Laserfiche WebLink
• Generic Large Mud Pit Design <br />OSM personnel have decided that mud pits are temporary impoundments thus <br />mud pits must be designed in accordance with 4.05.9. Mud pits are constructed <br />on drill sites to contain drill cuttings, water and drilling fluids. Large mud pits may <br />have a surface area of 10,000 square feet. <br />The Division may approve a temporary impoundment that relies primarily on <br />storage to control the run-off from the design event specified in 4.05.9(2)(c) when <br />it is demonstrated by the Operator and certified by a qualified registered <br />professional engineer, that the temporary impoundment will safely control the <br />design precipitation event, the water which shall be safely removed in <br />accordance with current prudent engineering practices. Such an impoundment <br />shall be located -where failure would not be'expected to -cause loss of life or - -- <br />serious property damage. <br />The volume of water stored in the mud pits, if released into one of the adjacent <br />perennial streams, would not significantly increase the water level in the stream. <br />Mud pits are typically located in remote areas where a failure would not be <br />expected to cause loss of life for serious property damage. <br />The design event for the mud pits will be 2.1 inches, the 25 year 24 hour event. <br />• The curve number for the drill sites will be 87, disturbed, soil type C. Run-off <br />from drill sites is directed away from the mud pits into silt fences for filtering. The <br />drainage area for the large mud pits is in the order of 2.0 acres. A mud pit would <br />need to contain 0.17 acre feet based upon the above run off factors. <br />A 10,000 square foot pond would need to have 0.75 feet of depth to contain the <br />design event. <br />Mud pits will be dewatered as necessary to maintain the required depth to <br />contain the design storm event plus 1.0 feet of freeboard. Dewatering will <br />typically be accomplished with a water truck. <br />Large mud pits may be up to 10 feet deep. They are constructed by a dozer or <br />backhoe. Large mud pits are incised in natural ground. The inside slope of a <br />large mud pit is not steeper than 2H:1 V. Since large mud pits are incised, the <br />5H:1 V combined upstream and downstream side slope of an embankment is <br />satisfied. Some fill may be required to maintain adequate run-off storage <br />capacity and freeboard. Construction of fill slopes will include the removal of <br />topsoil and organic matter. Fills will be compacted in lifts by routing excavation <br />equipment over the entire surface area of the embankment. <br />In no case will large mud pits be placed where the fill is greater than 3 feet high <br />nor will the pit have a storage capacity greater than 20 acre feet. <br />'M -V g <br />A PPPOve-D <br />Exh-8 -206i - <br />08/07 <br />