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Mr. Gary Halbert - 2 - 16 December 2002 <br /> o The use of a tailpipe (blank screen installed below the screened interval) in groundwater <br /> monitoring wells is questionable. Please explain why the tailpipe is needed. <br /> o The Well Design section of the report describes a 30-foot deep well, but Figure 4 presents a <br /> 37.5-foot deep well with 33-feet of the total depth either screened or gravel packed. This <br /> design will result in too much mixing of groundwater samples. Screened intervals should <br /> not exceed 15 feet, unless site specific conditions justify otherwise. Please submit a revised <br /> well design that maximizes the annular seal and monitors the first saturated interval. <br /> o Figure 4 shows a protective casing extending the entire depth of the well grout. If used, the <br /> casing must comply with California Well Standards 74-90 Part 2, Section 9.0 which <br /> requires, "A minimum of two inches of sealing material between all casings and the <br /> borehole wall within the interval to be sealed..." Please revise the workplan to comply with <br /> that requirement. <br /> o Figure 4 shows concrete as the annular seal material. Concrete is not an acceptable seal <br /> material and is not compliant with the San Joaquin County Environmental Health Division <br /> Well Standards Section 13.12.3. Please revise the workplan to comply with that <br /> requirement. <br /> o If a slip cap is used for the bottom of the well it must be secured with stainless steel screws. <br /> — The wells Will be installed in two phases with the second phase of wells to be located based on <br /> the information obtained in the first phase. Once the first phase wells are installed, you shall <br /> transmit to the Regional Board an addendum to the workplan that describes the findings of the <br /> first phase and the proposed well locations prior to installation of the second phase wells. <br /> — In the Well Logging, Installation and Design section of the workplan, the disposal of discharge <br /> water into the nearest irrigation ditch is desEribed. Such a discharge may require a National <br /> Pollutant Discharge Elimination System(NPDES)permit. Discharge of the well purging and <br /> development water on land adjacent to the well maybe acceptable if there is no reason to believe <br /> the groundwater quality has been impacted by contaminants. Please revise the workplan to <br /> address the information available on groundwater quality and handling of the extracted <br /> groundwater. <br /> — If the water levels in the wells recover slowly it is acceptable to purge the wells dry and return <br /> the next day to collect samples. However,the purge rate should not be at an excessively high <br /> rate to deliberately dewater the wells. Dewatering the wells can draw fines into the sand pack <br /> and/or aerate samples. <br /> — The Well Monitoring and Sampling section of the workplan describes disposal of <br /> decontamination water in the nearest percolation basin. Please describe the location and use of <br /> any percolation basins at the site. <br /> — Please provide additional information on the sample filters that will be used and the method of <br /> filtering the samples. <br /> — Please add the following analytes to the list of chemical analyses: pH, five-day biochemical <br /> oxygen demand,nitrate as nitrogen, total Kjeldahl nitrogen, and standard minerals(calcium, <br /> magnesium, sodium, chloride,nitrate, sulfate,total alkalinity(including alkalinity series), and <br /> hardness. <br /> V:I jngoo WIIVYP TlmjNmuTR Gtl VA131301 <br />