Design Verification Program - Lessons Learned from Pre-Application Assessments at In Situ Remediation Sites

Over the past 20 years, application of remedial substrates has had an uneven track record in terms of performance. Generally, speaking In Situ remedial performance outcomes are the result of multiple site specific technical factors. This program will focus on pre-application Target Treatment Zone assessment steps that directly improve existing design assumptions prior to field application. This program uses field-based assessment methods that provide significant insights into design and application method selection prior to application. Implementing these methods has resulted in improved remedial performance outcomes. The primary focus of this presentation is on identification aquifer characteristics that matter most, that can be documented using traditional field methods and provide the most insight into the remedial design and application programs. Specifically, this presentation will focus on those Target Treatment Zone (TTZ) characteristics that directly affect application programs and ultimately remedial outcomes. 

From a reagent delivery and coverage standpoint, the most important TTZ characteristics are: A) gross soil type B) the nature and extent of the flux zones and C) positional relationship between COC mass storage and transport/flux zone units. Sedimentary processes have a direct effect on the above relationships. These processes directly affect COC mass storage and distribution as well as remedial reagent selection and application methods. To assist design and application teams, a set of routine pre-application “Design Verification” steps have been developed and performed on select project sites (N=100). These steps are used to identify the relationship between COC storage and distribution units within the TTZ.  Identification of these variables has contributed to an overall improvement in application programs and is seen as a key element in higher remedial success rates. 

We will address the use of traditional field-based logging techniques that have been shown to provide valuable information that can be used to steer design and application programs prior to field mobilization. A summary of results to date will be presented.