Moisture Testing in Below-Grade Concrete Wastewater Structures

From JPCL, April 2016

Comment from Jerry Trevino, (5/5/2016, 9:02 AM)

Mr. Nixon, thank you for your perspective with respect to moisture measuring process and procedures when dealing with concrete structures, specifically underground sewerage structures. This highlights the difficulties in coating of industrial and municipal concrete containments, storm and sewer collection infrastructure. Typical moisture transmission in existing structures such as manholes, lift stations, wet wells, etc can better be measured with buckets and a stop watch versus using the ASTM F1869 process. The RH is almost always 95 to 100%. Moisture transmission is typically referred to as infiltration and inflow. Typical infiltration in existing concrete structures are in the 2 to 5 gallons per minute. Structures in outfalls, in lakes and rivers could have much higher rates of inflow and infiltration. Another condition which needs to be considered is the depth of the structure. 8 to 10 feet deep structures can have hyrostatic pressure such that streams of water entering the structure with such force that the streams shoots through the diameter if the manholes and hits the opposite wall. During rain events, the inflow and infiltration could be 10 to 100 times more volume, thus, the overwhelming of waste water treatment plants, where millions of gallons of sewerage contaminated water are released into creeks, rivers and lakes. The fact of the matter is that all these structures need to be coated and lined to stop the infiltration. I would venture to say that 99.9 percent of these existing structure have never been externally waterproofed.

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