Port of San Diego Treats Dredged Material with Solidification/Stabilization

Use of cement-based S/S allowed the Port of San Diego to safely and economically dispose of contaminated material dredged from the harbor. This project involved dredging, treatment, and disposal of approximately 12,500 cubic meters of sediment at the Tenth Avenue Marine Terminal. The dredged material was primarily storm drain runoff sediment from a storm drain outfall. Normal ocean disposal of the dredged material was prohibited since the sediment was contaminated with below hazardous levels of copper, zinc, lead, pesticides, and polychlorinated biphenyls (PCBs). A confined disposal facility (CDF) for the material was also not desired due to space constraints. S/S allowed disposal in a local municipal solid waste landfill (MSWL).

Contaminated sediment was dredged and placed into barges. Portland cement slurry was mixed into the material by a rotating mixing head while the material remained in the barge at port-side. S/S-treated material was removed from the barges and trucked to the MSWL. By operating two barges simultaneously the work was accomplished in only 30 working days. MSWL disposal criteria included a pH below 12 and above 2 and no free liquids per Paint Filter Test. More.

S/S Remedies Coal Tar Contamination at Appleton MGP Site

S/S was recently used to address contaminated soil at the site of a former manufactured gas plant (MGP) in Appleton, Wis. Cement and other reagents were mixed into coal tar-impacted soil while the soil remained in-place. This in-situ mixing was accomplished using large (12- and 8-foot) diameter reagent-injection soil -mixing augers as well as backhoes.

Coal tar is a by-product from the MGP process. S/S treatment is becoming increasingly popular for treatment of impacted soil at former MGP sites. At Appleton, over 1000 soil mixing columns were treated, some to a depth of 15 feet. In-situ S/S treatment was selected as a remedy for the site that is protective of human health and the environment and cost effective.

For more information on the project click here, or contact Williams Environmental Services, a Compass Environmental company.

What kinds of contaminants can be treated by S/S?

Cement-based S/S has been used to treat a wide variety of contaminants including inorganics, such as heavy metals like lead and arsenic, and organic contaminants, like creosote and petroleum products. The ability of S/S technology to treat such a wide range of hazardous constituents is one reason why S/S has been used to treat over 25% of the U.S. Superfund sites where the sources of contamination have been addressed.

Selecting the Right Performance Standards for the Project

Of the myriad of testing procedures written that can be used in S/S performance testing, which ones are appropriate for your project? Performance standards should be selected on the basis of the final disposition of the treated material. For example, consider in-situ S/S treatment of contaminated soil at former manufactured gas plant sites. This method of treatment protects human health and the environment by reducing transport of contaminants (leaching) from the treated area. This is accomplished by reducing the hydraulic conductivity of the treated material.

Typical hydraulic conductivities for S/S-treated wastes range from 1X10-4 to 1X10-8 cm/s. EPA recommends a hydraulic conductivity of less than 1X10-5 cm/s for treated waste. Durability of the in-situ treated material can be evaluated by using tests for unconfined compressive strength, wet/dry durability, and, depending on climate and cover design, freeze/thaw durability.

In another case, where treated wastes are destined for landfills, the Toxicity Characteristic Leaching Procedure or Synthetic Precipitation Leaching Procedure and Paint Filter Test may be appropriate. For your project, consider the final disposition of the material when setting performance standards. One very good reference on S/S performance testing is EPA’s publication titled Stabilization/Solidification of CERCLA and RCRA Wastes.

Case Studies Now Available in Print

New Bedford Harbor Superfund Site Area D Bulkhead Project (SR850)

Solidification/Stabilization Treatment of Dredged Material from the Port of San Diego (SR851)

PCA will be exhibiting or presenting papers at these conferences:

• Joint Services Environmental Management Conference
  April 11-14, 2005, Tampa, Fla.
• Deep Foundation Institute Annual Conference
  September 22-24, 2005, Chicago, Illinois


• Canadian Brownfields 05
  October 13 - 14, 2005, Ottawa, Ontario, Canada
• Remediation Technologies Symposium (RemTech 2005)
  October 19-21, 2005, Banff, Alberta, Canada
• Brownfields 2005
  November 2-4, 2005, Denver, Colorado

For more information or to register, click on conference name.