Implementation of In Situ Activated Carbon
Remedies at Contaminated Sediment Sites



MONITORING

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.

Performance Objectives
"Performance Objectives" are used here to evaluating an AC remedy and discuss the tools for monitoring performance. Remedies conducted for contaminated sediments sites will have specific Remedial Action Objectives (RAOs) and Remedial Action Levels (RALs) for the short, and long-term performance of the remedy. However, implementation of AC remedies is relatively new; specific RAOs or numeric RALs have not incorporated into Records of Decision.

Performance Objectives are part of a planning process similar to the Data Quality Objectives (DQOs) (EPA 2006). Objectives are defined, data requirements and tools to provide those data are identified, and acceptance criteria are articulated. Performance Objectives are used for the PSNS Pier 7, Hunters Point 2015, and Canal Creek Demonstration projects on the case study page. Other AC pilot project have used the DQOs (LDWG 2016), or Project Quality Objectives (NAVFAC 2014).

EPA's Contaminated Sediment Remediation Guidance (EPA 2005) recommends monitoring of short- and long-term remedy performance. EPA's monitoring recommendations are risk-based; focusing on monitoring evidence to demonstrate that chemical toxicity, bioavailability, or fluxes have been achieved and maintained. We recommend that

  • Placement Monitoring – did the remedy construction meet the design specification
  • Immediate and short-term physical and biological impacts
  • Reductions in chemical toxicity, bioavailability, and/or flux of site COCs
  • Long-term stability and efficacy

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.

Performance objectives, data requirements, tools to provide the data, and example success criteria are given in the table below. The table provides links to further information on the specific tools, and to the Demonstration Project reports on the SERDP/ESTCP web site. Additional planning resources referenced in this section are provided in the bottom of this page.

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. 
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.
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