Development of a Waste Disposal Embankment Cover Infiltration Test Cell

摘要

Envirocare of Utah, Inc. (Envirocare) hasrndeveloped and constructed a Test Cell to evaluaternpotential infiltration through the designed cover systemrnover the low-level radioactive waste disposalrnembankments incorporated at the facility. The generalrndesign of the Test Cell follows the recommendations setrnforth in the Alternative Cover Assessment Programrn(ACAP) that is currently funded by the U.S.rnEnvironmental Protection Agency (EPA) to assessrnpotential alternatives to conventional landfill coverrndesigns. The bulk of the Test Cell is below grade withrndimensions approximately 16 feet wide by 28 feet long.rnThe base of the Test Cell is a lysimeter built to the samerndimensions as compliance lysimeters within the disposalrnembankments at Envirocare. The lysimeter collects allrnliquids to a single low point and directs the liquidsrnthrough monitoring instruments within a manhole outsidernthe Test Cell. The lysimeter is constructed to simulate thern?top of waste? condition in Envirocare?s embankments;rnconsequently, the top of the lysimeter is sloped at anrnangle of approximately 2.8 percent, the design top slopernof the embankment. A replica of the embankment cover isrnconstructed directly above the lysimeter. This cover isrnconstructed exactly the same as final cover is constructedrnupon the waste disposal embankments, utilizing the samernQA/QC measures. The cover consists of (from bottom torntop): six feet of compacted clay with a permeability of 1 xrn10~(-6) cm/sec; one foot of compacted clay with arnpermeability of 5 x 10~(-8) cm/sec; six inches of a granularrnfilter layer; one foot of sacrificial soil; six inches of arnlarger granular filter layer; and 18 inches of large gradernerosion protection rock. Permanent monitoringrnequipment has been placed during construction at specificrnintervals throughout the Test Cell. Monitoring equipmentrnconsists of water content reflectometers (WCRs), matricrnwater potential sensors (heat dissipation units; HDUs),rnand temperature probes. The monitoring equipmentrnprovides cross-sectional data of the moisture content andrntemperatures throughout the constructed cover.rnAdditionally, surface water runoff is collected through arndrainage trough and measured in order to perform arnwater balance over the entire Test Cell. To aid in thernassessment, data collected from the site meteorologicalrnstation will be used, including: wind speed, windrndirection, air temperature, solar radiation, panrnevaporation, and precipitation. The data collectedrnthrough this Test Cell will be used to assess thernapplicability of the performance modeling that wasrnaccomplished as part of the original design of thernembankments. Analysis of the data generated throughrnthis Test Cell will be the subject of future technicalrnpapers.