COMPLIANCE INFO_1993-2007 - Laserfiche WebLink

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Andrew Keller - 3 - 17 January 2007 precise than those of laboratory -performed ASTM D 5084. Conversely, literature suggests that if soil smearing occurs during field-testing, then BAT results may lead to an underestimation of the hydraulic conductivity. Therefore, tests performed via ASTM D 5084 that do not meet the passing criteria of 1 x 10-6 cm/sec will be considered failing test results. That portion of the cap will be removed or reworked until the required criteria are met. BAT field test results are to be used as an indicator of ongoing construction quality control. 3. Increase the Plasticity Index from 30 to 52. Discharger Proposal: Based on recommendations from their geotechnical laboratory, Condor Earth Technologies (Condor), the Discharger proposed increasing the plasticity index (PI) of the low -permeability material (i.e., the cap) from 30 to 52. However, Condor cautioned the Discharger that excessive cracking of the cap may be a consequence of increasing the PI with the resultant need to re -design, add additional two to three feet of sand cover over the cap, remove and replace the vegetative cover, irrigate the cover in dry months, and/or install a vapor barrier layer. Condor cautioned that failure to closely maintain and monitor the progress of desiccation and cracking might result in surface water entering the landfill. Staff Comments: Staff does not concur with the Discharger's proposed recommendation to increase the PI to 52. As noted in Condor's letter, PIs larger than 40 may cause excessive desiccation and cracking that leads to water intrusion into the landfill. Therefore, the Discharger is encouraged to work with their clay materials -vendor and geotechnical lab to determine a mix -formula for blending soils that have a final product that meets both`the PI (<30) and hydraulic conductivity (1x10-6 cm/sec) requirements. Therefore, by 28 February 2007, the Discharger shall provide a mix - formula that will produce the material that meets the PI and hydraulic conductivity requirements. Discharger Proposal: The Discharger stated the existing groundwater monitoring wells MW -2 and MW -3 are not appropriately located for perimeter monitoring activities. The Discharger proposed that these existing wells be abandoned and that two replacement wells be installed eastward and at the property boundary. A proposed monitoring well replacement map was sent to staff via email. Staff Comments: Staff concurs with the Discharger's proposed abandonment of existing MW -2 and MW -3 and the replacement of those two wells with MW -2A and MW -3A. The replacement locations shall be as shown on "Figure 1, Proposed Locations of Replacement Wells" dated 22 December 2006, and received via email by staff. Upon completion of installation, a Monitoring Well installation Report shall be submitted to the Regional Water Board, as required by the CAO.