2014-12-19_REVISION - M1977526 - Laserfiche WebLink

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Worthing Pit Permit#M-1977-526 Technical Revision#04 December 19,2014 On December 14, 2012 the Division inspected the site due to a citizen complaint about elevated ground water problems on an adjoining property south of the area called the Expansion Area South (EAS) in the 2006 amendment . The corrective actions required was that Albert Frei & Sons, Inc. construct a drain ditch along the south side of the EAS along the outer edge of the filled area to connect it to a historic slough that was part of a historic river channel, to control the groundwater elevation. Frei completed the drain/historic river channel complex ditch (groundwater drain) by the end of December 2012 . As part of the corrective actions Frei began collecting data for monitoring wells #1 & 8 on a regular basis to determine if this was having any effect on the ground water levels. The trench successfully lowered the groundwater table to a point that the neighbors basement is no longer being flooded. This Technical Revision takes the mitigation plan to the next obvious step by improving the flow in the groundwater drain by installing a new outlet ditch at approximately 5000 feet that extends from the north end of existing groundwater drain to the river and doing improvements to the existing channel that lowers the water level in the groundwater drain to an elevation consistent with historic elevation on the property prior to mining. Review of records indicate that the Monitoring Well #8 groundwater elevation, prior to mining and backfilling, was approximately 5004 feet . GROUNDWATER MOUNDING MITIGATION PLAN The following three (3) steps are those Albert Frei & Sons, Inc. will use to mitigate the ground water mounding that appears to be occurring along the east and south sides of backfilled area on the southern parcel of the Worthing Pit . 1 . Install drainage ditch along the south and east side of the filled area in the EAS that connects it to the historic river channel (slough) to intercept groundwater and control the groundwater elevations on off site areas . 2 . Design and install new groundwater relief drain outlet (north outlet) on the north end of the drain to the river. Attached are the design plans prepared by Deere and Ault Consultants . Frei is committed to securing the rocks and boulders adjacent to the river and will blend the riprap on the out fall end with what exists on the river bank now. Once done the areas disturbed by construction will be revegetated to match existing conditions. 3 . Extend the groundwater drain to the west along the joint property line between the EAS and Bromley (our south neighbor) and install a second outlet (south outlet) using the same design prepared for the north outlet .