Offset Program
History of SRCSD's Involvement in Mercury Issues
Sacramento Regional County Sanitation District's (SRCSD) initiation into mercury issues began with our 1990 permit from the Central Valley Regional Water Quality Control Board (CVRWQCB). There was very little mercury data for the Sacramento River at that time and the District needed more complete water quality data to design any necessary treatment systems.
Coordinated Monitoring effort begun
In 1991, SRCSD began to monitor a number of water quality constituents, including mercury, and began the Sacramento Coordinated Water Quality Monitoring Program (CMP). This program, a joint effort by SRCSD, Sacramento County Water Resources Division and the City of Sacramento, examines water quality in the Sacramento and American Rivers. As part of the CMP, SRCSD helped develop clean sampling techniques and an analytical method for detecting low concentrations of mercury.
Federal Grants fund additional monitoring
In the mid 1990's, SRCSD partnered with the State and the EPA on a number of grants to identify mercury control projects in the Sacramento River watershed. In 1995, the District applied for a federal grant to begin the Sacramento River Toxic Pollutant Control Program (SRTPCP), which started the Ambient Monitoring Program in the Sacramento River watershed. The SRTPCP grant not only brought federal support into the monitoring effort, but was also a part of the early national dialogue on watershed-wide solutions. These monitoring programs helped identify the regional nature of the mercury issue and highlighted the importance of addressing mercury on a watershed wide basis.
Sacramento River Watershed Program is born
The toxics subcommittee of the SRTPCP conducted a series of stakeholder meetings to solicit input. Stakeholder interest in the objectives of the grant helped spark the formation of the Sacramento River Watershed Program (SRWP). This program is now a non-profit organization seeking funding to continue work in the watershed, including the Annual Monitoring Program. Stakeholder interest in mercury also led to the formation of the Delta Tributaries Mercury Council (DTMC) in 1997. The expert participants in the DTMC developed the Strategic Plan for Reducing the Risks from Mercury Exposure in the Sacramento and San Joaquin River Watersheds (pdf*)
California's Gold Mining Legacy
Mercury was mined from the northern California coastal range and much of it was used in hydraulic gold mining in the Sierra Nevada, as well as dredge tailings operations. There were more than 239 known mercury mines, and more than 200 individual prospects. An estimated 227 million pounds of mercury was produced from the early 1850's through 1981 (see photos 1 & 2). |
Photo 1
Collecting elemental mercury
from gas condensation.
(click on photo to enlarge) |
Figure 1
Mercury and gold mines,
and mineral springs in
the Sacramento River Watershed. |
Figure 1 shows the location of numerous mercury and gold mines in the Sacramento River watershed.
(click on graphic to enlarge)
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Photo 2:
Mercury ore, cinnabar and native Hg
Altoona Mine, Trinity County, CA.
(click on photo to enlarge). |
It is estimated that 1.6 billion cubic yards of landscape were hydraulically mined in the Sierra Nevada mountains. An estimated 8 million pounds of mercury was lost to the environment from these gold mining operations. The process stripped landscapes, and clogged drainage ways with sediments and debris, affecting rivers and major transportation routes. It also buried agricultural land in the valleys and caused major flooding in Sacramento and Yuba City. Another 3.9 billion cubic yards of the landscape were affected by dredging operations.
Historical Mining Photos
(click on photos to enlarge)
Undercurrents in Humbug Creek, S. Yuba River watershed. |
Hydraulic monitors in operation, North Bloomfield mine, circa 1880s, Malakoff Diggings, Nevada County. |
Biggs No. 2 Dredge, Butte County, California, circa 1910. |
Hydraulic mine, ground sluice system, circa 1870s, Scott Valley mine, Siskiyou County. |
The Behavior of Mercury in Our Environment
The behavior of mercury in our environment is complex. Mercury behavior in the environment is being studied by many scientists throughout the country, and in California and the Sacramento River Delta. At this point in time, very little is known about the factors that control mercury transformation and bioaccumulation. More information on the state of knowledge surrounding mercury behavior in the environment can be found on the CalFed Mercury Science Project web site at http://loer.tamug.tamu.edu/calfed/.
Figure 2
Mercury-impaired water
(click on graphic to enlarge)
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What is known at this time is that the entire Lower Sacramento River region is impaired due to the high mercury concentrations in fish (see figure 2). This is a simplified diagram showing the connection between various sources of mercury and fish that are consumed by humans and wildlife. An important step in this process is the transformation of mercury into "methyl mercury," which is the more dangerous organic form that accumulates in fish tissue. Disrupting the connection process at any point along the path can reduce the risk of mercury exposure to humans and wildlife.
Fish Advisories
People need to be aware of what they can do to minimize their risk from exposure to mercury. There are numerous fish advisories in the Sacramento region, including new guidelines for sport fish consumption for selected water bodies in the Northern Sierra Nevada Foothills (Nevada, Placer, and Yuba Counties) issued by the California Office of Environmental Health Hazard Assessment.
SRCSD - Treating Wastewater and Removing Mercury
SRCSD treats an average of 165 million gallons per day (mgd) of wastewater using an accelerated natural process. The Sacramento Regional Wastewater Treatment Plant (SRWTP) uses primary and secondary treatment, as well as an activated sludge process, to safely release treated water into the Sacramento River. SRWTP has a National Pollutant Discharge Elimination System (NPDES) permit with a mass limit of 5.1 pounds of mercury per year in the treated water released to the Sacramento River. SRWTP has never exceeded this limit, but anticipates future growth within SRCSD's service area and the resulting increase in flow to SRWTP will eventually increase the amount of mercury released to the Sacramento River.
The Plant is able to remove about 95% of the mercury it receives from the region's wastewater. SRWTP's contribution to mercury in the river is relatively small, about 1/3 of one percent. This chart shows the distribution of overall mercury loads to the Delta.
SRCSD's Pollution Prevention Work Plan
SRCSD's NPDES permit was renewed in August 2000, and required the development and implementation of a Pollution Prevention Work Plan to evaluate the ability to reduce mercury within SRCSD's service area, increase removal of mercury at the SRWTP and the feasibility of offsetting any future exceedence of the permit limit by reducing other mercury sources in the watershed. This work plan includes the following elements.
- A Mercury Source Reduction Program to lower the amount of mercury that enters the sewer system within SRCSD's service area.
- A Treatment Feasibility Study investigating the effectiveness and costs of additional treatment processes that can remove even more of the mercury from the flow that enters the SRWTP.
- A Mercury Offset Program to evaluate the feasibility of offsetting any future mercury discharged into Sacramento River that exceeds SRCSD's permitted amount by controlling another source of mercury in the watershed that provides the best environmentally effective opportunity.
Mercury Offset Program
What is an Offset?
An offset is a mechanism for improving water quality by allowing one party to maintain or increase their own pollutant load while reducing that pollutant at another location within the same watershed. |
The Mercury Offset Program is the only pilot study of pollutant trading involving a persistence bioaccumulative toxic chemical under the USEPA's Water Quality Trading Policy. If a feasible mercury offset program is developed, SRCSD and the regulatory agencies (EPA Region IX, the State Water Resources Control Board and CVRWQCB) will lead the nation as the first pollutant trading program involving a persistent bioaccumulative toxic chemical.
SRCSD completed a mercury offset feasibility study utilizing a stakeholder driven process to produce the legal and regulatory framework of an offset program and recommended criteria allowing identification and evaluation of feasible project(s) to offset any future increased discharge of mercury to the Sacramento River. SRCSD hosted a series of work group meetings that include regulators, land managers, scientists, other NPDES permitees, and interested parties. The consensus of the work group to date, is that the offset package should include three major components:
- Source or Mass Load Reduction (MLR)
- Research
- Outreach and Education
Mass is the current measure of mercury in SRWTP NPDES permit and the work group agreed in principle that there are ample opportunities in the watershed to remove mercury more effectively than what could be accomplished at the SRWTP. Possibly the most effective and direct means of offsetting the risk of mercury exposure is educating our community, especially our subsistence fishing communities and women of child bearing age, to encourage eating fish that present the lowest health risk. More information on current fish consumption advisories for locally caught fish can be found on the California Office of Environmental Health Hazard Assessment website at www.oehha.ca.gov/fish.html.
SRCSD has identified potential offset projects, developed research objectives to determine the relative bioavailability of mercury in effluent from SRWTP, and produced educational materials to inform the public about this issue. The final feasibility study report was submitted to the CVRWQCB in March of 2005.
SRCSD is working to develop a mercury offset project that is able to reduce the mercury load to the Sacramento River beyond what can be accomplished at the SRWTP, minimizing the impact to our ratepayers, while allowing for continued community growth.
For more information about SRCSD outreach and offsets trading efforts, please contact Vicki Fry, Associate Civil Engineer, at 916-876-6113 or fryv@sacsewer.com.
Or click on these PDFs for additional information:
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free reader, available here: |
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