Erosion, Flood, Stormwater & Watershed Standards 12.6 Water Supply Watershed Protection Regulations
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Example:
A 20-acres site is located in a watershed that has a 24% BUA high density development limit. The site has 2 acres of existing BUA constructed prior to the effective ordinance date. Redevelopment in an undeveloped portion of the site is proposed to increase the BUA by 4 acres to a total of 6 acres. The % BUA is calculated dividing the proposed redeveloped BUA acreage by the total project acreage less the existing pervious area as follows:
% BUA = [4 acres/(20 acres-2 acres)] x 100 = 22.2%
Since the proposed 22.2% BUA does not exceed 24% BUA, the project is considered Low Density. However, the total impervious surface area is increased to 6 acres or a total BUA of 30% which would be considered High Density. Option B: Redevel opment including the modification of existing BUA or “No Net Increase” in BUA Built-Upon Area (%) = [(Total Built-Upon Area of Redevelopment – Portion within Existing BUA) / (Total Parcel Acreage – Total Existing or Adjusted BUA Acreage)] x 100
Example 1
A proposed 2.1-acres site is located in a watershed that has a 24% BUA high density development limit. The site has 1 acre of existing BUA that existed prior to the effective ordinance date. Redevelopment is proposed for 0.5 acres of the existing 1 acres of BUA with an additional proposed 0.5 acres of BUA. The % BUA is calculated using the proposed redeveloped BUA over the total area minus the unmodified BUA area as follows:
% BUA = [(1 acre – 0.5 acre)/2.1 acre-1 acre)] x 100 = 45.5% BUA
Since the proposed 45.5% BUA exceeds 24% BUA, the project is considered High Density.
Example 2
A proposed 2.1-acre site is located in a watershed that has a 24% BUA high density development limit. The site has 2 acres of existing BUA that existed prior to the effective ordinance date. Redevelopment is proposed for 1.1 acres of the existing 2 acres of BUA with no net increase in impervious area. The % BUA is calculated using the proposed new BUA over the total area minus the unmodified BUA area as follows:
% BUA = [(1.1 acre-1.1 acre)/(2.1 acres-2 acres)] x 100 = 0% BUA
Since the proposed 0% BUA is does not exceed 24% BUA, the project is considered Low Density.
3. Drainage Area Considerations for New Development BAU Calculations:
Per 15A NCAC .0624 (4d), projects may receive split consideration according to natural drainage area boundaries. This split evaluation is not acceptable for all projects and must be approved in advance by the Town. Drainage area determinations should be made based upon the site area(s) within the project boundaries that drain to a common point. A proposed project site could contain multiple drainage areas that need to be evaluated individually. To determine the drainage area(s) of a particular project, locate the point at which a stream or drainage feature leaves the property. Any on-site area that drains
Town of Wake Forest Unified Development Ordinance – July 19, 2022
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