ISRR Document Review Sections 2.0 and 3.0 – In Situ Remedial Reagent Fluid Injection Mechanics and Pre-Design/Application Related Considerations
Commentary by Craig Sandefur, VP Technical Services, REGENESIS
Introduction: This series of blog entries focuses on a key technical report entitled: Subsurface Injection of In Situ Remedial Reagents (ISRRs) within the Los Angeles Regional Water Quality Control Board (LARWQCB) Jurisdiction. The report was spearheaded by REGENESIS in cooperation with the LARWQCB and the ISRR working group. The primary objective of the ISRR Working Group was to compile general tools and best practices into a reference manual to be used during the planning, design, and field implementation phases of ISRR projects. ISRR projects generally include soil and groundwater remediation via: in situ chemical oxidation, enhanced aerobic bioremediation, enhanced anaerobic bioremediation, in situ chemical reduction, etc. In addition, the Working Group also sought to convey that the safe and successful application of in situ remedial reagents requires a proper understanding of site characteristics, delivery methods, application equipment, and monitoring methodology. Finally, this technical document was also intended to guide practitioners of reagent based in situ remediation in performing cost-effective remediation projects while ensuring minimum impact to the public. Intended users of this technical report include regulators, consultants, and appliers of in situ remedial reagents.
Discussion: This review will begin in Section 2.0 of the ISRR Document with and cover Fluid Injection Mechanics as well as some of section 3.0 which emphasizes Pre-Design and Application Related Considerations. Section 2.0 provides a concise description of how fluid moves when injected in the saturated zone. It provides the reader with a specific discussion as to why fluid mounding occurs upon injection and why its dissipation rate is important in understanding how much remedial reagent the aquifer is likely to “accept”. This section also provides the reader with an introductory review of the mechanism of “day lighting” or “surfacing” of remedial reagents. The discussion in Section 3.0 is devoted to Pre-Design and Application Related Considerations that revolve around assessing the hydraulic characteristics of the target zone. In the pre-design discussion the focus is on relevant data, evaluation and testing that can be used by the reader to gain insight on the target zones relative ability to accept remedial reagents. In many cases evaluation of one or a few of these parameters and/or tests will yield significant insight into the likelihood of application success. The suggested data for collection range from the low-cost, low-resolution (such as review of existing boring log blow counts and/or GW well recharge rates) to dedicated high-resolution in situ logging methods, e.g. Hydraulic Profiling Tool (HPT), Cone Penetrometer (CPT). As personal note, I have had some direct and fairly recent experience with in situ logging technologies and I have found them to be very effective in defining the intervals that should most likely be targeted for remediation. Finally, this section concludes with pre-application recommendations that anyone contemplating ISCO should strongly consider since these lessen the likelihood of damaging subsurface infrastructure and/or “day lighting” remedial substrate. These recommendations are to locate subsurface utilities via a pre-application field inspection and use of Dig Alert and locate and inspect the seal of as many assessment or remediation boreholes as possible. Any borehole found to have inadequately seals should be re-sealed prior to beginning an in situ chemical oxidation field application program. This will potentially save the project manager a substantial number of down time hours. Finally, it is always advisable to obtain any injection permits (as necessary) from your local or state regulatory agency. In the next blog entry of this series I will continue the discussion on Sections 2.0 and 3.0 highlighting some of the more salient points regarding injection methods for the delivery of in situ remedial reagents.
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