Moffat Collection System Project: Construction Information

More than 800,000 cubic yards of material would be needed to raise Gross Dam. The primary building materials, called aggregate, include crushed rock fragments and sand. The majority of the aggregate needed to raise the dam would be produced at Gross Reservoir. The finer, sand-sized material is more difficult to produce on site, so this material likely would be supplemented with material from a Front Range supplier.

Other construction materials, such as flyash and cement, also would be delivered to Gross Reservoir.

The primary aggregate site would be located adjacent to the reservoir north of the existing boat ramp (Osprey Recreation Area), which was the source of aggregate for the original dam construction. Other sites within the project area may be used depending on the quality and quantity of aggregate available.

Two stockpile locations are planned on the south side of the reservoir. One would be adjacent to the aggregate site north of the existing boat ramp and another would be located just west of the dam.

A temporary aggregate-processing plant, located adjacent to the stockpile area, would be used for crushing and sorting aggregate. A temporary concrete production plant, located at Gross Dam, would be needed to mix aggregate, cement, flyash and water to produce concrete.

The concrete production plant likely would operate April through November, when concrete would be placed. Some activities may require concrete placement 24 hours a day.

There may be delays caused by slow-moving construction vehicles on County Road 77S, Colorado 72, Colorado 93, Colorado 128, U.S. 287, Arapahoe Road (U.S. 287 bypass to County Line Road), County Line Road and Colorado 2050 RD.

During construction, the volume of construction traffic would vary day-to-day and month-to-month, depending on the type and number of construction activities taking place.

Denver Water has met with the Colorado Department of Transportation to discuss the best way to use Colorado 72 during construction. The transportation department has requested that truck travel occur between 8 a.m. and 3 p.m. Though construction trucks may need to use the road at other times, Denver Water would make every effort to abide by that timeframe.

• Delivery vehicles: The number of haul and supply trucks traveling to the site would vary during the construction period. On average, about 20 trucks would travel to Gross Dam each day. During peak construction period, about 35 trucks would deliver material daily. Additional trucks would be used to remove trees and debris from the reservoir site.
• Commuting workers: The number of commuting workers would vary considerably. An average of 60 commuter vehicles would make daily trips to the reservoir, with about 100 expected on the busiest construction days. Denver Water would ask that contractors encourage carpooling to the work site.

Denver Water hired an independent consultant to evaluate using the railroad to transport material to the site. The consultant found that using the railroad would not be feasible for the project because it would be too expensive and would cause too many scheduling problems with the railroad company.

The consultant found that if Denver Water were to use the existing railroad siding to unload material, trains would need to be diverted or delayed, causing problems for the railroad company. If Denver Water were to construct a new siding to unload material, it would require a tremendous amount of material to be hauled in (likely using trucks), would cost about $20 million and would disrupt train schedules.

Denver Water is looking into alternatives for reducing construction traffic delays, including constructing and/or improving turnouts on Colorado 72 for slow-moving traffic.

Denver Water would develop a plan to prevent and control erosion from stormwater runoff, such as erecting silt fences and sedimentation basins. This plan would meet Colorado Department of Public Health and Environment requirements.

Denver Water also would comply with the Colorado Air Pollution Control Division to minimize dust during construction. Possible control measures include watering unpaved roads and enforcing speed limits for trucks on haul roads, among other measures.

Yes. Various road segments within the project boundary would be temporarily closed for safety reasons during construction. Denver Water would relocate certain road segments inundated by the expanded reservoir.

Access to and around Gross Reservoir would not significantly change once construction is finished. Denver Water would do what it can to allow public access to recreational facilities during construction while maintaining public safety.

The daily and seasonal operations of Gross Reservoir should not change during construction, as the reservoir would fluctuate based on water demand, not construction activities. Denver Water is preparing a recreation plan to keep recreational facilities open as much as possible without compromising public safety or construction progress. Certain areas would be restricted or temporarily closed as needed.

A buoy system would be set up near the dam to allow boating at the reservoir while keeping the public a safe distance from construction activities. The picnic area in the North Shore Recreation Area would remain open during construction. The picnic areas next to the dam (Dam Recreation Area) would be closed during much of the construction. The Osprey Recreation Area (Haul Road Recreation Area) could be closed during some phases of construction.

These areas likely would remain open until the enlarged reservoir begins to fill:

• Peninsula Recreation Area
• North Shore Recreation Area
• Winiger Ridge Recreation Area
• Winiger Gulch Inlet
• South Boulder Creek Inlet
• South Boulder Creek Outlet

• The dam would be 125 feet higher with a wider foundation.
• The reservoir would increase from 41,811 acre-feet of capacity to 114,000 acre-feet of capacity, expanding the surface area by 400 acres.
• Gross Reservoir would have a new spillway.
• There would be new recreational facilities, such as picnic tables and trails, to replace those moved because of the larger reservoir.