The Cherry Creek Reservoir Watershed
Phosphorus Trading Program in Denver is another innovative point/nonpoint
source trading program. The goal of this program is to allow point source
discharges to increase within a TMDL cap. Point and nonpoint controls have been
implemented to reduce phosphorus loadings in the watershed. Municipal
facilities must optimize controls and comply with permit limits, and BMP for
urban runoff must be implemented before a trade is approved (Paulson, 1997).
Credits generated from nonpoint source pollutant reduction facilities can be
used to offset growth upon a showing of need. Development and credit use are
required to be consistent with a basin plan established by the Cherry Creek
Basin Water Quality Authority, which was established by the state legislature.
Permits issued by the state must also be consistent with the basin plan and use
of credits approved by the Authority.
The TMDL requires urban nonpoint
sources to reduce loadings by implementing BMP's. Only those reductions beyond
the required BMP reductions can qualify for trading. Trading was not expected
to occur until growth caused point source loading limits to be exceeded and the
nonpoint source 50% baseline reductions are achieved (Apogee Research, Inc.,
1992). The Apogee report concluded that when the basinwide phosphorous limit is
reached, point source limits would depend on the nonpoint source reductions to
accommodate further growth. Alternatively, point source limits could be reduced
to compensate for nonpoint source loadings if the 50% threshold has not been
achieved.
One point source discharger has
requested phosphorus from the trade pool for a plant expansion, which is
currently under construction. The Authority has approved the trade credits but
must complete the trade program details before the transfer of trade credits is
final (Personal Communication from Ms. Rhonda Sandquist of McKenna & Cuneo,
September 28, 1998).
The Cherry Creek program is currently being revised to reflect baseline allocations under an updated TMDL.