6.3.1 Tier II - Leachate Quality Screen

6.3.1 Tier II - Leachate Quality Screen

The Tier II leachate screening procedure is based on equilibrium partitioning

principles and conservative (e.g., environmentally protective) application of

design and operating variables for CDFs (Myers and Schroeder 2000). The

evaluation makes use of site-specific data provided by the user and default values

for pertinent variables to calculate a predicted leachate concentration of

contaminants in groundwater.

A computerized spreadsheet program is available to perform all necessary

calculations. The spreadsheet, along with documentation, can be downloaded as

an ADDAMS module from the USACE DOTS web site at

www.wes.army.mil/el/dots. If desired, equations for manual screening

calculations are available (Myers and Schroeder 2000).

6.3.2 Tier II - Leachate Decision

After consideration of the Tier II leachate partitioning screen, one of the

following conclusions is reached for leachate:

1. Information is sufficient to reach a decision. In this case either:

a. Standards applicable to the intended use of the groundwater (Section

6.1.1) exist for all COC and are met for all COC after consideration

of attenuation. No further leachate evaluation is necessary.

b. Standards applicable to the intended use of the groundwater (Section

6.1.1) are exceeded for one or more COC after consideration of

attenuation, and management actions should be considered. A

decision to implement management actions for leachate, such as

design modification or leachate collection, may require more detailed

information prior to design of such actions. If management actions

are selected, no further leachate evaluation is necessary.

2. Information is not sufficient to reach a decision, which includes cases

where standards applicable to groundwater are exceeded for one or more

COC after consideration of attenuation, and more detailed information is

desired for a decision regarding the leachate pathway. Further evaluation

in Tier III, or management actions as an alternative to further evaluation,

should be considered. A decision to implement management actions for

leachate, such as design modification or leachate collection, may require

more detailed information prior to design of such actions. If management

actions are selected, no further leachate evaluation is necessary.

6.4 Tier III - Leachate Quality Evaluations

Tier III leachate quality testing and modeling consist of a number of steps and

procedures to gather more information on the effects of leachate and to reduce the

uncertainty of the results. All of the steps or procedures may not be necessary to

reach a decision. The testing options and procedures are a function of the

sediment salinity, the possible presence of Non-Aqueous Phase Liquids (NAPLs),

CDF site conditions, and the COC. The Tier III laboratory test results serve to

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Chapter 6

Leachate to Groundwater