International standards group ASTM has released a new method to measure the surface infiltration rates of permeable unit paving systems. The process involves a slow pour of a measured weight of water into a pipe fastened to the paving surface.

The ASTM International recently released a test method is designed to assess the surface infiltration rate of new and in-service permeable interlocking concrete pavements and permeable clay brick pavements.

Known as C1781, or the Standard Test Method for Surface Infiltration Rate of Permeable Unit Pavement Systems, the process involves timing a slow pour of a known weight of water into a 12-inch diameter pipe fastened to the permeable pavement surface with plumber's putty. The infiltration rate is easily calculated using a formula in the test method. The test method also provides guidance on how to locate the pipe on the unit-paving surface to measure infiltration that represents the pattern on the larger pavement area.

The test uses similar equipment and methods in ASTM C1701 Standard Test Method for Infiltration Rate of in Place Pervious Concrete. The similarities between C1701 and C1781 make the test results comparable.

"We are seeing more provincial, state and local permeable pavement specifications require surface infiltration tests to accept new permeable pavements and to evaluate their in-service infiltration for determining surface cleaning," says Craig Walloch, chair of ASTM Subcommittee C15.04 on Research, which helped develop the standard. "Now they have a method with specific guidance for testing unit paving with results that can be compared to that from pervious concrete and porous asphalt."

Walloch said that existing guidelines published by stormwater agencies have used C1701 to test surface infiltration of permeable unit paving. While the results from that test method applied to permeable unit pavement are useful, C1781 provides clear guidance on executing the test on these pavements.

C1781 is available for online purchase from ASTM at https://www.astm.org/Standards/C1781.htm. The standard retails for $42 and ASTM members receive a 10% discount.