FLOOD08154

• County: Adams
• Community: Westminster
• Stream Name: Big Dry Creek
• Basin: South Platte
• Title: Master Drainageway Planning Study
• Date: 3/1/1973
• Prepared For: Westminster
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

x-4

27. Maintenance access will in large part be provided by the construction
of new roads not presently planned in detail which wi 11 be provided
by some developers.

28. Burled broken concrete or dumped rock rlprap must be furnished at
numerous locations, especially near bf'idges, to provide siope prot.ec-
tlon. In certain areas a lOO-foot potentIal erosion easement or
appropriclte slope protection should bE> provided by the developer due
to the possibility of a shift. In the flood plain from continuous low
flow erosion combined with erosion from frequently occurring storms.
The option as to the appropriate steps Is more or less consistent
with current zoning regulations In the City of Westminster.

29. The Union Pacific embankment and culvE>rt should be left Intact so as
to limit the peak rate of runoff to Weld County. Certain key
features that wi 1 I allow for the continued exist,ence of the embankment
are (Sheets 2, 3, 4 and 5):

a. Const.ructlon of a chute-bridge-energy disslpator combination for
Colorado Boulevard. All strw:turE>S lIsted In this Item are to be
mode I - tes ted to ass u re p rope r des I gn.

b, A flow guide Is to be constructed from near County LIne Road and
the Union Pacific embankment to the wes'~ t.o Insure that overtoppIng
flows do not flow out of the bas In into '!<Ield County In an unCOn-
t ro I I ed manner.

c. The combination of flow guide and the slope of the Union Pacific
embankment combine to control the overflow for the design flood
so that the overflow occurs near County Line Road In the shallow-
est part of the flood plaIn b,~hlnd the "l11bankment. Therefore,
erosional damage would not calJSeS, larg" scale release of water
under design conditions.

30. Most bridges in the area are des I'lned to me"t oVI~rtoppIng requirements
for the 100-year future runoff that wi 11 mel,t thl~ cr I ter I a of the
Denver Regional Council of Governments' Urb.~~)rm Dralnaqe Manual.
In Isolated Instances such as 160th Avenue, It has been found des Ir-
able to design a structure for the 25-year occurrence. This Is pri-
marily due to the fact that It is costly to ralsl~ the embankment an
additional two feet and expand the width of the bridge by 30 feet
s Imply to meet road criteria.

31. The alignment of the 156th Avenue bridge should be straightened. (Sheet 6),

32. In areas where geometric channels are to be constructed, low flow
channels shal I be provided. In most Instanc:'~s It Is not possible
to carry a low flow channel through bridges.. FOlc this situation
and to al low pedestrIans to keep theIr feet dry, it Is recommended