news from the waterfront by Tim Matson
In the Northeast, we're coming out of one of the wettest summer/fall seasons on record. The effect on pond owners has been generally positive, especially after the previous two summers of record droughts.
The rain has recharged springs, wells, aquifers, water tables, etc. For most ponds, the result has been full basins. Some pond owners did encounter alga blooms, often due to nutrients washed into the ponds by all the rain. Overcast skies causing low oxygen levels due to diminished photosynthesis may have added to the effect. Excessive rain also caused some turbid waters.
The rain hasn't helped contractors. It's been tough to build a pond or do repairs in steady rain on saturated soils. Pumps have been needed. Many jobs have been prolonged or postponed.
As I write these pondology notes, I realize that one of the best things about doing design and consulting work is the chance to see so many new ponds, successful or not. I thought I'd pass along some recent observations which might be useful for pond owners and builders.
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When I am consulting on a project, I always recommend that land owners hire contractors with thorough pond building experience. This summer I saw a few examples of failed ponds to confirm that. One was a small shallow pond built on ledge with a plastic liner. It didn't work out because the pond was too shallow, lacked sufficient inflow, and the second- hand liner leaked. The pond will have to be relocated, and a better source of water developed.
On a larger scale, another pond built on ledge turned into an expensive failure because of poor dam construction and leaks through the ledge. This pond would have been a challenge for even the most experienced contractor, and certainly would have stood a better chance if an engineer had been engaged to help with the plans and permitting. Beware ledge!
On the other hand, flaws sometimes bring unexpected benefits. Another pond I worked on had a plugged overflow standpipe. Consequently the water level rose a foot and then stabilized. The owners were delighted with the new effect. The pond increased in size and depth. They now plan to remove the obstruction and add an extension to the standpipe to permanently establish the new water level. The dam is not any more vulnerable to flooding because of the capacious standpipe and emergency spillway.
I find that many ponds with high freeboard would be more attractive if the water level were raised -- or the dam lowered. However, when reducing freeboard keep in mind that there must be a large enough primary and/or secondary spillway capable of handling 50 or 100 year floods, without overtopping the dam!
That's it for this edition of pondoIogy. I'll be posting more pondology notes periodically.