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3 Simple Ways to End I&I in Collection Structures

3 Simple Ways to End I&I in Collection Structures - Efficiently, Economically, and Perpetually


The U.S. Environmental Protection Agency has deemed that as much as 60% of groundwater infiltration arrives through sanitary sewer manholes. For over 50 years, chemical grouting is one of the oldest techniques used to stop ground water infiltration into sewer collection systems.  


There are three basic methods for sealing manholes. The first, and most basic method is commonly referred to as 'oakum/ soak 'em' and is used to seal leaking cast concrete joints and pipe entry points, and manholes with missing or broken bricks. This method utilizes a water reactive urethane chemical such as Hydrogel SX and jute rope commonly known as oakum, which is mixed together to form a permanent seal. This practice is commonly around pipe interfaces or used when gaps in the structure is present and exhibiting groundwater infiltration.       


A second method utilizes a low viscosity permeation (1-2 cps) AR 800 Acrylate or PR10 ACLM Acrylamide chemical. This technique requires a stainless steel plural component pump that injects the grout under pressure through the manhole (using probes or a packer) into the surrounding soil. The permeation grout does not expand, but saturate the soil immediately outside of the manhole (with a desired gel-time) that permanently stabilizes the soil and creates a barrier against ground water entering the manhole. This can even be done in moisture saturated soils, however a faster gel time may be desired.

The third method utilizes a water-reactive hydrophobic Prime Flex 920 urethane.  This method requires a single-component pump to inject the grout.  When mixed with water, the grout expands under pressure chasing water through the cracks subsequently filling the cracks and voids adhering to the soils outside the manhole.  This hydrophobic chemical binds with the soil to offer greater tensile strengths than chemical gel grouts, thus creating what is commonly know as “grout columns”.  




As mentioned, when as much as 60% of groundwater inflow and infiltration entering through vertical collection structures, the rehabilitation of aging infrastructure has never been so important.  Although chemical grouting can be used as a stand-alone practice, more municipalities are combining this procedure with the rehabilitation of the structures; as these methods require a dry substrate for the application of proposed coating. With the multitude of proactive technologies in the trenchless industry, this time-tested technique of chemical grouting has been the only proven method to remediate inflow and infiltration: AT THE SOURCE.  

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