COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Stantec L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Summary of 2012 Annual Monitoring and Sampling February 1, 2013 0.00098 (MW-34) to 0.15 mg/L (MW-9). Arsenic concentrations appear to be relatively stable with the exception of A-Zone wells MW-25, MW-31, and MW-45 where a slight increase has been observed based on data collected historically and during 2012. Graphs depicting arsenic trends in selected A-Zone wells within the petroleum hydrocarbon plume (MW-9, 2AMW-12, MW-18, MW-20, MW-21, MW-22, MW-23, MW-25, MW-28, MW-31, MW-34, and MW-45) are included in Appendix H. Arsenic trends will continue to be evaluated during the 3Q13. 5.11 2012 ANNUAL SITE SUMMARY Groundwater elevations, groundwater gradient, and chemical concentrations throughout 2012 were generally consistent with historical data. The area of greatest impact to groundwater by petroleum hydrocarbons, in the shallow zone wells, is centered in the vicinity of well 2AMW-14, which has consistently reported the presence of SPH sheen. Petroleum hydrocarbon impacts and SPH in this area are currently addressed with the operation of the DPE/ASVE/SVE system. The area of greatest petroleum hydrocarbon impact within the deep zone wells is found off Site in the southern section of the Water Front Towers parking lot, in wells MW-43, MW-47, MW-48, MW-49 and MW-50, and in the northern section of the L&M OU site, in wells MW-17 and MW-52, which have contained measurable SPH or sheen since their installation. SPH in this area is currently addressed with quarterly (at a minimum) extraction events. Stantec plans to install a free product removal system in early 2013 to address offsite product in deep zone wells in the WOTOA parking lot area. Once the system is installed, Stantec will cease quarterly product removal and commence using the free product removal system on a consistent basis. Any remaining onsite and offsite wells that were previously part of the quarterly SPH removal operation and that will not be hooked up to the new free product removal system will be addressed using either additional skimmers, installation of Soakies®, or using a field technician to manually bail/purge several casing volumes of water in the well and then treating the water through the onsite remediation system. The shallow impacted groundwater plumes are generally delineated to the south, west, and north by the current well network and the Deep Water Channel. The deeper impacted groundwater plumes are generally delineated to the south and west. Additional assessment is needed to define the plumes originating east of the Site at the UOU and MOU. All accessible petroleum hydrocarbon-impacted soil has been removed from the L&M OU and off-site to the north in the Water Front Towers parking lot as a result of pipeline removal and soil over-excavation activities conducted on behalf of the L&M OU Group, except for a small portion of impacted soil that remains beneath the on Site remediation compound which existed prior to excavation activities. Additional assessment and remedial activities have also been performed by the SRDA to address contaminated soil and remaining pipelines east of the site at the UOU and MOU, and north of the site to the west and north of the Waterfront Towers parking lot. The results of the UOU and MOU excavations are included in Treadwell and Rollo's Removal Action Completion Report Unocal Operable Unit on Area 2A dated August 5, 2009 and the results of the excavation north of the Site and to the west and north of the Waterfront Towers parking facility are in Wallace Kuhl's Underground Storage Tank Removal Report Former North Edison Street dated June 8, 2009. I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.8