EPA extends comment period, meets Feb. 1 for Carson River Mercury Superfund proposed plan

The U.S. Environmental Protection Agency will hold a public meeting and has extended its public comment period for a proposed plan to the Carson River Mercury Superfund Site.

EPA Region 9 seeks comments on its proposed plan for Operable Unit 2 of the Carson River Mercury Superfund Site.

Public Meeting:
EPA will host a public meeting on Feb. 1 from 6:30 to 8:30 pm. Join the meeting online via Zoom here or by telephone at: +1 669 254 5252 / Meeting ID: 160 411 9316.

EPA representatives will describe the proposed plan, answer questions about the plan, and take formal comments. The meeting will be conducted in English, although questions may be asked and comments may be given in Spanish.

Public Comment Period Extension:
Public comments will now be accepted until February 28, 2022. Go here for a summary and where to send written comments.

To learn more about the proposed plan, visit USEPA’s website here. This website includes the proposed plan and a summary brochure, a recorded video presentation on the proposed plan, an interactive story map, the full administrative record (site files), and additional site information.

According to the plan that can be found here, the Nevada Division of Environmental Protection, the U.S. Environmental Protection Agency (EPA) proposes to protect human health and the environment through an interim remedy for the Carson River Mercury Superfund Site (CRMS) Operable Unit 2 (OU2).

NDEP and EPA will use an interim remedy to protect human health. When new technology and/or more extensive evaluation of Lahontan Reservoir and Washoe Lake is available, a final remedy can be determined. EPA has, administratively divided CRMS into two operable units (OUs): OU1 includes former mill sites near Carson City, Virginia City, and Dayton, Nevada.

OU2 includes soil and sediment in waterways from the mill sites extending more than 130 miles down the Carson River to the wetlands. As shown in Figure 1, this includes the Stillwater and Fallon Wildlife Refuges, Carson Sink and Carson Lake, among others, according to the plan.

This plan describes the remedial alternatives that we are considering and identifies our Preferred Alternative for implementation. We believe the Preferred Alternative will effectively address human exposure to mercury contamination. The public will have opportunities to learn about the Proposed Plan and send written comments about it during a minimum 30-day public comment period.

EPA is concerned about mercury at this site. During the Comstock mining era beginning in 1859, miners used mercury to separate gold and silver ore. They released these mercury-contaminated tailings into the river, which then got into the sediments where it continues to bioaccumulate in the food chain.

The river carried the tailings downstream to the floodplain and the wetlands. Tribal members who practice a traditional way of life by eating game fish, wild plants and waterfowl have potentially elevated human health risks. Mercury contamination also poses health risks to adults and children who eat Sacramento blackfish, commercially harvested from Lahontan Reservoir and game fish from certain areas of the river and lakes.

In 1990, the Carson River Mercury Superfund Site became part of the National Priorities List. This list consists of some of the most toxic Superfund sites in the country. The Carson River Mercury Superfund Site covers five counties, about 330 square miles and more than 130 river miles in Northwestern Nevada. Historic mill sites in Carson City, Virginia City, Dayton, Washoe Valley and Pleasant Valley have mercury contamination. Waterways located next to mill sites spread mercury from the 100-year floodplain of Carson River to the terminal ends. EPA’s site investigation found mercury in soil, sediments (earthen materials that settle to the bottom of a water body), fish and wildlife.

Since becoming a Superfund Site, EPA and NDEP have excavated (dug up) and removed mercury-contaminated tailings and soils from the site.

Proposed Solution
EPA’s Preferred Alternative is an interim approach using a combination of Land Use Controls (LUCs), compliance and monitoring to help prevent mercury exposure and keep contamination from spreading. This alternative reduces human health risk in the floodplain by discouraging people from eating contaminated fish, wild plants and waterfowl through a comprehensive communication and public education program.

Environmental Covenants (ECs, a voluntary title notice) would be placed on properties to help prevent exposure to mercury-contaminated soils. The interim action includes several prioritized actions that will reduce human health risks. They are intended to be consistent with and support a final cleanup action that will be selected in the future. Working with state partners, EPA will use English and Spanish signs, annual surveys, community outreach and educational programs to discourage fish, wild plant and waterfowl consumption.

The preferred alternative also recommends against the current practice of stocking the Carson River or Washoe Lake with game fish other than trout, while a fish advisory is still in place to reduce people’s exposure to mercury contamination. In addition, EPA recommends that the state no longer issue permits for the commercial harvest of Sacramento blackfish for human consumption.

This alternative also expands upon the current Long-term Sampling and Response Plan (LTSRP) used in the OU1 area since the 1995 Record of Decision for this particular area. The LTSRP addresses construction in residential and non-residential properties in the floodplain and/or active channels. EPA and NDEP would oversee soil sampling and possible remediation by commercial and residential developers in areas where mercury contamination may require action (i.e., removal or containment) to prevent it from further spreading. The Preferred Alternative would initially require annual monitoring of surface water, sediments, wild plants, waterfowl and fish tissue. This approach uses the latest science and technology to address mercury contamination.

As long as monitoring results indicate mercury levels that pose human health risks or until a final remedy is implemented, EPA and NDEP will continue to require compliance with the LUCs, according to the proposed plan.