news from the waterfront by Tim Matson


I keep encountering folks who are considering purchasing property with a pond, or maybe just bought a place with a pond, so the timing seemed right to revisit "How to Buy a Used Pond", from the original Earth Ponds. I intended to write another installment on keeping a pond history, but looking over October's Pondology I see I pretty much covered the bases. Well... not quite. I will say one more thing about researching your pond ancestry. Be careful what you dig up! If your pond has some "issues" with old piping or other structural elements, yes, it might be helpful to find the old plans to aid in repairs. But if your search leads to government agencies that may have had a hand in getting the pond built, and they discover these flaws, well, who knows what hornet's nest you might stir up. Just sayin...

And now on to How To Buy a Used Pond!

At first glance buying land with a pond seems like a good way to shortcut the effort and risk involved in building one from scratch. No preliminary siting work, no searching for the right contractor, no hassles over permits or machinery chewing up the yard. Perhaps this explains why a house with a pond often sells faster than a similar one without. A realtor told me not long ago, "A lot of people who want ponds just like to make a quick phone call and write a check." A lot of the same people quickly discover that buying a used pond is like buying a used car: you just bought someone else's troubles, but they're underwater.

How to evaluate an existing pond? Begin with a walk around the edge, noting the water quality. Is it clear, cloudy, blooming with algae, infested with weeds? Is water flowing out of the pond through an outlet or spillway, or is the water static?

Clear, or even slightly cloudy water, usually indicates good water quality, while the presence of algae and weeds can spell trouble. A continuing flow of water through a pond is a good indicator of healthy oxygen levels and temperature, while stagnant water is liable to threaten fish and hasten euthrophication, the natural aging process of a pond. Of course, water quality will vary with the season, and evidence of algae during hot weather doesn't necessarily mean the pond is terminal. Depending on the nature of the pond, there may be wild areas of cattails and other aquatic vegetation purposely included as protective cover and a food source for wildlife.

Another real estate broker observed that prospective buyers are usually repelled by algae and weeds. "People see green stuff and they get turned off, especially people who can't imagine fixing up a small problem." Conceivably a poorly maintained pond might work in the buyer's favor, as leverage to help lower the price tag. Naturally you'd want to be confident that pond could be rejuvenated at a reasonable cost. Conversely, a good looking pond clearly enhances property value. "The key work is good looking."

A pond diagnosis doesn't end with a weed survey.
Leakage is often a problem. Water that drops a foot or so below overflow level during the height of summer isn't a sure sign the pond is doomed. But low water during periods of more generous precipitation hints at problems with leakage, inadequate inflow, or both.

Note whether it is an excavated or embankment pond. An excavated pond, dug into the ground with little or no dam, is less likely to give you trouble with leakage. If the pond has an embankment, check the outside slope to be sure there is no leakage.

Check for signs of erosion, particularly around the overflow area. If the pond has a natural spillway, the channel may need work to stabilize erosion. Check piping to be sure there are no leaks around the outside of the pipe, as well as inside, which could indicate faulty piping or leakage through the dam. Older ponds with metal outlets are particulary vulnerable to leakage due to rust.



Sometimes leaks due to porous soil can be remedied by lining the basin with clay. But this is tricky and requires good prep work and execution. In extreme cases plastic membrane liners may be used to overcome leaks, but that usually means lining the entire pond. Supplementary water also can be use to make up for water losses. It's a rare pond that won't respond to some treatment.

Next, check the shore area around the pond. The slope into the water should be roughly 2:1 or 3:1, except perhaps in shallower beach areas. Shallow slopes are almost certain to nurture weeds and algae; excessively steep slopes can erode. It's important to know the pond depth throughout the basin. Areas shallower than four or five feet will encourage weeds and algae. Depths greater than six or seven feet are preferred. Occasionally prospective buyers interested in confirming pond depths take out a boat and use a weighted line or pole for measuring.

Inflows, particularly year-round streams running into the pond, are likely to carry in silt, reducing depth and nurturing weeds. Examine the inflow area to determine if silt removal is necessary. Springs feeding a pond from uphill areas sometimes erode shoreland. Is this a problem that may need repair? Sometimes diversion ditches and/or piping are necessary to correct erosion. If the pond is fed by a pipe from a nearby stream or other source, be sure the feed pool is maintained to prevent plugging. Inflows carrying in sediment can often be remedied by excavating a small silt pool in the stream near the pond.

Trees growing up around older ponds can threaten
the integrity of an embankment, and it may be necessary to remove them. Roots boring into the dam
seeking water can trigger leaks. Moreover, the closer the trees, the more leaves and needles will wind up in water, adding to the nutrient load and potential algae problem.

The watershed that drains into the pond should be
free from contaminants and nutrients, whether from livestock, septic systems, eroded runoff, or other sources. For example, how near is the pond to public roads or driveways? It's not helpful to have road salt leaching into the pond, or debris kicked up by snowplows or road graders. Ditches, berms, or silt fence barriers can help deflect roadside contamination. If you plan to stock fish, check the water quality with a water test kit to determine pH and other chemical parameters, including water temperature. Discuss your findings with a fish supplier to confirm the pond's fish suitability.

Abridged from Earth Ponds: The Country Pond Maker's
Guide to Building, Maintenance, and Restoration. 

November 1, 2014

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