FLOOD00031

• Designation Number: 38
• County: Jefferson
• Community: Lakewood
• Title: Major Drainageway Planning - Sanderson Gulch, North Sanderson Gulch, and Weir Gulch Volume I
• Date: 8/1/1972
• Designation Date: 12/1/1974
• Floodplain - Doc Type: Floodplain Report/Masterplan

SECTION VIII

I
I

MASTER PLAN DRAWI~G5

Volume II of this report presents the major drainageway 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 ar.d limitations of the drawings as presented.

The accuracy of the proposed design is highly influenced by the
inten<1ed 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-
roundi~g utilities, streot grades, house elevations, and other
factors as is always necessary for construction design of a pro-
ject.

'{'he accuracy of the d.rawings has been severely limiteu in the L"ke-
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 utilizing 5 foot
contour maps with the same degree of accuracy, as in the ~reas
using l foot contour ~nterval maps. The normal Gegree of dOOULdCY
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 will be off by 5 fcct. In designing drainage facilities,
we are deil1ing 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 pe used tor stud~es ot this type ~n the future. How~ver, the
stream profiles are considered adequate for purpo~es of flood
plain zoning because of the use of supplepcntal field survey data.
One of the most importa:1t uscs for the l".lIster plan drawing will
be in acqulsition 0: property prior to construction. The drawings
ill'..strate the approximate location o~ existing puLlic 'Ownership.
l<equ~red .didths of righ.t-of-',,'ay acquisition are indicated on the
plans '~'here public right-o::-'~'ay :"loos no': pr""ently exi~t. Where

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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
associated with drainage.

The a?curacy ?f ilvailable information on utilities is highly
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 ilssumed locations on the mas-
ter plan drawings. Detailed field surveys must be completed
on existing utilities prior to designing 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 ilnd 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 great benefit to the designer of final channel improve~~nts,
it by no means solves all the problems of construction design.

GENERAL DBSCI<lPTION OF Ull'l<OVBMENTS

The following general description of imyrovement~ proposed is
orgimlzed to coincide ...H_n thp indivi.dual desion sheets. Inforrn-
~ti0n contained hprpin i~ generally ~upplement~l to that por-
trayed on the master planning sheet.

Drawing No. 5-1
The existing culvert under valley Road shall be left in place
and flow exceeding its capacity allowed to discharge across Valley
Road. The area between Valley Road ilnd the railroad track is
located below the back water curve f,om ViiI lev Road and should
be filled to remove it from the flood plain. "The existing rail-
rc~d bridge ca~ bc i~provcd to pass the 10 year runoff although
it will be overtopped by greater storm occurrences. Any 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
chilnnel encroilchment in the vicinity of the railroad. bridge by
industrial building necessitates the use of a vertical walled
channel. The proposed cross section utili>;e" gilbion basket:;,
although reinforced concrete retaining walls might be substituted
in final design. At the illignment of Lipan St. an existing sani-
tary sewer crosses the gulch 5 feet above the channel invert.

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