Pondology news from the waterfront by Tim Matson


It doesn't happen often, but for some pond owners the day may come to subtract a pond. There are several basic reasons to erase a pond. The pond may have been built poorly, with no chance to fix, or at least no affordable fix. The pond watershed may have changed enough to affect the pond negatively, hence the need to remove. Or the pond may have been built illegally, usually in violation of wetland protection rules or municipal zoning laws, and need to be refilled.

Recently, I've seen a few ponds in need of erasing, and they support the reasons mentioned above.

One pond was built in the days before the era of strict wetland protection rules. It was built with a direct stream feed, and in fact performed well for decades. One problem it never had was lack of water. But it was a small pond and the stream was big, and it got bigger. A couple of elements figured into the stream enlargement. Climate change, especially here in the northeast, triggered an increase in general rainfall, and periodic flooding. The result was an increase in stream erosion and hence sediment loading in the pond. Along with sediment loading came several flood incidents that caused the pond to breach
the dam. Another negative effect on the pond was a change to the upstream watershed. Logging by an uphill neighbor removed trees which had previously wicked up rainfall and snowmelt; the result was an increase in watershed runoff.

At first the owners tried to deal with the sediment loading with periodic cleanouts. They also lowered the pond waterlevel to prevent the pond from breaching the dam. But after more than a decade of sediment cleanouts and flooding, it became clear that the pond had to go. The plan is to fill it and restore the stream.

Another cause for pond removal is illegal construction. For instance, siting the pond in a protected wetland. The ideal site for a natural (earthen) pond is often in an area with ground water near grade, or too near (or in) a stream. Unfortunately such a location is likely to also qualify as a protected wetland. A land owner planning a pond in a wet area should make sure the pond does not need wetland permitting. Check with the state DNR agent or the US Army Corps of Engineers to find out. Other factors that may trigger pond permitting include pond water volume, dam size, and spillway design.
Build a pond without permitting in a protected area, and you may have to remove the pond and restore the land.

Another reason for pond removal is flatout failure. This usually means the pond doesn't hold or receive sufficient water to maintain a healthy waterlevel. Ways to overcome this might include installing a liner and/or adding supplementary water from a well or other source (roof runoff/watershed drainage). But these remedies can turn out to be expensive and uncertain, so to be practical the pond is removed. Failure can also result from poor construction that is impractical to correct.

Finally, pond failure may be due changes in the upstream watershed. The runoff water supply might be diverted, polluted, or altered in some way that spoils the pond supply.



December 1, 2017

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