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0 0 <br /> Re-Manufacturing, Ltd. -6- 26 June 1991 <br /> Closure Plan <br /> 22 April 1991. A discussion of the water quality data is included in the annual <br /> inspection report. Although contaminants have been detected in the ground water, <br /> they are not at concentrations that would warrant the expense of ground water <br /> treatment at this time. Quarterly sampling should continue. <br /> 2. Staff stated that monthly ground water level measurements should continue for 12 <br /> consecutive months. Monthly water level measurements were collected 9 October, <br /> 5 November, and 5 December 1990, and 27 February, 20 March, 9 April , 22 April , and <br /> 22 May 1991. The gradient is flat and varied from the northeast to the southeast. <br /> Water Work Corp. 's explanation for the variation in gradient was inconclusive and <br /> they stated that further monitoring is necessary. We concur that monthly ground <br /> water level measurements should continue. <br /> 3. Section 25208.8(f) (3) of the Health and Safety Code requires estimates of <br /> transmissivity, permeability, and storage coefficient for each water bearing zone <br /> which could be affected by leachate from the surface impoundment. A lab <br /> permeability test was run on one soil sample collected form the water bearing zone <br /> in each of the three well borings and showed low to moderate permeability. The <br /> results were determined to be acceptable permeability estimates. An estimate of <br /> the transmissivity and storage coefficient was also included in the recent HAR <br /> addendum. Using the permeability estimates, Water Work Corp. calculated an <br /> estimate of the transmissivity of the water bearing zone. Those values appear to <br /> be reasonable when compared to literature values for the soil type. An average <br /> storage coefficient was estimated for the water bearing zone based on log <br /> descriptions and hydraulic conductivities. <br /> 4. We asked Re-Manufacturing to sample additional borings at their facility to locate <br /> NO or background levels of contaminants. On 3 May 1991, samples were collected <br /> from the surface impoundment and Mormon Slough. Those results are included in the <br /> closure plan and were discussed above. The lateral (to the south) and vertical <br /> extent of the surface impoundment contamination must still be further defined as <br /> discussed on pages 2 and 3 above. <br /> The lateral extent of the surface impoundment soil contamination to the east and <br /> southeast was defined (for the purposes of the TPCA) at the 18-inch storm drain, <br /> with the condition that the area east and southeast of the impoundment will be <br /> investigated outside of the TPCA. A time schedule was included in the closure <br /> plan that showed the non-TPCA investigation will be conducted concurrently with <br /> the final excavation of the impoundment. However, a sampling plan must be <br /> submitted for the remaining site investigation. The plan must describe the <br /> lateral extent of the proposed investigation, number of samples to be collected <br /> and analyzed, proposed sample depths, proposed sample analyses, etc. . A map <br /> showing proposed sample locations must also be submitted. <br /> 5. We asked that Re-Manufacturing prepare a three-dimensional picture of the <br /> subsurface showing the lateral and vertical extent of contamination, as well as <br /> graphically showing where they have determined the contaminants attenuate to ND <br /> or background levels. Because of the difficulties already expressed in defining <br /> ND or background levels in the area of the surface impoundment, further <br /> investigations for the purposes of the HAR would not be cost-effective and would <br />