Typical pollutants originating from nonpoint sources include sediment, nitrogen, phosphorus, fecal
coliform bacteria, and pesticides.
An extensive discussion of the importance and magnitude of nonpoint sources is available in
Novotny and Olem (1994). Annual June literature reviews in the journal Water Environment Federation
on nonpoint source pollution control research have been compiled by Line et al.(1995, 1996, 1997).
188.8.131.52 Urban and Industrial Sites
Urban Pollutant Runoff. The findings of the Nationwide Urban Runoff Program (NURP) are
particularly applicable to screening-level estimation of urban NPS pollutant loads. The NURP study
(USEPA, 1983) included 28 projects with wide geographic representation in sites. Pollutant runoff
concentrations and storm runoff volumes were monitored to assess urban land use pollutant export.
Projects reported results in a consistent, transferable manner making statistical data analysis possible
across projects and regions. The general results of the NURP study showed:
Urban pollutant runoff concentrations were essentially independent of
hydrologic regions or geography.
Pollutant concentrations were essentially uncorrelated with storm runoff
volumes especially for dissolved constituents and somewhat more correlated
tot runoff volume for particulate constituents.
Pollutant loads were highly correlated with storm runoff volumes.
We provide an event-based urban pollutant loading function modified from Schuler
(1987): The urban loading function is not restricted to dissolved constituents as the
rural model given in equation 1.1.15. The urban model is, for source area k, at time t:
LDkt = 0.1 Cdkt Qkt Ak
LD = pollutant load (dissolved or solid phase) in kg
Cd = pollutant runoff concentration (mg/l)
Q = storm event source area runoff depth (cm)
A = source area (ha)
The pollutant concentration (Cd) may be determined from site-specific monitoring
studies or the default values listed below in Table 1.1.7. These median and 90th percentile