Case Studies: Full-Scale Operations and Delivery Systems - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 348

13.4.1.5 QC and Results

Quality control samples were taken every 1000 yd 3 to ensure effectiveness of the
treatment and compliance with regulations. Typical results of TCLP testing of the
treated soil are shown in Table 13.1, along with the raw waste analyses and the
regulatory limits imposed upon the project. Routine test results on the Q.C. samples
consistently met the compliance standards applicable in 1989 for this project. The
treated soil had an unconfined compressive strength of greater than 1.0 ton/ft 2 . Other
pertinent data on the project are:

Volume Treated: 48,700 yd 3

Treatment Rate: 2000 yd 3 per day

Time: 1989

Treatment Cost: $67 per yd 3

Disposal Method: Engineered backfill on-site

The project was successfully completed and the site is now a county park.

13.4.2 C ASE S TUDY #2: I N S ITU S TABILIZATION OF M IXED W ASTE

C ONTAMINATED S OIL 5

13.4.2.1 Background and Purpose

The X-231B Unit at a Department of Energy (DOE) facility at Portsmouth, Ohio,
was used from 1976 to 1983 as a land disposal area for waste oils and solvents. The
soil consisted of subsurface silt and clay contaminated with up to 500 mg/kg of
volatile organic compounds (VOCs) (primarily trichloroethylene [TCE] and other
halocarbons) and lower concentrations of lead (Pb), chromium (Cr), uranium 235
( 235 U), and technetium 99 ( 99 Tc). Ranges of contaminants at subsurface depths of
up to 5.4 meters are given in Table 13.2. The shallow groundwater was also con-
taminated, with TCE well above drinking water standards. Part of the Unit closure
required reduction of VOC mass in the 0- to 6.6-m depth range while controlling
the leachability of heavy metals and radionuclides. The X-231B Technology Dem-
onstration project initiated at Oak Ridge National Laboratory (ORNL) by DOE and
Martin Marietta Energy Systems, Inc. (MMES) in November 1990 evaluated in situ
treatment at the site. Three treatment processes — vapor stripping, chemical oxida-
tion, and S/S — were evaluated in treatability studies at bench and pilot scale prior
to the full-scale project demonstration being conducted. This case study documents
the work done on S/S. Design, implementation, and operation of the S/S process
were awarded to Chemical Waste Management, Inc. (CWM) in Columbia, SC, and
Millgard Environmental Corporation (MEC) of Livonia, MI.
Cement-based S/S techniques have been widely used for remediation of soils
contaminated with heavy metals, but many have questioned whether organic con-
taminants can be effectively stabilized in a cement-based grout. In addition, high
concentrations of organics are known to interfere with cement solidification pro-
cesses. However, recent laboratory research has indicated that specific organic com-
pounds can be effectively immobilized in cement-based systems. 6-8