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STATE ENGINEER GUIDELINES FOR LINING CRITERIA FOR GRAVEL PITS JULY 1999 1.0 Design Standard The intent of the reservoir lining design is to achieve ground water inflow (leakage rate) into the reservoir that is not greater than 0.03 ft'/day/ftZ (1 x 10S cm3/cmZ/sec) multiplied by the length of the perimeter wall in feet multiplied by the average vertical depth of the perimeter wall as measured from the ground surface to the bottom of the liner system, plus 0.0015 ft3/day/ftZ (Sx 10' cm3/cmZ/sec) multiplied by the area of the bottom of the liner system or natural bedrock bounded by the perimeter wall. It is recommended that the applicant submit design and construction plans for review to the State Engineer. 2.0 Construction Standards The applicant must demonstrate that the materials quality control program for aclay- compacted liner arsoil/bentonite slung trench cutoff wall has met or exceeded the standards established by the American Petroleum Institute (API) and the American Society of Testing and Materials (ASTM) for test and minimum testing frequency for all materials, slurry mix and backfill mix. Appropriate geotechnical and geophysical testing may also be required on the bedrock formation to indicate that the design standard can be achieved to a reasonable probability. 3.0 Performance Standards The Performance Standard shall be three times the Design Standard as described above. The Performance Standard shall be applied to an initial test of competency of the liner, as well as to the ongoing operation of the reservoir. 3.1 Initial Liner Test For mined pits: The unregulated ground water inflow to the reservoir will be tested by evacuating the contents of the reservoir and observing the inflow of water over a period of ninety days. The start of the test will be under essentially dry conditions. For unmined pits: The unregulated ground water inflow to the reservoir will be evaluated by constructing a dewatering sump at the lowest portion of the pit and then dewateruntil asteady-state condition is achieved. Once a steady-state condition exists, the amount of the unregulated ground water inflow will be determined. This process will generally require the installation of piezometers to be located on the inside and outside of the lined pit in the unmined area in order to determine whether a steady-state condition has been achieved. A water balance must be done to demonstrate that the balance of the inflows (e.g., precipitation and ground water) and outflows (e.g., evaporation) equals the change in storage Lining Criteria for Gravel Pits.doc 1 07/27/99