Amendment 0002 -WQC-Clarification.pdf

DEQ 401 WQC, 2013-172-1, U.S. Coast Guard, Marine Safety Unit Portland, Maintenance Dredging Page6

May 2018 [USAGE, National Marine Fisheries Service (NMFS), U.S. Fish and Wildlife Service (USFWS), U.S. Environmental Protection Agency (EPA), DEQ, Washington Department of Natural Resources (WDNR), Washington Department of Ecology (Ecology), and Idaho Department of Environmental Quality (IDEQ)]. The Applicant must follow all recommendations of the Portland Sediment Evaluation Team (PSET) Memorandum dated July 16, 2024. Table 1. summarizes the suitability determination for the dredge prism and post-dredge surface for aquatic exposure through January 2029.

Post-dredge surface management is required for stations MSUP-02LZ, MSUP-03LZ, and MSUP-04ZL (i.e. over-dredge and/or place 12 inches of clean sand). The Applicant shall coordinate with EPA Cleanup and PSET at least 9 months prior to the recency expiration.

Table 1. Suitability Summary DMMU Dredge Prism Post-Dredge Surface 2024 dredge area Unsuitable* Suitable (lZ, 2Z [post-dredge sampling]) Remaining dredge area Unsuitable* Unsuitable (3Z, 4Z)"'

* Biological testing required to finther evaluate unconfined. aquatic placement.

" Post-dredge smface management required.

Rule: OAR 340-041-0036, OAR 340-041 Justification: DEQ must ensure that pollution does not enter waterways.

16) Dredging and Disposal Methods: The PSET determination provides recommendations regarding the suitability for sediment disposal in water. The Applicant and its contractors must follow these recommendations and the following additional conditions:

a. Not Suitable for Unconfined In-Water Disposal

i. Dredging method is limited to diver assisted hydraulic suction, hydraulic suction, closed-lipped bucket, or excavation in the dry, unless another method is specifically authorized by DEQ;

ii. Discharge to waters resulting from dewatering during dredging or release of return water from an upland facility is prohibited except as provided below.

1) All water removed with sediment must be contained and disposed of at an appropriately sized and sealed upland facility by evaporation or absorption by inert material (such as shredded paper).

2) A Modified Elutriate Test (MET) may be performed for the known contaminants of concern (CoCs) with results compared against DEQ freshwater chronic water quality criteria. If Coe concentrations are below the criteria , criteria are not applicable, or DEQ Cleanup offers a determination of acceptability; dewatering and return water discharge are not limited.

a. The MET must be performed before dredging.

b. DEQ must approve the list of CoCs and analytical method prior to the Applicant performing the MET.

c. DEQ must review the results and provide approval of discharge from dewatering and return water in writing prior to dredging.

3) Discharge of return water from contaminated dredged material

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DEQ 401 WQC, 2013-172-1, U.S. Coast Guard, Marine Safety Unit Portland, Maintenance Dredging Page?

that exceeds a chronic or acute toxicity water quality standard is prohibited.

4) Water removed with contaminated dredged material that could or does exceed chronic water-quality criteria must be contained and disposed of at an appropriately sized and sealed upland facility by evaporation or infiltration.

iii. Dredged material disposal must be upland or at a landfill permitted to accept hazardous waste. DEQ Solid Waste Letter of Authorization, or clean fill determination is required, which may include contaminant specific limitations.

iv. A leave surface management plan per PSET, DEQ Cleanup, or 401 WQC program is required prior to dredging.

b. The Applicant or its contractors must employ the following techniques to minimize sediment disturbance and distribution through the water column:

i. Sequence or phase work activities to minimize the extent and duration of in-water disturbances;

ii. Employ an experienced equipment operator;

iii. Implement bucket control techniques, such as:

1) Do not overfill the bucket.

2) Close the bucket as slowly as possible on the bottom.

3) Pause before hoisting the bucket off of the bottom to allow any overage to settle near the bottom.

4) Hoist load very slowly.

5) If dewatering is permissible, pause bucket at water surface to minimize distance of discharge.

6) "Slam" open the bucket after material is dumped on a barge to dislodge any additional material that is potentially clinging to the bucket.

7) Ensure that all material has dumped into the barge from the bucket before returning for another bite.

8) Do not dump partial or full buckets of material back into the wetted stream.

iv. Implement suction dredge control techniques, such as:

1) Operate with the intake head at or below the surface of the sediments being removed during all periods of active dredging.

2) Slow cutter head rotation or lessen horsepower.

3) Slow swing arm speed.

4) Clean out slurry by pumping in river water before shutting down rather than purging.

5) If purging becomes necessary, raise intake line no more than 3 feet from the bottom.

c. Dredging of holes or sumps below maximum depth and subsequent redistribution of sediment by dredging, dragging, or other means is prohibited.

d. All anthropogenic debris greater than 1 foot in dimension must be removed from dredged sediments prior to in-water disposal and transported to an appropriate upland disposal site.

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