SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

California Regional Water Quality Control Board Central Valley Region Robert Schneider,Chair Winston H.Hickox Gray Davis Secretaryfor Sacramento Main Office Governor Environmental Internet Address: http://www.swrcb.ca.gov/—rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Phone(916)255-3000•FAX(916)255-3015 23 August 2001 d �2 �� 10 Mr. Doug Stidham City of Escalon 1854 Main Street Escalon, CA 95320 INADEQUATE GROUNDWATER IMPA CT E VAL VA TION REPOR T, CITY OFESCAL ON WASTEWATER TREATMENT PLANT, SANJOAQUIN COUNTY I have reviewed the Groundwater Impact Evaluation Report, City of Escalon Waste Water Treatment Plant, "prepared by Geological Technics, Inc., dated 10 July 2001. The report was prepared in response to Waste Discharge Requirements (WDRs) Order No. 5-00-142, Provision F.4 which required an evaluation of the groundwater quality after four quarters of data had been collected. The WDRs state that if the Groundwater Impact Evaluation Report indicates wastewater has degraded groundwater quality beyond background concentrations, the Discharger shall submit a Wastewater Disposal Mitigation Plan within 90 days of request by the Executive Officer. After reviewing the report, I have the following comments: Upzradient Well Considerations The report states that no upgradient wells exist at the site. Based on the expansion of the treatment plant, that statement may be correct, however Well MW-2R likely represents the natural background groundwater quality better than the other site wells. Review of the available groundwater flow directions and analytical data indicates Well MW-2R is a good candidate for use as an upgradient well. Samples from the well are notably lower in total dissolved solids (TDS), sodium, and chloride concentrations as well as nearly all the other monitored analytes. In addition, Well MW-2R is generally located cross gradient to Ponds 23 and 22. Those ponds were constructed in year 2000 and therefore have not received large amounts of wastewater over time, reducing the likelihood of groundwater degradation in the area of Well MW-2R. However, it is recognized that Morrell Industries (a neighboring industrial facility) operates a storm water pond approximately 50 feet to the north of Well MW-2R which might also locally influence groundwater quality. Statistical Evaluation o Data The statistical evaluation of the data presented in the report employs the intrawell method of comparison. Use of the intrawell comparison method is not appropriate at this site. The site clearly does not meet a basic prerequisite, as described on page 7 of the report, "That previous contamination does California Environmental Protection Agency ca Recycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swreb.ca.gov/rwgcb5