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WASTE DISCHARGE REQUIREMENTS 3 <br /> J. R. SIMPLOT COMPANY <br /> LATHROP, SAN JOAQUIN COUNTY <br /> CLASS II SURFACE IMPOUNDMENTS <br /> Engineered Alternative <br /> 15. The Discharger proposes to retrofit the asphalt-lined pond with a double synthetic liner <br /> consisting of a 40 mil PVC liner overlain by a 45 mil Hypalon liner as an engineered <br /> alternative to the composite liner as required by Section 2541 of Chapter 15. <br /> 16. The Discharger also is proposing to retrofit the two hypalon-lined ponds with a new 45 mil <br /> Hypalon primary liner underlain by an LCRS as an engineered alternative to the composite <br /> liner as required by Section 2541 of Chapter 15. <br /> 17. The Discharger has demonstrated pursuant to Section 2510 (b and c) of Chapter 15 that the <br /> construction standard is not feasible and will be ineffective to meet the performance standards <br /> per Section 2581 of Chapter 15 because of the incompatibility of the waste (calcium sulfate) <br /> with clay liners. <br /> 18. The proposed engineered alternatives will contain a leachate collection and removal system, a <br /> synthetic drainage layer and vadose zone monitoring and will be consistent with the <br /> performance goals addressed by the construction and prescriptive standards of Chapter 15 <br /> and will provide equivalent protection against water quality impairment. <br /> Certification <br /> 19. Kenneth B. King, a registered Civil Engineer, has certified that the engineered alternative <br /> described above will be consistent with the performance goal addressed by the standard, and <br /> will provide equivalent protection against water quality impairment. <br /> DESCRIPTION OF THE SITE <br /> 20. The facility is south of the city of Lathrop in the San Joaquin Valley. The site is underlain by <br /> a complex sequence of interbedded sand, silt ,and clay characteristic of the Laguna Formation <br /> and overlying Victor Formation. <br /> 21. There are no known Holocene faults within 1000 feet of the facility. The closest fault is the <br /> Stockton Arch, which is approximately 10 miles north of the facility near Stockton and <br /> Tracy. This fault is pre-Holocene and is stable. <br /> Ground Water Hydrology <br /> 22. The first water bearing zone is approximately 10 feet below the WMU's. There are four <br /> ground water monitoring wells that are associated with the WMU's at this site, as shown in <br /> Attachment B. There are an additional 63 monitoring wells at and surrounding the Lathrop <br /> facility that are associated with the remediation of the site under the terms of the Stipulation. <br /> Ground water flow direction is generally to the southwest. <br /> 23. The ground water monitoring network consists of four ground water monitoring wells (LP-1 <br /> through LP-3 and PW 1). Background monitor wells indicate that ground water in the area <br /> contains concentrations of TDS ranging from 800 to 1000 milligrams per liter(mg/1). One <br />