Expert Advice Series: Injection of Remedial Reagents

ISRR Document Review Section 3.0 – Pre-Design Considerations and Application Related Issues(Will the Target Section Accommodate the Anticipated Reagent Volume Applied?)

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.

This section provides a useful discussion of data that can assist in determining if the ISRR target zone will be conducive to application and acceptance of the remedial reagent volumes anticipated. In short, will the target section accommodate the anticipated reagent volume applied?

A brief discussion is provided on each of 9 varying types of data that can be used to gain a more complete picture of the target zones acceptance capacity. These data in total can assist you in judging the target zones’ ability to accept the application volume and possibly even assist in determining a relative rate of application (fast or slow). I think it’s interesting to note that this discussion incorporates some of the low resolution data that may not be a typical consideration by user/appliers. These data range from the low tech blow counts (soil boring logs) to the latest innovations such as Hydraulic Profiling Tools (HPT) and Cone Penetrometer Technology (CPT) data.  This discussion also provides some helpful logic as well as context for using these various data in order to gain a richer view of the target zone.

The second part of this section discusses some of the important application related issues that must be factored into the Project Managers (PM’s) thinking when considering injection of high volume ISRR’s. If overlooked, these issues may range from a lot of unneeded stress to a costly mistake. Of critical importance is the location of subsurface utilities, I don’t think that this needs much more comment beyond its mention however it is always a consideration and you must call “Dig Alert” two or more days ahead of the application date. The second consideration is the location of previous boreholes. This often overlooked pre-application consideration becomes clearly evident after the 2^nd or 3^rd application point is injected and ISSR materials daylight. This can be a particularly difficult problem with more reactive oxidants or excessively high volume reagents like emulsified vegetable oils etc. Day lighting or surfacing of any reagent can require a significant amount of on-site reactive management. Even though the management of such occurrences is not terribly difficult to implement (I will discuss in upcoming posts) it invariably causes a slowdown in application rate and loss in field efficiency. It’s my experience that if a significant set of older generation boreholes are present on a shallow groundwater site that it’s always a good idea to equip the application team with plenty of bentonite and hand tools to allow proper re-sealing of the older set of boreholes. Alternatively, if these are known to be a likely problem, the proper repair and sealing of these boreholes prior to application can end up saving time and money.

To access this entire section of the ISRR document visit here.