STORMWATER

Coastal wetlands provide a necessary buffer for runoff and flooding. Wetland soils are very special as they have the ability to absorb and store a large volume of water, which it then releases as a nutrient-rich trickle. Removing these soil regimes, we are faced with devastating floods. Unfortunately, coastal development is occurring at a rapid rate and many of the coastal habitats have been altered or removed. Since 1900 we have lost about half of our coastal wetlands. The recent storms in the Gulf of Mexico give an example of the importance of a wetland buffer. In Nature, everything tries to stay in balance. Years of drought are usually followed by very wet periods. Hurricanes often provide the equalizer. Recent weather related events have certainly gotten the attention of local, regional and national agencies tasked with protecting life and property. The record number of Category 5 hurricanes and tropical cyclones forming in the Atlantic Basin has a number of atmospheric scientists sharpening pencils and adjusting forecasts. Who knows, in just a few years the Northwest Passage may be available for shipping traffic. The northern shores of Siberia are nearly ice-free in the summer and the permafrost is thawing in areas of Alaska and Canada.

How does any of this have an effect Old Saybrook? This town is at, or just above sea-level. We are subject to major storm surges from the south and the town is adjacent to a river that originates in Canada. And don’t forget all those little streams that are tucked away to the north and west. Small creeks can turn into raging torrents following a major rain event. The Army Corps of Engineers suggested expensive improvements to the Mississippi River levees in the 1980s; just too expensive. A serious review of the flood control and mitigation methods developed and deployed in the Netherlands, need to be studied and employed in low-lying areas. The Netherlands made it a national priority to hold back the North Sea and have successfully protected the “Low Country”. Waiting for the big storm to hit just doesn’t seem like much of a plan. Evacuation plans are being revisited; how would you relocate 5 to 7 million people? A minor accident on any of our Interstate highways can result in hours-long delays. And that is on a “normal” day; how do we address the catastrophic?

These are global issues; do we have any application in Old Saybrook? Zoning or Wetlands commissions expend considerable energy in reviewing applications and decisions are never easy. Denials almost always get appealed.

A number of new products have entered the stormwater mitigation and erosion control marketplace. Everything from plastic drain basin protectors, manufactured fiber products and several unique streambed stabilizing technologies are now available. Interlocking concrete blocks, in combination with filter fabrics, can be used to clearly define a drainage swale or constructed wetland and also improves maintenance accessibility. Old-fashioned storm drains, silt fence and bales of hay will continue to be used. The manufactured fiber products are more resistant to harsh weather conditions and actually promote the growth of beneficial vegetation. Silt fencing requires frequent monitoring as excess silt or damage during construction could compromise the material. In the past, storm drain protection usually amounted to a piece of filter-fabric draped over the grating. This can be effective, as long as silt and debris are kept off of the fabric. Once silt and debris deposit on the fabric, it simply falls through, so much for protection. A better solution is a flexible filter, rigid frame, insert that goes under the grate.

Why don’t we see more of this new technology? Typically, contractors and engineers tend to use the “tried and true” equipment. We are all guilty of resisting change.

On a recent trip, south of the Mason-Dixon Line, I observed a plastic drainage system being installed as part of the road bed construction. The engineer explained that many intersections are low-lying and tend to form large puddles during rain events. Using this under-pavement drain and shoulder drains allowed the stormwater to infiltrate the surrounding soils and runoff much quicker than simply relying on storm sewers. Paper, plastic and other refuse have a tendency to block storm drains when they are needed most. Some cities have to retrieve “man-hole” covers following a rain event. The force of water backing up in a storm sewer can actually lift and transport those heavy covers. (Another reason for not driving through a flooded intersection.)

Separation of solids from the stormwater remains an important feature in modern design. Some applications simply use screens or grates, others have begun to use swirl pattern designs. These devices push the solids to the side, allowing the stormwater to flow through unimpeded. Lifting the cover provides access for maintenance and cleaning. Regardless of the design, a schedule of cleaning and preventive maintenance will be necessary.

Parking lots present a difficult situation. Large impervious areas tend to concentrate stormwater flows. The scouring action will clean the parking lot, however, grit and refuse are combined with the water. By filtering the stormwater and directing the flow into chambers under the parking lot, clogging of the infiltration devices can be minimized and sufficient volume will reduce the impact from runoff. Stormwater draining from a roof should be dealt with in a similar manner.

Have you noticed the number of pervious driveways being installed around town? It seems to be catching on!

Steve Luckett

WPCA Coordinator