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Home My WebLink AboutDrainage Report for BLD99-0431 - BLD Engineering / Geo-tech Reports - 7/26/1999 Engineering Services Associates, Inc. North Mason United Methodist Site Drainage Report By: Pat McCullough, PE. 7-26-99 INTRODUCTION: This report presents the analysis of the existing and proposed drainage for the North Mason United Methodist Church site development proposal near Belfair, Washington. The site is approximately 2.5 acres in size and is located at the top of the hill on SR3 just East of Belfair on the South side of SR3. A drawing of the proposed site development has been included with this report. This analysis and the proposed facilities are intended to meet the conceptual intent of the Mason County Growth Management Plan and the requirements of the Mason County Department of Public Works. The analysis was completed using a site topography map, the USGS Belfair Quadrangle (15 minute) and 1994 aerial photos of the watershed (scale: 1"=400'). A "walk about" survey was made of the watershed directly above and around the site and in the watershed to the West of the site. REGIONAL DRAINAGE FEATURES: The significant regional drainage features are as follows: 1 . WSDOT has redirected the drainage to the West and North of the site to a 6 foot deep by 6 foot wide ditch that they constructed on the East boundary of the their borrow pit. In doing so, they directed over 92 acres of runoff to a low area in the Northwest corner of the church site. The existing low area is drained by a catch basin and 18" concrete pipe. The existing catch basin has been known to plug with debris which results in the water ponding on the church property until it can flow over a small ridge into the 18" concrete culvert located approximately 100 feet to the East on Engineering Services Associates, Inc. WSDOT right of way. The low area in the Northwest corner of the site would make an ideal location for the retention of the majority of the storm water from the site, however, WSDOT has illegally dumped water on the church property and forced NMUMC to construct water retention facilities upstream of the existing natural low area on their property in order to comply with MCDPW development requirements. Allan Tahuja of the Mason County Dept. of Public Works has visited the site and is aware of the situation. 2. The majority of the runoff from the site will drain to two 18 inch concrete culverts that cross under SR3, thence to the North onto the Johnson's proposed industrial park property, thence overland in ditches or in a storm drain system (future) to a natural sump located on the Eastern side of the Johnson's property and Western side of the of the Shear's property. Runoff from the area has traditionally drained to the this depression where it has infiltrated into the ground. It is our understanding, from discussion with the MCDPW, that the storm drainage facilities for the Johnson's industrial park have anticipated the storm runoff from the properties to the south. 3. Approximately 1 .2 acres of the existing church site currently drains to a natural depression on the South side of the church property and the North side of the Overton's property where it infiltrates into the ground. SITE DRAINAGE: Site Soils: The entire site is covered with Everett Series (generally gravel and sand) soils. Approximately 12 to 24 inches of silty loam top soil overlays the sand and gravel. The sand and gravel has lenses of silt hard pan up to 12" thick - in places - that are interspersed in the soil horizon. These silt lenses are not typically connected each other and thus seldom form a drainage barrier. 2 Engineering Services Associates, Inc. , , { • if a A CN of 76 was selected for this soil in its existing condition because of site conditions and the silt loam top soils. Before construction began on the site, approximately 0.67 acres had been cleared and the ground compacted by wheel loads. The author has constructed several drainage ponds in Everett Soils and observed that an infiltration rate of 2 inches per hour is a conservative but acceptable infiltration rate for use in design of retention ponds. Generally, the bottom of the pond becomes plugged with silt but the sides of the pond remain pervious and maintain the infiltration ability of the structure. The actual infiltration capacity of this soil, when clean water is used for percolation tests, is in excess of 5 inches per 10 minutes. Site Drainage Basins: The existing site has three drainage basins (See enclosed map entitled "Methodist Church Existing Drainage Patterns") The proposed site has 5 drainage basins (See enclosed map entitled "Proposed Watersheds"). Results of Computer Analysis: The computer model analysis of storm water runoff follows this written report. Copies of the Water Engineering Services Associates, Inc. Works Basin Reports, Structure Report, and Discharge Structure Report have been included for review. Plot of the final site existing and proposed hydrographs are also shown. The following table summarizes the computer model reports. Existing Conditions Proposed Conditions Storm Runoff Storm Runoff 2 Year Storm 0.36 CFS 0.24 CFS 100 Year Storm 1.23 CFS 0.92 CFS It is anticipated that there will be no outflow of the proposed retention pond during normal rainfall events even though the computer model indicates that there will be discharge from the pond during a 2 year storm event. The computer model is based on a conservative approximation of the rate of infiltration of storm water into the bottom and side of the retention/detention pond, Structures: A summary of the pipe sizes and the storm water inlet elevations and depths is shown on the enclosed plans. The proposed detention/retention basin is a 4 foot deep, 70 feet long excavated pond with a 15 foot bottom and 3: 1 side slopes. The bottom elevation is 283. The first outlet pipe is a 3" orifice (drilled cap) on a 4 inch pipe set at elevation 283.5. The overflow pipe is a 6 inch CMP or plastic pipe set at elevation 285.5. The top of the dike is elevation 287.0. The bottom of the pond Xto be covered with large rock or cobbles. The side slopes of the pond are to be blended into local landscaping. Top soil should not be put on the side slopes of the pond. 4 C \ y 4 1 y g �, . y,� ��, � Ca « < r'��<y' Y� �nTR :•�,�. `�. �".•�,s�.�♦"��4 ♦dC,�?J��a+ }:,C q 2. o �'�� r .fix �'+ ''73` ` '' . 3�' � ��w�,•P�'2a5y�SK y� 'x a , t. � :`F`' a Isa .4 � s°8 Cy�,�a� `a' �' `��\,r�� 'wit, ', �yt.♦ � nK � �R1�,ri�yr+��p" •: d �, v a A♦fin' ri Axe •S, `+'G"+. �hi•� a ati i ...1'�1�. ys'" - t` a 'F. P e ?7$?�S4T"'NP� 1`r „:,ti.; ��x��,. fi�� - \� � ✓";"�K.4\ ��1:-' s ,�. !,. 'E t�.Y`e L'�^`. .'�•G`y,.�jlas�'i )'"x� :' "�'d � r �,•C'' • �. ,+L'� � �' �aft M �• �a "�' ♦''�� 9 .Y. ) *� F ��♦ �i �w v=.�kSa � L ,4 ,fee. .34 RE ro <`�,f9ry'v N N a��'w4��`�` a 1��,'�. �h � EYE'♦ �mh♦ � �i�a'c �♦v .}, ��"�� R4'aa �'�Zy�, R L�r .• �� °�. 4ej�'�{ "`y � tyy ^`�u1 �a� .�S�<2 � � '�a.`� . > y♦'. � �{+,t� � � `��f C��"`" �tiA ♦ ♦�< < 1 1 ! �♦K '�� n �y��Ea�l� r�\tce\� 1� 1 aye •;<`x � .:.s � �., ,n Yr:'. a �. .:' °✓v t ja1:S � r �. 4 �p 1+ s :, � ..; V•4�'dJ.+nvtiL f Y<2�� pt�fi�: � + s*.:% (� `�'� +t YY-° sir •^4 Gib '(a!t � - �. 2 4 1• �. f "(¢ fM i j�s'`a fyr p 5 /j54"� Y y`�"4�!(i 'l IF3 ♦ b \ �.,w; pA. ''-°' �rcr a 1 F. ts. �tS� Y,�' '�� di�tyfi �•� � " .-.`� �y�'; �; ) syf, ,� ^. �`eh4 y ".0 �i{ s's S � ♦ ��,�y� �x vt ;r `\��`�',� .. .y�4eC�ki' p .�.��zr,,� �^�v.R <'��u -„*�Sa s°y'� 4s =''yr 2 a�e,�s,t�,Yst �•'. _a�� :.aJ� :£;'iE ': F`�T � Y lft'<� �<2 L f 33 , < a�k r „' �ee�,,, l�lK 4 » •, f. '$j<�. ♦ . ... Qt }a� �`� ...,Y �' 1 �t F it �i&- '3� Cx��¢ :: M �; `� ��... k '� �:<'�'��y �e�.1\ rvY'`�� '/�� ..j�^, ♦JSt. '" 'SS <�' �\dry �.♦ e2�{ :.�i♦ \�)�- N. t 3.f✓ l y i .� s e � ,� a � y •r,@ r,�,y \a:, a:',♦,�. 3e�;�y�,t G 4iat.. a �. _ ~ '� •+"fit\u`',��'��. �� , . rslC"� h K a c �" 41 ' f5 h�� ;C♦ METHODIST CHURCH DRAINAGE STUDY REGIONAL DRAINAGE SYSTEM MAP Regional Storage Area on Johnson's and Shear's Proper / gH■ , ■ •/ // ti Q 18" Culvert This Watershed Drains to the Northerly 18" Culvert A 18" Culvert 18" Culvert and Catch Basin Church Site 1N-53 AC r vel ' 2S= 92 AC. _ ., This Watershed Drains To the 18" Culvert 352X f C7 i + O The Church Site Drains to both the Southerly 18" and the 18" Culvert. . „ N MN 0 1 2 1 MILE 1go 1000 0 1000 2000 3000 4000 FEET METHODIST CHURCH EXISTING DRAINAGE PATTERNS r GRAPHIC SCALE 'p J 1MM&.0 a CuLym IN GE AR A 3 E .7 A . ,6' ooNatETE cuvorr N45 5 10.000. t� / OF J A AREA 2 D REA 0.89A EA = 1.2 SOILS ARE ALL CLASS D SOILS UNDERLAIN r UNDERLAMI BY CLASS A SOILS / 1 1 ( ` �► `h� DRAINAGE AREA TO THIS DEPRESSION HAS BEEN MODIFIED BY THE WSOOT FROM MINIMAL MURAL LOW AREA M A WATERSHED OF 92 ACRES. 1 / WITH NO OUTLET APPROX AREA - .4 At BORROW PIT �• } PROPOSED WATERSEHDS �' GRAPHIC 3CALB ,a roes) ti INLET NO. 7 1 r ea INLET 0. A)ol VN 416 ,r aaNaiera aavatr / AREA =0.5 AC _ I oop AR =0.42 AC ® I � .. OF, w.er Na lN& NO. ZC — — — / ` e wLEr 0e d Na I rTlTl M-n AREA #1=1.41 AC -14 ICOR INLET J IQ„ �i LONO N4i a"rMMM asv OF MU NO BORROW s�>�aria wvm +s PIT L c o,sm NM m am It o r= AREA #5=0.2�C an+0 MONO comma[ 4 / g too '�� / 4+0 s \64b, b (ORNNS�Mf�IwAh �\ �\ r E OM TCH BORROW '°' PIT \ SITE GRADING PLAN SCALE: 1"=60' PROPOSED DRAINAGE SYSTEM PIFERN INETN] TYFE 'APSEN IEaPV INETF6(9i RFEOA RFELBlo1Fi CNRA%8 FEET Me FEET M1OM 10INHA2 INHO OTC KET 2%Z 292Z MN 8 73 / INET1R101NETA3 INE OT TA2 CINET 2929D 2OZ MN 8 81 INETA0101NETA14 INEfA3 OTC INO 2708D 2860 MN 12 13D GRAPHIC �ilu INE WDINEA6 IN HIM OTC INET 239Z FI.Z MN 12 88 INETA510BASN INETAS 0TC KU 29D55 Bi'0 3 12 83 1p INHA8 WBASN INETAB OT ET C IN 2E75 Z475 MN 8 116 * INErV101NETAB IN.EfA9 OTC INET 21D27 2BR20 MN 8 22 INHA810CRNal INETAB WC INET 2XI20 2%70 25 8 Z .4 NLET NO. 7 A r•a >L INEA2101NET24 INETA64 0TC P1ET 2940D �00 MN 8 53 INET2B101NEfB KUM OTC INET ZQA 22220 25 8 10 INEfBWINEM INH= 03C INET 29470 292M MN _8 25 0. \ \ if AV 0'DIX CY 1r avaNTE altvaeT� /•' — I \ N4NL30 o ar w \ y ' &IE eLEY4.moD INLET AM A. .,/ I j 11g 11N ET N0. le LET NCL / i NO. 2C / / ` \ INLET 45 Na z/ T. FFMI-n ! li *\NLET 13W-12'HICOR INLET J BORROW �Q PITAFPIKK o-It a rMM \ S1 00E UMM 00TUM C".-3150 KM KID LANDSUFM s GUIXT / IalN'!r Sk AT C"JIUA LVM-r M&AT DEV.21 LO SAM AT=GRACE 7IMML10NT. \ OOMER 001T 701F1 LMM OD3ISEf \ METHODIST CHURCH DRAINAGE STUDY ISOPLUVIALS OF 100 YEAR 24 HOUR STORM FOR STUDY AREA 15403530 25�,,�� .. 25 25, 40 z f r A ,A11OrX10 o1ST Cuec f� S r� goo �E�� 5"ro��= •s /�fou,e 0 N LEGEND Hyd No. 2 Hyd No. 3 CFs xis Tin/Gi /42-0, 24j ! /�Z Ji Q 9Z i i 6 12 18 24 30 36 Time in Hours Hyd No. : 2 Rate: 0.92 cfs Time: 8. 50 hr Vol : 0.76 Ac-ft Int: 10. 00 min Hyd No. : 3 Rate: 1 .23 cfs Time: 8.00 hr Vol : 0. 52 Ac-ft Int: 10 . 00 min r�D.Z�7is T C41ZCe4l 2 Y� S'Ta e/V/= 3- LEGEND Hyd No, 1 Hyd No. 3 1 w U L 1 1 D. 3 ------------- -------- 3 6 9 12 15 18 21 24 27 30 Time in Hours Hyd No. : 1 Rate: 0. 24 cfs Time: 10 . 33 hr Vol 0 . 35 Ac-ft Int: 10 . 00 min Hyd No. : 3 Rate: 0 . 36 cfs Time: 8 . 00 hr Vol 0. 19 Ac-ft Int: 10 . 00 min L , 17-1W Y� SU�I ED Z " �l✓�Li�7 T Ohl 2�Tc Co�.5e� l%4 T/ YE• LEGEND Hyd No. 2_ Hyd No. 3 1 4 u c 1 y 1 Q Z y�,e 5 Ta,ei✓I Sires o F��-rc.J 3 6 9 12 15 18 21 24 27 30 Time in Hours Hyd No. : 2 Rate: 0. 28 cfs Time: 8. 00 hr Vol : 0.38 Ac-ft Int: 10 . 00 min Hyd No. : 3 Rate: 0 . 36 cfs Time: 8. 00 hr Vol 0. 19 Ac-ft Int: 10 . 00 min 7/25/99 page 1 METHODIST CHURCH 100 YEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: Al NAME: PROPOSED DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1 .41 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 20 Acres 1 . 21 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 98 . 00 TC. . . . . 10 . 00 min 10 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 200 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE: 1 . 74 cfs VOL: 0 . 69 Ac-ft TIME: 480 min BASIN ID: A2 NAME: PROPOSED DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 15 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 03 Acres 0 . 12 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 98 . 00 TC. . . . . 10 . 00 min 10 . 00 min ABSTRACTION COEFF : 0 . 20 TcReach - Sheet L: 200 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE: 0 . 18 cfs VOL: 0 . 07 Ac-ft TIME: 480 min BASIN ID: A3 NAME: PROPOSED DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 42 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 41 Acres 0 . 01 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 98 . 00 TC. . . . . 15 . 56 min 10 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 100 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE : 0 . 28 cfs VOL : 0 . 12 Ac-ft TIME: 480 min BASIN ID: A4 NAME: PROPOSED DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 55 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 54 Acres 0 . 01 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 72 . 00 98 . 00 TC. . . . . 15 . 56 min 10 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 100 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE: 0 . 36 cfs VOL: 0 . 16 Ac-ft TIME: 480 min 7/25/99 page 2 METHODIST CHURCH 100 YEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A5 NAME: PROPOSED DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 23 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6. 50 inches AREA. . : 0 . 22 Acres 0 . 01 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 98 . 00 TC. . . . . 10 . 00 min 10 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 100 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE: 0 . 17 cfs VOL: 0 . 07 Ac-ft TIME: 480 min BASIN ID: M1 NAME: EXISTING DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1 . 20 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6. 50 inches AREA. . : 1 . 20 Acres 0 . 00 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 0 . 00 TC. . . . . 27 . 09 min 0 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 200 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE : 0 . 65 cfs VOL: 0 . 34 Ac-ft TIME: 490 min BASIN ID: M2 NAME: EXISTING DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 75 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPE1A PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 75 Acres 0 . 00 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 0 . 00 TC. . . . . 15 . 56 min 0 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 150 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0900 PEAK RATE: 0 . 48 cfs VOL: 0 . 21 Ac-ft TIME: 480 min BASIN ID: M3 NAME: EXISTING DRAINAGE BASIN SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 .89 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 6 . 50 inches AREA. . : 0 . 89 Acres 0 . 00 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . . 72 . 00 0 . 00 TC. . . . : 15 . 00 min 0 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 200 . 00 ns : 0 . 4000 p2yr: 3 . 50 s : 0 . 0400 PEAK RATE: 0 . 57 cfs VOL: 0 . 25 Ac-ft TIME: 480 min 7/25/99 page 1 METHODIST CHURCH 100 YEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- STORAGE STRUCTURE LIST TRAPEZOIDAL BASIN ID No. POND Description: POND Length: 70. 00 ft. Width: 15 . 00 ft. Side Slope 1 : 3 Side Slope 3 : 3 Side Slope 2: 3 Side Slope 4: 3 Infiltration Rate: 30.00 min/inch 7/25/99 page 2 METHODIST CHURCH 100 YEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id VOL (cf) ----------------------------------------------------------------------------- INFILTRATION POND ............ 1.74 1.74 POND COMB1 286.08 1 6008.44 cf 7/25/99 page 2 METHODIST CHURCH 2 YEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- DISCHARGE STRUCTURE LIST COMBINATION DISCHARGE ID No. COMB1 Description: POND OUTLET CULVERTS Structure: OUTLET Structure: Structure: OUTLET2 Structure: Structure: INLET CONTROL CULVERT ID No. OUTLET Description: OUTLET TO POND Diameter (ft) : 0 . 25 Entrance type: 1 Length ( ft) 25 . 00 Invert Elev : 283 . 50 Slope ( ft/ft) : 0 . 0200 No. of Clvrts : 1 Mannings n 0 . 0260 Max Ponding el : 287 . 00 Stg-Dis Increment : 0 . 10 INLET CONTROL CULVERT ID No. OUTLET2 Description: OUTLET TO POND Diameter ( ft) : 0 . 50 Entrance type: 1 Length ( ft) 25 . 00 Invert Elev : 285 . 50 Slope ( ft/ft) : 0 . 0200 No. of Clvrts : 1 Mannings n 0 . 0260 Max Ponding el : 287 . 00 Stg-Dis Increment : 0 . 10 7/25/99 page 3 METHODIST CHURCH 2 YEAR STORM LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id VOL (cf) INFILTRATION POND ............ 1.74 1.74 POND COMB1 286.38 1 6937.06 cf Engineering services Associates, Inc. August 30, 1999 Jodie Holdcroft i) Sanitarian, Mason County Department of Health n` P.O. Box 1666 %1 Shelton, WA. 98584 f%E nr-�iTe Dear Jodie, In response to your design review memo of 8/30/99. 1. The flow was supposed to be 5 gallons per person per day and not 50 gallons per person per day. Opps! 2. The use of the building is primarily for Sund x Services. The sanctuary is designed to seat 200 persons. Given that Mason County is th&�nchurched county in the United States, the meth- odists would hope to have more people but currently those are the design standards that I have been given and feel comfortable with. Obviously there will be weddings and other events with larger crowds but we use average figures for design of septic systems. Three to five staff will occupy the building during the week from 8 to 5. Small meetings will be held at the facility during the week. I estimate that the daily flow during the week will not exceed 500 gallons per day except for large events. No preschool is planned. There is a small kitchen. This system is not designed to serve a building expansion but could be easily expanded when the time comes. 3. 1 did not use the LOSS guidelines because it is not required to use LOSS guidelines for a system of this type and flow. The flow to the system during the week will be about half the design flow. The strength of the waste water will be equivalent to residential waste. 4. 1 will inform the NMUMC that they have to record an O and M agreement. 5. Allan Tahja informed me that the surface water plans are approved - call him. 6. The highway easements lines shown on the plans are surveyed in the field and I have checked them. The drainage basin is designed such that the storm water will enter the facility and soak into the ground. The drainage facility has a bottom elevation approximately the same as the bottom of the drainfield and neither system is down gradient from the other. The drainage pond will only have water in it for short periods during storm events of more then 1.5 inches of rain in a day, which is the exception and not the rule. Otherwise the water will enter the pond and soak into Engineering Services Associates Inc. 210 N.E.Cherokee Beach,Belfair,Washington-98528 (360)275-7384 Engineering services Associates, Inc. the gravelly soils through the cobble bottom and not pond. This pond in not a surface water feature and should not be considered as such. To line the structure with concrete would negate the purpose of this drainage facility. The 50 foot clearance provided is according to code for this type of drainage facility. 7. 1 have increased the size of the pump tank to 1500 gallons. A 1500 gallon tank offers 448 gallons per foot of storage. There is two feet of working storage in the tank or 896 gallons. If we assume that the pump comes on 8 times a day and pumps a 125 gallons, then an event that happens in a three hour period would have 1021 gallons of storage available to it - the entire days design flow. 8. Observation ports - Two per infiltrator, one on each end, is enough and meets the require- ments. 9. 1 changed the specification to Class 200 PVC - my calculations are exact and the tables are cook book approximations. 10. The orifices are spaced at 2 feet in a 3 foot wide infiltrator - 6 sq. feet per orifice. 11. The calculations are correct. 12. The duplex pump station adds pump redundancy in the event one pump fails. Something that should be required for all commercial systems. Hydrotex valves are a maintenance problem and used to be not allowed but I am happy to hear the department now thinks they are ok. Concerning one field getting more effluent then the other. Even if it did work out that way in the short term the flows will average out over time. This an empirical science at best, it will not harm one drainfield if it gets a little more flow then the other drainfield if they are both getting less then the design flows. 13. We have an elapsed time meter and counter for each pump. 14. Mistake - no Jandi valves are used in this design. 15. Done 16. 1 am not using LOSS and am not required to use LOSS guidelines for a system of this type. Yours Truly, Z��w C Pat McCullough, PE President, ESA Engineering Services Associates Inc. 210 N.E.Cherokee Beach,Belfair,Washington-98528 (360)275-7384 w UO lb N � U � C� I