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STATE ENGINEER GUIDELINES FOR LINING CRITERIA FOR GRAVEL <br />PITS- <br />- AUGUST 1999 <br />1.0 Design Standard <br />The intent of the reservoir lining design is to achieve ground water inflow (leakage rate) <br />into the reservoir that is not greater than 0.03 ft3/day/ft2 (1x 10-5 cm3/cm2 ./sec) multiplied <br />by the length of the perimeter wall in feet multiplied by the average vertical depth of the <br />perimeter wall as measured from the ground surface to the pit bottom along the toe of <br />the pit side slope, plus 0.0015 ft3/day/ft2 (5x 10-7 cm3/cm2/sec) multiplied by the area of <br />the bottom of the liner system or natural bedrock bounded by the perimeter wall. <br />Appropriate geotechnical evaluations and analyses should be performed to indicate that <br />the Design Standard could be achieved with the proposed design to a reasonable <br />probability. It is recommended that the applicant submit design and construction plans <br />for review to the State Engineer. <br />2.0 Construction Standards <br />The applicant must demonstrate that the constructed liner meets the requirements of <br />the design by performing appropriate quality control observations and tests. The <br />applicant shall provide written documentation of the work performed and results of <br />quality control field and laboratory tests. Tests performed shall meet or exceed the <br />standards established by the American Petroleum Institute (API) and/or the American <br />Society of Testing and Materials (ASTM) as applicable. <br />3.0 Performance Standards <br />The Performance Standard shall be three times the Design Standard as described <br />above. The Performance Standard shall be applied to an initial test of competency of <br />the liner, as well as to the ongoing operation of the reservoir. <br />3.1 Initial Liner Test <br />For mined pits: The unregulated ground water inflow to the reservoir will be tested by <br />evacuating the contents of the reservoir and observing the inflow of water over a period <br />of ninety days. The start of the test will be under essentially dry conditions. For unmined <br />pits: The unregulated ground water inflow to the reservoir will be evaluated by <br />constructing a dewatering sump at the lowest portion of the pit and then dewatering until <br />a steady-state condition is achieved. Once a steady-state condition exists, the amount <br />of the unregulated ground water inflow will be determined. This process will generally <br />require the installation of piezometers to be located on the inside and outside of the <br />lined pit in the unmined area in order to determine whether a steady-state condition has <br />been achieved. <br />A water balance must be done to demonstrate that the balance of the inflows (e.g., <br />precipitation and ground water) and outflows (e.g., evaporation) equals the change in <br />storage volume by a minimum of a 90-day test. Ongoing monitoring of the water <br />balance may also be required as determined by the Division Engineer. The frequency of <br />accounting and monitoring as well as the type and accuracy of the monitoring devices <br />shall be determined after consultation with the Division Engineer.