Implementation of In Situ Activated Carbon
Remedies at Contaminated Sediment Sites



MONITORING

PASSIVE SAMPLING

Passive sampling tools provide an analytical measure of the the bioavailable fraction of site contaminants in pore water or surface water. Demonstrating the sequestration of contaminants and the reduction of bioavailability to benthic organisms and fish is the most important metric for demonstrating success in the AC remedy. Passive samplers may be deployed alone, or coupled with direct measures of bioaccumulation via in situ or ex situ bioassays. The utility of the passive sampler is in the ability to deploy large numbers of samplers across a site, and the ability to measure the contaminants below the AC, within and above the AC, as well as in the surface water above the site.
Commonly employed passive sampling materials at activated carbon remedy sites include:

  • Low Density Polyethylene (LDPE)
  • Polydimethylsiloxane (PDMS)
  • Polyoxymethylene (POM)

    sampling_methods_background

Passive samplers deployed in sediments or water pick up contaminant molecules in similar fashion to bioaccumulation in benthic infauna, shellfish, or fish.  Sampling materials can include LDPE, POM, and SPME (adapted from EPA and SERDP/ESTCP 2017).

Passive samplers have been part of the long term monitoring programs at virtually all of the AC remedy sites to date. Passive sampling was first effectively demonstrated at the first field-scale demonstration of AC at the Hunters Point Annex in 2005. Other sites using passive samplers, and/or biological measures of contaminant sequestration are listed in the table below.

Site Contaminant Year Constructed Passive and Biological Sampling Media Project Web Link
Low Density Polyethylene (LDPE) Solid-Phase Micro-Extraction (SPME) Polyoxy-methylene (POM) Ex Situ Pore-water Ex Situ Bioaccumu-lation Benthic Infauna
USN Hunters Point 2015 Pilot Study PCBs 2017 ü       ü ü Hunters Point 2015 Demonstration Project
Activated Carbon Pilot Study,
Lower Duwamish Waterway, Seattle, WA		 PCBs 2017 ü       ü ü LDWG Web Site
USN Sierra 1B Pier
Pearl Harbor, HI		 PCBs & mercury 2015 ü ü     ü   USN Sierra 1 B Case Study
Mirror Lake Restoration
Dover DE		 PCBs 2014 ü   ü       Mirror Lake Case Study
Puget Sound Naval Shipyard
Bremerton, WA		 PCBs & mercury 2012 ü ü   ü ü ü PSNS Case Study
Berry’s Creek, NJ Mercury & PCBs 2012 ü ü ü   ü   EPA, 2013
ESTCP ER-200835
Lower Duwamish Slip 4
Seattle, WA		 PCBs 2011 ü           Slip 4 Lower Duwamish
Canal Creek, MD PCBs & mercury 2010 ü ü   ü ü ü Canal Creek Case Study
ESTCP ER-200835
Naval Air Station,   Cottonwood Bay,
Dallas TX		 PCBs, PAHs, chromium, lead 2009 ü ü ü       SERDP ER-1493
NAVFAC TR-2366-ENV Technical Report
Bailey Creek, Fort Eustice, VA PCBs 2009 ü   ü   ü   Bailey Creek Case Study
Grasse River, Massena, NY PCBs 2006 ü   ü       Grass River Pilot Project Web Site
Hunters Point 2005 Pilot Project
San Francisco Bay, CA		 PCBs & PAHs 2005 ü       ü ü SERDP-1207
ESTCP ER-200150
Hunters Point 2005 Case Study
Abbreviations
PAH - poycyclic aromatic hydrocarbons
PCBs - polychlorinated biphenyles


Guidance Documents for Passive Sampling
There are several good documents available to plan for the use of passive sampling for remedial monitoring.

The joint USEPA and SERDP/ESTCP Laboratory, Field, and Analytical Procedures for Using Passing Sampling in the Evaluation of Contaminated Sediments is the definitive guidance document. . The User’s Manual provides chapters covering use of POM, PDMS, and LDPE for hydrophobic organic compounds, and diffusive gradients in thin-films (DGTs) for metals. The User’s Manual also includes field deployment and retrieval methods, selection and use of performance reference compounds, quality assurance and quality control procedures, and methods for laboratory analysis.


Integrating Passive Sampling Methods into Management of Contaminated Sediment Site: A Guide for Department of Defense Remedial Project Managers provides remedial project managers guidance on how to integrate passive sampling into management of contaminated sediment sites, including AC remedy sites. Written as a companion document to the User’s Manual, the author team conducted extensive interviews with RPMs (DoD and EPA), scientists, analytical laboratories, and practitioners. The Guide focuses principally on passive sampling of hydrophobic organic compounds (e.g. PCBs, dioxin/furans, PAHs) using POM, PDMS or LDPE. Topics covered include what do passive samplers measure, how can they be used in remedial investigations feasibility studies or remediation, examples of use in the RI/FS and remediation process, a list of commercial laboratories that can do this work, and how to use the results in the decision-making process.


Practical guidance on using polyethylene or solid phase microextraction samplers may be found at the SERDP and ESTCP Bioavailability web site. Additional excellent on-line scientific publications on passive sampling include papers by Oen et al (2011), Ghosh et al (2014), and Greenberg et al (2014). Additional resources may be found at the bottom of this web page.

Logistical Considerations
Whether POM, PDMS, or LDPE is the sampling material, specialized frames hold the material are needed to allow for ease of insertion and recovery, while also protecting the material during deployment and retrieval. The logistics of getting the samplers safely and efficiently into and recovered from the sediments include consideration of the following.

Deployment Hand-placement of the sampler frames in shallow water is convenient, inexpensive, and allows for vertical insertion (i.e., the frame does not go in at an angle). Pole-extension can be used to extend the depth, but generally this is limited to less than 15 ft of water depth. Divers have most-often be used for placement in deeper waters, or under piers or docks. Divers offer the same advantages as hand-placement, with the noted exception that they are much slower and expensive to use. Vessel-deployed samplers have recently been developed as an alternative to diver-placement. These are discussed further, below.


Examples of Field-Deployed Passive Sampling Frames From Menzie et al 2016 (see Additional Resources below)

Sediment bed conditions, the type of sediment and presence of rip rap or other debris on the sediment surface need to be considered. Placing samplers into soft sediments is relatively easy, but having to push samplers through a sand layer or past surface debris may require coupling the sampler to a drive system. For example, at a site on the Lower Willamette River in Oregon the bedded sediment varied from soft silt/clays, to harder sands with cobble. A diver- operated impact hammer was needed here to drive in the samplers. Due to the abundance of glass, nails, cables, rocks, a sampling plate was attached during the drive, and then removed by the diver.


Waterway activities can directly affect the success of recovering the samplers at the end of the exposure period. Vessel wake, propeller wash, maintenance or remedial dredging, dragging barge tow chains, or even deployed fishing gear in an industrial water have all contributed to the loss of deployed passive samplers. While avoiding high activity areas is the preferred method for preventing loss, in many cases the AC remedy will be in those active zones. For those cases, longer samplers driven deeper into the mud, or fixed with rope tethers, may need to be considered.

Retrieval /Recovery of the sampling frame and material also needs careful consideration. In quiescent water bodies attaching a line and surface float to the frame is simple and generally reliable. But in active areas those surface floats may become tangled with vessels, or pulled up by curious boaters. Other options include use of a underwater acoustic pingers attached to the samplers to guide a diver back to the sampler, or use of acoustic or timed release

Hand and diver-deployed LDPE and SPME samplers

  

A pair of LDPE samplers being handed off to a USEPA diver on the Lower Duwamish Waterway at Seattle, WA. For these samplers, the diver inserts the frame up to the white tape to leave 10 cm sticking up out of the bed and 40 cm of PE penetrating down into the sediment. Gschwend et al 2013. Obtaining Measures of Freely-Dissolved Polychlorinated Biphenyls (PCBs) in Pore Water of the Lower Duwamish Waterway (LDW) Sediments Using Passive Polyethylene Samplers

  

Surface water SPME samplers were deployed 1 ft above the sediment surface by attaching them to the top of an inserted sampler (Figure from Thomas et al. 2012)


SPME fibers are inserted into tubular frames which then can be driven by hand into shallow water sediments, or alternatively be placed by divers. For both SPME and LDPE, inserting the frames into the sediment with a portion in the surface water can provide data on whether contaminants are leaching up out of the sediments, or alternatively if contaminants are moving onto the sediment surface from other sources.


Passive Sampler Extreme Underwater Deployment
Lower Willamette River, OR

An extreme end of logistical considerations for passive sampling are illustrated at site located within the Lower Willamette River Superfund Site in Portland, OR. The nearshore area had docks and old pilings, which necessitated the use of commercial divers to safely install and retrieve the samplers. LDPE was
selected as the sampling media, and the frames used were the same as those originally developed by Massachusetts Institute of Technology. Vibracores previously collected showed that the sediment varied from soft silt/clays, to harder sands with cobble. The surface of the sediment was strewn with wood debris, glass, nails, cables, and rocks. The site is an active berthing area with large ships and tugs generating wake and propeller wash.

Surface floats could not be used in these active shipping lanes. The passive samplers had to be driven into the hard, compacted sediment bed. A diver- operated impact hammer was made to fit the passive sampling frame and included the hammer assembly (A), a plate cover to protect the LDPE during the drive (B), and a fixed depth-stop (C) to ensure consistent depth-of- placement of the LDPE. The LPDE was fit into the sampling frame at the laboratory; the cover plate was placed in the field and the entire assembly handed to the diver. Prior to the dive, the sampling location was located with GPS and fixed with an anchor.

The diver descended with the assemble down the rope to the anchor, drove the assembly into the sediment. To ensure that the samplers were not lost to propeller wash, screw anchors were placed upstream/downstream of the samplers, and the sampler frame fixed with rope to the screw anchors. An acoustic pinger was then cable-tied to the frame for later relocation. The last step was to remove the cover plate from the sampler.

After 90 days the divers re-located the samplers following the acoustic beacon. All samplers were recovered with the LDPE completely intact.

Remote Passive Sampler Deployment and Retrieval

A diver-less deployment/retrieval system is being demonstrated under ESTCP. The system consists of 3 modular components: the passive sampler frame, the deployment system, and the retrieval system. This system is shown in Figure-1. The sampling media (e.g., LDPE, SPME, PON) is loaded into a sampler frame to which the retrieval buoy is affixed. The frame slides into guides on the deployment system, lowered to the sea floor, and pushed to a pre-set depth below mudline. This triggers a release mechanism that allows the deployment system to be pulled back to the boat, leaving the sampler and retrieval buoy in place. The retrieval system consists of a user-specified timed-release mechanism. The float releases at the assigned time and date, and the sampler can be pulled in from a boat.

The sampler frame was adapted from the frame used by the Massachusetts Institute of Technology (MIT) in other SERDP/ESTCP projects ( ER-1496, ER-2429, ER-201431). Two deployment systems have been developed a hydraulic Power Deployment System (PDS) (Thompson et al 2017) and a weight-driven Passive Push system developed by US Navy SSC-Pacific (NESDI Project #529). Both the PDS and DFS have recently been successfully tested with PE passive samplers. These systems differ in that the DFS is viewed as being more effective for deployments in soft (silt to silty sand) sediments from smaller boats and is more portable, while the PDS allows for deployments into harder substrates (e.g., compacted sediments, cobble), but requires larger vessels and is less portable.

Integral to the remote deployment/retrieval system is a timed-release pop-up float that works effectively to within a time resolution of about 5 minutes when deployed for weeks to months.

        

Universal Sampling Frame

  • Modified from MIT frame
  • Holds 10 x 50 cm PE
  • Fits PDS and DFS drive
    systems
  • Can hold POM, SPME, DGTs,
    and POCIS samplers
   

Power Deployment System

  • Hydraulic Driven
  • Adjustable setting for push depth
  • Vibrator can be turned on to aid
    placement
  • Effective to > 200 ft
  • Use in ER-2429 to place > 40 frames
    per day
   

Passive Push System

  • Same sampler frame as
    other sytems
  • Pin in drive shaft to set penetration depth
  • Spring-loaded release pin
    to tethered to frame
  • UW Camera to monitor
    from surface
  • Effective to > 100 ft
   

Time Release Floats

  • Based on customized
    Subsea Sonic burn wire
    timed release
  • Buoy comes to surface
    at programmable release
    time
  • High-strength line for
    pulling sampler

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8 - 9

The passive sampling media (e.g. LDPE) is fixed on the sampler frame. Similar to the MIT samplers, the polyethylene (or other media) is fastened to the frame with exposure occuring in the frame window. The retrieval system is fixed to the sampler frame.

The retrieval system includes a user-specified timed-release mechanism, and the retrieval buoy line.

The assemble frame/retrieval system slides into guides on the deployment system, is lowered to the sea floor, and pushed to a pre-set depth below mudline.

This triggers a release mechanism that allows the deployment system to be pulled back to the boat, leaving the sampler and retrieval buoy in place.

The retrieval system float releases at the user-specified assigned time and date, and

the buoy rises to the surface with the line to the sampler which is pulled in from the boat.

  

Drive-Frame Deployment

  

Time-Release Float Operation



Additional Resources

Passive Sampling Methods

Webinars and Podcasts