Barriers are used to stop or filter runoff--like gravel dams, sock dams, cloth barriers, and filters over storm sewer inlets. But based on my observations of construction sites during storms, I believe that some of these traditional methods are not very effective.
- Locate suitable terraces, within several blocks along the flow path, and gain the cooperation of residents, if possible.
- Before the construction site begins, dig out the entire terraces at selected sites to below street level. If the curb or sidewalks need to be shored up, add gravel.
- Cut two notches in the curb to allow entry (and exit, when full) of water into the terrace depressions.
- Repeat with enough of these terrace basins to handle most of the expected runoff.
- Block any storm sewer entrances along the runoff flow.
- When the construction project is finished, fill the terrace depressions back to the desired depth, and plant with native plants (or whatever the homeowner desires). Organic street sweepings could be used to enrich the soil.
Advantages for construction sites:
- Relatively inexpensive
- Overcomes space or other limitations at the construction site
- More reliable and more complete (100%) filtration of runoff
- Recharges groundwater
- Improves the watershed and neighborhood permanently by leaving a garden
- Flexible and fast--more terrace basins can be built when more capacity is needed.
- Can only be used where slopes and terrain are suitable
- Some residents may object