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18-102326-SFRECEIVED M=MA1RA11 n11M Date: May 24, 2018 To: City of Federal Way Public Works Department From: Anna Nguyen, P.E. Subject: Drainage Design Project Address: 27xx S 282"d Street, Lot 1 v www.ConceptBusinessGroup.com muftnnd byr. L*A.A� el— ��� 0936WAA4134C9,.. 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) 2,364 Proposed Driveway 648 Proposed Walkway 18 Total NEW Impervious Surface 3,030 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 C — 27xx S 282nd 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 2,364 SF (roof) + 648 SF (driveway) 64LFx2'Wx2'D = 128 SF x 2' D 32LFx4'Wx2'D = 128 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 C - 27xx S 282nd 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 /y ��pl�y� �p���y� �p �p�py 6XEE1 v�,EARF ai GRAD i � IEW M'1WT1 SHEETREF—KNO. 1 ^� 1 V T^ ' s�il•11I R.fn ) I I EROSM �R� PLANS M 3F - - - - - - - 2, KEE'P OFFS 1. ALL WORK D STREETS CLEATERIALS M N AT ALL TIMES FLUSHPIER CITY OF ING STREETS WAY SHALL NOT BE ALLOWED. ALL STEIFTS �r� SHFE'fS / I �• - ARDS - SHOULD BE SWEPT. 3. ADDITIONAL ROSIONISENMENT CONTROL MEASURES MAY BE REQUIRED BY CITY INSPECTOR. 4, WHEN WORK ISSTOPPED/COMPLETED INAN AREA, THE CITY INSPECTOR MAY REQUIRE POST -CONSTRUCTION '^ EROSION CONTROL INCLUDINGSEE0 NO OR DITHER MEASURES. MEASURES. LOCATIONS SHOWN OFEN XISTGLFnIL IESAEAPPRO%IMATE.ITSHALLBETHERESPONSIBILRYOFTHE '1F, CONTRACTOR TO VERIFY THE CORRECT LOCATIONS TO AVOID DAMAGE OR DISTURBANCE 6.ITSHALLBETHE RESONSIBILITYOFTHE CONTRACTOR TOOBTAIN STREET USE AND OTHER RELATED PERMITS cn PRIOR TO ANY CONSTRUCTION. N I— LU � O NSTATLORANGEHIGH r I yq~y 7. ALL GROUND COVR IS TO REMAIN UNDISTURBED OUTSIDE OF CLEARING AREAS. lL 00 1 /JJ I I �^y^SSS B. THE TEMPORARY ROSIOWSEDIMENT CONTROLS SHALL BE INSTALLED, INSPECTED, AND OPERATING BEFORE wCo (). PER WESUDT STFENCE 130-17d0 I I I I °J• ANYGRAONG OR EXTENSIVE LAND CLEARING. THESE CONTROLS MUST BE SATISFACTORILY MAINTAINED UNTIL O Q Q / {r, - FOR TRE¢TNppiEClgH(IYY) I Iul CONSTAUCTION ANO LANDSGPINGARE COMPLETE _ 1 B. TIE IMPERVIOUS SURFACES ROOF, STREETS, DRIVEWAYS, ETC.) TO COMPLETED DRAINAGE SYSTEM AS SOON Z /r w."f •:M1 I r AS POSSIBLE Q 10 A PRELONSTRUCTKIN MEETING WITH THE CONSTRUCTION DIVISION AND ALL PERMITS MUST BE COMPLETED W Z Q BEFORE START OF CONSTRUCTION. �! CN • . ! g • % w "��� - ' 11. CLEARING LIMITS SHALL BE LOCATED BY A LICENSED CIVIL ENGINEER OR LAND SURVEYOR N J Z 12.APPROVAL OF THIS TEMPORARY ERSIONISEDIMENTATION CONTROL(TESC) PLAN DOES NOT CONSTITUTE AN ][ U) QN fJ4 -•f� I� ' I m i00F 11ELgYED ~,\� ' I I I 13. DESIGN- THISA PROVAL FOR TESC IS VVAROVAL OF PERMANENT ALLID OR COR IONSTRUCTIN BETWEEN MAY I AND SEPTEMBER 30 THIS V `y' W APPROVAL FOR TESC IS NOT VALID FOR THE RAINY SEASON (OCTOBER 1 THROUGH APRIL 30) C w Utn I9r5EWER u- EkSEMEN 1I1 - r/ I�• ',. R• ,: ////r I I r R[C. M 1VQiWp1IFSOOLIMENCIM If 1. FIAG OR LIMITS. TM��GV4iCIRiC F ///,� �� ;, •, -J i 2. INSTALL CATCH BASIN PROTECTION IF REQUIRED, �� '1 CYiVFA WfIH PRASTIG jfi.k9PSF-9,14ACR1q I1� I I I I 43. . NSTDEAND INSTALL ALLP PERIMETER PROTECTION (SLLT FNSTRUCTION ENCE, BRUSH BARRIER, ETC.). P .'j RNBTALL SILT FSTr" l� R DETAKMSWAT CIO 5. MAINTAIN RSION CONTROL MEASURES IN ACCORDANCE WITH CITY OF FEDERAL WAY STANDARDS AND PR DfjTAYON ONTXTq r I I I MANUFACTURER'S RECOMMEN TIONS Ira' 6 THEEROSI AND SEDIMENT CONTN! CONTROL ROL IS ALWAYS ES OR INSTALL NEW MEASURES SO THAT RCHANGE SITE CONDITIONS S IN WITH CITY OFREDMONDEDMOND EROSION AND ENTR SEDMENTCONTROL STANDARDS. 7. COVER ALL AREAS THAT WILL BE UNWORED FOR MORE THAN SEVEN DAYS DURING THE DRY SEASON OR TWO'T^`� DAYS DURING THE WET SEASON WITH STRAW, WOOD FIBER MULCH, COMPOST, PLASTIC SHEETING OR EQUIVALE STABILISE ALL AREAS THAT REACH FINAL GRADE WITHIN SEVEN DAYS. SEED OR SOD ANY AREAS TO REMAIN UNWORKEO OR MORE THAN 30 DAYS. I+L IEA MISNDMyMGE I I I 1 10 UPON COMPLETION OF THE PROJECT, ALL DISTURBED AREAS MUST BE STABILIZED AND BMPS REMOVED IF g 1 I APPROPRIATE L!£ IC; EARTHWORK VOLUME ESTIMATES !>SrAU COIWTRUCTLON FHTpANCB g :: iI REROETArON61EETC] =i i I I i LOCATION ancc» Pi.L(cr) A 1�nye;i I I I SITE A OUNDATION 150 60 �xp I �r r? I I I oo=x Ex s•Pre:FABL�RENr I , •-...,,,IJ � -.'r• $� REc..aTwwllu� y� •fir. . S.S7W: - r +, ;,, s j 4 PRgPBRi1'LIRE F7GC1 I of - - - - - - - - - - - - - AOJACENTPROPERTY LINE u.f ••aT~ II I'. \ - - RIBHF OFWAY WEE HOAUOXL4 cur = — RIOHT OF WAY CENTERLINE N S 10 s o s 10 Call t.. Y Q. . - EX. EASEMENT LINE wgTm 11M- YW ar2r,.r �e II / ro % E. / _— — — — — — — — — x,s i / I. J — -- I PROPOSED SFR RM=42L25 G4RASE=425.25 COriMTMTION NOTE$ tlLSTALL a2 LF a•PVC 510E SEWER LRT5RALpa-PDX LaN 1--1--�_ INMAU A LF,'WAIM URYIC£ LM I '. ©):'WATER METE, BEY LA,[EILAVEM WATER AND SEWER DISTRICT) CONSTRUCTORMwAr,MOFIMOTwa I O,FLTRATKW TREND LLF14rEGf I [4WLO17 x2Dj PAR OFFAL ION S,fFFW 1. I pi51M1. MTYPE I DR AREA VA&WWTTH 50LO to E l I RIM"24,TS 1 I I M> m o UMALL IO LF W PYC SD R 200%arc © INSTALL S LF P M RD" QftQM CO[LEQTQR®2W%MIN, • OB INSTALL r Lf4'SOIb PVC FOOTING GRAIN ] I 0OILECTORQ2m%w1 i I p cmTmxT37ASPHALrORNEWAYA„PROACN PFR OYIP H0. rs ilr$'j1EF1, SEELEGEI@b MwnATM I ® CGMSiRUCT CONCRETE GMEWAY. Sr-E LEGEND vnuff _ IPOWFI,i�CQMAiNN1CATKw[ I ®F$TALL IP' LONG, V WOE SLOrrmOPA,I IOVA/,r M2P RATE6 TR,VFTG Lb I I � ®ws,ALL9IF4'PYCSP@�oo+LN.,. rl I I I � "" EHCE SHFETNO. ` C2 1 NnawwhArst*1Qw, Gall heroro you dIy- 1 HD'420NTAL 0AH6C55CnLE10 L� M NwCD irch . ,U R LLI 00 M m w _�� 0 w c\1? 4'PVC DOWNSPOUT GRAIN LINE K N J GRADE 0 w > w •-RAL,IFAL LL r-PROVr0E IFMINCOVERAGE OF DRAIN WITH uyW , w-TAN' WAS EDROM EQUIVALENI) 1 NOTES L- x• PERFORATED P/C FOOTING DRAIN LONE 1 I I OH,ERAL NOTES ORAtl+LLNC5 TP 0E SFyEPA.TE AIIO PO,IT. PROVIDE CLEAN OUTS. ELBOWS i I I I. CONTRACTOR SHALL FIELD VERIFY ALL ANDOTHERFR-RNO,.ASUEEDED, L I I J GRADES PRIOR TO CONSTRUCTION. [.WNJEGi Tp PaL I I li -DRAINAGE DE 1 SECTM)N A M P "BM SCALE: NONE P SEWE7t10+@ I ]5,;1W �FJLLEVYEIR MAIN I !; I SrTE DATA � 1rneQ>E.n.5r6BF I I NEWINIPERVgUAY�M86FB SURF ACE: I GRIVEW CGLNC, WA<?.WAY • 1a ISF - - - - - - -- ROOF LNOLUDE OVERIW1Ci _ _ I- 'I COVERED PORCH I PAM-i,1W SF TFFAL IWERYLOUS SLWXI-E-o,OTO SF E,LBPSE E4.9LENTJ REc,�iramTpS, . PO'A'ED PgIE+ . . • m VTATCA HAP, - - _ - _ _ & 282AID STREET L I 1..L�W PROPERTY LINE .. - _-_________ AW4CENri`RWfiRTT IY✓f - - - - RIG Tr OF WAY LINE - - RIGHTOFWAYCENTERUNE - EASEMENT LINE ��AEPH4Li PA1�MENT [0.76 MANR I?,F'56LT20YER 0.,P OSTC OVER DAY C3007 CONCRETE PAVELv,t fT• CQRCd 0 4 SHEE 2 OF QZQ JIL J U JOINTS BL M; FANK: SHLLL BE SPLK�M AT FCSTA USE STAPLES. WIRE RINGS. OR CONTRACTOR TO PROTECT MUD FROM BEING TRACKED ONTO THEPUBLIC ROAD�f IN' MIN 00 EDONALIIR TO ARACIIFADRK: TD POSTj, rXA%ARDSWwN �� IF STANDARD STRENGTH FABRIC USED. T FABRJCUSEE . KLSFR FAlPC EDGE OF 4 � 11 R t k n --11 P PAVELVIT s' 11 �1F.-......._� __1F�•.�w�.. _. E{...-. -�Na1/N0 I . _ INSTALL T)WV{WAY CULVEI(T MVL k IS PROym W THEPE IS A ROADSIDE DITCH OF INGRESSIEC it 11 [I v MAY. � d� rpeN PER 6INDTAIMIYROAGSTAHG6RLC GEOTE)M EUNDMWE 4•m6•ouwRV SPAY^ s 'OCT EPACM MAY lE IRMSASM N07ED 1' TO C a-Y1RiE $�C![ONi 6 UT.EL BACKFILLTRENCII WTTN AS PER KING COUNTY ROAD STANDARDS, 0 IVEWAYS SHALLBE PAVED TO THE EDGE OF NATNE SOIL YX4•W000 POSTS. STEELFEDUIVAL RIGHT CFWAY PRIOR TO INSTALLATION OF THE CONSTRUCTION ENTRANCE TO AVOID DAMAGWD OF NT E GRAVEL REBAR, OR EOUNAIENT WASHED GRAVEL THE ROADWAY. NCqM FILTER FABRIC FENCES SHALL BE INSTALLED ALONG CONTOUR WHENEVER POSSIBLE IT IS RECOMMENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE ROAD, SLT FENCE MAL CONSTRUCTION E1fTRANCE DETAIL PER 2016 KCSWDM FIGURE C.3.6A PER 2016 KCSWDM FIGURE C.3.1A SCALE: NONE SCALE NONE TOE IN SHEETING PI MINIMUM 49L4' TRENCH PROV[I ATTQE T Ai TpE ri L' 3 SANDBAGS, OR EQUIVALENT MAY BE USED TO WEIGHT PLASTIC SEAMS BETWEEN SHEETS MUST OVERLAP A MINIMUM OF 12• AND BE WEIGHTED OR TAPED PLASTIC COVEFM MTAL PER 2016 KCSWDM FIGURE C.3AA SCALE: NONE Nrl �I - n fRTFpq fl111r111v RJIT I•a0.11w A-4 - A-*j V•1DE AREA PwEoR PLAN VEW NTS ROOFI ROOF DOWN SPWT WITH C.K314•-11I2• OVERFLOW WYEAND PERFORATED PIPE a 0.0% SPLASH BLOCK _-rE]tlSi/1D GROUND --- tiY4 FINE MESei 3CPEFie S ELEVATION VIEW 3� NTS BACrFRx_ - (CXIS704GROUND BASIN OR AREA DRAIN ROCK ENTIRELY BR(C I TYP) L�_ _ _.. WOlEVEL TTTPL j WASHED ROCK 3N'-II-rrYP) 4 I DANEWAY 1 ROOF 1 FOOTM ff—L RATION TRENCH 29AM 0 SCALE: NONE _ _ PIPE J1CM;L �Er IE UD OF ' O ^ �a7 3 cr) F CD W W Do Q O T. 9 J � C-4 ' Q' N J Y cl) 0 �y^CC ¢W N W LL 5 ag -,I'z m i3, A 3 MW � ry z� yy3 C IVEK MEMORANDUM CITY OFFEDERALWAY COMMUNITY DEVELOPMENT 4701 SW Admiral Way, Ste 353 • Seattle, WA 98116 ■ T 206.446.1291 ■ www.ConceptBusinessGroup.com Date: May 22, 2018 To: City of Federal Way From: Anna Nguyen, P.E. Subject: Infiltration Assessment i 3. Project Address: 27xx South 282n1 Street (Lots I and 0 —OmuSlgned by: —4-/I.AL -/— A ��u C-A' �—M363AWA 134C8.'. 4 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 Ti I I (Qvt). !lffl" 2 St co project ' s -1 location h,`'� -�.o 7 28$t 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 282n1 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 2.0 2 SP ', compacted brown sand with some gravel, 2.5 -&40. no mottling or water seepage 3.0 3.5 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 0.0 1 � top soil 0.5 — ---.-- 1.0 1.5 compacted brown sand with some gravel, 2 0 2 SP no mottling or water seepage 2.5 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 based on USDA Soil Textural Classification. Estimated Long - *Short -Term Term (Design) Infiltration Correction Infiltration Rate Rate (in./hr) Factor, CF (in./hr) Clean sandy gravels and 20 2 10�' gravelly sands (i.e.. 90% of the total soil sample is retained in the #10 sieve) Sand 8 4 2*** Loamy Sand 2 4 0.5 Sandy Loam 1 4 0.25 Loam 0.5 4 0.13 ,Frow iVEF' 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 c) 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 (Ide ip) Idesign = Imeasured x Ftesting x Fgeometry x Fplugging ** FINE SAND Where: Imeasu,ed = infiltration rate measured in the field Resting = 0.30 for EPA Falling Head Method, 0.50 for Small -Scale Pilot Test Fg ,,rn,, y = (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 Ioams and sandy Ioams = 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 Imeasumd = 1.50 inch/hour Ftesung � 0.30 per EPA Falling Head Method Fgeometry = 1.55 assumed D = 0.75 ft, W = 2.0 ft Fplugging = 0.80 fine sand Idesign — 06 inch/hour Project Address: 27xx South 282nd Street aot 8) 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: i.5Q inch/hour Step # 2: Calculate design infiltration rate (Ide ign) Idesign = Imeasured x Ftesting x Fgeometry x Fplugging ** FINE SAND Where: Imeasured = infiltration rate measured in the field 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 Fplugging = 0.7 for Ioams and sandy Ioams = 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 � 1.50 inch/hour Ftestlng = 0.30 per EPA Falling Head Method Fgeome" = 1.55 assumed D = 0.75 ft, W - 2.0 ft Fplugging - 0.80 fine sand Ideslgn — 0.6 inch/hour