Pond Building 101
Designing and building a pond is as much of an art as it is a science. Ponds, like most things in life, can vary in a multitude of ways. Starting with functionality, the purpose for which the pond is built is the most critical. Is it a retention or detention needed for state wastewater permitting? How about an irrigation pond to use as a water source for your burgeoning micro-farm? Or is it strictly an aesthetic thing where you love the view and sound of water? Or my favorite of all, the organic swimming pond. These ponds utilize the biological power of good bacteria, natural filtration systems and mother nature's harmonizing effects to balance the water conditions, to provide safe, low maintenance swimming areas, viewing ponds and irrigation reserves, all in one.
Once a purpose is decided on, size and site location are the next hurdles. Depending on your needs, it could be as small as a couple hundred gallon fish pond with a small water feature, or may be several acres of former pastureland. Without getting into the nitty gritty, the size of a pond does have some state imposed restrictions that need to be taken into consideration, so bear that in mind. (Learn more about the state guidelines here https://dec.vermont.gov/watershed/lakes-ponds/private-ponds)
Provided that their are no issues with permitting the pond, site and soil tests should be done to better understand the composition of the soil and likelihood of retaining water without adding a liner. This can be done, usually within a day, by hiring an excavation contractor to dig several test pits in the anticipated location of the pond. The pits will generally be as deep as the proposed pond and the quantity will vary depending on the size of the pond. If the soil has enough clay and there are no underground issues like large boulders, ledge or other hindrances, then pond layout and construction can begin.
In the event the soil is not conducive to retaining water naturally, a pond liner can be purchased. There are two primary types, RPE (reinforced polyethylene) and EPDM (ethylene propylene diene monomer). While each has their own benefits and drawbacks, we prefer to use RPE when possible due to its longer lifespan and light weight relative to EPDM. However, EPDM is more cost effective and can be easier to install because of its rubber-like qualities allowing it to bend and form into shape more easily.
Next we need to consider the water source feeding the pond as well as the overflow and drainage locations. If the water source is spring fed or comes from a small stream or creek; fantastic! It means a constant flow of water will keep the pond full and useful nearly year round. If it's fed by groundwater runoff then the size of the pond will be limited by the amount of acreage providing the groundwater to the designated pond area. If there isn't enough runoff to keep the minimum volume of water flowing into the pond, then the pond will need to scale down so that there is sufficient volume to support it. Nobody wants their pond to run dry in August because it's under fed!
Lastly, at least for this post, is the drainage system. Nearly all ponds will collect more water than they can hold at some point, so overflow systems are designed to handle that safely and without damaging the pond or surrounding areas. Typically they consist of an appropriately sized pipe that is set vertically with the top at the same level as the max water depth. If more water runs into the pond, the water will rise until it reaches the level of the overflow, ultimately entering the top of the pipe and exiting the pond through the outlet side, which is trenched through the pond dam and ran to the desired location.
All things considered, this is a very rough idea of the information we need and process we take when building ponds for our clients. It goes without saying, this is only one way to do it and other contractors will have their own methods. We take pride in what we do and believe this to be an effective and cost efficient approach to pond design and building.