In situ chemical reduction using calcium polysulfide
- Total of 40 injection well points installed along an embankment, each 10 ft apart to allow for a 5-ft radial distribution of reagent from each well.
- Wells installed to depths ranging from 5 to 25 ft.
- Treatment performed first in western portion of embankment area, followed by eastern portion.
- Total of 56,800 gallons of calcium polysulfide reagent (18% solution) injected.
- Additional area (4 injection points) on western embankment added to in situ treatment area.
- Post-treatment soil borings collected from locations of pre-treatment borings and analyzed for total chromium and lead (off-site laboratory) and field screened for hexavalent chromium.
One Congress Street, Suite 1100 (HBR)
Boston, MA 02114-2023
Telephone: (617) 918-1278
696 Virginia Road
Concord, MA 01742
Telephone: (978) 318-8220
Weston Solutions, Inc.
37 Upton Dr.
Wilmington, MA 01887
Telephone: (978) 657-5400
GZA GeoEnvironmental Inc
27 Nack Road
Vernon, CT 06066
Telephone: (860) 858-3111
Chromium, zinc, and lead
1994: Soil chromium concentrations of 100,000 mg/kg, and surface water hexavalent chromium concentration of 210 µg/L. Zinc concentrations above ambient water quality criteria.
1999: Total chromium in soil as high as 129,000 mg/kg and hexavalent chromium as high as 31,000 mg/kg in surface soils located on residential property, the embankment, and areas adjacent to the pond, and levels of total chromium as high as 10,800 mg/kg in soils and sediments in the culvert and cove areas.
Chromium-laden pigment from former paint factory used as fill material for improving railroad embankment around the culvert.
Type/Quantity of Media Treated:
Soil; approximately 1,025 cubic yards treated in total.
Purpose/Significance of Application:
In situ treatment of chromium-contaminated soils at a railroad embankment where excavation of soils deeper than 4 ft was determined not to be practical or safe due to slope stability and structural concerns.
Regulatory Requirements/Cleanup Goals:
Non-binding goals for treatment: hexavalent chromium - 200 mg/kg (total) and 1 mg/kg using the Toxicity Characteristic Leaching Procedure (TCLP).
Post-treatment concentrations in the western portion of the embankment:
- Hexavalent chromium: zero to 5,600 mg/kg (with pre-treatment concentrations as high as 11,400 mg/kg)
- Total chromium: 140 to 67,000 mg/kg (with pre-treatment concentrations as high as 97,000 mg/kg)
- Total lead: 24 to 11,000 mg/kg (with pre-treatment concentrations as high as 32,3000 mg/kg)
Post-treatment concentrations in the eastern portion of the embankment:
- Hexavalent chromium: zero to 5,000 mg/kg (with pre-treatment concentrations as high as 11,700 mg/kg)
Total chromium: 92 to 35,000 mg/kg (with pre-treatment concentrations as high as 59,000 mg/kg)
Total lead: 23 to 220 mg/kg (with pre-treatment concentrations as high as 440 mg/kg)
Total cost of approximately $119,719.
- EPA noted that cost for calcium polysulfide injection was $69,296, plus about $13,900 for ERRS contractor labor (injecting reagent), in addition to $36,523 paid to GZA Geoenvironmental, Inc., for installing the injection wells and collecting pre- and post-treatment soil borings.
The Morses Pond Culvert Site is located in Wellesley, Massachusetts. The southern portion of the site includes an earthen railroad embankment, divided by a culvert into eastern and western portions. It is suspected that chromium-laden pigment from a former paint factory was used as fill material for improving the embankment and was the source of chromium contamination at the site. Due to slope stability and structural concerns with the steep embankment area, in situ chemical reduction using calcium polysulfide was selected as the remedy for treating chromium-contaminated soil at the site.
The injection system consisted of a total of 40 well points installed to depths ranging from 5 to 25 ft bgs. A total of 56,800 gallons of calcium polysulfide reagent was injected, treating 1,025 cubic yards of soil. The non-binding goals of treatment for hexavalent chromium were 200 mg/kg and 1 mg/kg using the TCLP. Post-treatment hexavalent chromium concentrations ranged from zero to 5,600 mg/kg in the western embankment, and from zero to 5,000 mg/kg in the eastern embankment. Total chromium concentrations after treatment ranged from 140 to 67,000 mg/kg in the western embankment, and from 92 to 35,000 mg/kg in the eastern embankment. According to the work plan for the site, calcium polysulfide was selected over ferrous sulfate for this application for several reasons, including that less calcium polysulfide would be needed compared to the ferrous sulfate. The total cost for the treatment was approximately $119,719, including $69,296 for the calcium polysulfide, $13,900 in labor costs, and $36,523 for installing the injection wells and collecting pre- and post-treatment soil borings.