BOARD00205

• Board Meeting Date: 3/10/1998
• Description: CF Section - Boulder and Left-Hand Irrigation Company
• Board Meetings - Doc Type: Memo

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pipe is not indicative of a concrete pipe embedment through the embankment The headwall
itself is about 8 inches thick.

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We proceeded to photograph the inside of the conduit using the Sled. Photos were taken
at six-foot intervals up the pipe, starting witb the camera at one foot inside the pipe. (See the
attached photos,) Refusal of the sled was met at the upstream gate, with the camera at 61'-8"
into the pipe; the point of the front runner' of the Sled was subsequently measured at r past the
camera position. and so the total length of the pipe is 62'-3",

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The photos show the full length of the pipe to be in about the same condition as the
downstream section which was photographed last March. A few dark streaks (seeps')} and areas
of rust are apparent, particularly toward the downstream end, and several bright streaks of
orange are notllble, By the time the camera is 13 feet into the pipe, the streaks are no longer
apparent and we pipe appears to be fairly uniform in shape and color. At 31 feet in. the pipe
starts to appear more of a brownish-red rust color, which continues up to the gate. Also at 31
feet (top photo, sheet 4), what could be a wet or slightly open joint appears along the crown and
left side of the pipe about 6 feet funher up, but the camera has advanced past this feature by the
next photo. No other obvious holes or open joints are apparent from the photos, and the pipe
appears reasomwly circular and watenight The gate leakage shown in the last two photos is
coming primarily around the sides of the gate, mostly from the right side (looking upstream),

Although the photos do not show obvious severe corrosion of the pipe wall in most areas,
the pipe has to I>e considered suspect along its length due to the conditions observed first hand at
the downstream end Judging from the photoS, this is likely to be the worst area of corrosion _
along the pipe length, but it is probably indicative that the pipe is reaching tbe end of its service _
life, especially likely if it is of 1948 vintage. While the only obvious area of perforation is at the
downstream encl, other areas of the pipe are probably not far behind Since the previous set of
photos did not, by themselves, lead me to believe that the pipe had corroded through at any
location, even wough the problem would have existed then, the photos should not be relied upon
to the exclusion of other physical evidence. The suspected condition of the pipe was discussed
with Lee and John,

Conclusions

I believe that this outlet conduit, based on its observed condition, needs to be =*"-
rehabilitated in the near future. Probably the most viable method would be by sliplining, which
should be rather easy to do if accomplished before funher degradation of the existing pipe
occurs. The problem is not yet critical, but should be addressed expeditiously before problems
do develop, and to take advantage of the apparent integrity of most of the eJcisting pipe, I will
therefore prepare a letter to the owner requiring rehabilitation of the outlet conduit within the
next 3 years,

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