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GENERAL31966
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Entry Properties
Last modified
8/24/2016 7:54:48 PM
Creation date
11/23/2007 7:09:10 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981017
IBM Index Class Name
General Documents
Doc Date
6/26/2006
Doc Name
Request for Permit Termination-Coal Basin Sediment Pond Reclamation Stormwater Permit
From
Stormwater Permit Ponds Folder
Permit Index Doc Type
Reclamation Project
Media Type
D
Archive
No
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The pond footprint was to be left in place, with a maintenance free outlet created so that <br />the ponds could dewater without over-topping the embankment. The embankments were <br />to be seeded with an uplands seed mixture, while the perimeter of the pond at or near the <br />water level elevation was planted with seed and transplants appropriate to a wetlands <br />environment. <br />In order to create these maintenance free wetlands areas from the existing sediment <br />ponds, the CMP dewatering devices had to be removed, and a durable, maintenance free <br />dewatering device was to be installed. The cut slopes created as a result of CMP <br />removal, and any other adjacent or incidental disturbances were to be revegetated. <br />The construction sequence followed was identical at each pond, and generally proceeded <br />as described below: <br />- The pond was dewatered if necessary to below the invert elevation of the <br />corrugated metal pipe dewatering device. Any water pumped from a pond was <br />passed through silt fence prior to discharging to a receiving stream. <br />- The corrugated metal pipe dewatering device was excavated from the <br />embankment. <br />- Once exposed, the dewatering devices were lifted from the excavation and placed <br />on a trailer for removal from the site. <br />- Typically, an excavated cut approximately five to six feet deep by five to six feet <br />wide at the base by twenty feet long was created within the embankment at each <br />pond as a result of excavating the dewatering device. The side slopes of the <br />excavation were graded to a 2H:1 V or shallower configuration. The slope of the <br />base of the excavation mirrored the gradient of the base of the corrugated metal <br />pipe dewatering device, prior to its removal, thus the water surface elevation of <br />the pond did not change. <br />- The cut created during excavation of the corrugated metal pipe dewatering device <br />was used as the principle spillway after reclamation was finished. The cut was <br />lined with native rock riprap along the base and partially up the sides. The cut <br />area above the riprap was severely scarified and then seeded. Scarification acts to <br />disrupt surface flows and to promote revegetation potential. <br />- Silt fencing was placed below each excavation following completion of work to <br />inhibit sediment transport from the site unfil vegetation became established. <br />The side slopes of the CMP excavation, as well as the top of the embankment were <br />seeded using an appropriate, upland seed mixture. Wetland species appropriate to site <br />conditions were planted around the margins of each pond. In addition, willows collected <br />from nearby areas were transplanted along the perimeter of any ponds where water <br />availability seemed capable of supporting such species. <br />Evaluation of the portions of the ponds covered by the permit during the 2005 field <br />season indicates that each excavated area is stable and non-erosive. The base and lower <br />portions of the excavated cut slopes are stable as a result of the riprap placed in these <br />locations. No undercutting or by-pass of the riprap was observed. Vegetation has <br />_ ..~.. <br />.~.. <br />
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