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Gross Reservoir

Gross Reservoir Expansion Project will impact recreation

Construction for the Gross Reservoir Expansion Project has started. Since March 14, there has been no public access to the following Gross Reservoir recreation areas and amenities on the south side of the dam. This will continue through the duration of the project:

  • Osprey Point boat launch.
  • Osprey Point trailhead.
  • The Inlet Trail.
  • Miramonte picnic area.
  • Windy Point picnic area.
  • South Side picnic area.
  • Scenic overlook.

On-water access (starting the Friday of Memorial Day weekend) and parking will be relocated to the North Shore. Additionally, a full closure to recreation for 2 to 3 weeks in May will prepare for enhanced access to the north side for the upcoming boating season. After this, the North Shore and South Boulder Creek Trail (below the dam) will remain open to the public throughout the project.

Access to the Winiger Ridge campground will remain largely unchanged until tree removal activities begin in 2025. Visitors will be able to access hiking, fishing, picnicking and nonmotorized boating (overnight camping permitted only at Winiger Ridge) amenities from these locations.

Please note, these areas may be subject to intermittent closures during the Gross Reservoir Expansion Project to maintain public safety. Portions of Gross Reservoir for nonmotorized boating may also be closed to the public via surface water buoy lines.

Anticipated Recreation Access Impacts During Construction

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, the current Gross Dam contains some 627,559 cubic yards of concrete. Once construction is complete, the dam will stand 417 feet and contain about 1.5 million cubic yards of concrete.

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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.
  • Follow Gross Dam Road north until you reach the North Shore Picnic Area parking lot.

From Boulder:

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

Activities, 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. 
  • No body contact with water is permitted: swimming, wading and cliff jumping 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. Vehicles parked in “No Parking” zones may be subject to ticketing and/or towing.
  • Pedestrian use only on all Gross Reservoir trails.
  • Domestic animals shall be kept on leash 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.
    • Glass bottles or containers, except within an enclosed vehicle.
    • Depositing litter or waste in any place other than waste receptacles.
    • Dumping of household waste or hazardous materials on Denver Water property or in Denver Water waste receptacles.
  • Motor vehicles — including cars, trucks, motorcycles, minibikes, snowmobiles, four-wheel drive or other recreational vehicles — are prohibited outside of areas specifically designated and posted to permit the operation of such vehicles.
  • No available parking for trailers/campers/RVs/ and buses.
  • Launching and landing drones/RC airplanes is prohibited on Denver Water property.

Gross Reservoir: Boating and Paddleboarding

  • All Colorado Parks and Wildlife boating regulations and statutes are strictly enforced at Gross Reservoir.
  • Watercraft are allowed on the Friday of Memorial Day weekend through Sept. 30.
  • Using watercraft during posted emergency closures is prohibited.
  • It is Colorado state law that each person aboard any watercraft must possess a U.S. Coast Guard-approved life jacket or personal flotation device (PFD) while on the water. Children under 13 years of age MUST be wearing their life jacket/PFD at all times.
  • 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 nonmotorized 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).
    • Trolling motors.
    • Remote-controlled boats.
    • Sailboats.
    • Belly boats.
    • Single-chambered flotation devices, such as inner tubes and inflatable mattresses (single chambered paddleboards are permitted).
  • Information on Colorado Parks and Wildlife's aquatic invasive species
  • Information on Colorado Parks and Wildlife's aquatic invasive species boat inspections and decontamination

Winiger Ridge Camping

  • Campers at Winiger Ridge are subject to U.S. Forest Service rules and regulations for the area.
  • Camping is permitted in numbered, designated campsites only (where metal fire rings are present).
  • Fires are only permitted in designated metal fire rings at designated campsites.
  • All fires are subject to Boulder County and state fire bans.
  • There are no bathrooms or waste receptacles.
  • Camping is limited to 14 consecutive days and 28 days in a 60-day period.
  • Campsites are first come first serve and cannot be reserved. There are no required fees.
  • Vehicular access to Winiger Ridge via County Road 359 is closed during winter months.

Directions to Winiger Ridge 

  • From State Highway 93, take State Highway 72 (Coal Creek Canyon Road) west toward Pinecliffe — 15 miles.
  • Turn right on County Road 97 just past the Timberline Fire station — 1 mile.
  • Turn right on Magnolia Road (County Road 132) — 2.5 miles.
  • Turn right on County Road 68 — 2 miles.
  • Turn right on County Road 359 at the Forsythe Canyon Trailhead parking lot.
  • Continue down County Road 359 to designated campsites and to the Winiger Ridge parking lot.

Gross Reservoir: Fishing

  • 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. Possession limits may apply. For more information, see Colorado Fishing guide.
  • Snagging kokanee permitted Oct. 1 to Dec.1 only.
  • Live aquatic bait is strictly prohibited.
  • Fishing prohibited sunset to sunrise.
  • Fish are stocked annually by CPW at Gross Reservoir. 
  • 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.

Gross Reservoir: Hiking

  • During construction during the Gross Reservoir Expansion Project, all hiking trails managed by Denver Water begin at the North Shore Picnic Area parking lot.
  • All hiking trails and gated Denver Water service roads are for pedestrian use only.
  • Visitors must stay on trail at all times.
  • Visitors must adhere to all Denver Water restricted areas and local private property lines. Violators will be fined.
  • Bikers and equestrians are permitted on Gross Dam Road only.
  • Forsythe Canyon Trail is managed by the U.S. Forest Service. This trail provides access to Gross Reservoir on the west side near Winiger Ridge.
  • County Road 359 is available year-round for pedestrian use and also provides access to Gross Reservoir on the west side through the Winiger Ridge campground (managed by the U.S. Forest Service).
  • Twins Sisters Peak trail is not accessible from Denver Water property. This trail begins along County Road 68J. High clearance four-wheel drive vehicles are required to access this hiking trail.
  • Denver Water does not manage any off-highway vehicle (OHV) trails near Gross Reservoir. Please contact the U.S. Forest Service Boulder Ranger District at 303-541-2500 or the Boulder County Sheriff's office at 303-441-1500 for details.

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Sights

Activities

Camping

Camping

Canoeing

Canoeing

Fishing

Fishing

Hiking

Hiking

Ice Fishing

Ice Fishing

Kayaking

Kayaking

Picnicking

Picnicking

Seasons and hours

Public access from sunrise to sunset. 


Full recreation closure, which will be phased, for Gross Reservoir Expansion project:

  • A closure will occur May 4 through the afternoon of May 6 to prepare for work.
  • Recreation access will reopen for the weekend of May 7-8.
  • Full closure will begin again May 9 and is expected to last until May 20.

Open for boating/paddleboarding Friday of Memorial Day weekend to Sept. 30. 

Kokanee snagging: Oct. 1 to Dec. 1.

No fees or reservations required to visit Gross Reservoir. 

Contact

Denver Water (Gross Reservoir recreation ranger): 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