What Are Key Characteristics of the Watershed?
 Under a grant from EPA, a draft report "Summary of Existing Watershed Conditions Big Dry Creek Watershed"
was prepared by Wright Water Engineers, Inc., and released in February 1998. This report summarizes key characteristics
of the Big Dry Creek watershed for the purpose of establishing a common base of information for watershed stakeholders. This
information can be used to help identify and prioritize future measures to improve watershed conditions. Key conclusions
and recommendations identified in the report include the following:
- A significant number of studies pertinent to the Big Dry Creek watershed have been conducted on a wide variety of
topics such as wildlife habitat, aquatic life, water quality, stormwater management, and open space planning. As the
Watershed Association plans future monitoring and special watershed projects, care should be taken not to "reinvent
the wheel" or restudy issues that have already been addressed.
- A variety of efforts to protect water quality are currently in place in the watershed. The Watershed Association
should seek to complement and stay abreast of these efforts. Key efforts currently in place include extensive water
quality monitoring and protection programs at Rocky Flats and Standley Lake. Large amounts of water quality data are
available through these efforts. The Association should continue to include water quality data from these ongoing efforts
in the Big Dry Creek Water Quality Database.
- The Big Dry Creek Monitoring Program conducted by the cities of Broomfield, Northglenn and Westminster should
continue because it provides useful data for stream characterization from Standley Lake to the South Platte. The data
set obtained from this program is the primary source of water quality information in the watershed below Standley Lake.
- Stormwater quality and quantity impacts to Big Dry Creek are not well-characterized although a variety of
stormwater impacts such as streambank erosion can be reasonably inferred from field observations. As the Clean Water Act
Phase II stormwater regulations are promulgated and implemented over the next few years, the cities will likely be impacted
by Phase II requirements. It will be important for the cities to develop an understanding of stormwater impacts to receiving
water quality and implement best management practices (BMPs) to minimize these impacts. Several master drainage plans have
been completed in the watershed that identify existing and proposed patterns of stormwater flows (i.e., outfalls, flow
volumes, etc.). This information can be helpful in designing stormwater quality monitoring programs and developing an
overall understanding of stormwater issues in the watershed.
- Documented pollutant sources in the watershed include discharges from municipal wastewater treatment plants and Rocky
Flats, and spills and releases from facilities regulated by the Comprehensive Environmental Response Compensation and
Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA). Stormwater runoff from urbanized
areas and overland flow from agricultural lands are also expected to be relevant sources of pollution, although studies
of these sources are not known to have been conducted in the watershed.
- Groundwater quality and groundwater-surface water inte
 ractions are not well-characterized along the main stem of
Big Dry Creek. These issues may be worthy of study in the future, particularly with regard to understanding the role
that groundwater plays in the hydrology of Big Dry Creek.
- Although the main stem of Big Dry Creek has not been identified on the 1998 303(d) list, which would trigger the
total maximum daily load (TMDL)process for the creek, Big Dry Creek will be affected by the ongoing TMDL process in
Segment 15 of the South Platte River. The Big Dry Creek Association should monitor and participate in the activities
of the South Platte Urban Watershed TMDL Advisory Committee.
- Ecological studies along Big Dry Creek suggest that aquatic life in the stream is limited due to poor habitat
conditions. Future projects in the watershed could consider areas of potential habitat improvement. In planning these
efforts, hydrologic information in the various master drainage plans and flood hazard delineation areas should be
taken into account.
- In the area downstream of I-25, agriculture is the predominant land use. Cattle grazing and watering in the stream
and runoff from adjacent croplands impact water quality and streambank conditions. Quantitative studies are not known
to have been conducted to correlate agricultural activities with water quality in this area; however, the Natural
Resource Conservation Service (NRCS) indicates that these impacts are potentially present. In the event that a waste
load allocation (WLA) for nitrate is developed for Big Dry Creek as a result of the TMDL process for Segment 15 of the
South Platte, additional quantitative study of this issue may be needed. Similarly, the Association should work with
the NRCS and farmers in the area to determine what measures should be taken to minimize water quality impacts associated
with agricultural practices through measures such as streambank stabilization and riparian buffer area preservation/
restoration.
- All of the cities in the Big Dry Creek watershed have stormwater and construction ordinances in place for new
development that address water quality. The Association should work with the cities to encourage enforcement of ordinances
requiring the implementation of BMPs at construction sites, since much of the watershed area is rapidly developing.
Similarly, as the population within the watershed grows, water quality impacts associated with urbanized areas will
increase. Public education would be a worthy effort of the Association to promote proper handling and disposal of
household waste, application of fertilizers and pesticides, and other practices that reduce pollutant loadings to the
stream.
- The City of Westminster and Jefferson County Open S
 pace are actively pursuing preservation of open space, particularly
along Big Dry Creek. The Association should support these and other similar efforts because of the value that preserved
riparian corridors play in protecting water quality, maintaining streambanks, enhancing aquatic habitat, etc.
- Geographic Information Systems (GIS) mapping is available from various entities in the watershed for a large portion
of the watershed, excluding Weld County. Although Broomfield and Northglenn do not have GIS systems in place, the mapping
is in electronic form that should interface with a GIS system. With some coordination, a good GIS map could be developed
for the watershed as a tool for linking water quality and quantity with various geographic features.
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