The Challenges
Members of the 21st Civil Engineering Group and base engineer Fred Brooks realized the status quo was no longer acceptable and something innovative had to be done to correct this problem. All agreed there were limited options available and a number of constraints. The affected area contained many older buildings which drained onto Paine Street. Down spouts ran directly into flat areas, causing minor flooding in the low lying areas around the buildings.

Upon final review, the best possible option for detention, flow control and cost was the use of a permeable interlocking concrete paver with an aggregate storage layer.

A multitude of drainage issues including standing water and rutted pavements in areas not designed for water can cause nightmares for any engineer. This is precisely what was occurring on Paine Street at Peterson Air Force Base.

The Pavers
After extensive research, Brooks chose the Eco Priora?EUR??,,????'?????????????? produced by Pavestone Company, Colorado Springs. The pavers, licensed through Uni-Group USA, meet or exceed ASTM C-936 specifications criteria for MR 5.1 and 5.2, Materials Resources, Regional Material.

The design (drainage) area incorporated 35 acres which was primarily pavement and given a curve number of 91, medium industrial, indicative of Peterson AFB. The 21st Civil Engineering Group calculated a time of concentration of 50 minutes, the time it would take for precipitation to travel from the furthest extent of the drainage area to an outlet source.

Project specifications called for the 3 1/8 inch thick Eco Priora?EUR??,,????'?????????????? paver, installed on a 2-inch bed of #89 stone, a 4-inch lift of #57 stone and a 6-inch lift of #2, which was mixed with recycled asphalt from the original pavement. As the area would see traffic and provide parking for the buildings, a 500x geo textile was included between the #2 and sub-base. The clean, crushed rock was then compacted to 95% (modified Proctor compaction test) over an existing silty/sand subgrade.

Eco-Priora ?EUR??,,????'??????????????
The joint profile of the permeable interlocking concrete pavers allows surface water to infiltrate into the pavement and its sublayers. With initial permeability average flow rates of over 100 inches per hour, the pavers, even with extended use, will still meet the majority of current stormwater management plans (SWMP).

A portion of Paine Street was serviced by a storm sewer system which was at capacity, while the other discharged directly into Sand Creek. They were unable to increase the discharge into the creek without a method of controlling the release rate. As the surrounding area was completely developed, a detention pond was impossible, while a complete storm sewer upgrade and replacement was too expensive.

Cost Justification
In tough economic times, everyone must make difficult choices on how to allocate funds, so protecting and restoring the environment in a cost effective way is a key determining factor. Cost justifications have to be made, so looking at the big picture is not only wise, but a fiscal responsibility.

Permeable paver installation typically cost more than standard asphalt, but has the advantage of reducing additional stormwater storage and will have lower maintenance costs. ?EUR??,,????'?????<