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I "7,1 WOMW�: , ._ 9 199C16.ANDERSON S ASSOCIATES, INC. ( GHN L• -GROUNDWATER-I .P O71 9-TOTR5-LAjB5W cYRY SERVICES 1 ��G SACRAMENTOOFFICE CORPORATEOFFICE Gp' 4229 Northgate Boulevard Suite 3 22 Houston Lane a-��co (MMeei.eaa� Saaram91 °'920lirfornia 9-9267 5834 Lodi,Callfbrnla267-3 95240 01 _ ( (2.09 367-3iQ1 S S a C%VI w.r STCCKF�io�s�rav (9161851-4455 FAV(69)16)16)929-T269 FARC; 09) 33'38303 October 21., 1999 KE-H_S. past-it*Fax Note 7671 vi7- nWxhM2W Health Vivisiou ;° D t+►� '(0a k.,V FrGma f� ( 304 E.Weber Mmue c� �' �f�/st _ ff Al- Go \AG(A t A'6. LIC- �O Floor Pwwe a LL4 a '3 j r47 Phone f 'i Stocltcm, CA 95202 Fax a t( t!—Uf'.Sl F"uL# 3 RE: Soil Suitalyil4fNjtnAe Loath*Study Report Dated 9f24M.Tab No.599244 Mausco(?we pwducts 17950 ViaNicolo Tracy,California Bear Mr_Yodku7m, per Our Moet=p today,you requested a letter clarifyi if proposed new septic systes att the Niusco obve SAO will mot negaUvaly impact the odsting ground water. I understand your concem is that aur report dad not iusnestigdte the relationship between the emstiug nitrate levels fuuud in the wzter well and the nka loadirw esdrn2dW from the septic*,a=n and cam waster(the two sources of nitrate cMaminatiam). The wester well and septic syswm are separated by approximately 13M feet distance with the reponal grauM watex gradient mush liWy flawitg east:tavrard the valley_ The geologic f0mafims along tho east side ofthe Diablo Rmsge dip toward the east. In a c0Ilfsl'ied aquifer,groxmd water will move east along peable zonas imthe data&ccdan at the dip angle ofthe foxanaci s. Inspe c nofthe Musca Olive well log campleti m report attached m the App+mdix ofthe rferemced repast indicates the se&MeOU are quite hctefO&Meous and are cooposed ofthim imbedded sands,clay,and shale. Clay and stale and other farce-grimed itstend to limit the veltieal percolaum of iramMl wd other ground water rectarge m addiftoo to prorvi&i g a ground water mi,�ingbat7riex(aquifigge,aquitatrd,aquicluds). Our 40 foot bonng foul similar cor>diticros in the shaUcw sccfi0lr sandy zos "separated byfma grained matigmithat imclude clay. Noground water was encountered- It is a reasonable assumption tbat* conditiams accuz tbrougbot t the site. Mw res iks oftliewater smxple fiu mthe ousite well indicated the nitrato-N%co*DWftztioMwas is 16.9 � _ is value to 3.81 m -N.The LI LkM Status Geologic Survs3y paroduced a lsirolessiOnal zug11.-NO3 '� � � Paper(1401-A)titled�Crrcamd Water in the Central Valley,Calif ilia-A Summary Report"stating on page A-4o, `Nall (1984) estimated that maximum cmceutratim of nhTate under natiwal ccuditims of the Sacramenw Valleytobe 3 ingA(citrate-N)and consideredtbat areashaving 5.5 m,4(uitrad-.-N)arethose in which nitrate emcemratims:tray be increasing." If similar conditions prevail here.the nitrato cmemAration ofwell water 3.81 mgfl-N(drkking water standard of to mgJ1 N)is very chase tothat ofnatural cmcemtraticans I found in the Sacramento Va4ley. We believe the septic effiugit-mll mmwith rain water as assiunedbythe nitrate mass balance formula ofHantssche- This formula predicts the mate cmceatration vfthe recharv,-water to be bdowlhe maximum contaminate level for nitrate of ground vrAer(14 mg/1-N), The percolating effiuera may travel down gradient along impermeable layers and most hkcely not travel deeply. Evapora on,evapctramspirataOn, sorption and demupos-ition to Na,gas within the shallow soils will MA likely Omur. Demise of the 711 A tr7WOH '00'0V4" � uosaapuq '0 1 !6h! WdH :9 6661