2008-02-22_APPLICATION CORRESPONDENCE - C2008086 (42)

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feet above the existing area topography (Photos 4-6). Polygons F and G are remnants of a previous ditch and are subject to seepage from the elevated irrigation ditch in polygon C (Figure 5). Polygon C passes through a culvert under an access road into the concrete ditch in Polygon S. Broken portions of the concrete ditch and vegetation-induced blockages have caused the ditch to leak water into the Hwy 6&50 borrow ditch. It also overflows into the old agricultural fields to the south, widening the wetland footprint (Photos 7-10). Polygon S flows west through a culvert under an access road and into Polygon T. Polygon T terminates at a culvert that conveys the remainder of flow into Mack Wash just south of Hwy 6&50 bridge (Figure 5) (Highway 6&50 is also known as M 8/10 Road in this part of Mesa County). Vegetation in these polygons is dominated by cattails along the outer edges, except for polygon T which is dominated by Reed canarygrass (Photo ll). Soils are mapped as the Sagers and Homko series and show redoximorphic features and low chroma colors in the first 12 inches. Polygons P, Q, and R appear to be ditches that are raised above the natural topography. They receive water from an irrigation ditch that passes under the railroad near flag P-l . Polygon P curves around a disturbed fill area. The water passes through a culvert to the west into Polygon Q and flows between an access road and the railroad. Polygon Q conveys water through a culvert under the access road to Polygon R which follows the railroad west (Figure 5). The dominant species in polygons P, Q, and R is cattails. The wetland in Polygon R continues another 500 feet west beyond the limits of the project boundary (Figure 5). The remaining water from the ditch empties into a confined channel that west eventually flowing into Mack Wash, approximately 1.5 miles down stream of the 6&50 bridge. Soils are mapped as the Sagers and Homko series and show redoximorphic features and low chroma colors in the first 12 inches. Polygon U is emergent fringe wetlands along Maclc Wash. Polygon U extends from the Hwy 6&50 Bridge upstream approximately 800 feet (Photo 17 and Figure 5). The polygon includes 1 potential crossing of Mack Wash and an alternative restructuring of the Hwy 6&50 bridge. Fringe wetlands along Mack Wash are dominated by tamarisk. Soils are mapped as Ustiffuvents and showed gleying within the first 12 inches. Mack Wash flows year round except in years of extreme drought. Polygon V is a proposed crossing along Government Highline Canal (Figure 6). Wetland vegetation along the canal is limited to a 1 foot wide row of cattails on the canal edges. Soils did not show redoximorphic features and were highly compacted. Hydrology is supplied by irrigation water diverted from the Colorado River during irrigation season. Water is withdrawn from the Colorado River near Palisade, CO and the canal terminates near West Salt Creek, west of Mack, CO. De-Watered Wetland Marsh Polygon L appeared to be two manmade ponds that were connected by a ditch (Figure 3). Soil borings in wetland Polygon L had redoximorphic features with sharp and distinct boundaries indicating relict redoximorphic features. WestWater biologists observed declines in wetland vegetation (reduced re-establishment and dead vegetation). Lack of wetland hydrology in WestWater Engineering Page 5 of 75 January 2008 DBMS 426