ARCHIVED REPORTS XR0000979 - Laserfiche WebLink

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CONCLUSIONS The groundwater elevation in all of the wells is approximately 1.1 feet lower than last sampling event. It is typical for Fall groundwater elevations to be lower than Spring and Summer elevation in the City of Stockton. Up gradient monitoring well MW-3R has produced samples with lower concentrations of TPHg than previously tested. The down gradient monitoring wells (MW-1R & MW-2R) have a higher concentration of TPHg than last tested. RECOMMENDATIONS To date, two of the CPT's located on the Olivarez Property have been completed and a report from Gregg Drilling & Testing, Inc. has been received. Currently Foothill Engineering is working with Caltrans to secure an access agreement to install a third CPT in the parking lot under the viaduct of the Crosstown Freeway(State Route 4).The area directly north of the Lafayette Street is a restricted access area and requires a special permit from Caltrans Headquarters. This final CPT will be installed when the Caltrans permit is obtained. It is recommended that quarterly water sampling be continued on only the replacement wells. Sampling ofthe original monitoring wells should only be resumed ifthe groundwater elevation drops and the over screen condition has been eliminated. . PRELIMINARY REPORT OF CPT WORK CPT INSTALLATION TO THIS DATE Two of the three proposed CPTs have been installed and all proposed data has been collected. The installation of third and final CPT has been delayed due to the time required to secure the necessary permit from Caltrans. The original proposal was to install CPT#3 in the sidewalk on the north side of Lafayette Street. This sidewalk area was too small for the CPT truck and this location had to be abandoned. The area in the parking lot under the State Route 4 Viaduct will accommodate the CPT truck. CPT PROCEDURE The subcontractor, Gregg Drilling, used a 20 ton CPT push truck with a Ultra Violet Induced Fluorescence(UVIF) Piezo Cone Penetrometer.Data collected was recorded by Cone Investigation Ltd. software with hard copy printout.Data was collected continuously for cone bearing(Qc),sleeve friction (Fs), pore pressure (Ut), and UVIF volts. The procedure required one push run with the Penetrometer for data collection and one adjacent push with sample collection equipment for soil and groundwater samples. Groundwater samples were extracted by push-type screened cone and a small stainless steel bailer. Soil samples were extracted with 1.25 inch stainless steel sieve push sampler. FINDINGS Soil and water samples from CPT#1 show various levels of gasoline contamination to 85 feet of depth. Soil samples taken at 55 and 85 feet bgs.produced lower levels of BTEX contamination than a sample taken at 75 feet bgs. All soil samples from CPT#1 were below detection levels for TPHg. 2