Summitville road set for 60 day closure

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BY: STAFF REPORT
07-24-2008

From the Valley CourierPosted: Thursday, Jul 24th, 2008 BY: STAFF REPORT Construction at Superfund Site affects travel SUMMITVILLE — The Colorado Department of Public Health and Environment, Hazardous Materials and Waste Management Division will construct several surface-water management structures at the Summitville Mine Superfund Site this summer, affecting area traffic. State officials said the work is necessary for safe site operation and proper floodwater management. From July 28 through Oct. 31, construction on the southeast corner of the site will close the adjoining roads, Forest Service Road 330 and 244. This closure will affect people traveling between the Pinos Creek Road and several connecting Forest Service roads. The road closure is required because the construction will involve major excavation, possible rock blasting and heavy equipment maneuvering within a small area. Construction began on June 11 and will extend though the end of October. The project has five major components: upgrades to the Summitville Dam Impoundment spillway channel; enlarging the Wightman Fork Diversion channel; construction of a water diversion ‘turnout’ structure; installing a seepage collection and return system; and installing a penstock in preparation for a micro-hydro power plant to be built in 2009. All components are designed to increase efficiency and safety of surface-water management at the site during spring melt and storm water runoff according to state officials. The dam spillway and Wightman Fork Diversion channels currently are undersized and cannot safely convey runoff from storms greater than a high-intensity precipitation event occurring, on average, once every 25 years. The upgrades will result in the ability to pass 100-year precipitation events through the Wightman Fork Diversion and 500-year precipitation events through the combined capacity of both the Wightman Fork Diversion and the dam spillway. The State Engineers Office, in charge of dam safety, has reviewed all aspects of the Wightman Fork Diversion and Summitville Dam Impoundment design. Officials at the State Engineers Office approved the project and will inspect key activities during the construction process. Further, Colorado Department of Public Health and Environment has contracted with the design engineer for full-time construction observation to assure the project conforms to approved design drawings. The turnout structure will be the seventh on site, and will be located in a ditch between the “North Waste Dump” and the “Chandler Bowl.” Turnout structures provide the option to either send contaminated water into the dam impoundment for eventual treatment by the on-site treatment plant, or to divert clean water directly into Wightman Fork, which drains into the Alamosa River. Metals concentrations determine the site-based definitions of contaminated and clean water. And based on weekly monitoring results, the turnout structures divert the water through manually operated slide gates. Currently, water seeps out of the dam impoundment embankment. To remedy the seeps, the project team will install a collection system at the toe of the embankment. This system will collect contaminated water seepage and return it to the reservoir for treatment. The fifth construction component is the penstock, a 16-inch diameter pipe that will divert water from the Wightman Fork to a future power plant downhill. Since the Summitville site is located in a mountain environment with substantial elevation drop, the power of water flowing through the Wightman Fork Diversion can be harnessed by a micro-hydro power plant. Power generated with micro-hydro power will be fed back to the Xcel Energy grid and will be used to offset the cost of power usage at Summitville. Plans are for the power plant to be constructed in 2009. Signs announcing the road closure will be posted on surrounding roads that receive a significant amount of traffic. The Summitville Superfund Site is approximately 21 miles southwest of Del Norte on Forest Service Road 330 in Rio Grande County. Maps showing the Summitville Mine Superfund Site where the road will be closed and Forest Service roads around the site are available for download at: www.cdphe.state.co.us/hm/summitvilleroadclosure.pdf