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r i Y PUBLIC HEALTH SERVICES a • SAN JOAQUW COUNTY ENVIRONMENTAL HFALT14 DTVISICIN 1 Karen Fursi:,iAD ,M.P.H_, Healrh Officx r z � 304 Easc Weber Avenue, Third Floor * Scockton, Cry. 95202 � I' 209/46a-3420 3 , r r HENRY CECCi�= OCT � � I CECCHSNI CECCHMNI & GIOVANN0N2 3000 E EIGRTEEI+7TH ST Fly I ANTIOCE CA 94509 (000 RE , DELTA TRUCK (former) SITE CODE. 1800 3535 E Cherokee Road RO#00011 a Stockton, CA 95206 San Joaquin County Public Ser Aces, Environmental Health Division (PHS-EHO) 11as remewed the 16 August 2001 "Problem Assessment Report" (PAR) submitted by Advanced GeoEnvironmentai Inc an August 28, 2001 and has the following comments. a PHS-EHD ano a representative from: the Central Valley Regional Water Quality Control Board (CVRWQB) evaluated the comments and conclusions included in the PAR and have concluded � that the "No Further Action" requested cannot be granted at this time. Due to the large mass of residual petroleum contaminated soil and elevated levels cf Methyl tertiary butyl ether (MtBE) and 1,2,-dichloroethane (DCE) still present in the groundwater at the site, further investigation in areas described below must be completed The gro'undwater"grab' sample collected at 70' below ground surface ('bgs)from soil boring "B- 17" adjacent to the former unleaded gasoline underground storage tank (UST) #6 detected E MtBE at 9,700 lig/l during June 1999 The lateral extent of this contaminant must be dellneated Additionally, the 950 p.gfl of DCE detected in monitoring well "UST-5,when last sampled during June 2001 must be delineated Contamination was detected in sail samples collected from monitoring well "UST-1"during it's construction in September 1994 at 50' to,70' bgs UST-1 was constructed with the screened interval passing from a sand lents interval at 83'-8T bgs through a clay layer from 87'-97' bgs and ending in another sand layer at 97'-103' bgs. It appears that the construction of this monitoring well is allowing contaminants (DCE) in the upper stand zone to migrate downward to the lower sand zone and contribute to rias degradation. It is the conclusion of PHS-EHD and the E CVRWCB that this monitoring well be destroyed by over-boring it to it's total depth with a minimal 10" hollow stem auger In order to address the unresolved concerns with both MtBE and OCE at this site, PHS-EHD will Crequire a multi-zoned investigation north-northwest of'B-17" and "B-12" and south of"B-8" The permeable sand zone at 55' bgs is to have a monitoring well installed so that it's screened interval is constructed to overlap this zone No more than five feet of screened casing should be'placad at this depth. The other zone of concem in this same area is the sand zone from 8C to 90' bgs No more than ten feet of screened interval of casing should be Installed in this well If separate monitoring well bonngs a're to be installed, ensure that the wells are no closer than I five feet horizontally from each other: A nested monitoring welll is acceptable and so is the neve 1 7" OD extruded polyethylene/Teflon multi-level pre-constructed easing. Your cost-effective analysis and Cleanup Fund pre-approval will determine the mast acceptable type of well IA Division of San Joaquin County IH=kh Care Scxv= n