ISRR Document Review Section 4.0 – Injection Specific Design and Safe Application
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.
Section 4: This section focuses on injection specific design and provides the reader with useable recommendations for the safe application of ISRR. This section provides some insight into using a site specific aquifer characteristic as derived by various methods in the derivation of maximum pressures. It is very important to keep in mind that every application is site specific. Many times the success or failure of an application is a result of the applier’s ability to “artfully blend” scientifically derived aquifer characteristics with instinct and previous experience.
Sub-sections 4.1 and 4.2 provide a discussion as well as equations for calculating maximum application pressures for various injection programs. This section also provides rules of thumbs that should be used with these equations to derive a “not to exceed fracture pressure” for a given targeted aquifer section. This is followed by a set of specific recommendations for injection of substrates and includes a table that provides the user with recommendations on soil type specific targets for application base on:
- Pore filling
- Injection solution percentage
- Rates (volume per minute)
- Pressure (psi)
- Point Spacing
In Sub-section 4.3 the reader is provided some details on how pre-application site testing can help to get a better handle on the site specific conditions associated with application of a given ISRR. This section provides some solid advice on how to perform a clear water test in order to identify or rule out hydraulic limitations of high volume ISRR’s.