AP2400573 (4) - Laserfiche WebLink

Home Browse Search

ekienvironment & water conditions near storage ponds and as recommended in the "Engineering Feasibility Study Findings Report".3 In addition to the Spring sampling event, monitoring wells CLSP-11 and CLSP-12 were also sampled during the first quarter of 2023 (2 February 2023). The MRP states that new monitoring wells shall be sampled on a quarterly basis for a minimum of eight consecutive quarters. Monitoring wells CLSP-11 and CLSP-12 were installed on 22 August 2017 and 23 August 2017, respectively, and have now been sampled for twenty-four (24) consecutive quarters and will remain on a quarterly sampling schedule until the existing WDRs are revised; the WDRs were officially rescinded by the RWQCB on 22 June 2023. Subsequent report tables only include data collected between 24 March through 5 April 2023; all water level measurements and water quality constituents analyzed are reported in Appendix B and Appendix C, respectively. All data collection and analyses used standard US EPA methods.The following tables only include data for current compliance wells listed in the MRP; all monitoring well data are reported in the appendices. 2.1 Groundwater Level Measurements Groundwater elevations relative to mean sea level (msl) North American vertical Datum of 1988 (ft NAVD 88) were calculated by subtracting the depth to water from the measurement point elevation at each well. FGL Environmental (FGL) measured water levels in Mossdale, CLSP, CTF, and Pond S6 monitoring wells, and ENGEO, Inc. (ENGEO) measured water levels in River Islands monitoring wells'. All water level measurements were taken using a water level sounder, which is accurate to 0.01 foot, and are included in Appendix B. 2.2 Sample Collection and Analysis FGL performed all well-water sampling. All monitoring wells were purged and sampled using a submersible pump. Purged water was stored in tanks for later disposal, disposed of at well sites, when appropriate, or in adjacent agricultural fields. A minimum of three casing volumes were purged prior to sampling. Table 1 reports the calculated volume of each compliance well casing and the number of casing volumes purged for each compliance well. Field parameters (pH, electrical conductivity, temperature, dissolved oxygen, and oxidation-reduction potential [ORP]) were monitored using a YSI Model 556 multimeter and flow cell. The multimeter is calibrated at least twice a day and more frequently as needed depending on sample pH and electrical conductivity. Appendix A contains groundwater purging and sampling logs for all monitoring wells sampled. 3 Engineering Feasibility Study Findings Report, Former Land Application Area LAS-2, prepared by HydroFocus, Inc. for the City of Lathrop,dated 12 December 2016. a FGL also measured depth to water in MWR-28 and MWR-32 while collecting water quality samples. City of Lathrop 2 13 July 2023 EKI B90088.03