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Dan Michael, Neptune and Company, Inc

VSP application: Sample design to support ecological risk associated with mercury and other munitions constituents in sediments. Dan Michael, Neptune and Company, Inc. Problem Background.

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Dan Michael, Neptune and Company, Inc

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  1. VSP application: Sample design to support ecological risk associated with mercury and other munitions constituents in sediments. Dan Michael, Neptune and Company, Inc

  2. Problem Background • Historical DoDoperations at this former ammunitions depot included storage, manufacturing and transport of munitions. These activities have potentially resulted in releases of chemical constituents into the Bay from several sources including: • Discarded military munitions (DMM) • Outfalls from munitions fabrications operations • Runoff from former burn areas • Groundwater plumes • Historical sediment sampling revealed Hg, Cd and phenols above State screening thresholds • Supplemental sediment and tissue data collection efforts are needed to fill a number of identified data gaps related to understanding whether the current concentrations of chemicals in sediment at this site pose an unacceptable ecological risk.

  3. Decision • Are chemical constituents in Bay sediments present at concentrations that potentially pose an unacceptable risk to ecological receptors (benthic invertebrates, fish, mammals, birds) at the site? • Is the average Hg concentration > 0.41 ppm?

  4. Inputs • Data on the present levels of chemicals in Bay sediment including data on munitions constituents, propellants, and first order breakdown products • Identify the list of potential munitions constituents and their primary breakdown products • Ensure analytical methods are capable of detecting constituents present above screening thresholds • Develop screening thresholds for constituents that have no screening benchmarks using equilibrium partitioning methods

  5. Boundaries • Surface sediment: 0 – 10 cm • Geographic boundaries of the Bay • Special areas of interest include: • Sediment around the piers • Sediment offshore the two former burn areas • Sediment offshore outfalls • Sediment down gradient from a known Benzene Release Area groundwater plume.

  6. Evaluation of Existing Hg Data

  7. Areas of Relative Homogeneity CHANNEL BURN AREA OPERATION AREA

  8. Variability of Historical Hg Data

  9. Use of VSP to Determine Sample Size • EPA analysis of sample sizes • Utilized a subset of historical data • Calculated sample size for entire bay • Concluded DoD’s first proposal (not based on statistical analysis) was inadequate. • Neptune incorporated all historical data, evaluated variability w/in the three areas, determined DoD’s tolerance for uncertainty, and used VSP to calculate sample sizes required for each area

  10. Setting up the Problem in VSP • Pull in Shape File and historical samples • Define three sub areas based on analysis of variability of historical mercury measurements • Highlighting one area at a time, input error tolerances, delta, historical variability for that area, and determine sample size/allocation. • Save the file • Start over for next area, and repeat, saving as new file

  11. Negotiated Design

  12. VSP • Benefits • Visual, Transparent, Flexible • Facilitates use of statistical design by non-statisticians • Rapid ability to modify error tolerances, estimates of variance and develop negotiated design • Ability to evaluate sensitivity of design • Wish list • Stratified sampling design

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