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<br />access road flattens near the intersection of Cedar Heights <br />Drive. Conversations with the guard house attendant indicated <br />that runoff from basins HR-6 and HR-7 causes erosion damage and <br />sedimentation on a fairly frequent basis. Eventually the <br />sediments carried by the runoff are deposited in the Black Canyon <br />Drainageway via the 5430 inch culvert. <br />Erosion of the natural Swale downstream of the proposed HR-6 <br />r_ulvert has caused sediment to be deposited within the Cedar <br />Heights Drive street section. The runoff and sediments <br />originating within basin HR-6 and the natural Swale are <br />eventually deposited near the existing 24-inch culvert under <br />Cedar Heights Drive approximately 400 feet south of the F~roposed <br />culvert "A" identified in the Obering Wurth report. <br />Sediment mainly consisting of rock chips oaring in size from 1/4- <br />i.nch to 1!Z-inch have been deposited along the quarry access road <br />presumably by the operator of the quarry. This material can be <br />found along the natural Swale downstream of the HR-6 ba~;in and <br />along the east side of the quarry access road. This material can <br />also be found at several locations along Cedar Heights Drive. <br />Runoff from the HR-6 basin will continue to carry this material <br />to downstream areas until such time the material is removed or <br />otherwise stabilized. This material has apparently been used to <br />construct a truck ramp in the vicinity of the outfall point of <br />the HR-6 basin. <br />Review of Alternative Options <br />As a result of the preparation of the Obering Wurth HR-6 Synder <br />Quarry CAP and the subsequent review of this report by the= MLRD, <br />seven alternative drainage plans have been developed. A <br />discussion of each follows. <br />Option 1: This option consists of the construction of a 24-inch <br />culvert under the quarry access road at the outfall point of the <br />HR-6 basin. This culvert has the capacity to convey the 5-year <br />flow under the road and into the natural Swale. The overflow <br />(i.e., the flows exceeding the 5-year discharge), are proposed <br />to be conveyed in a roadside ditch aligned along the west side of <br />the quarry access road and outfall to the existing 54/30-inch <br />culvert. The total flow estimated to reach the 54!30-inch culvert <br />in a 100-year event is 108 cubic feet per second (cfs). This <br />exceeds the culvert capacity and would cause flow t.o overtop the <br />roadway in the vicinity of the guard house. ~ This opticn is in <br />our opinion unacceptable since no provision for stabilization of <br />rOQ~S,,Q,P the natural Swale has been proposed. This concept implies that <br />o{ flow will be diverted from the historic flow path. This option <br />~ ~ 6~would simply shift the existing concer.~s to another location. <br />Q'')~ The roadside Swale proposed for this option would have <br />~ Pa« <br />~0 Cv~v~evl ~,( wk <br />i i <br />2 ~~0~ ~f~y <br />'< <br />