAINAGE DETAIL SECTION A —A _- `� .'.-••. .__ .•• •. CEN34AL NOTES LOTSIZE=IQSWSF SCALE' NONE J� a • r.-r1 _ 1. CONTRACTOR SHALL FIELD VERIFY ALL GRADES PRIOR TOCONSTRUCTION. NEW IMPERVIOUS SURFACE DRIVEWAY. 376 EF , "' • NBATSAWCUTLINS WALKWAY-1B SF ROOFINCLUDEOVERHANGA f 4- _ - p/�g� a S.2V I IIC� a EA—Tg-H mwwq - — - - PARCEL NLWWR 2312400080 COVERED PORCH I PATIO =2.0%SF TOTAL IYPERVIOU8e2,440 8FIO HOMZOMIL ORNML SGIE 5 0 5 ID CONSTRUCTION NOTES: II O7 INSTALL 22 LF 4- PVC SIDE SEWER LATERAL Q 2.00% MIN ©INSTALL 15 LF4- PVC ROOF DRAIN COLLECTOR@ 2.00% MIN- I@ MTALL22 LF 1T DI CULVERT ® INSTALL 50 LF 4- PVC SO®Z00%MIN. LEGENDCaliae(P6Eycu(11p O2 INSTALL 37 LF V WATER SERVICE LINE (D INSTALL 13 LF 4-SOLID PVC FOOTING DRAW ® 6.00% PROPERTY LINE ASPHALT PAVEMENT (0as' HAM CL 10. PG 64-M OVER Q Y' WATER METER (BY LAKEHAVEN WATER AND SEWER DISTRICT) COLLECTOR®20D%MIN. 1© BEVELED PIPE END WITH(10'. 89 APRON OF - - - - - ADJACENT PROPERTY LINE CAT CSTC OVER OA2' CSBC) R 4 O CONSTRUCT ROOF/ FOOTINGIDRIVEWAY ID CONSTRUCT IB'ASPHALT DRIVEWAY APPROACH SHEET. 2-4' QUARRYSPALLS. IE-427.1E ----RIGHT OF WAY LINE CONCRETE PAVEMENT (4-CONC) INFILTRATION NCH PER DWG NO.3S THS SEE LEGEND 1 UTILITY TRENCH ® TDR PER DE 1 T) ' (3W •35'Lx2TJ)PER DETNLITHS SHEET OB CONSTRUCT CONCRETE DRIVEWAY. SEE LEGEND ( POWER A COMMUNICATION) - RIGHT OF WAY CENTERLINE PROPOSED STRUCTURE o O5 INSTALL CB-TYPEIGRAREADRAINWTRISOLIDUD WSTaco-TYPE 1 WITH VANED GRATE 1®INSTALL 5 LF 6-PVC SO®2A0%MIN. ...................... OVERHAN3IFAVE IE bAi 1 ® INSTALL ITLONGK SWIDESLOTTED DRAIN(DURA) - - - - - - EXEASEMENTIINE 1E ($1►i24Jp 11=0 RASED 1RAFFFC L1O --.-ZE SHEET MNO. 2 C2 z w � M i c _F—¢ J_ Wzr '0 Y de N L. � 0 cf) N W LL MPFAMPAIUM M Date: May 22, 2018 To: City of Federal Way From: Subject: RESUL m-FTED JUL 032018 CITY OF FEDERAL WAY 206.446.1291 • www.ConceptBusinessGroup,com Anna Nguyen, P.E. - '�a, `� rs �� w - ❑WUSIgneeny' ssf Infiltration Assessment J- EMWA2AA413403 . Project Address: 27xx South 282d Street (Lots I and 0) Geologic Setting The Geologic Map of the King County, by Derek B. Booth, Kathy A. Troost, and Aaron P Wisher, published in March 2007, was referenced for the geologic and soil conditions of the project site. According to this publication, the surficial soil unit at the project site and its immediate vicinity is mapped as Till (Qvt). 2' St A m project" location f-.�y `r �.� QW 288i St - St Figure 1 - Geologic Map of King County (Not -to -Scale) Soils Investigation Soils on this property were investigated under my supervision on May 12, 2018. Three (3) test pits were excavated in the vicinity of the proposed stormwater BMP location. In accordance with Section C.2.2 of the 2016 King County Surface Water Design Manual, soil logs are required to be excavated to a minimum depth of 5 feet. Soil log explorations were excavated to a depth of 6.0 feet at this site. Refer to Figure 2 for the test pit locations. ANEW DIMENSION OF DESIGN PERCEPTION 27xx S 282"d St Page 2 of 4 Groundwater The soil sample was collected during the dry -season. No groundwater seepage was observed. It should be noted that groundwater levels vary seasonally with rainfall and other factors. Hydraulic Restrictive Layer The test pits were excavated to a total depth of 6.0 ft. There was no restrictive layer or hardpan clay at this depth. EPA Falling Head Infiltration Test Infiltration tests were conducted at the site following the EPA Falling Head test methodology. Data from Lot B and Lot C were consistent, with the most limiting measured percolation rate of 1.50 inches/hour for both sites. Figure 2 - Soils Test Pit Location (Not -to -Scale) THE CONCEPT GROUP 27xx S 282nd St Page 3 of 4 Depth (FT) Sample USCS Graphic Description 0.0 1 top soil 0.5 1.0 1.5 r y��r 2.0 2 SP compacted brown sand with some gravel, 2 5 no mottling or water seepage ��" 3.0 3.5 ,1�rYP�f ! 4.0 4.5 5.0 3 SP compacted gray sand with some gravel, no mottling or water seepage 5.5 6.0 Lot 1 Depth (FT) Sample USCS Graphic Description 0.00.5 — 1 top soil 1.0 1.5' t� compacted brown sand with some gravel, 2 2 SP no mottling or water seepage 2.5 MEN 3.0. - 3.5 — 4.0 4.5 3 SP compacted gray sand with some gravel, no mottling or water seepage 5.0 5.5 — 6.0 — Lot 2 Figure 3 — Representative Soils Log (Not -to -Scale) Soils Classification The soils encountered at 3 to 4 feet below grade in the proposed infiltration area and the results of the infiltration test are consistent with fine sand classification, according to the USDA textural analysis recommendations per Table 3.7 of the DOE Stormwater Manual, Volume III, page 3-76. THE CONCEPT GROUP 27xx S 282nd St Page 4 of 4 Table 3.7 -- Recommended Infiltration Rates Eased on USDA Soil Textural Classification. Estimated Long - *Short -Term Term (Design) Infiltration Correction Infiltration Rate Rate (in. hr) Factor, CF (iu./hr) Clean sandy gravels and 20 2 10" gravelly sands (i.e., 90% of the total soil sample is retained in the #10 sieve) Saud 8 Loamy Sand 2 4 0.5 Sandy Loam 1 L 0 25 Loam 0.5 4 0.13 *From ATEF/ASCE, 1998. Figure 4 — Table 3.7 Limitations The conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the test pits are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples in test pits. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. This report has been prepared for the exclusive use of the property owner and its representatives for specific application to this project and site. Our recommendations and conclusions are based on observed site materials and engineering analyses. Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in stormwater design. THE CONCEPT GROUP Project Address: 27xx South 282nd Street (Lot Q Date: May 10, 2018 Infiltration Rate Calculation (per 2016 KCSWM 5.2.1) Assumptions: Step # 1: Measured percolation Rate time interval= 10 minutes water level drop = 0.25 inches percolation rate: 40.00 minutes/inch percolation rate: 1.50 inch/hour Step # 2: Calculate design infiltration rate (Idesign) Idesign = Imeasured x Ftesting x Fgeometry X Fplugging Where: Imeasu,ed = infiltration rate measured in the field ** FINE SAND Ftesting = 0.30 for EPA Falling Head Method, 0.50 for Small -Scale Pilot Test Fgeometry = (4D)/W +0.05 Where: D = depth from the bottom of the proposed facility to the maximum wet -season water table or nearest impervious layer, which ever is less W = width of facility Fpl„gging = 0.7 for loams and sandy loams = 0.8 for fine sands and loamy sands = 0.9 for medium sands = 1.0 for coarse sands or cobbles, or any soil type in an infiltration facility preceded by a water quality facility Imeasured = inch/hour Ftesting = 0.30 per EPA Falling Head Method Fgeometry = 1.55 assumed D = 0.75 ft, W = 2.0 ft Fpl„gging = 0.80 fine sand Idesign — 0.0 inch/hour Project Address: 27xx South 282nd Street (Lot 8) Date: May 10, 2018 Infiltration Rate Calculation (per 2016 KCSWM 5.2.1) Assumptions: Step # 1: Measured percolation Rate time interval= [Ainch/hour minutes water level drop = inches percolation rate: minutes/inch percolation rate: Step # 2: Calculate design infiltration rate (Idesign) Idesign — Imeasured x Ftesting x Fgeometry x Fplugging ** FINE SAND Where: Imeasured — infiltration rate measured in the field Fte5f1ng = 0.30 for EPA Falling Head Method, 0.50 for Small -Scale Pilot Test Fg,,mety = (4D)/W +0.05 Where: D = depth from the bottom of the proposed facility to the maximum wet -season water table or nearest impervious layer, which ever is less W = width of facility Fplugging = 0.7 for loams and sandy loams = 0.8 for fine sands and loamy sands = 0.9 for medium sands = 1.0 for coarse sands or cobbles, or any soil type in an infiltration facility preceded by a water quality facility Imeasured= t.:-w inch/hour FtesOng = 0.30 per EPA Falling Head Method Fgeometty = 1.55 assumed D = 0.75 ft, W = 2.0 ft Fplugging = 0.80 fine sand Idesign — U.6 inch/hour