Expected power-consumption effect of increasing the
size of a frozen-ground waste containment pro ject at
Ft. Detrick, Maryland
Steven A. Grant1
Introduction
(6.096 m) wide, and 10 feet (3.048 m) deep. The
two frozen-ground walls along the length of the iso-
lated volume were to be installed at 45◦. The two
The Baltimore District of the Army Corps of Engi-
sides would meet at the lengthwise centerline of the
neers was considering installing an artificial ground
project. The end frozen-ground walls would be in-
freezing system for waste isolation at a site in Ft.
stalled vertically.
Detrick, Maryland. The size of the proposed water-
isolation system had increased. This report presents
the cost effect of this change in system size.
Site information
The site had a clay soil. A perched water table was
located at 10-15 feet. For purposes of this report,
a depth to the perched water table of 4 m (13.21
Revised design
feet) was assumed. The depth to groundwater was
not available but was assumed to be greater than
45 feet. Scenarios in which the perched water ta-
The revised design would be 50 feet (15.240 m) long,
ble was 2, 4, and 6 m thick were considered. As
45 feet (13.716 m) wide, and 45 feet (13.716 m) deep.
was conventional, the soil temperature was assumed
The installation angle of the freeze pipes along the
to be equal to the mean annual temperature, which
length of the isolated volume would have to be 63.4◦
in Frederick, Maryland, was 12 ◦C. It was assumed
to achieve this geometry.
that the soil had a porosity of 0.4 m3m-3 and that
unsaturated soils had a volumetric water content
of 0.2 m3m-3. The pertinent thermal properties
Length of freeze pipe needed
used in calculations are presented in Table 1. The
coolant temperature was assumed to be 25 ◦C. At
this temperature, both saturated and unsaturated
The length of pipe needed was based on a 0.1-m-
soils should contain about 0.015 m3m-3 liquid wa-
diameter pipe, placed at 1-m increments around the
ter [Grant et al., 1999]. Water's enthalpy of fusion
perimeter of the system. These increments were
was 337.7 kJkg-1.
smaller than was conventional design practice but
were chosen to reduce the time needed to form the
barrier [Sanger and Sayles, 1979; Andersland and
Original design
Ladanyi, 1994].
The original design for the frozen-ground waste iso-
Original design
lation project was 30 feet (9.144 m) long, 20 feet
The original design would require 18 4.30-m-long,
1U.S.
Army Engineering Research and Development Cen-
ter, Cold Regions Research & Engineering Laboratory, 72
4 3.048-m-long, 4 3.05-m-long and 4 1.52-m-long
Lyme Road, Hanover NH 03755.
pipes. The total length of pipe would be 107.87 m.
1
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