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MONITORING OF ACTIVATED CARBON REMEDIES
Monitoring of an AC remedy is similar in many respects to monitoring the effectiveness of other remedial alternatives such as Monitored Natural Recovery (MNR), Enhanced Monitored Natural Recovery Natural, or even a capping remedy – depending upon how the AC remedy is implemented. For example, if the AC remedy is placed directly onto the contaminated sediment, the monitoring objectives and tools will be similar to MNR from the standpoint that while the bulk contaminant concentration remains the same, the bioavailability is reduced, and the biological system would improve over time. If the AC is placed onto contaminated sediment, and then covered with a layer of clean sediment or sand, in effect the remedy is both sequestration and isolation; the tools used to monitor EMNR or capping could be used here. The monitoring tools and measures will be dictated by the design of the constructed remedy, and by the short and long-term performance objectives. Additional resources describing tools for monitoring MNR, EMNR, and capping are provided in the Additional Resources at the bottom of this page.
Two important elements not included in this performance objectives table are treatability study monitoring, and baseline monitoring. Prior to remedial design it may be necessary to (1) verify the amendment performance in the lab to reduce bioavailability and (2) that the planned amendment delivery method will result in the AC reaching to sediment surface. Baseline monitoring should always be included in a long-term monitoring plan. The specific tools will depend upon the selected data requirements and success criteria. The same tools listed in the Performance Objective table can be used for baseline monitoring.
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Performance Objective | Data Requirements | Tools | Success Criteria |
Placement Monitoring | |||
Confirm AC amd/or placement during remedy construction meets design specfications | Measures to confirm that the horizontal and vertical material placement meets remedy design specifications | Sediment Core Profiling | Visual analyses of multiple cores demonstrate horizontal
coverage of 100% of target coverage area, with a minimum vertical
distribution ≥ the contract specficiation. For remedial designs incorporating a sand or gravel cover over the placed AC, visual confirmation of horizontal distribution of 100% of target area and vertical distribution of ≥ the design specficiation. |
Sediment Profile Imaging | Compare baseline and post-placement SPI images. Images able to distinguish AC from native sediment and accuracy in identifying mixing depth within 50% of estimates indicated by visual AC and grain size analysis of sediment cores. | ||
Visual/Video Inspection | Visual confirmation by divers and/or video surveys that 100% of the targeted area was covered. Immediate post-placements may also use measuring device to confirm vertical distribution of ≥ the design specficiation. | ||
Analytical measures of total organic carbon (TOC) and black carbon (BC) | Bulk sediment analyses of TOC and BC | Confirmation that the TOC and BC levels are greater than baseline, and at or above the AC design criteria | |
Depth of placed AC captured in the sediment trap | Sediment Traps | Sediment traps placed on the remedial area collect ≥ the design specificiation of AC | |
For remedial designs including a sand or gravel cover over the AC, elevation changes between baseline and construction | Bathymetry/Side Scan Sonar | For remedial designs incorporating a sand or gravel cover over the placed AC, visual confirmation of horizontal distribution of 100% of target area and vertical distribution of ≥ the contract specficiation. | |
Friction Sound Probe | For remedial designs incorporating a sand or gravel cover over the placed AC, confirmation of vertical distribution ≥ the design specficiation. FSP measurements should be able to distinguish placed material from native sediment and accuracy in identifying mixing depth within 50% of estimates indicated by grain size analysis of sediment cores. | ||
Post-placement Physical and Biological Impact Monitoring | |||
Confirm the post placement persistance, permanence and mixing of AC with underlying native sediemnts | Measures to confirm that the placed AC remains onsite and is mixed into the underlying contaminated sediments | Sediment Core Profiling | Visual analyses of multiple cores demonstrate horizontal coverage of 100% of target coverage area, with a minimum vertical distribution ≥ the contract specficiation. |
Sediment Profile Imaging | Compare baseline, construction, and post-placement SPI images. SPI camera able to distinguish TLC from native sediment and accuracy in identifying mixing depth within 50% of estimates indicated by grain size analysis of sediment cores | ||
Bulk sediment analyses of TOC, BC, and grain size | Compare baseline, post-cap placement, and short-term monitoring results. AC remains evenly distributed laterally while mixing vertically over time. | ||
Demonstrate that there are no short-term effects to biological resources, or if so, document the recovery rate of those resources | Pre- and post-AC placement benthic taxonomic surveys | Benthic infaunal surveys | Measure of various indices using baseline, post-placement, and
long-term monitoring data. Indices may
include total taxa; percent dominant species; similarity index; species
diversity index; percent tolerant species; percent intolerant species; IBI; and abundance. |
In-situ bioassays and bioaccumulation testing | SeaRing | >80% survival of the test species placed into the SEA Ring
test chambers. Demonstration that bioaccumulated levels of COCs are signficantly reduced (> 50%) post-remedy as compared to baseline levels. |
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Reductions in Toxicity, Bioavailability, and/or Flux of Site Contaminants | |||
Demonstrate reduction in contaminant bioavailability | In-situ bioassays and bioaccumulation testing | SeaRing | >80% survival of the test species placed into the SEA Ring
test chambers. Demonstration that bioaccumulated levels of COCs are signficantly reduced (> 50%) post-remedy as compared to baseline levels. |
Porewater Measures | Passive Sampling | Reduction of COCs in post-remedy porewater concentrations ≥ 50% of baseline.
Where a porewater RAL is required, demonstration that the porewater COC concentration is at or below the RAL. |
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Laboratory-exposed benthic organisms | Ex situ bioassays | Demonstration of >80% reduction in lab-exposed organisms to AC-amended sediment collected from the site | |
Reduction in flux of COCs from the sediment to the overlying surface water | Porewater and Surface Water Measures | Passive Sampling | Passive sampler media placed at sediment/water interface do not
show flux of contaminants into the water column. Contaminants measured in water-only portion of sampler do not exceed the associated water quality criteria or site RAL. |
Trident Probe Ultra Seep Meter |
Groundwater and/or flux of contaminants from sediments into the water column do not exceed the associated water quality criteria or site RAL. | ||
Long Term Stability and Efficacy of the Remedy | |||
Long-term permanence of the placed AC | Measures to confirm that the placed AC remains onsite and is present in the sediment column | Sediment Core Profiling | Visual analyses of multiple cores demonstrate horizontal coverage remains at 100% of target coverage area. Allowing for surface depostion and vertical mixing, persistence of black carbon is ≥ 50% of that observed during post-placement monitoring. |
Sediment Profile Imaging | Compare baseline, with long-term SPI images. Over-time, SPI camera may not be able to distinguish AC from native sediment. | ||
Bulk sediment analyses of TOC, BC, and grain size | Compare baseline, post-cap placement, and long-term monitoring results. TOC and black carbon remain at the design specification. | ||
Demonstrate reduction in contaminant bioavailability | In-situ bioassays and bioaccumulation testing | SeaRing | Continued reduction in contaminant bioaccumulation measured in passive samplers or tested organisms is sustained over time. |
Porewater Measures | Passive Sampling | ||
Laboratory-exposed benthic organisms | Ex situ bioassays | ||
Reduction in flux of COCs from the sediment to the overlying surface water | Porewater and Surface Water Measures | Passive Sampling | Groundwater and/or flux of contaminants from sediments into the water column do not exceed the associated water quality criteria or site RAL. |
Trident Probe Ultra Seep Meter |