FLOOD08848

• Designation Number: 37
• County: Jefferson
• Community: Lakewood
• Stream Name: Sanderson Gulch, North Sanderson Gulch, Weir Gulch
• Basin: South Platte
• Title: Major Drainageway Planning - Volume I - Sanderson Gulch and Weir Gulch
• Date: 8/1/1972
• Designation Date: 12/1/1974
• Floodplain - Doc Type: Floodplain Report/Masterplan

~~ile development of the hydrology was underway, research was
initiated into the field of benefit/cost analysis. Data was
obtained from the U.S. Army Corps of Engineers presenting the
depth of inundation versus damage potential ~or various type
structures. This information was converted tnto useable forms
for this particular project.
Storm runoff values were then converted into flood plain inunda-
tion areas for evaluation of damage potential. The methods of
developing the damage potential are covered in greater detail in
the Benefit/Cost Analysis Section of this report.
The next step in Phase A was to develop alternative plans for
the channel. The channels were broken down into various reaches
with similar characteristics. Alternative plans for each reach
were developed which could be combined in numerous combinations
for an overall alternative to that particular gulch. Each alter-
native plan was compared on a cost basis to the benefits derived
from its implementation. The cost for each alternative together
with the benefits derived were presented on summary sheets for
review by all involved entitie~.
During the analysis stage, Mr. Rafael Moses, noted Colorado water
attorney, was retained to provide the legal opinions on the pro-
posed project. Review of the particular problems of this,project
led to the decision to have Mr. Moses' legal work deal wLth the
problem of irrigation ditches and reservoirs w~iCh are common
to all possible alternatives, rather than to d1scuss each of
the myriad of possible alternative solutions to the project.
Once all information had been assembled, reviewed, and organi~ed
into presentation drawings, verbal presentations were given be-
fore the District Board, the District's Technical Advisory Com-
mittee, the City of Denver and the City of Lakewood.
Subsequent to these presentations Mr. Scott Tucker, Executive
Director of the Urban Drainage and Flood Control District, prepared
formal written recommendations for improvement to each of the
gulches. These recommendations,were formally accept7d bY,the
Board of Directors of the Distrtct and became the gutde lLnes
for Phase 8.
Phase 8 - Phase B of the study was initiated by conducting a
thorough review of the hydrological studies. performed in Phase A.
The studies were refined to reflect actual 1mprovement contemplated
including revised storage and reservoir spillway structures.
While the final hydrological studies were under,way, de~ign, .
criteria was developed specifically for the prOJect. ThLs,crLterLa
depends highly upon that set forth in the Urban Storm DraLnage

,
f
,
I

-5-

Criteria Manual while remaining compatible with the requirements
of the City of Denver and the City of Lakewoocl.
Map preparation became a very involved process since three differ-
ent sources of mapping were to be utilized. Each type of mapping
was at a different scale, used different datums, and different
contour intervals.

Sanderson Gulch through Denver utilized existing Denver Park
Department maps which had been compiled at a 1" equals 50 foot
scale with a 2 foot contour interval on Denver datum. These
maps were reduced to In equals 100 foot scale and reproduced on
plan and profile sheets.
Mapping was prepared especially for the section of Weir Gulch
through Denver by Kucera and Assoc. at a scale of 1" equal 100'
with a 2 foot contour interval on D.S.G.S. datum. These maps
could be reproduced directly on plan and profile sheets.
The most difficult section of mapping were those portions in
Lakewood and Jefferson County which were to utilize existing
1" equal 200' scale mapping with S' contour interval at D.S.G.S.
datum. The original contour mapping including only the 5' contours
and outlines of streets and major buildings such as schools and
shopping centers. It became evident that this did not portray
enough information to truly represent the situation along the
channel. Supplemental aerial photographs were obtained and super-
imposed on the existing contour mapping. It was impractical to
obtain perfect matches between the photographs and the contour
mapping, but close enough matching was possible to portray physi-
cal features such as houses, trees, fences, and other aspects
pertinent to drainage design. The overlay of the contour mapping
and aerial photograph was then superimposed on plan and profile
sheets for dcsig~ purposes.

Once the plan and profile sheets were available, approximate
channel requirements were outlined on maps and presented to
the city of Denver and City of Lakcwood for review by the Engineer-
ing, Planning, Parks, and Traffic Divisions. Particular emphasis
was put on maintenance aspects of the proposed channel during these
conferences.

With these items of background, master planning work
",as initiated on all channels. AL.t;dS r.-,q\.iiring flu"u pl/lin
zoning were analyzed using the Bureau of Reclamation's method
"B" computer program for backwater profiles. In areas where
improvements are proposed, calculations were completed on culverts,
bridges, channel cross sections, drop structures, check dams,
and other hydrologic design aspects.

-6-