Size and Location are Key
Once you’ve decided on the purpose of your large pond, it’s time to determine the appropriate size and location to ensure its success.
Regarding location, consider surrounding terrain and access for maintenance purposes. Choosing a spot with easy access for stocking fish, applying herbicides or fertilizers, and adding water if needed is essential. If your pond will host boats or other recreational activities, ensure your site has the necessary amenities, such as a dock and boat launch.
If your pond already exists, you can enlarge it, but moving it is certainly not practical, so you may be forced to reconsider its purpose if building an entirely new pond isn’t in the cards. During the planning phase, consider these factors:
Pond Size:
Consider the intended use of your pond and determine the appropriate size based on your needs. The pond should be deep and wide enough to support the intended use. For example, if you plan to use the pond for fishing or swimming, it should have a broad surface area to accommodate those activities. Remember, though, that deeper water maintains a more regulated temperature year-round, and fish need areas with a minimum depth of 4-5 feet to stay healthy and safe, so sacrificing depth for surface area may be a poor compromise. If you want to create a firefighting resource, a deep pond is more useful to accommodate dry hydrants, snorkels, and dipping buckets. Deep ponds also hold substantially more water in a limited surface area. Ensure the pond provides an adequate water supply; 10,000 to 20,000 gallons is often recommended but consult your local fire department to verify their guidelines.
Pond Location
The location of your pond should be carefully chosen to optimize its functionality and minimize potential risks. Consider the proximity to water sources, livestock grazing areas, and the ease of water transportation. For example, if your plans include a recreational pond doubling as an emergency fire pond, a location relatively close to your house would be ideal. Make sure the pond is away from potential sources of contamination, and keep in mind the need for both sun exposure and shaded areas if you’re contemplating recreational uses.
Soil Conditions
The composition of the soil at the pond site affects water retention. Clay and silty-clay loam soils are preferred for their slow permeability, while sandy, gravelly, or fractured rock soils should be avoided. The good news is even poor soil quality can be managed with an impermeable liner. However, rocky soil usually requires additional preparation and may require an underlayment to protect the liner.
Topography
Look for an area with gentle slopes to control stormwater runoff and prevent damaging erosion. A hill or ridge near the pond can act as a wind barrier if that’s a concern. If the pond is on a slope, the pond will be shallower on the downslope side, so you may want to add a wall or berm to raise the water level.
Budget Considerations
Finally, you'll need to factor in the cost of building your pond. The cost will vary depending on the size, shape, and materials you choose, as well as whether you choose to tackle it yourself or hire professionals. Here are some cost areas that might surprise you.
Clearing, grading, and excavation.
Unless you’ve got a spare bulldozer handy, you’ll probably need to rent the equipment and pay an experienced operator to do most of the work. An advantage here is that a skilled dozer operator can quickly and neatly manage details like irregular boundaries and depth variations. A good dozer operator can also clear most brush and small trees, but large trees will need to be handled by a tree service.
Once you’ve begun to dig, you’ll need a place to put all that dirt (and brush from the clearing step). Five acre-feet of soil make quite a mountain, so it’s a good idea to have a dump truck or two to collect and haul it off as you go. Consider whether you’ll have to pay dumping fees, as well.
Filling the Pond.
Can you wait for those spring rains to come and fill up your yet-to-be swimming hole? Depending on where your water comes from and your patience reserves, you could find yourself trucking in water for the initial fill. Look at your planned depth and dimensions to calculate how many gallons it will take to fill your pond, then consider how many 5,000-gallon water trucks you’ll need. For a starter, consider that a 1-acre pond with an average depth of 5 feet contains over 1.6 million gallons of water.
If you choose to truck in water for the first fill, contract with a reputable company. You don’t necessarily need potable (drinking water) quality water. Still, it should be filtered and treated so it’s free of waterborne diseases, parasites, and chemicals that may originate from industry and agriculture wastewater.
Construction Materials.
Concrete ponds are considerably more expensive than excavated ponds with clay or geotextile liners, but it’s hard to imagine who would opt for an acre-sized concrete pond. Unless perhaps you’re repurposing an old skate park with a gnarly vert bowl? An upcoming article will discuss the pros and cons of clay and geomembrane liners.
Equipment and Maintenance.
These can vary widely, but possible expenses include aerators, pumps, and filters. Smaller ponds where you want the water crystal clear need all these, but large, more natural ponds can often get away with one or more good aerators. Depending on where your pond is located, you may be able to power your equipment with a small solar generator. Otherwise, you’ll have to factor in the cost of extending power to your pond.
If your pond is fed, even partially, by streams or surface runoff during storms, you will have sediment build up over time, which will gradually fill your pond. Once it has entered, the only way to deal with sediment in a large pond is to dredge it out. Various types of equipment are available for this job, but it can be a costly chore.
Once you've considered these factors, you'll be ready to start seriously designing your pond. Our next article will cover some basic design principles for large ponds.
