Although the new permeable pavers on Main Ave are garnering attention for their new aesthetic appeal, they were not just installed for their looks. Their major purpose is to provide water quality treatment to the storm water runoff. They are capable of doing this because of a few reasons.
Read more from the Clinton City Engineer’s Office (image included of the permeable paver included
Normal pavement does not allow for any infiltration and simply conveys the rainwater to the gutter, and into the storm sewer system. This is often a filthy process which encourages pollution to the downstream discharge point. The storm water picks up contaminants along the way to the storm water intake and these are carried all the way to the river.
These new pavers are permeable, which means they allow water to flow through them. Also as you will notice there are gaps between the pavers called ‘Permeable Joint Material’, this space between the pavers themselves allows water to infiltrate into the ground below. The ground below the pavers is the next item that makes this new permeable pavement system better suited for handling storm water. In Figure 1, this aspect is called the Open-Graded Bedding Course, Base, and Sub-base.
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These aggregated gradations gradually increased in size below the surface. The term ‘open-graded’ refers to a rock that is free of ‘fines’. Fines, like sand, are small particles that when added fill the space between the rocks. These are removed from the base courses because they prevent the rain water from easily passing through the three bases. Once the storm water has traveled through all three gradations, the runoff is conveyed to the storm sewer system via a plastic underdrain pipe. The benefit of this system is threefold.
1. The storm water is treated as it passes through this filtration system, as heavier pollutants settle out into the base layers, providing a much cleaner runoff than a conventional street drainage system. The system on Main Avenue is able to treat up to a 1.25” rain event. The discharge into the Mississippi will be much cleaner due to the treatment capabilities of this project.
2. A percentage of the storm water runoff will actually permeate through the drainage system and into the groundwater table. This will reduce the volume of runoff directly into the river, thereby reducing pollution.
3. The open graded base material beneath the pavers provides a storm water detention benefit. That is, the peak runoff volume from the drainage basin will be reduced due to the temporary storage effect of the underlying open graded base.
Permeable Paver (Brick) Maintenance
FAQ about Maintenance:
1. Will the bricks be pulled up by my shovel or snow plows?
a) A shovel will work just fine. In a light snowfall a broom might be an equally effective alternative to a shovel. Snowplows should attempted to main approximately 1” clearance from the top of the pavers. Additionally a Rubber/Teflon guard or similar alternative attached to the bottom of the blade is highly recommended. The remaining 1” of snow should easily melt and drain as discussed above.
Please do not hesitate to contact the City Engineering Department with any questions about snow removal on these permeable paver surfaces.
2. What about salting the area? Will that reduce the systems effectiveness?
a) You are absolutely able to spread salt on the permeable pavement system. However, the use of sand, grit, or ash is prohibited. Material with fine grains such as these three will plug the void spaces between the pavers and render the system useless. Prohibiting the use of these materials is for the same reason that we use an open-graded rock base.
3. Are there any other practices that can be administered to maintain the pavers?
a) Keeping the surface clean in general will help to ensure that this system will be effective for a long time to come. Small tasks like keeping the surface free of sediment like dirt and sand, or the excessive buildup of leaves will help maximize the paver’s effectiveness.
4. What will the city be doing to maintain this system?
a) The city will be performing regular inspections of the new permeable areas along Main Ave. It will be checking to make sure the surface is sediment free and will address areas with sediment build up. Regular checks following rain events will ensue to check for dewatering between rain events. There will also be checks to be sure the pavers surface is holding up over time and not deteriorating.
Activity Schedule
Ensure that the permeable surface if free of sediment Monthly & After Rain Events
Check to make sure that the system dewaters between storms
Ensure surface is clear of debris As needed, based on inspection
Vacuum sweep permeable surface to keep free of sediment Semi-Annually
Inspect the surface for deterioration or spalling Annually
Please contact the Engineering Department at 563.244.3423 with any questions.
