Appendix C: Nitrogen Export Calculations (see Neuse River Basin: Model Stormwater Program for Nitrogen Control)
Figure 2a: Method 1 for Quantifying TN Export from Residential Developments when Building and Driveway Footprints are Not Shown
Step 1: Determine area for each type of land use and enter in Column (2).
Step 2: Total the areas for each type of land use and enter at the bottom of Column (2).
Step 3: Determine the TN export coefficient associated with right-of-way using Graph 1.
Step 4: Determine the TN export coefficient associated with lots using Graph 2.
Step 5: Multiply the areas in Column (2) by the TN export coefficients in Column (3) and
enter in Column (4).
Step 6: Total the TN exports for each type of land use and enter at the bottom of Column (4).
Step 7: Determine the export coefficient for site by dividing the total TN export from uses at the
bottom of Column (4) by the total area at the bottom of Column (2).
|
(1) |
(2) |
(3) |
(4) |
|
Type of Land Cover |
|
|
|
|
Permanently protected undisturbed open space (forest, unmown meadow) |
0.6 |
||
|
Permanently protected managed open space (grass, landscaping, etc.) |
1.2 |
||
|
Right-of-way (read TN export from Graph 1) |
|||
|
Lots (read TN export from Graph 2) |
** See Graphs Below **
Figure 2b: Method 2 for Quantifying TN Export from Residential / Industrial / Commercial
Developments when Footprints of all Impervious Surfaces are Shown
Step 1: Determine area for each type of land use and enter in Column (2).
Step 2: Total the areas for each type of land use and enter at the bottom of Column (2).
Step 3: Multiply the areas in Column (2) by the TN export coefficients in Column (3) and enter
in Column (4).
Step 4: Total the TN exports for each type of land use and enter at the bottom of Column (4).
Step 5: Determine the export coefficient for site by dividing the total TN export from uses at the
bottom of Column (4) by the total area at the bottom of Column (2).
|
Type of Land Cover |
Area (acres) |
TN export coefficient (lbs/ac/yr) |
TN export from use (lbs//yr) |
|
Permanently protected undisturbed open space (forest, unmown meadow) |
0.6 |
|
|
|
Permanently protected managed open space (grass, landscaping, etc.) |
1.2 |
||
|
Impervious surfaces (roads, parking lots, driveways, roofs, paved storage areas, etc.) |
21.2 |
||
|
TOTAL |
- |
Graphs for use with Method 1: Residential Sites with no known building footprints.
