There are many questions about Beaufort County's recently adopted ordinance on stormwater runoff management for single family residences. The first question is: "Who has to meet this ordinance?"
Only new single-family houses in unincorporated areas of the county that are not in an approved community stormwater runoff system and single-family houses that are renovated in excess of 50 percent of the appraised value of the building will need to address the stormwater runoff in accordance with the ordinance. Even if you are not required to meet the ordinance, for the health of our rivers, please consider mitigating the stormwater runoff on your property.
The second question is: "How can I reduce the amount of stormwater that needs to be mitigated?" The easy way to reduce runoff is by reducing the amount of impervious surfaces on the property. This includes reducing the size of your house and roof -- consider a two-story house instead of a one-story house; use gravel or pervious pavers for your drive; and limit the amount of patios and terraces or pave them with pervious pavers.
Next you might ask "What are my options in managing excess stormwater runoff?" The best management practice is to collect and store the rainwater for reuse or slow infiltration. There are two options for collecting rainwater: a rain barrel or a cistern. Both are connected to your gutters and downspouts. A rain barrel is used to collect water for use in your garden. Be sure that the rain barrel has a cover so that it is not a mosquito nursery. A cistern is larger and is the storage tank portion in a complete rainwater harvesting system that filters and stores water for any normal household use. If the water is to be used for potable needs, it must go through additional filtration and water purification.
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Another option is a rain garden, which is a shallow, bowl-shaped depression of loose absorbent soils that is planted with deep-rooted native perennials and grasses. The rain garden should be positioned near a runoff source such as a downspout or driveway. The runoff slowly soaks into the ground and reduces the amount of runoff entering our marshes and rivers.
The final questions are "How do we know how much runoff we need to mitigate and if we have met the ordinance?" The county has a very easy-to-use online worksheet that walks you through the process at http://stormwaterworksheet.createandsolve.com. To determine the total excess runoff to be mitigated, you will need to know the following information before you begin: the square footage of your roof; the square footage of other impervious areas; the square footage of your lot; your soil type - sandy or clay; and the area of your lot that is irrigated. Next, you enter the number and size of storage and reuse systems you want to use. The worksheet then computes thenatural infiltration capacity of the lot to control runoff. If the first two practices do not control all of the rainwater, the worksheet determines the size of a raingarden to capture all of the runoff.
Note that collecting and storing your rainwater in a rain barrel or cistern is not required but is considered the best management practice method. If you don't collect and store the rainwater, the rain garden will need to be much bigger.
Jane Frederick, AIA, LEED AP is a principal in Frederick + Frederick Architects. Contact her at 843-522-8422.