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Blue Lake is the primary source of drinking water for the City of Sitka. Low concentrations of dioxin have been detected in the sediments in Blue Lake. Some members of the community are concerned that this contamination may be impacting the water supply. The community in Sitka, Alaska requested the Agency for Toxic Substances and Disease Registry (ATSDR) to determine if the water supply is safe.

ATSDR reviewed available environmental data for sediment and water samples collected from Blue Lake. In addition, ATSDR reviewed turbidity and total suspended solids data. ATSDR concluded that adverse health effects are not expected as a result of exposure to contaminants detected in water samples or sediment collected from Blue Lake. Due to the low levels of dioxin found in the sediments, it is unlikely that exposure to water from Blue Lake would result in any significant exposure to dioxin. The average estimated exposures to dioxin from using water from the Blue Lake supply are substantially less than the Minimum Risk Level (MRL). The potential exposure to dioxin is minimal and these exposures are not of public health concern.

This site is categorized as Hazard Category C: Indeterminate Public Health Hazard. The limited data do not indicate that humans are being or have been exposed to levels of contamination that would be expected to cause adverse health effects from the Blue Lake water supply. However, data or information are not available for all environmental media to which humans may be exposed. If data become available suggesting that human exposure to hazardous substances at levels of public health concern is occurring or has occurred in the past, ATSDR will reevaluate the need for any follow-up.


In December 1997, ATSDR held informal, individual public sessions to learn about the Sitka community's public health concerns regarding the APC site. The residents expressed concerns about how past emissions from the APC facility might be impacting their health. One of their main health concerns involved the possible contamination of their drinking water supply which comes from Blue Lake; they were especially concerned about the Blue Lake sediments having been contaminated with the chemical dioxin.


Blue Lake is the primary source of drinking water for the City of Sitka. The lake is located about five miles east of the city and 1.25 miles northeast of APC. Low concentrations of dioxin have been detected in the sediments in Blue Lake. Because the City of Sitka is not required to filter water distributed to the public, community members are concerned that the contaminated sediments may be resuspended in the water delivered to their homes, thereby, resulting in exposure to dioxin. Community members are concerned that these potential exposures may affect the health of the community.


    Site Description

The Alaska Pulp Company (APC) was closed in 1993. The mill produced pulp for 34 years from its opening in 1959 until it suspended operations in 1993. APC is located at Sawmill Cove in Silver Bay, Alaska. The APC covers approximately 70 acres of land and is located five miles east of Sitka. The site is composed of three main areas which include the Mill Waste Water Treatment Plant, the Mill Filter Plant to the north, and the main mill area to the south. These areas are surrounded by a security fence. The Wastewater Treatment Plant and the main mill area are bounded on the northeast by Sawmill Creek; to the north, north east, and west by the University of Alaska Trust Lands and by the Tongass National Forest; and to the south by Sawmill Cove. The Filter Plant is located east of Sawmill Creek and is bounded to the north and west by Sawmill Creek, and by Bear Mountain to the east. (Appendix B, Figures 1 and 2 for site maps.)

    Public Water System in Sitka, Alaska

Blue Lake has been the main source of water for the City of Sitka Public Water Supply since 1986. Prior to 1986, water was supplied from Indian River. The Indian River system remains functional as a backup water supply. The Indian River system is used during times when the Blue Lake system is taken off line to complete required inspections and maintenance.

Blue Lake is a reservoir surrounded by mountains and steep terrain. The reservoir has a surface area of 1,330 acres at normal maximum levels with a drainage area of 37 square miles. The watershed is formed by steep mountain slopes that plunge to narrow glacial valleys. Sawmill Creek (formerly known as Medvetcha River) was dammed to raise the level of Blue Lake from 205 feet mean sea level to 342 feet mean sea level. The reservoir has a mean depth of 171 feet with a maximum depth of 468 feet. A topographic map of Blue Lake is included in Figure 3 in Appendix B.

In addition to drinking water for Sitka, Blue Lake is also used to power the smaller of Sitka's hydroelectric plants and was used for process water at the APC (when the plant was open) [1]. Ordinance No. 92-1091 [2] of the City and Borough of Sitka does not allow swimming, wading, washing, and other forms of water contact activity at the lake. Camping is allowed with a permit issued by the City and Borough of Sitka. The lake supports some limited recreational fishing [1]. Fishing occurs from a small portion of the south shoreline that is accessible and from small boats that are carried into the area. Due to limited road passage, boat trailers cannot access the area.

Approximately 3.2 million gallons of water from Blue Lake is used per day for drinking water. This is approximately 0.007% of the total flow of the lake. The municipal drinking water system includes a water intake structure at the lake, the water treatment plant for addition of chlorine and fluoride, and a distribution system consisting of two storage tanks and distribution water lines. The water intake structure for the Sitka municipal water supply is approximately 130 feet below the water surface (actual depth depends on water elevation of the lake). The intake centerline is at elevation 210 feet (mean sea level) and the crest of the spillway is at elevation 342 feet. The two storage tanks are located at Charteris Street (1.2 million gallons) and Harbor Mountain Road (700,000 gallons). The system does not include a filtration system because the City and Borough of Sitka meet Environmental Protection Agency (EPA) regulatory requirements that allow a wavier of filtration. A schematic of the current water control program is included in Figure 4 of Appendix B.

The municipal water system in Sitka is regulated under the Safe Drinking Water Act (SDWA). The purpose of the SDWA is to protect the public from contaminated drinking water. Additional information relating to the SDWA is included in Appendix A.

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