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Milir J �' __ ,rk, - w,r c6��"` k } Texaco Environmental Services September 11, 1991 02320 0075 Page 2 A soil venting pilot test was performed on May 21, 1991 to determine if soil venting could be used to remadlate the subsurface soils. Existing MWs were used as vapor extractIon points during the test,and vapors were extracted using a 1.5-horsepower(hp)regenerative blower. Results from the pilot test Indicate a conservative radius of Influence of 25 feet. Air samples collected from PAW-4 and MW-5 contained total petroleum hydrocarbons as gasoline(TPH-G)of 71,000 and 150,000 pg;i,respectively. 'Awa se the. S ire a ssned t per. lgys .*,Or:sts Viand;sands se�N vapors may have been prefe�e��t•"arr Trt�'df��'�e cap �ary"firirge In the'f�a0�r`�' 5�'�t�eregore 1the�rau��.rrf�o�n�.4*�test mdyi ,.. , ncrk car at ttta,ca[x33. r►t i tha upper clay self trorizon where the!'Mbrlty of t.�e adsorbed hydros rboet 3.0 PROPOSED SCOPE OF WORK 3.1 SOIL_VAPOR EXTRACTION WELL INSTALLATION �A tE< a?.�:f wA. sedlr s f_lnllsleitce, vhp�tFtts€n�a 1; Ahp rag66eM0 bl'C' er fov',vapor4� extraction,weft wrll be n;crired #o tpm. diate}he subsurface ecils.,Jin an attempt_to Isolate Individual/ tratlgraphfC MYLr Ons for son venting;thri.upper clay and lower silty,sand},tyio ufYJs MIM be nested ft►,eacf,r ti Four 12-Inch diameter soil borings will be drilled to a depth of 40 feet BGS,and each VEW will be constructed using 10 feet of 4-in6e diameter PVC well screen and blank casing to the surface. Screen will be placed at depths of 5 to 25, and 3o to 40 feet BGS,a 2-to 34eet tKck bentonite seal placed between the two sections of screen will isolate the nested VEW's from one another. A sand pack equivalent to number 3 Monterey sand will be placed in the annulus around the screened sections,and cement grout will l complete the wells to the surface. FIgure 5 (Appendix A) presents a construction diagram of the VEW. Figure B (Appendix A) presents the VIEW locations, their estimated radii of influence and the estimated horizontal extent of Impacted soils in the subsurface. I 3.2 SOIL VAPOR EXTRACTION TEST A soil vapor extraction test will be performed using the VEWs upon completion. Prior to conducting the test,permission will be acqu;red from the San Joaquin County Air Pollution Control District(SJCAPCD). The test will be conducted to determine the radius of Influence and the hydrocarbon concentrations In soli vapors extracted from the VIEWS. Vapors will be drawn using a 1.5 hp regem-!ative blower. Flow rates during the test will be altered to aid In determining the size blower that ltilif be required to achieve the desired radius of influence. Air samples collected during the test will be sent to a state-certified laboratory Com:GROUNDWATER TECHNflLOGY,IPiC. 0O75COSTYRO i