WWTF
MGD
L/Gallon
mg/L N
Actual 2,500,000 3.785 10 94.625 34,538
Permit 3,000,000 3.785 10 113.55 41,446
OSTDS
The amount of N input from septic tanks was determined by estimating the total number of
people within the basin that were not on municipal water supply multiplied by the per capital load
of 4.2kg N/yr. The total annual load from septic tanks was estimated to be 48,817 kgN/yr.
Table 4-3. Estimated nitrate-N load from On-Site Sewage Treatment Discharge Systems (Septic
Tanks)
OSTDS
Population kg-N/yr per capital kg-N/yr
11,623 4.2 48,817
Land Uses
Urban. To calculate the amount of nitrate loading associated with urban land-use the area
of urban land (8,400 ha) was multiplied by the per-area load (7.4 kgN/ha-yr) for a total of 62,160
kgN/yr.
Improved Pasture. To determine the nitrate load from improved pasture lands the area of
coverage (20,500 ha) was multiplied by the loading rate (1 lkgN/ha-yr) for a total of 225,500 kg-
N/yr.
Row Crops. The estimated load from row crops was determined by multiplying the
loading rate of 38 lbs/ac-yr (42.6 kgN/ha-yr) by the amount of hectares of row crops in the basin
(1,300), for a total of 55,380 kg-N/yr.
Kg/day
kgN/yr