FLOOD07908

• Designation Number: 260
• County: Jefferson
• Community: Unincorporated Jefferson County
• Basin: South Platte
• Title: Major Drainageway Planning - Sanderson Gulch/Weir Gulch Volume I
• Date: 8/1/1972
• Designation Date: 12/1/1987
• Floodplain - Doc Type: Floodplain Report/Masterplan

SECTION VIII

I
I

MASTER PLAN DRAWI~GS

Volume II of this report presents the major drainQgcway planning
drawi~gs in the form of plan and profile sheets. It is impor-
tant the UserS of the drawings understand the accuracy, intended
use and limitations of the drawings as presented.

The accuracy of the proposed design is highly influenced by the
intenued use of the drawings. The statement on each dr<lwing
summarizes the situation as follows: "This drawing is a master
planning sheet representing preliminary and conceptual engineering.
It shall not be used for construction purposes." The information
portrayed on the sheets is sufficiently accurate to allow for
staged development in separated portions of the channel with the
assurance that the constructed facility will be compatible with
the overall system when the design is completed., Individual
street crossings and private development may proceed with the
assurance that facilities constructed will al~o he compatible
with the overall drainage system when completed.

The drawings are not sufficiently accurate to justify final design
of individual structures without detailed investigation of sur-
rounding utilities, street grades, house elevations, and other
factors as is always necessary for construction design of a pro-
ject.

'{'he accuracy of the drawings has been severely limited in th", L"",,,,-
wood area through use of the existing 5 foot contour interval maps.
Although the maps were supplemented by field surveying at criti-
cal locations, it is impossible to plan facilities utili~ing 5 foot
contour maps with the same degree of accuracy, as in the ~reas
using l foot contour ~nterval maps. The normal uegree of doouLdey
for aerial photography mapping is for 90% of the contours to be
within one-half interval of the actual elevation. This means
that the average contour may be off by 2 to 3 feet and that many
contours ~ill be off by 5 feet. In designing drainage facilities,
We are dealing with vertical elevations in which 6 inches is ofter,-
times an excessive deviation. Portraying actual field conditions
as obtained from ground control is often very misleading since it
is significar.tly different than that indicated by the contour !:lap.
It is strongly reconmendcd t~at 5 foot contour interval maps shOUld
not pc used tor stud~es of this type ~n the future. However, the
stream profiles are considered adequate for purpo~es of flood
plain zoning because of the use of supplepental field survey data.
One of the most importa:1t uses for the l",aster plan drawing will
be in acqulsition of propcrty prior to construction. The drawings
ill'..strate the approximate location o~ existing puLlic 'Ownership,
l<cqu~red 'didths of righ.t-of-',,'ay acquisition are indicated on the
plans '~'here public right-o::-'~'ay :"lcos no": pr""ently cxi"t. Wh",re

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right-of-Way acquis~tion is indicated, it represents the minimum
width of acquisition necessary to construct an adequate drainage
channel. If the Parks Department wishes to purchase additional
land for development, it should be considered as an extra cost not
associ~ted with drainage.

The a?curacy ?f available information on utilities is tighly
questlonable ~n the Lakewood area. In many instances existing
sanitary sewers are not indicated on the district as-built maps
and are therefore portrayed in the assumed locations on the mas-
ter plan drawings. Detailed field surveys must be completed
on existing utilities prior to dasigning any street crossings
where possible conflicts are evident.

Many existing local drainage problem areas exist along the gulches.
Where these problems had a direct bearing on design of the facili-
ties, data concerning them is reproduced for the use of the local
entities who may design drainage facilities in the future.

Complete final construction plans and specifications must be pre-
pared on any portion of the gulch prior to construction of facili-
ties. The construction plans would deal with structural design
of all facilities, detailed grading plans, treatment of individual
utilities, and the myriad of other points whiCh are handled in a
cursory manner in this report. Although the master plan will be
of gre~t benefit to the designer of final channel improve~~nts,
it by no means solves all the problems of construction design.

GENERAL DESCRIPTION OF Ull'ROVBMENTS

The following general description of improvement" proposed is
orgimlzed to coincide ...H_h thp indivi.dual desien sheets. Inforrn-
~ti0n contained hprein i~ generally ~upplement~l to that por-
trayed on the master planning shcet.

Drawing No. 8-1
Thc existing culvert under valley Road shall be left in place
and flow exceeding its capacity allowed to dischargc across Valley
Road, The area betwecn Valley Road ~nd the railroad track is
located below the back watcr curve f,om Viii lev Road and should
be filled to remove it from the flood plair.. "The existing rail-
rc~d bridge ca~ be i~provcd to pass th~ 10 year runoff although
it will be overtopped by greatcr storm occurrences. Ar.y improve-
ments in addition to those indicated on the master planning draw-
ings should be at the expense of the C&S Railroad. The extreme
Channel encroachment in the vicinity of the railroad bridge by
ind~strial building necessitates the use of a vertical walled
channel. The proposed cross section utili;ocs g"bion basket:;,
although reinforced concrete ret"ining walls might be substituted
in filial design. At the "lignment of Lipan St. an existing silni-
tary sew",r crosses the g~leh 5 feet above the channel invert.

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