Lake Chelan GRP
- Open for full review: 2021
- Tentative publish date: 2022
- Interim update: N/A
- Last full updated: 2015
- Public Comment: GRPs@ecy.wa.gov
- Contact: David Prater and Kaitlin Lebon
Table of Contents
This chapter provides a description of the area’s geography, hydrology, and climate, and includes an overview of oil spill risks in the Lake Chelan area. The condensed plan covers Lake Chelan between Lucerne Landing and the City of Chelan, plus a notification strategy in Stehekin.
Lake Chelan is both the deepest and largest natural lake in the state, and the third deepest lake in the country. Over fifty miles long but averaging just one mile wide, it cuts northwest to southeast at a roughly forty-five degree angle. At the northwestern top of the lake is the Stehekin River, which provides almost 70 percent of the annual water to the lake. The rest of the inflow is provided by creeks and streams draining the surrounding Cascade Range and Chelan Mountains.
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The majority of the land surrounding the lake is federally-owned natural area. The Lake Chelan National Recreation Area covers the northern watershed and the northern five miles of the lake, down to the border of the Okanogan-Wenatchee National Forest. Within the Forest include the sub-areas of the Lake Chelan Sawtooth Wilderness on the east and the Glacier Peak Wilderness to the west. The Chelan Ranger District controls the central portion of the lake. The southern seven miles of the lake contain the vast majority of the residents and developed areas.
The largest population center is the city of Chelan, population 4000, which wraps around the southeastern point of the lake. There, the lake drains to the Chelan River, passing through town to the Lake Chelan Dam before emptying into the Columbia River. The only other developed areas along the lake are an unincorporated suburb of Chelan called Manson, population 1500, and the community of Stehekin at the northeastern tip of the lake. Stehekin is only accessible by ferry (The Lady of the Lake), boat, seaplane, or by foot over Cascade Pass. While Stehekin Airport is open July, August and September, it is considered a difficult landing spot, and is sometimes commandeered for wildland fire response. Due to the transport limitations to the central and northern portions of the lake, it is unlikely that the year-round population there will significantly increase in the future. Nevertheless, Stehekin is a popular spot for tourists and private boaters during the summer. The Lake Chelan National Recreation Area sees between 35,000 and 45,000 annual visitors.
Lucerne Landing is a ferry stop located about seven miles south of Stehekin, on the west shore of the lake. Eleven miles west of the landing is Holden Village, a Lutheran retreat center that hosts 5,000 visitors annually and houses 60 to 100 year-round residents. Next to Holden Village is the decommissioned Holden Mine, which produced copper, zinc, gold and silver between 1930 and 1957 before closing abruptly. It is currently undergoing remediation as a Superfund site. Visitors and supplies can only arrive via boat or seaplane to the dock at Lucerne Landing, and are then driven on a gravel forest road that parallels Railroad Creek up to Holden Village and the mine.
Table 2-1: Lake Specific Information
Officially known as the Chelan Hydroelectric Project, the Chelan Dam was built in 1928 and is located less than a mile from the river’s mouth. It is a steel-reinforced concrete gravity dam, 40 feet high and 490 feet long. Chelan County Public Utility District Number 1 controls the dam outflows and maintains the water level in the lake.
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The flow into the lake from the Stehekin River, Railroad Creek and other tributaries is largely determined by snowmelt, rather than direct runoff from rainfall. The water level in the lake is lowest in early spring, before the snow has melted. Snowmelt in April and May leads to peak water levels from June through September, remaining steady around 1098 feet. The Chelan County Public Utility District’s license encourages the lake level to stay between 1100 feet and 1079 feet elevation, but maintaining ideal flow to the Chelan River takes precedence. The output through the Chelan Dam is generally steady throughout the year.
Climate and Winds
Lake Chelan’s climate is similar to the rest of eastern Washington, with near-desert levels of precipitation. The annual average precipitation at Lake Chelan is 11.4 inches. Rainfall is fairly evenly distributed throughout the year, but in mid-summer it is not unusual for a month or six weeks to pass without any measurable rainfall. The wettest month is November, with an average rainfall of 1.77 inches. Summer high temperatures tend to be in the 80’s and winter lows tend to be in the 30’s.
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Winds on Lake Chelan are strong from April through July, particularly in the upper part of the lake between Stehekin and Lucerne. Sustained winds over 20 miles per hour (mph) are common, with gusts near 40 mph. Stronger winds are unusual but gusts of over 80 mph have occurred. Wind direction is usually “down lake” (from NW to SE) in late spring to early summer, but direction and speed can vary significantly throughout the day. The rest of the year winds are calmer and more varied in direction. Winds are lower in the lower section of the lake, near Manson and Chelan, but follow the same seasonal pattern.
Tides and Currents
Lake Chelan has no discernible tides or currents. The flow from the tributaries to the Chelan River is generally north-to-south, but the rate at which the lake empties is so low that it should have no major impact on the movement of oil. Wind direction and speed will be the most significant factor in the direction of travel.
This condensed plan is written to address the oil spill risk presented by a barge transporting fuel to the Holden Mine Superfund Site, along with above-ground diesel storage tanks at the site. At a future date this plan will be expanded to include other areas of Lake Chelan. Rio Tinto mining is responsible for the cleanup project and their Spill Prevention, Control, and Countermeasure plan has been approved by several state and federal agencies.
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A 120 foot unmanned barge and 25 foot tug depart the Chelan Staging Area and dock at Lucerne Landing, where a fuel truck carrying up to 4,600 gallons of diesel drives off the barge and follows the gravel-topped Forest Service Road 8031 for 11 miles along Railroad Creek. The largest fuel storage tank at the cleanup site holds 10,000 gallons of diesel, with another two 5,000-gallon tanks nearby. Vehicles and construction equipment hold under 100 gallons of diesel each. Mountain Barge Services , who operate the tug, are also spill responders who maintain equipment at their headquarters in Chelan. There is a trailer of spill response equipment that can be transported on the barge, or stationed in Chelan or Lucerne.
Barges also deliver gasoline and diesel to the residents of Stehekin. This is the most significant spill risk in the northern part of the lake past Lucerne Landing, and will continue to be a risk after the Holden Mine project is completed. Recreational boating is also popular in this area during the summer, and smaller spills from these watercraft are possible.
Other areas at risk from significant spills are in the city of Chelan and its suburbs. The bridges at West Woodin Avenue and Webster Avenue/Highway 97 span the Chelan River, where road based spills would flow south towards the dam. Highway 97, Highway 150 and Highway 971/Lakeshore Road all parallel the southeastern five to ten miles of lakeshore and pose a potential threat from tanker truck accidents.
Shoreside businesses, personal boats, ferries and seaplanes are the other oil spill risks in the area. There are no pipelines, railroads or oil terminals in the watershed.