Laserfiche WebLink
15660 Harlan Read, Lathrop <br /> Page 2 <br /> The work plan proposed placing a well screen across Sand A and Sand B with the <br /> screen placed from 5 to 35 feet. Screen lengths for monitoring wells are to be limited to <br /> 20 feet in length. Therefore, the screen interval for Sand A and Sand B wells should be <br /> limited to 5 to 25 feet. Details on placement of sand, bentonite, and grout around and <br /> between the well casings were not provided in the work plan: A well construction <br /> diagram should be included in the work plan. The cost and benefit of clustered wells <br /> instead of nested wells should be evaluated. <br /> Well development must be discussed in the work plan. Also during purging of water <br /> from the wells,temperature, pH, and electrical conductivity readings should be <br /> measured to show water stability prior to obtaining the water sample <br /> Analysis for Gam 17 metals is not required by EHD. if it is required for off site disposal <br /> of soil or groundwater than this should be clarified. EHD was informed that analysis for <br /> Total.Dissolved Solids was a requirement of the City of Lathrop for disposal of <br /> groundwater to the city disposal conveyances. This analysis can be performed on water <br /> from current monitoring wells on an as needed basis for the City of Lathrop and must be <br /> clarified in the work plan. <br /> EHD again recommends that the alternative of extracting and disposing of contaminated <br /> water from monitoring wells with the highest concentration of MTBE on an interim basis <br /> to reduce the concentrations of MTBE in the groundwater on and off site be conducted. <br /> This may be more cost effective than installation of additional monitoring wells and <br /> monitoring and sampling of the wells in order to determine where the contaminant plume <br /> has migrated. <br /> A new work plan for defining the MTBE contaminant plume that addresses the above <br /> comments is to be submitted to EHD by December 28, 2006. <br /> If you have any questions contact me at(209)468-3449: <br /> Donna Haran; RENS, Director <br /> Environmental Health Department. <br /> Margaret agorio, REHS <br /> Program Coordinator Unit IV <br /> c CVRWQCB—Jim Barton <br /> Environmental Remediation Group—Jim Keegan <br />