FLOOD01619

• Designation Number: 320
• County: Jefferson
• Community: Arvada
• Stream Name: Lower Ralston, Van Bibber, Leyden Creeks
• Title: Major Drainageway Planning
• Date: 2/1/1986
• Prepared For: Arvada
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Mr. Ben Urbonas
September 12, 1984
Page Three

Mr. Ben Urbonas
September 12, 1984
Page Four

OPINION:

A significant portion of the engineer's recommendations call
for channelizing the upper reaches of Ralston Creek and
channelizing the lower reaches of Van Bibber and Leyden
Creeks. The obvious purpose of these improvements is to
alleviate current and future flooding problems for pro-
perties along those channels. Just as obvious is the
physical fact that with these improvements, plus the opening
of bridge underpasses, the rate of flow of floodwaters
reaching the outlet will be increased. Therefore, the area
at the outlet should be cleared or improved in some manner
to accommodate these increased flows.

1. In general:

The following general legal premises are used by me in
evaluating the physical Characteristics of a drainage basin
and the recommendations made by the engineer:

a. In drainage matters, a municipality (Arvada) or a
county (Jefferson), or the District, can be expected to be
treated like a private party. 2 Farnham, Water and Water
Rights, pp. 975 and 977, adopted by the Colorado Supreme
Court in City of Boulder v. Boulder and Wh1te Rock D1tch
Co. 73 Colo. 426, 216 P. 553 ( 1923).

b. Any improvements upstream must be made taking into
account the outlet capabilities downstream (long line of
case law predicated on theory that it is no improvement if
your action causes someone downstream additional problems).
The Colorado State LegiSlature recognized this premise in
county (unincorporated) areas by requiring developers of
such areas to detain greater than historical flows. 1973
C.R.S. ~ 30-28-133 (4) (b).

If a major arterial is to be constructed in the
Ralston Creek floodplain, all of the above recommendations
also apply. Any highway improvements must be made on the
basis that the 100 year floodplain is not constricted or the
flood profile increased in elevation. Current Arvada and
District floodplain regulations, together with state
statutes (H.B. 1041) require careful design in this regard.

c. The owner of a reservoir in Colorado cannot be
exempted from strict liability where the evidence shows that
the owner could have foreseen a flood of the magnitude that
occurred by use of the maximum probable flood technique.
Barr v. Game, Fish & Parks, 30 Colo. App. 482, 497 P.2d 340
(1972). (H.B. 1052, enacted by the 1984 r,egislature, pur-
ports to exempt an owner of a reservoir, in the absence of
negligence, from liability for damages res~lt1ng.f~om flows
of water from such reservoir Wh1Ch are of 1nsuff1c1ent
magnitude to exceed the limits of the 100-year floodplain.
~ 37-87-104(2.5)).

At the confluence of Ralston and Van Bibber Creeks,
the engineer recommends routing floodwaters down the once
natural thalweg (which is now the parking lot for the North
Jeffco Ice Skating Rink). The safest course to follow in
all drainage matters is the natural water course. Colorado
courts have consistently followed this principle.

d. If you are not going to maintain it, then don't
build it. City and County of Denver v. Pilo, 102 Colo.
326, 79 P.2d 270 (1938).

In some areas of Ralston Creek above its confluence
with Van Bibber, the engineer's proposed "European Channels"
will go through the middle of city blocks where the
constricted channel now flows. Communicating and
discussing the proposed channelization with abutting
property owners will be most important. Constructing a
deeper and wider channel, which entails using some of their
property for their benefit, has to be clearly delineated
to insure maximum cooperation.

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2. Specific comments on Alternatives:

a. Ralston Creek - One of the key recommendations by
the engineer is the relocation of the trailer court at the
confluence of Ralston Creek and Clear Creek. This trailer
court is at the outlet of this large 91 square mile basin.

b. Van Bibber Creek - Channel and conduits above and
through the Arvada Shopping Center to convey the 15-year
flood are recommended. Flow limiting structural improve-
ments are also recommended. However, by eliminating the Van
Bibber Creek reservoir proposal of previous years, and
phasing the Oak Street detention facility to subsequent
years, the recommended improvements (as on Ralston and
Leyden Creeks) are not meant to protect against the 100-year
flood. This decision, if it is made by the legiSlative