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Gross Reservoir

Final federal approval secured for Gross Reservoir Expansion Project

On July 17, 2020, the Federal Energy Regulatory Commission ordered Denver Water to proceed with design and construction to expand the reservoir.

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Treasure tucked away in a quiet canyon

Named for Denver Water former Chief Engineer Dwight D. Gross, the reservoir was completed in 1954. It serves as a combination storage and regulating facility for water that flows under the Continental Divide through the Moffat Tunnel. Standing 340 feet above the South Boulder Creek streambed, Gross Dam contains some 627,559 cubic yards of concrete.

Gross Reservoir
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By the numbers

41,811

capacity in acre-feet

7,282

elevation at spillway in feet

440

surface acres on the reservoir

10.9

miles of shoreline

% full

Directions

From the Denver metro area:

  • Take Highway 93 north from Golden to Highway 72.
  • Turn left (west) on Highway 72 toward Pinecliffe to County Road 77/Gross Dam Road. The intersection has the Coal Creek Canyon Improvement Association Hall and United Power offices. If you have passed Last Stand Tavern on the left or the fire station on the right you have gone too far.
  • Gross Dam Road will take you to both the north and south access points.

From Boulder:

  • Take Flagstaff Road west until it turns into Gross Dam Road.

Recreation notes

Recreation map

Fishing: Cold water, stocked by Colorado Parks and Wildlife. Ice fishing when conditions permit.

Boating: Car-top non-motorized boating only, allowed on the Friday of Memorial Day weekend through Sept. 30. Kayak access to the river below the reservoir is available at the parking area below the dam.

Hiking: North Shore picnic area (trailhead to Rocky Point), South Side Dam, Miramonte picnic area and Osprey Point (trailhead), to South Boulder Creek inlet.

Camping: The Winiger Ridge campground is currently open. The site is comanaged by Denver Water and the United States Forrest Service and is subject to state or local fire bans that may be in posted.

Picnicking: Limited picnicking is now available, though larger picnic area shelters located on the east side of the reservoir are closed until further notice.

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Rules and regulations

Gross Reservoir: General rules and regulations

  • These rules and regulations are in addition to, and do not supersede, any otherwise applicable county, state and federal laws. For more information call 303-634-3641.
  • Public use permitted only from sunrise to sunset. Gate on south dam road subject to being opened and closed by Denver Water staff.
  • No body contact with water is permitted: swimming, wading and diving are prohibited.
  • Parking is permitted only in designated parking lots or defined spaces. Vehicles may not be left parked and unattended at any time from sunset to sunrise, even in designated areas.
  • Pedestrian use only on all Gross reservoir trails.
  • Domestic animals shall be kept on leash or lead and under human physical control at all times. Pet waste shall be removed immediately. Pets are not permitted to enter the water.
  • Prohibited: Firearms, fireworks or any projectile weapons of any kind. Trespassing is prohibited on dam structure or within any fenced area, facility or areas posted with closure or danger signs.
  • Motor vehicles — including cars, trucks, motorcycles, minibikes, snowmobiles, four-wheel drive or other recreational vehicles — may not be operated unless the area is specifically designated and posted to permit the operation of such vehicle in the area.
  • Prohibited: Glass bottles or containers, except within an enclosed vehicle; depositing litter or waste in any place other than waste receptacles. No household waste, hazardous materials or materials not from the reservoir site may be placed in any Denver Water waste receptacle.
  • No available parking for trailers/campers/RVs/ and buses.
  • Launching and landing drones/RC airplanes is prohibited on Denver Water property.

Gross Reservoir: Boating regulations

  • Watercraft are allowed on the Friday of Memorial Day weekend through Sept. 30.
  • Using watercraft during posted emergency closures is prohibited.
  • All watercraft are subject to U.S. Coast Guard and CPW safety standards and will be subject to safety inspections.
  • It is unlawful to operate watercraft under the influence of alcohol or drugs.
  • Only non-motorized car top boats are permitted on reservoir (car top boats are those that can be lifted onto and taken from the top of a passenger vehicle and are no more than 18 feet in length).
  • Prohibited: Trailer-hitched boats, motorized boats (gas or electric), sailboats and belly boats; single-chambered flotation devices, including inner tubes and inflatable mattresses.

Gross Reservoir: Camping regulations

  • Overnight camping on Denver Water property is prohibited.
  • Ground or open fires of any type are prohibited. Fires of any kind are only permitted in grills and fire grates provided at designated sites. All fires are subject to county bans.

Gross Reservoir: Fishing regulations

  • Fishing is subject to all state regulations enforced by Colorado Parks and Wildlife statutes. The reservoir will be open to monitoring and enforcement by CPW.
  • Snagging kokanee permitted Sept. 1 to Jan. 31 only.
  • Ice fishing allowed only when conditions permit. Denver Water does not monitor ice conditions, therefore it is important to be aware of changing ice conditions. Proceed at your own risk.
  • Only portable ice fishing shelters are permitted and must be removed from surface of lake when not in use.

Sights

Activities

Camping

Camping

Canoeing

Canoeing

Fishing

Fishing

Hiking

Hiking

Ice Fishing

Ice Fishing

Kayaking

Kayaking

Picnicking

Picnicking

Seasons and hours

Open year round, sunrise to sunset

Boating: Friday of Memorial Day weekend to Sept. 30

Kokanee snagging: Sept. 1 to Jan. 31

West side U.S. Forest Service closes late fall to early spring

Contact

Denver Water (owner, operator, east side recreation manager): 303-634-3641 or Customer Care Contact Form.

U.S. Forest Service Boulder district: 303-541-2500

Boulder Sheriff: 303-441-1500

Colorado Parks and Wildlife: 303-291-7227

Gross Reservoir Expansion Project

Project website

Recreation during and after construction