FLOOD05827 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I GEOLOGY region, which includes Boulder. This study will result in a wastewater management plan for the urban region for the next 20 years. A water quality analysis of Boulder Creek by DRCOG indicates that there are some existing water quality problems along its entire length. Phosphate levels are unacceptable from a stream aesthetics standpoint. Bacterial concentrations are also a problem. The water quality is marginally acceptable for secondary contact recreation as well as for urban and agricultural irrigation because of the level of fecal coliforms. Fecal strep, primarily of animal origin, makes the quality of the water unacceptable for urban and agricultural irrigation. Finally, near the mouth of Boulder Creek, the level of ammonia in the stream flow is marginally acceptable from a warm-water fishery standpoint. Precambrian rocks are exposed in the mountainous watershed upstream from Boulder. They consist of metamorphic schists and gneisses intruded by igneous rocks. Sedimentary beds of sandstones, shales, and limestone of Cretaceous to Tertiary age underlie the plains. Alluvium consisting of sands and gravels Covers the Boulder Creek floodplain in Boulder to depths of 15 to 25 feet. Shallow layers of clay underlie the alluvium. Shale bedrock underlies the clay. Shale exists at shallow depth along the bluff on the south side of Boulder Creek. The shale is unstable if disturbed or oversteepened. WATER QUALITY The water quality stream classification for Boulder Creek was upgraded in 1976. The old classifications were Bl above the mouth of Boulder Canyon (at State Highway l19 crossing) and B2 from that point to the mouth. These two classifications are for waters suitable for all uses except primary contact recreation with Bl suitable for a cold-water fishery and B2 for a warm-water fishery. The new classifications are Al upstream from 75th Street, the location of Boulder's sewage treatment plant, and A2 downstream from 75th Street to the mouth of Coal Creek. The new classifications are for waters suitable for all uses, including primary contact recreation, with Al being suitable for a cold-water fishery and A2 for a warm-water fishery. To improve the quality of Boulder Creek, the Water Quality Management Task Force for the ORCOG study, made up of local citizens and officials, have recommended that the stream classification of the creek be changed again to Al for the entire length of the stream from its headwaters to the confluence of Coal Creek downstream from Boulder. The Denver Regional Council of Governments (DRCOG) is presently conducting a 208 wastewater management study for the five-county Denver urban The 208 plan provides some recommendations to meet the more stringent classification. Nonstructural alternatives are recommended to reduce the pollution coming from urban stormwater runoff. The plan also recommends that the present wastewater treatment facility located at 75th Street be retained and upgraded by the addition of nutrient removal. The City is presently planning for the addition of facilities, including nutrient removal. The implementation of these two components should result in the reduction of problem pollutants identified 1 5