Implementation of In Situ Activated Carbon
Remedies at Contaminated Sediment Sites

CONSTRUCTION

ARTICULATING CONVEYOR

Telescoping-articulating conveyor (tele-belt) have been adapted for application of aggregated activated carbon (e.g., SediMite, Aqua-Gate+) for projects featured in the Case Studies web page. Additional sites where a tele-belt conveyor as used include a pilot study on the Lower Columbia Slough, in Portland, OR (ODEQ, 2016), and a permeable active carbon cap installed at River Mile 10.9 on the Lower Passaic River (Hicks and Collins, 2017).

Site

Contaminant

Year Constructed

Project summary

Target AC

Delivery Methods

Project Web Link

AC Projects Completed in North America

USN Hunters Point San Francisco Bay, CA

PCBs & PAHs

2015

1 acre pilot study that includes ca 0.5 acres of SediMite and 0.5 acres of AquaGate+PAC.

4 - 6 %

Telebelt ®

USN Hunters Point Case Study

AC Placement at the PSNS
The remedial demonstration project at the Puget Sound Naval Shipyard Pier 7 (PSNS) is representative of tele-belt method for AC deployment. At PSNS the test area required placement in an open-water area, and an under-pier area. The engineering design specifications required the placement of 2 inches of AquaBlok® PAC. The site contractors developed the method for placing the material across the open and under-pier areas (click here to view specifications), and prior to onsite placement tested the method upland on a parking lot.

The AquaBlock+PAC® was placed in both open berthing and under pier areas from a tug-operated, moored barge that contained the staged product packaged in "Super Sacks". A backhoe loader moved each bag to a hopper feeder, and a truck-mounted conveyor belt-type (Telebelt®) broadcast conveyor system. The broadcast application obtained a rapid, relatively uniform placement of about 143 tons (130 metric tons) of product over the target area. The equipment was able to place the product both in the open access berthing area and under the pier by accessing the under-pier areas between existing pilings during low tide.

VIDEOS

Once the barge was moored in the desired position, distribution of the product occurred relatively quickly, resulting in cycle-time of about 3 min/sack to distribute the product. A video link showing the placement methods is provided above.

Navy divers were on site to observe placement of the final two sacks during daylight hours. Diver observations of product delivery showed that the small pebbles were resistant to the current velocities and sank slowly to the bottom settling on the existing bottom substrate, without any untoward impact to sea life on the bottom, such as sea anemones, sea stars, crabs, and flat fish. No turbidity plumes associated with the placement were observed. A video link showing the Aquablok+PAC falling through the water column is provided above.

Diver surveys, sediment cores, and SPI camera monitoring of the placement area showed that the PAC covering had released from the aggregate, as the light-colored aggregate was plainly visible on the seafloor. Initial observations indicated that the amendment was placed effectively over the target area; however, variation in thickness was observed and there was some overspray or drift of the amendment slightly beyond the edge of the target area. A video link showing the post placement diver survey is provided above.


AC Placement at USN 2015 Hunters Point
The process for placement at the USN 2015 Hunters Point pilot study was similar to the PSNS placement. For the pilot project, both SediMite® and AquaGate+PAC® were placed by placing the aggregate AC into a hopper that fed the articulating conveyer-belt. To confine the placement of material, a special shroud was constructed to funnel the AC directly under the end of the belt, where a GPS receiver was located. The GPS allowed the operator was to "see" the placement path using commercially-available navigation software to plot the conveyor track lines.




AC Placement at Mirror Lake
A tele-belt system was also used at the Mirror Lake Remediation and Restoration project to place SediMite® over PCB-contaminated sediments. Additional detail may be found at the Mirror Lake Case Study page.




Additional Resources
Installing an Activated-Carbon Sediment Amendment at the Puget Sound Naval Shipyard and Intermediate Maintenance Facility, Bremerton, WA. Johnston et al, 2013. Battelle Seventh International Conference on Remediation of Contaminated Sediments.

Demonstration of In Situ Treatment with Reactive Amendments for Contaminated Sediments in Active DoD Harbors. ESTCP Project ER-201131.

Pilot-Scale Performance of In Situ Treatment with Reactive Carbon Amendments for Contaminated Sediments at an Active DoD Harbor Site. Webinar on the PSNS pilot project by Dr. Bart Chadwick. December 2016.

Hunters Point Naval Shipyard Work Plan for the Demonstration of Activated Carbon Amendments. US Naval Facilities Engineering Command Southwest. May 2015.

ODEQ 2016. Pilot Study Implementation Report Lower Columbia Slough - Pacific Meats Cleanup Site Portland, Oregon ECSI No. 145. Oregon Department of Environmental Quality. January 2016

Hicks and Collins, 2017. Modeling and Construction Overview for Passaic RM 10.9 Active Cap. Poster Presentation at the 2017 Battelle Sediment Remediation Conference.