Final Baseline Hydrology Report - October 2012 - Urban Drainage ...

Sanderson Gulch Major Drainageway Plan
Baseline Hydrology Report October 2012
includes recommendations for nature theme enhancements to the Newton facility and new nature play
nodes above Irving Street and below Raleigh Street. Existing under-performing play/ exercise nodes exist
along the trail. Other recommendations include sheltered seating areas. The 2009 Gulch Master Plan
includes a recommendation for the potential acquisition of the existing residential property on the south side
of the channel at the corner of S. Tennyson Street at W. Colorado Avenue.
Water Quality. Water quality improvements were recommended in the 2009 Gulch Master Plan along the
north side of the channel at surface outfalls along W. Mexico Avenue. The existing water quality treatment
areas on the north side of the channel at S. Mabry Way, S. Michigan Way, S Newton Street and S. Stuart
Street are performing poorly.
Reach 5 – S. Tennyson Street to Sheridan Boulevard (Denver)
Reach 5 includes a road crossing at S. Xavier Street which has less than 10-year capacity. There are two
existing drop structures in the reach, both in reasonably good condition. One of these, a near vertical
gabion and gunite structure above S. Xavier Street, has a 5 foot drop height and does not meet current
UDFCD criteria for vertical drops. The upper half of the reach above S. Wolff Street has a concrete-lined
invert. Below this point, channel slopes alternate between fairly flat sections and informal riprap riffles,
resulting in an overall slope approaching 0.8%. Additional grade control is planned for the steeper reach.
Maintenance. Maintenance includes mowing to a height of approximately 4-6 inches once or twice a
growing season after grass species have gone to seed. Removal of dead wood material and trash occur on
an as need basis after storm events. In those areas where the regional trail traverses along the gulch,
maintenance responsibilities are shared between UDFCD and DPR. Those areas that are not accessed by
the public, west of Wolff Street to Sheridan Boulevard, are generally maintained exclusively by UDFCD.
Reach 5 is approximately 2,800 feet in length and
extends from S. Tennyson Street to the dividing line
between the City and County of Denver and the City of
Lakewood (Jefferson County) at Sheridan Boulevard.
The formal wide linear park corridor of Sanderson Gulch
ends at S. Tennyson Street, and the remainder of the
reach within Denver up to Sheridan Boulevard is
contained within a narrower corridor. At Tennyson Street
the gulch corridor is initially 100 feet in width and then
reduced further to 60 feet for the upper half of the reach
starting near S. Wolff Street. The pedestrian path
extends only east of S. Wolff Street. West of Wolff Street
to Sheridan, the channel has a concrete lined invert.
East of Xavier the Sanderson Gulch channel is
confined to a narrow corridor without good
maintenance access.
Landscape and Ecology. Tall fescue grass species are predominant along the channel regardless of the
bottom condition and they extend up the slope coincident with the two-year storm event. Non-irrigation
upland grass species include fescue, wheatgrass, buffalograss, grama grass and sand dropseed.
Pockets of riparian vegetation have been observed on the concrete pan. These include softstem bulrush
and Eleocharis species and the occasional coyote willow. Mature cottonwoods and the peachleaf willows
are sprinkled along this reach of the channel in addition to Siberian and Chinese elm.
Invasive species (thistle, kochia, smartweed, bindweed, prickly lettuce, common mallow, barnyard grass,
Johnsongrass, pigweed, rag weed, halogeton, redstem filaree, alfalfa, Siberian elm, Chinese elm and the
occasional Russian olive and curly dock) are present along the channel as well as in the upland grass
areas. Baby’s breath was observed near the gulch at S. Xavier Street.
Parks and Recreation. The 2009 Denver Parks & Recreation Gulch Master Plan includes a
recommendation for the potential acquisition of one (1) residential property on the south side of the channel
below S. Tennyson Street, four (4) existing residential properties on the south side of the channel above S.
Tennyson Street, and three (3) residential properties on the south side of the channel between S. Wolff
Street and S. Xavier Street.
Water Quality. This reach is generally too narrow for additional surface water quality treatment. The
following storm outfalls exist within Reach 5 and discharge directly to the low flow channel:
• 54-inch from the north in Utica Street
• 30-inch from the south in Vrain Street
• 42-inch from the south in Wolcott Court
• 42-inch from the north in Sheridan Boulevard
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