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PgU1N 2' '' Z m. < THOMAS M. GAU I DIRECTOR "gGiFOt+ei P. O. BOX 1810 - 1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201 (209)468-3000 FAX(209)468-2999 www.sigov.org/pubworks MICHAEL SELLING DEPUTY DIRECTOR u ` t STEVEN WINKLER DEPUTY DIRECTOR ROGERJANES BUSINESS ADMINISTRATOR August 25, 2011 Ms Wendy Wyels, Supervisor Waste Discharge to Land Compliance and Enforcement Unit 11020 Sun Center Drive #200 Rancho Cordova, California 95670-6289 SUBJECT: REVISION TO SAMPLING METHOD - EVALUATION MONITORING PROGRAM WORK PLAN, CORRAL HOLLOW SANITARY LANDFILL Dear Ms Wyles: Enclosed, please find Revision 1 of the Evaluation Monitoring Work Plan for the Corral Hollow Landfill, the original version of which was submitted August 8, 2011 in accordance with Item 1 on Page 4 of the Water Code Section 13267 Order dated July 7, 2011. 1 understand that you and Mr. Todd Del Frate have discussed this revision, and are provisionally in accord. This letter and enclosed revised document presents what we believe to be an improvement in construction method to address a difficulty which arises due to our need to pre -qualify the location of the permanent groundwater monitoring wells. Originally, we proposed to drill full -diameter bore holes, install casing, sand pack, and bentonite, then take a VOA sample and measure groundwater elevation. The sanitary cement seal would be postponed for approximately two weeks until the results of the VOA analyses from the first water.samples are available and evaluated, and the appropriateness of the well location assessed. The difficulty with this procedure is the potential for soil to slough from the sides of the bore during those two weeks. If excessive soil falls into the borehole, then we will be forced to re -drill that well if the location is appropriate. An alternate method, proposed by our friends at Gregg Drilling, would involve drilling a smaller hole to the approximate depth of the aquifer, then driving a hydropunch sampler past the hole into the saturated zone. We would take a VOA sample and measure groundwater elevation through the hydropunch casing. This information will allow assessment of the appropriateness of those locations for permanent wells. If the locations are appropriate, then the hydropunch casings would be withdrawn, and permanent wells installed in boreholes drilled at those locations. Although somewhat more costly, this procedure removes the risk that we might need to abandon a partially -installed well due to slough of soil from the borehole interior. C