ARCHIVED REPORTS_XR0002060 - 1 - Laserfiche WebLink

Home Browse Search

Workplan for Vertical Groundwater Investigation And Bench Test for In-Situ Oxidation 7835 Thornton Road, Stockton, CA Page 5 of 8 All drilling and sampling equipment will be decontaminated between uses. Soil cuttings generated from drilling activities and wastewater produced from equipment decontamination will be contained on site in lined 20 cubic yard roll off bins pending waste characterization and disposal. Well Development, Surveying and Groundwater Sampling The elevation of the well casing collar will be surveyed to an accuracy of 0.01 feet. A minimum of 48 hours after completion, an experienced field technician will measure static depth to water, and then develop the well by pumping and surging until turbidity is minimized. A minimum of three casing volumes will be purged from the well. Groundwater samples will be collected into the appropriate containers after pH, temperature, and electrical conductivity have stabilized and water has recharged to minimum of 80% of static levels. The samples will be placed into an ice chest refrigerated to a temperature of approximately 4°C for shipment to a State-certified laboratory under chain of custody protocol. Groundwater samples will be analyzed for BTEX and MTBE using EPA Method 802113, TPHg using EPA Method 8015M, and lead using EPA Method 6010 or equivalent. PROPOSED REMEDIAL ACTIONS Despite the lack of groundwater plume migration and the limited volume of impacted soil remaining below the excavated area, contaminant concentrations in groundwater remain elevated. Although historical analytical results exhibit a declining trend in contaminant concentrations, at the current rate of attenuation it would be decades before concentrations fall below drinking water standards. As a result, EHD requested remedial actions be implemented at the site. We propose to evaluate the potential for the injection of an oxidizing solution to accelerate the pace of cleanup. We have selected in-situ oxidation over groundwater extraction and treatment for the following reasons: 1. The City of Stockton will acquire 3,282 square feet of the property for the Hammer Lane widening project; much of the acquired land is around well MW5, the heart of the contamination plume. The land acquisition would render much of the heart of the plume inaccessible to an extraction well. However, an oxidizing solution could be injected through borings placed within the City right of way under an encroachment permit issued by the City. Mr, Mike McDowell of the City of Stockton indicated that such a permit is feasible for soil borings advanced within a negotiated time window, but that the City would not permit installing a well. In-situ oxidation would allow access to a greater portion of the plume than would groundwater extraction. 2. Based upon calculations of residual contaminant mass in soil and groundwater beneath the site, more than 95% of the contamination remains sorbed to saturated soil. Groundwater G:%GROUNDZEIKNOW LES.HAMIREPORTSIW KPLAN_deepwell_bench2.doe