Evaluation of Two Natural Resource Damage Assessment and Restoration Cases to Restore Mussels in the Clinch and Powell Rivers in Virginia and Tennessee.

Last edited 10/06/2021
Tennessee Bean (Venustaconcha trabalis) mussels produced at the Aquatic Wildlife Conservation Center. Photo: Ryan Hagerty, USFWS.

Authors: J. Murray Hyde and Jess W. Jones

The Office of Restoration and Damage Assessment would like to announce the recent completion of the subject study and related report that the Office funded.  The ORDA Mussel Restoration & Monitoring Final Report is now available for download.

Executive Summary

The Certus, Inc. and Lone Mountain Processing, Inc. Natural Resource Damage Assessment and Restoration (NRDAR) cases in the upper Tennessee River basin of Virginia are among the first and largest cases involving injury to freshwater mussels due to release of hazardous substances in the United States. The Certus, Inc. spill in 1998 released 1,350 gallons of Octocure-554 revised (a rubber accelerant) into the upper Clinch River, killing approximately 18,000 mussels, including individuals of three endangered species. The Lone Mountain Processing, Inc. (LMPI) spill occurred in the Powell River in 1996 and released 6,000,000 gallons of coal slurry, affecting mussels over a 65-mile section of river.

Chapter 1 discusses how NRDAR settlement money from these two cases was used to propagate and release mussels at population restoration sites in the upper Clinch River, VA and in the Powell River, TN and VA. It summarizes the production and release of mussels from 2003–2019 by the Virginia Department of Wildlife Resources’ Aquatic Wildlife Conservation Center (AWCC) and Virginia Tech’s Freshwater Mollusk Conservation Center (FMCC). A total of 8,456,191 juvenile mussels of 34 species were produced by AWCC and FMCC, with a total of 861,845 mussels of 26 species released at sites in Virginia and Tennessee over this time period. Of the released mussels, a total of 152,182 were 20–40 mm long and 1–3 years old.

In Chapter 2, mussel monitoring data collected from 2015-2017 in both rivers, the mussel release data from Chapter 1, and a Leslie matrix model were used to estimate the expected mussel survival and abundance at nine sites, including two sites in the immediate impact zone of the Certus, Inc. spill. We compared the expected numbers of released mussels from 2004–2017 to density estimates from quadrat surveys and mark-recapture surveys at the sites monitored from 2015 to 2017.  Monitoring data show that restoration efforts for the Certus, Inc. and LMPI NRDAR cases were successful in that species impacted by both spills have been restored and are persisting for many years (6-8 years) post release at all release sites in each river, including the endangered Golden Riffleshell (Epioblasma aureola) and Tennessee Bean (Villosa trabalis), and that populations of several other Epioblasma species and numerous non-endangered species have been established ~40 miles downstream in the Clinch River in Russell County, VA, and in the Powell River in Claiborne County, TN, and Lee County, VA. 

In Chapter 3, a Resource Equivalency Analysis (REA) was developed to retrospectively analyze injury to mussel populations in terms of discounted mussel-years (DMYs) lost for the Certus, Inc. NRDAR case. The expected gains as DMYs for hatchery-reared mussels released from 2003 to 2019 to restore populations lost due to the spill showed that DMYs gained from mussel restoration exceeded those lost during the spill for this case. Further, new insights pertaining to restoration gains for both cases, and to injury losses for the Certus case, were uncovered through the application of the REA in full-establishment and reduced-establishment scenarios.  While the REA developed in this study should prove useful for future freshwater mussel NRDAR cases, further refinement of the REA is needed for those single event, acute exposure cases with a complete loss.

In Chapter 4, annual operating costs at AWCC and FMCC from 2003 to 2019 were examined by compiling available financial records and costs to produce freshwater mussels. All costs were converted to real costs (2020 $) using the Consumer Price Index for All Urban Consumers. The cost of propagating, raising, and successfully establishing a mussel at restoration sites under the scenarios used for the REA – the full-establishment and reduced-establishment scenarios were determined. The mean cost per established mussel at AWCC was $16.81 under the Full Restoration Scenario and $67.23 under the Reduced Restoration Scenario, and similarly, the mean cost per established mussel at FMCC was $14.75 under the Full Restoration Scenario and $59.02 under the Reduced Restoration Scenario. These resulting cost estimates may assist case managers in the future when planning for restoration, but should be used cautiously, as all cases are unique and require consideration of many factors that may have not been evaluated in this study.

Further Reading:

ORDA Mussel Restoration & Monitoring Final Report

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