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HomeMy WebLinkAboutHydrogeologic Consultants Report - COM Engineering / Geo-Tech Reports - 7/18/1994 MASON COUNTY PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shelton, Washington 98584 INTER-DEPARTMENTAL COMMUNICATIONS DATE July 18, 1994 TO: DON BRUSH, DCD - Planner FROM: AIAN A. TAHJA, P/W - Hydraulic Engineer SUBJ: ACE Paving Co./McDonalds Ccmmlercial Site, Belfair Don, Attached please find a copy of a Hydrogeologic Consultants' report prepared for the proposed ACE/McDonalds site in Belfair, Washington. The report was prepared by GEDENGINEERS INC. of Tacoma Washington under the supervision of Gary W. Henderson, P.E. , and supports the stormwater design proposed by MAP LTD. of Silverdale, Washington. This report was prepared and submitted at the request of Mason County Public Works and satisfies Public Works concerns regarding potential impacts to surrounding (downgradient) property owners. With this additional information, the proposed stormwater infiltration design is considered acceptable. Also attached please find an IDC submitted to Jason Manassee on May 31, 1994 which contains other features that may still need further attention. I am in possession of a set of plans dated June 15, 1994 prepared by MAP LTD. which satisfies Public Works requirement that the parking lot water be pre-treated prior to delivery to the infiltration facilities. I cannot find an executed copy of a Maintenance and Operation declaration tprepared by the applicant, but otherwise, find no objections to the June 15 proposal. ITM A 4 . 1;:V t 7k A. TARTA attach. 1-9 page Geotech Report 1-1 page IDC addressed to Jason Manassee File: H:\WP\LETTERS\MAC-D2.IDC JASON MANASSEE, Planner - DCD ALAN A. TABJA, Office Tech. - P/W McDONALD'S - Belfair, Ace Site, Stormwater/Runoff Drainage Proposal Jason, I've reviewed the stormwater/drainage proposal prepared for McDonald's in Befair, Washington by MAP Ltd. The proposal provides for water quality treatment of a 6 month storm event and provides for infiltration of the runoff from a 100 yr storm event. The engineer has employed a flow splitter that delivers flow quantities less than a water quality design storm to an infiltrating bio-swale. Larger storm event runoffs are directed around the bio-swale and are delivered to an underground infiltration trench. I expect this arrangement to work well in handling McDonald's runoff and in helping to alleviate the surface drainage problem that exists in Belfair under normal operating conditions, but I feel the Engineer should incorporate an emergency spill separator to pre-treat the parking lot runoff prior to delivering the stormwater to either the bio-swale or the infiltration gallery. In the event of a parking lot spill, petroleum products could be delivered directly to their bio-swale or to their infiltration trench, resulting in the passibility of introducing petroleum contaminants into the area's groundwaters. I have been in contact with Mark Eisses, P.E. , a principle of MAP Ltd. and he understands my concern and will be submitting a revised plan sheet which incorporates an oil/water separator into one of the catch basins. I requested that he furnish us with three copies of the revised page of the Drainage & Grading Plan. The number of parking spaces appears to be adequate for the building size and the aisle widths appear adequate for the parking angle chosen. An Operation & Maintenance document should be prepared and submitted as part of the proposal. Enclosed please find an edited version of Kitsap county's standard O&M document. The enclosed document has not been approved by our County Prosecutor's Office, so if a document fashioned after this example is submitted, it will need reviewing by the Prosecutor's Office before final acceptance. I have furnished Mr. Eisses a copy of this same document for editing and submittal. Attached you should find a four page Drainage and Grading Plan, a 16 page calculation brief, and a sample O&M agreement. ALAN A. TABJA File: H:\WP\LETTERS\MAC-D.IDC r.0.Box 720. 9119 Ridgetopp 80ulevarel N.W. Silverdale,WashingtO m 98381e 682-5574 5liverclale 692-5525 5e (206) Fox(206)696-0546 Engineerirlg • 5urv&Ying • Punning ! AZ TR !► litl[ YTTA BSEET i FROX !AZ Mo. (20 f) 4!a•0 S,6 • • A • • A • • A A A • A • A • • • • • • • • A A • A A • • A • • DATE s 9 TO: Q r - COxPAW S FAX no: FROM: VROJZCT DZSCRIPTI0X/IVSTRVCTl0N9 i TOTAL NO. OF PAGES, INCLUDING COVER PAGE: TO CONFIV t I•.OR Am PROBLzma CONTACT )ILAILID NOT I@IILSD 1T (,20f). if=—SS2S OR (log) $92-5574 _r .� Ql� d•'bd �b�9859997 61 :80 b55t/ZZ!L 07%08/94 08, 42 01 206 471 0521 GEOENcINEERS INC l4t]U01 �eo� 1�eers 6,240 Tacoma Md181vd Saito 318 E Tacoma,W&Shiopon 9Ed09 79 FAX 'TRANS1VII'TI'AL TelephPvc(�471-= To: Map, Ltd. Date: July $, 1994 1410: 3738-001 TO3 Fax Number: 69SALW Attealloa: Mr. Mark Fiwa go8ardie38 Propond McDaoald'•-Whir. Ws. paw Date Dosaipdoo 1 O7M/94 Fax TrmmitW + 07 06/24/94 T!IydmgwkWo C'cowlVAOS Total Pages: 08 Commenm Suaed: Awn AAbm7 Z0 39VJ Ql� d'�W �bS�i85999Z 6Z:80 b66t/ZZ,'L9 09/0$/94 W 42 V1 206 471 0521 GEOENGI\EERS INC Z 002 Ge0 qp•. �� Engineers : Juno 24; 19% Geoteclmlcal, Geoetavlrexmeruat and Geolo&Services Atc Paving , P.O. Box 4100 Bremerton, WashiVor► 98312 Hydrpgeologic Consultation On-site.lufiltration Evaluation Proposed McDonald's "fair. Washington File 14o,1758-001-T03 INTRODUCTION ANp SCOPE This letter presents the results of our hydrogeologioconsultatiotl with respect to the on-site storm water infiltration systemn at the proposed MgDonald's site in Belfair, Washington. The location of the site is shown on the Site Plan/vicinity.Map. Figure 1. Our understanding of the development plans is based on conversations with Mr. Mark Eisacs and Mr. Alan Todd of MAP. Ltd. Based on the information provided by MAP, Ltd., it apMrs that approximately 50 percent of the developed site will be impervious surfaces: rW of the water collected from these surfaces is proposed to be infiltrated oft-site. The storm water-is proposed to be collected and directed to a biofiltratioa owale then to the subgrade infiltration utric h to be located along the west side of the site. The infiltration trench will be about 14-het wide, 6 feet deep. and 163 feet long. On-site disposal of sewage is also planned for the-developn=t. It is also our understanding that some total residents are concerned that the on-site infiltration of storm water will detrimentally impact dgwngradient areas. The purpose of our servicrs was to evaluate the potential off site ibVwu of the infiltration systems. Specifically,our scope of services for this project Includes the following: 1. Explore the subsurface soil and ground water conditions in the vicinity of the proposed infiltration system. 2. Perform i visual reconnalmance of the site and the surrounding area. 3. Evaluate potential off-side impacts as a result of the infiltrulon system. 4. Provide ec our rorrunendations"for mdueiag off-slte•Impacts, as appropriate. 0+c&+ltAVL1% 4240 Twma MWI Vvd,Since 319 . TAWMI,WA 9" • 1''*h=(XO 471VAN a fix(W 4405121 E0 39tid Gib d`M 9VS0$6990z 6Z :60 b66L/ZZ/L0 U7/08/83 08: 43 =1 2013 471 0521 GEOENGINEERS INC IZ003 Ace Paving • June 24, 1994 Page 2 5. Prepare a writtan r"rt containing our obsorvi ations, conchnions and reconuneadations along with the supporting data. 4 . SITE CONDITIONS SURFACE CONDITIONS The subject property is located in an upland arc& along SR 3 (Stage Route 3) out of the intersection of SR 3 and SR 300 in Belfair, WuWngton am Hood Canal. The property is bounded on the north and out sides by undeveloped wooded sites. Developed commercial property is located to the south of the site. Low-density residential areas are heated across the highway and west of the property. An old gravel pit is located directly west of the site. The property generally slopes upward to the north. Cut slopes are located near the northern and eastern property lines. Threc buildkii pads have been constructed by cutting and filling portions of the property. The building pad&are relatively level and each pad steps upward to the north. As indicated on the site plan, the,proposed McDonald's site is the central building pad. We understaud that the, property was previously wooded. Logging and clearing were perfortned prior to site grading. The ground surfaces are currently bare. No evidence of ground water seepage, surface runoff or puddled water.was observed during our site visit. SUBSURFACE CONDITIONS Subsurface conditions in the site vicinity were evaluated by reviewing available subsurface data, observing exposed soils on and in the vicinity of the site, and by excavating one text pit in the area of the proposed inTiltration systein. Tie available subsurface data reviewed includes boring logo from a nearby site where we performed explorations. The test pit was dug using an excavator and extended to about 17 feet below the existing ground surface. The excavation was continuously monitofed by our representative who examined and classified the soils encountered, observed ground water conditions, and maintained a log of the subsurface conditions. The soils were classified in general accordance with the system described in Figure 2, ASTM D-2488. The tat pit log is includod as Figure 3. Rased On our explorations, we conclude that the site is generally underlain by advance outwash deposits of sand with variable amounts of silt and gravel. The upper 6 feet of the soil encountered in the test pit is fill consisting of on-site material. The fill appears to have been compacted and is in a dense condition. Underlying the fill to the full depth of the test pit is native dense band with silt arid gravel. Bassi on our review of the boring logs and our observations of the cut slopes in the gravel pit, it appears that the upper layer of sand with silt and gravel is underlain at some depth by very dean sandy gravel and gravelly sand. The gravelly material was onevuntered to the fu1150-foot + depth of the teat boring on the rarby site. in the gravel pit, the sand and gravel extend to the base of the pit which is at about Elevation 100- • G s e r z File No.3758-001.IV3 b0 31Dt7d Ql-i dVW 9V9026990Z 6i :80 b66Z/TI/L0 rVV rr• „-Jc• �r�rGrvbinGCl(J lvl ���� Ace Paving June 24, 1994 Page 3 No ground water seepage was observed in the test pit. Ground water was also not encountered in the 50-foot teat borinS. WATER BUDGET A water budget quantitatively describes the relationship between the input of water (primarily precipitation) and the loss of water(mainly through avapotranspiration,overland flow (runoff), shallow subburf we storm flow and ground water rerliarge). As the site is developed, much of the natural vegetative cover at the site will be replaced with hard/impervious surfaces and landscaped areas. No changes in ground water recharge are expected if post-development recharge conditions are,equivalent to the existing conditions. We understand, however, that septic effluent is proposed to be infiltrated on-site. We also expect a net increase in recharge due to a reduction in evapotranspiration. We have computed water budgets for sites with similar annual rainfall and soil types. These water budgets were computed using an average of SO inches of precipitation per year, the soil and vegetation at the site and information on the land use in the vicinity of the site. Evapotranspiration values for the water budget were based on monthly precipitation and tettmperaturc data. Storm water runoff values were based on SCS (Soil Conservation Service) properties fvr the site soils. Based on SCS maps. it appears that the upland area with permeable soils in the immediate vicinity of the site encompasses about 500 to 600 acres. Based on a typical water budget analysis, we expect that there will be a net increase in ground water recharge of about 6 inches as a result-of the reduction of the original vegetative cover. Based on a septic design of 1,000 gallons per day, we expect that the septic effluent will contribute about I inches per year to the recharge. The sum of these is in effect about a 40 percent increase in ground water recharge at the site, oq an average annual basis. The additional recharge will, in theory, create, a mound of ground water below the site. Given the permeable nature of the soil,however,the ground water mound is not likely to exceed about I Inch. At locations downgradient the ground wader mound would be even less. CONCLUSIONS AND 1RECOMIANOATIONS Based on the results of our research, site reconnaissance and subsurface explorations, it is our opinion chat the site is suitable for the proposed development. It is also our opinion that the on-site septic and collected storm water-can be infiltrated on-site without signifmawly impacting existing ground water conditions or slope stability.At the site or on adjacent properties. The net change In ground water recharge will be the difference in the amount of evapotranspiration between pre- and post-developmont conditions and the additional septic influx. It is our opinion that the net increase in recharge at the site will have no measurable effect on the ground water table. , GenAnlinaera He No.373MI-TO3 SO 39bd Ql-1 d"M 9VG086990Z 6T:80 b66L/ZZ/LO r. vv. .ti vo.�• va cvo 411 UOLL bbUbr1(■1l bbXS INC fm00s Ace Paving June 24, 1994 Page 4 LIMITATIONN We have prepared this report for Ace Paving and joembers of their design team for use to evaluating a portion of this development. The report may be made available to regulatory agencies or others. Our conclusions regarding the subsurface conditions are based on shallow test pit explorations, borings, adjacent slope exposures and our review of available geologic information and should not be construed as a warranty of the subsurface conditions. Actual sub.;urfare (xinditioasi may vary with space and time. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No warranty, express or implied, should be understood; We trust that this report masts your present.aecds. If there are questions concerning this report or if we can provide additional cervices, please call. Yours very truly, GeoEngineers, Inc. 7�? MR ?�� Susan M. Ashbury Geo hnieal Engineer SBf�NAyft� Gary W. Henderson Prinelpal SMAIGti MYC t3oconxnt tU: 375MI.CON Attachmwft Two copies submitted e . i O e o E n a i e e r s Re No.37SE4oI= SOIL CLAS5IFICATION SYSTEM GaOUP� MAJOR DIVISIONS SYMBO� GROUP NAME GRAVEL WAN GW "LL-OP.&HO OPAVEL.FINE TO COARSE O11Avt� COARSE GRAVEL QRAINEO GP POORLY-Gw►oeu 6MrVEL SOILS More Teton 50% of Coorss Fraction GRAVEL GM SILLY GRAVEL Retuned WIT"ENE' GC CLAYSY tlltAvfL on Me.4 Sieve More Than 50% 'ANC CLEAN SAND sw• wELt.ORApEO s.rro.Fwc To COARE!SANDRetained on No.200 Sieve SIP POORLY-*RADEQ S AM More Then 60% SAND SM SILTY sArlC of Coarse Frection Passes WITH•PINES SG CLAYEY SANO�,, No,4 Slew FINE SILT AND CLAY SILT GRAINED INORGANIC SOILS CL CLAY Lic"d Urrit Less Then 50 ORGANIC OL 9"ANIC SILT.QPGAN[C CLAY SILT AND CLAY MH &tLT OF NIGM n AaT&MY, RAETIC SILT More Than SO% INORGANIC Passes CM CLAY OF 1410m sLASTICrrr. FAY CLAY N e.2W Sieve uqAd Unit ORGANIC psi ORGANIC CLAY.ORGANIC SILT s0 or More HIGHLY ORGANIC SOILS PT FEAT NOTES: SOIL MOISTURE MODIFIERS: 1. f44d classification is based on vt;ual MI ll[+adafl of roil Cry• Abscnce of rwolatufa,duty,dry to the touch in general.eevrdonoo with ASTM 0249S•90. Moist- DonW,but no visible water 2. Soil classification using labarstary tests is bssid olt ASTM D2407.90. Wet- Visible free wetar or saturated. usually soil is Obtained from below water table 4. Descriptions of soil density or consistency are based on intorprots(ion of blow count data,visual 9"FunO0 of spite,and/or fast data. SOL CLASSIFICATION SYSTEM Geo Engineers FIGURE z Oman 80 �cr� Ql� d'7VJ 9b�0869907 6Z:80 7661/TT/L0 07/11/1994 08:19 2066980546 MAP LTD 3N� ddSI I >i PAGE 07 roo �NOSdw 9 N3a2�9tl3A3• 0."f R a LL ` :.ia�+01Jy] O •3 a3J.3d ��j � W W LU .� ri�Yi + LU -lie h I r+rr � �p v N d At- W II a !•• •> p ;t- v .� „ l,/ �... cry +•.i ••`•`� f � ,:)� / l•.....,. • ;� �• '� fir. r� o •{K•}; . •�� ti•. � S' err .� f .r�i, J cif Q�L lr4' •\ \•. '` It..� ' `! 1 � , r / 1r6/IX�j yNr aLcv1 9001� atil SZl3H\I91;3C139 TZOO Uf 901 T42 9r:90 D8"90/40 07;08 94 08;46 VI 206 471 0521 GEOENGIN'EERS INC IZ 008 LOG OF TEST PIT DEPTH VmOW SOIL GROUP GROUND SURPA6E CLASSOCATICN wmi n SWAROL yi DtI6CMFTiON 7m"r1 0.0-b.0 SF brown saw wilt gmvel and sill(fir,Ok*l*(du) 4.0- 17.0 SP amwn z4volly mw with a into of tilt(don",MOW Tot pit completed at a dcpb of 174 f6a on 06/01/94 No gseund w*tar wMe observed No Cavi4 cbscsvcd i r i . 1 { THE DE8M oN TH8 7TST Frr Low,ALTROUOii SHOWN TO 0.1 FOOT.AM 1iASM ON AN AVERAGE OF MEASLIRRMSrM ACAOSS THB Tim PIT AND SHOULD BE CORSWIMW ACCUMTS TO 0.3 FOOT. + LOG OF TEST PIT Geo Engineers FIGURE 3 60 3r'`jd Ql1 dy4'J 8ti��8559© 5T:80 f266T/TT/-0