How is a backyard pond built?

What the job involves

Most ponds fall into one of two types. A dug pond is excavated below the existing grade and holds groundwater or runoff. An embankment pond uses a dam across a low spot or draw, with the water backed up behind it. Many are a mix of both. The type decides almost everything else: how much soil moves, how much can go wrong in a storm, and which rules apply.

Virginia law treats the dam part seriously. The Code of Virginia defines an impounding structure as "a man-made structure, whether a dam across a watercourse or other structure outside a watercourse, used or to be used to retain or store waters or other materials".^[1] DCR says "dams of specified height and impoundment capacity are regulated by the Virginia Department of Conservation and Recreation and are required to comply with the Virginia Dam Safety Act".^[4] It adds that DCR's dam safety staff "works to ensure that dams are properly and safely designed, built, operated and maintained".^[4]

Where the size limits fall

Whether your pond is a regulated dam depends on two measurements, height and storage. The Code counts "all dams that are twenty-five feet or greater in height and that create an impoundment capacity of fifteen acre-feet or greater",^[1] and "all dams that are six feet or greater in height and that create an impoundment capacity of fifty acre-feet or greater".^[1] Height is measured as "the vertical distance from the natural bed of the stream or watercourse measured at the downstream toe of the dam to the top of the dam".^[1]

Many small backyard ponds fall below those figures, which is why many owners never deal with the dam regulations, but height and storage have to be measured, not assumed. The definition also leaves out "dams operated primarily for agricultural purposes which are less than twenty-five feet in height or which create a maximum impoundment capacity smaller than 100 acre-feet".^[1] An owner who qualifies can validate the exemption by filing an Agricultural Exemption Report, and the rule says the report "may be verified by the department through a site visit".^[2] Whether your pond counts as agricultural is a question for DCR and your engineer, not a guess.

Design comes before digging

For a pond that is regulated, the rules require that structures be "constructed, operated and maintained such that they perform in accordance with their design and purpose throughout the life of the project".^[3] The spillway is the part owners overlook. The regulation says "the spillway capacity shall perform at a minimum to safely pass the appropriate spillway design flood".^[3] In plain terms, the outlet has to carry the big storm around or over the embankment without the water eating through it.

Even a pond below the regulated size benefits from the same thinking. A competent contractor or engineer will look at:

• how much land drains into the pond, since that sets how much water arrives in a heavy rain
• what the soil can hold, and whether it needs a clay liner or other sealing
• where overflow will go, and what is downstream
• how the banks will be shaped and stabilized

Permits and utilities

Digging a pond is excavation, so the Virginia utility notification law applies: "no person shall make or begin any excavation or demolition without first submitting a locate request to the notification center".^[6] Your contractor normally handles this, but confirm that it has been done.

Local erosion rules may apply too. Montgomery County, for one, says "a land disturbing permit is required when disturbing more than 10,000 square feet of land", and that this includes "clearing, grading, excavation, transporting and filling of land".^[5] Rules differ by locality, and if the pond touches a stream or wetland there are federal permits to consider and state agencies to ask. See whether you need a permit to build a pond in Virginia.

What it costs and who builds it

Pond cost depends on the soil that has to be moved, access for equipment, the engineering and the finish work. The details are in how much a pond costs in Virginia.

When to call a licensed pro

For the whole job. Virginia's Board for Contractors says that "if the work you are considering is valued at $1,000 or more, a valid Virginia Contractor’s License is required for the license category in which the contractor is to work".^[7] A pond contract can easily exceed that, and a Class C licence covers a single contract over $1,000 but less than $30,000,^[8] Class B covers $30,000 or more, but less than $150,000,^[8] and Class A covers $150,000 or more.^[8] Check the licence before you sign, and ask for a written contract that names who designs the dam and spillway.

Loclis lists licensed local businesses. Browse excavation services, read more excavation answers, or describe your pond project once and licensed excavation businesses will quote it.