4    POND CLOSURE USING IN SITU SOIL STABILIZATION:
A CASE HISTORY
Virgil A. Paulson, Project Engineer
Gary J. Schnettgoecke, Project Engineer
B&V Waste Science and Technology Corporation
Kansas City, Missouri 64112
The wood-preservation industry was one of the first targets for remediation following passage of
state and federal hazardous waste regulations. This paper describes the authors' experiences in accomplishing a remedial design and construction of a pond closure at a wood-preserving site under those
regulations.
A client of our firm operates a manufacturing facility in northern California that includes a wood-
preserving operation. When this operation was added to the facility, a storm water collection system
and a 1-1/2-acre surface impoundment (pond) were also constructed to control runoff from the large
paved area of the site. The general layout of the site is shown on Figure 1. The pond was designed as a
zero-discharge retention facility that relies on evaporation and percolation in the dry season to
manage the runoff collected during the wet season. The pond was a cut-and-fill earthen structure
constructed of native materials with 8-foot-high compacted clay berms. Figure 2 shows a simplified
cross section of the pond, including the general soil geology and relative water table beneath the
structure.
When state and federal regulations controlling designated hazardous substances were implemented,
the client was required to eliminate the pond. The initial regulatory concern was the potential for pond
waters to contaminate the ground water, and the California Water Quality Control Board sought to
close the pond under the California Toxic Pits Control Act. A water treatment plant was designed and
constructed to manage storm water in place of the surface impoundment, and the pond was dewatered
and removed from service. This action relieved the immediate concerns of the Water Quality Control
Board, and the California Department of Health Services (DHS) then assumed the role as the lead
regulatory agency for closure of the pond. The DHS began negotiations with the client for closure of
the pond under the California Hazardous Waste Regulations (California Administrative Code Title
22). These regulations are essentially the same as those established for the federal Resource Conservation and Recovery Act (RCRA) in 40 Code of Federal Regulations (CFR) 264. The regulations allow a
surface impoundment to be closed either with the wastes remaining in place or with the wastes totally
removed from the site. Both options require that a closure/post-closure plan be prepared describing
the actions to be taken to close the facility and to monitor the site following closure. A plan was
submitted to the DHS indicating that the closure would be accomplished without removal of the
wastes.
The first step in the process of designing an acceptable closure was an extensive site investigation,
including collection of sediment and soil samples in and around the pond. The analytic results of the
sampling program were then incorporated into a detailed feasibility study that was to support the
closure option to leave the wastes in place. This study, entitled "Engineering and Environmental
Analysis of Storm Water Retention Pond Closure Alternatives" (E&EA), evaluated the available
options for closing the impoundment and established the criteria to be followed in the closure design.
A critical element in closure design was that all materials exceeding hazardous waste levels must be
managed. California regulations define hazardous waste in several different ways. The two applicable
definitions for this closure action are as follows:
• Waste material has a total contaminant concentration exceeding a designated Total
Threshold Limit Concentration (TTLC).
• Waste material has a soluble contaminant concentration exceeding a designated Soluble
Threshold Limit Concentration (STLC).
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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