ETL 1110-3-487
1 Mar 98
containing the contaminated soil would be susceptible to leaching. A laboratory analysis was per-
formed on the contaminated soil by the Corps of Engineer's North Pacific Division (NPD) asphalt
testing laboratory. This analysis included performing a Toxicity Characteristic Leaching
Procedure (TCLP) on the contaminated soil. The contaminant levels of the soil varied from less
than 100 to more than 10,000 ppm (EPA 8100 MOD). The NPD laboratory also performed an
analysis using the diesel contaminated soil as part of a cold mix asphalt mixture. The mixtures
produced with and without contaminated soil were constructed using CRD-C 649 and were
analyzed with leachate tests. The CRD method is the standard CE procedure used to produce and
test Marshall specimens and is similar to the American Society for Testing and Materials (ASTM)
test method D-1559. Nine Marshall samples were made from each mixture and allowed to cure at
room temperatures. These samples were divided into groups of three and then tested for Marshall
Stability at 7 and 14 days at room temperature; one group was tested at 60 degrees C
(140 degrees F). The stability values obtained show that an adequate road construction material
could be produced using diesel contaminated soil and a cold mix construction method. TCLP
extract tests on mixtures with and without contaminated materials showed that unacceptable
levels of leaching would not occur.
(4) Design
(a.) The contaminated materials were to be incorporated into an improved gravel surfacing
for the Ski Lodge Road. The existing roadway was approximately 1.3 km (0.8 mi) long with a
gravel surface. The length of roadway that received the contaminated soil base course was
approximately 550 m (1800 ft) long and 7.3 m (24 ft) wide. This road provides access to the
Ravenwood Recreation Area, which consists of the local skiing area and skeet range. The
roadway receives the majority of its traffic during the ski season and there is very little heavy
vehicle traffic.
(b.) The design of the roadway cross-section was intended to maximize the use the available
contaminated and waste materials and provide the Air Force base with an improved gravel
surface. This use of contaminated soil gave the double benefit of providing locally available,
inexpensive roadway construction materials and minimizing waste disposal costs by providing an
alternative to landfill disposal or incineration. The design used was intended to seal the
contaminated material between layers of asphalt materials with a multilayer design. Consideration
of the volume of materials available resulted in a cross-section design consisting of a subbase,
base course, and surface course. The subbase layer consisted of two 150 mm (6 in.) lifts of the
asphalt cement and asphalt contaminated soils from the asphalt lake and a silty-sandy granular
material blended at a ratio of 1:1. The base course layer consisted of a 100 mm (4 in.) lift of RAP
blended at a ratio of 1:20 with the contaminated soil. The base course was stabilized with a CSS-
1 asphalt emulsion. The surface course was a 75 mm (3 in.) lift of RAP also stabilized with a
CSS-1 asphalt emulsion. The planning and performance of this project was done in accordance
with the "Cold Asphalt Recycling" section (pages 14 and 15) of the Alaska Department of
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