Technical Bulletin 91-001 Nitrogen Loading - Cape Cod Commission

Technical Bulletin 91-001 (FINAL)
NITROGEN LOADING
April, 1992
EXAMPLE RESIDENTIAL LOADING CALCULATIONS
Home (3 bedrooms)
Lot Size: 1 acre (43,560 ft 2 )
Impervious Surfaces: Roof Area: 2,000 ft 2 ; Paving Area: 500 ft 2
Natural Area: 41,060 ft 2 ; Lawn Area: 5,000 ft 2
Title V Flow: 110 gallons/day per bedroom
WASTEWATER
Title V (2 people per bedroom)
3 bedrooms 110 gpd 3.785 L = 1,249.0 L/d 35 mg = 43,716.8 mg/d
bedroom gal
L
Actual (assume 2.5 people/unit average occupancy within the town)
3 bedrooms 110 gpd
bedroom
3,785 L
gal
2.5
6
= 520.4 L/d 35 mg
L
= 18,214.6 mg/d
IMPERVIOUS SURFACES
2,000 ft 2 40 in ft 28.32 L 1 yr = 517.3 L/d 0.75 mg = 387.9 mg/d
yr 12 in ft 3 365 d
L
500 ft 2 40 in
yr
ft
12 in
28.32 L
ft 3
1 yr
365 d
= 129.3 L/d 1.5 mg
L
= 194.0 mg/d
LAWN
5,000 ft 2 3 lbs 1 yr 454,000 mg
1,000 ft 2 *yr 365 d
lb
0.25
= 4,664.4 mg/d
NATURAL
43,560 ft 2 - 2,500 ft 2 = 41,060 ft 2
41,060 ft 2 1.5 ft 28.32 L 1 yr = 4,778.7 L/d
yr
ft 3 365 d
SUMMARY
Title V Flow
Actual
43,716.8 + 387.9 + 194.0 + 4,664.4 mg 48,963.1 mg
= = 7.34 ppm
1,249.0 + 517.3 + 129.3 + 4,778.7 liters 6,674.3 liters
18,214.6 + 387.9 + 194.0 + 4,664.4 mg 23,460.9 mg
= = 3.95 ppm
520.4 + 517.3 + 129.3 + 4,778.7 liters 5,945.7 liters
Final Calculation (7.34 + 3.95)/2 =
5.65 ppm
Water Resources Office 17
Cape Cod Commission