ARCHIVED REPORTS XR0000882 - Laserfiche WebLink

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On May 2 and 3, 2000 the soil borings for both MW#5 and MW#6 were made as described in the work plan of 311712000. Monitoring wells were installed in both of these soil bores. The work plan of 3/17/2000 also included a soil bore and monitoring well (MW#4)to be installed in the sidewalk on the north side of Lafayette Street. This soil bore was not completed as planned. An unknown underground storage tank was encountered in the direct path of the soil bore. As a result of this encounter, the soil bore was abandoned and the local agencies were notified. A work plan to expand the horizontal definition of the contamination plume was approved in December of 2000.This work plan called for the installation of three new CPT's within the Caltrans R/W to the north of the project site. These CPT's were completed on March 8, 2001 and soil and water samples were extracted to a depth of 125 feet. Also, included in the work pian of December 2000 was the installation and testing of four new monitoring wells,MW-8S,MW-8D,MW-7,MW- 9, to be placed on the project site or the adjacent property. These monitoring wells were completed on April 11, 2001. In January of 2002 the owners of this property removed the apartment house structure on the east side of the property. At the time of this report that portion of the property is clear without any structures or other improvements. On August 9 & 10, 2002 the extraction well installed for the pump test was completed and developed. In December of 2002,work crews under the control of others,removed the buildings on the lot directly East of the site. This lot is not owned by the Olivarez's. Monitoring wells MW-8S and MW-81)were damaged and the caps and covers were removed along with the upper portion of the casing by the crews removing the buildings. These monitoring wells were repaired in March of 2003. REPORT OF FINDINGS FOR THE THIRD QUARTER MONITORING EVENT Procedure On September 25,2003,Del Tech Geotechnical Support Services extracted water samples from all of the monitoring wells on the above stated property and extraction well EW-1. The work was supervised by Foothill Engineering. All samples were extracted using the tube with check valve pump system with exception of EW-1. Purge rates were+/- .5 gpm on monitoring wells and the physical properties of the groundwater can be found in the Del-Tech Field Report which is attached and part of this report. All three replacement wells were found to be dry on the date of this sampling event. The original monitoring wells (MW-1,MW-2,MW-3)were sampled for analysis.The original monitoring wells (MW-1, MW-2, MW-3) were used to establish the groundwater elevation and hydraulic gradient. All samples were transported under chain of custody to Sherwood Labs of Hilmar, California for analysis by EPA method SW 8020F. Samples were transported under chain of custody from Sherwood to Entech Analytical Labs for analysis by EPA Method 8260FA for oxygenates including 1,2-DCA and EDB. All water sample analysis and groundwater elevations are summarized in the attached tabular recap sheet. Copies of the original laboratory data sheets from this sampling event are also attached and are a part of this report. . Findings The groundwater elevation at time of monitoring was about 1'lower than the last monitoring event. MW-1 continues to have the highest concentration of the monitoring wells with gasoline 2