Twenty-four Years of Dredged Material Disposal Site Monitoring in Puget Sound (PSDDA/DMMP)

Transcription

1 Twenty-four Years of Dredged Material Disposal Site Monitoring in Puget Sound (PSDDA/DMMP) Gene Revelas, Integral Consulting Inc., Olympia, WA David Kendall, Ph.D, USACE Seattle District Celia Barton, Washington Department of Natural Resources

2 Presentation Outline 1. DMMP Program History 2. DMMP Program Elements 3. Dredged Material Testing and Disposal History 4. Monitoring Program Design 5. Summary of Monitoring Program Results 6. Refinements and Challenges

3 PSDDA Program History and Focus In 1984, loss of shoreline permit for key disposal site precipitated a 4.5-year, $4.5 million interagency study called the Puget Sound Dredged Disposal Analysis (PSDDA), resulting in two EISs Established state-of-the-art environmental testing procedures for evaluating dredged material Established eight new disposal sites in areas buffered from human use and natural resources conflicts Established disposal site management plans PSDDA/DMMP program implemented in December 1988

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5 DMMP Nuts and Bolts Sediment Testing Chemistry, bioassays, bioaccumulation Suitability Determinations Interagency documentation of sediment suitability for open-water disposal, beneficial use, antidegradation Site Monitoring Physical, chemical, and biological assessment of disposal sites Biennial Report Project summary and monitoring results SMARM Sediment management annual review meeting

6 DMMP Testing History Volume Tested (cy) Thousands 6,200 6,000 5,800 5,600 5,400 5,200 5,000 4,800 4,600 4,400 4,200 4,000 3,800 3,600 3,400 3,200 3,000 2,800 2,600 2,400 2,200 2,000 1,800 1,600 1,400 1,200 1, (Average = 1.9 mcy/yr) Suitable Volume (cy) Unsuitable Volume (cy)

7 DMMP Disposal History Thousands 1,800 1,700 1,600 1,500 1,400 1,300 1,200 Average = 825 kcy/yr Volume (cy/yr) 1,100 1, Average = 344 kcy/yr DY89 DY90 DY91 DY92 DY93 DY94 DY95 DY96 DY97 DY98 DY99 DY00 DY01 DY02 DY03 DY04 DY05 DY06 DY07 DY08 DY09 DY10 DY11 DY12

8 Monitoring Questions 1. Does the dredged material stay onsite? 2. Is the onsite condition* being met? 3. Are unacceptable effects due to dredged material disposal occurring to biological resources offsite? * Minor adverse effects = potential sublethal effects, but no acute toxicity

9 1. Does the Dredged Material Stay Onsite? Based on: Sediment profile image (SPI) mapping Perimeter station chemistry Interpretative Criteria: Less than 3 cm dredged material layer at perimeter stations Perimeter chemical concentrations do not increase over time

10 Dredged Material Mapping Using SPI Recent footprint (red contour) is within the disposal site boundary Disposed dredged material is optically distinct (color, texture, stratigraphy). Can detect relic (yellow contour) and recent footprints Port Gardner Disposal Site, 2010

11 2. Is Onsite Condition Being Met? Based on: Sediment chemistry levels Sediment bioassay testing Minor Adverse Effects Criteria: Onsite chemistry less than the DMMP maximum levels Onsite bioassays meet nondispersive site guidelines Hg (ppm-dry wgt) PCB (ppb-dry wgt) Mercury Trends at Elliott Bay Disposal Site predisposal 1988 baseline Postdisposal average* ML SL Onsite: Station Z01 Onsite: Station S02 Onsite: Station S04 PCB Trends at Elliott Bay Disposal Site predisposal 1988 baseline Postdisposal average* SL Onsite: Station Z01 Onsite: Station S02 Onsite: Station S04

12 3. Are Unacceptable Effects Due to Dredged Material Disposal Occurring to Biological Resources Offsite? Feeding Voids Tubiculous Polychaetes Based on: Offsite benthic infauna Offsite bioaccumulation Interpretative Criteria: Reduction in major taxa abundance more than 50% Body burdens of target benthos increase over time Sea cucumber (Molpadia intermedia)

13 Disposal Site Management Objectives Achieved?

14 Program Management Changes Based on Monitoring Results Monitoring frequency has decreased over time as site monitoring has verified that site management objectives were being met At Commencement Bay site, disposal zone moved to keep footprint onsite and is moved periodically to increase site capacity.

15 Monitoring Program Refinements under Consideration Enhance physical site mapping More frequent multibeam bathymetric surveys (track site capacity/manage disposal zone) Revise offsite biological assessment endpoints Bioaccumulation(move from comparison to baseline values to target tissue levels) Benthic infauna metrics (Puget Sound reference values, SPI indices)

16 Program Challenges Persistent Bioaccumulative Toxic (PBTs) Compounds Dioxins, PBDEs, PCB congeners Relationship between DMMP and WA State's sediment cleanup program undergoing revision; background/antidegradation policy Beneficial Reuse of Dredged Material Nearshore cleanup, habitat restoration, and construction projects

17 For Further Information on the DMMP: