SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

California Regional Water Quality Control Board Central Valle Region Steven T.Butler,Chair Gray Davis Winston H.Hickox Secretary for 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 ,,7 I N 21 December 2000 2 Mr. Doug Stidham, City Engineer City of Escalon 1854 Main Street Escalon, CA 95320 INADEQUATE GROUNDWATER WELL DISINFECTION WORKPLAN, CITY OF ESCALON WASTEWATER TREATMENT PLANT, SAN JOA QUIN COUNTY I have reviewed the "Work Plan: Disinfection of Groundwater Monitoring Wells, City of Escalon - Waste Water Treatment Plant, " prepared by Geological Technics, Inc., dated 7 December 2000. The workplan was received at the Regional Board's office on 12 December 2000. The plan was prepared in response to concerns raised about the elevated coliform concentrations observed in groundwater monitoring wells at the City's wastewater treatment plant. Inadequate time was included in the workplan to allow review of the proposed well disinfection procedures. The workplan project schedule stated the work would be performed on 14 December 2000. On 13 December 2000, Geological Technics was contacted by telephone to inform them that the workplan would not be approved and the work should be delayed. On 14 December 2000 I was informed that the first phase of the well disinfection (treatment of the wells with Clorox) had been performed on 13 December 2000. Better communication is required to prevent misunderstandings and the additional costs of having to repeat tasks. In this case, the work that was performed may not have been adequate to disinfect the wells and may result in additional disinfection requirements or further investigation of the reported coliform concentrations in the monitoring wells. After reviewing the workplan, I have the following comments: • The workplan is not wet stamped and signed by the registered professional responsible for the work. • It is noted that the volumes of Clorox proposed for use in the wells is adequate to maintain the target concentration in the well casing,but may not be enough to maintain the concentration in the filter pack. The method of introduction of the disinfection solution is not described. For example in Well MW-7, 15 ml (0.51 fl. oz.) of Clorox was added to the well. It is unclear if the volume of Clorox was mixed with water prior to addition to the well or if it was simply poured into the well which would likely result in a portion of the Clorox smearing along the well casing rather than being mixed with the groundwater. California Environmental Protection A,;ency_ ca Recycled Paper