Laserfiche WebLink
Foothill Sanitary Landfill - 2 - 16 January 2015 <br /> San Joaquin County <br /> Well Screen Decrease of GW Projected Service <br /> Well ID Length level' Life <br /> MWAA 20 0.50 feet/year 40 years <br /> MW-2R 40 0.47 feetlyear 85 years `' <br /> MW-3 20 0.35 feet/year 57 years <br /> MW-4 20 0.70 feettyear 28 years <br /> MW-5 20 0.60 feet/year 33 years <br /> MW-6 3 25 0.60 feet/year 41 years <br /> 1. Calculated from well data provided in Revised Work Plan dated <br /> 23 December 2014. <br /> 2. Derived from screen length of well divided by decrease of GW <br /> level/year. This does not take into account current GW elevations relative to <br /> top and bottom screen elevations. <br /> 3. Potential well screen length and service life. <br /> Based on the table above, it appears that when adequate screen lengths are used to construct <br /> site wells that acceptable service life is realized based on the groundwater conditions present. <br /> The information above provides evidence that although groundwater levels beneath the site are <br /> decreasing, that site wells are viable monitoring points with a service life of decades when <br /> constructed appropriately. Furthermore, options such as increasing the screen length and <br /> maximizing screen lengths by setting the top of screen at first encountered groundwater should <br /> be considered first before proposing an alternate design such as a multi-screened well. Staff <br /> has contacted the Local Enforcement Agency (LEA) and discussed approval of an alternate <br /> screen length for this well. Staff understands the LEA is willing to review an alternate screen <br /> length for well MW-6. <br /> Based on the information provided in the Revised Work Plan, staff does not approve the <br /> installation of the revised well design for MW-6.t Staff recommends a longer well screen and <br /> setting the top of well screen at an elevation no more than 10 inches above first encountered <br /> groundwater. A possible well design with projected service life is shown in the table above. <br /> Staff recommends the Discharger revert back to the well design approved in the letter dated 30 <br /> September 2014. Staff also recommends the Discharger contact the LEA and request <br /> permission to install a longer screen length and to install the top of well screen at an elevation <br /> that maximizes the screen length in the aquifer. <br /> Staff understands the Discharger wants to progress quickly with this installation. By <br /> 28 January 2015 please provide confirmation of the well design and drilling schedule, as well <br /> as a copy of the well permit from the LEA. <br /> If you have any questions please call me at 916-464-4737 or email me at <br /> tdelfrate cxwaterboards.ca.aov. <br /> ZaRATE, P.G. 7394 <br /> Engineering Geologist <br /> WDRs Compliance and Enforcement <br /> cc: next page <br />