Bid Package 08 North Well Field - Garney Construction

Colorado River Municipal Water District
Vertical Turbine Submersible Pumping Units
Ward County North Well Field
to the concrete well seal block with stainless steel expansion anchors at least 6 inches in
length and of a diameter as recommended by the pumping unit manufacturer.
G. The Contractor shall install the conductors in the conduit and incidental items necessary
for installing the power cable from the wellhead junction box to the motor controller. The
electrical work shall be done by a licensed electrician. All conduit and wiring shall be
sized, installed, and grounded in accordance with the National Electrical Code or as
modified in the plans or specifications.
H. After the equipment has been installed it shall be checked for proper operation as
indicated in Part 1, System Startup, Owner’s Instruction, and Commissioning.
3.2 Disinfection of Well (by others, not in this Contract)
A. The Contractor is advised that all wells were previously disinfected after construction and
were found to be absent of coliform. Three consecutive days of testing were performed
during the step-drawdown test. The disinfected condition of the wells is unknown and
will be required as part of this contract after the permanent pumping equipment is set.
B. It shall be the Contractor’s responsibility to disinfect the wells in such a manner as to
comply with the requirements of TCEQ Chapter 290, Water Hygiene. Official testing for
coliform will be conducted after the permanent pump has been installed. A minimum of
10 casing volumes shall have been evacuated prior to obtaining the official samples for
testing. Disinfecting the wells shall be accomplished by the Contractor in accordance
with AWWA C654-97, Disinfection of Wells, including the safe disposal of high
concentrations of chlorinated water.
C. Merely introducing a chlorine solution into the well will not be considered satisfactory.
The water in the well casing shall be treated with chlorine to give an average chlorine
dose of 50 mg/L to the entire volume of water in the casing. After the chlorine has been
applied, surge the well at least three times to improve the mixing and induce contact of
the chlorinated water with the adjacent aquifer. Surging of the well to induce mixing of
the disinfectant may not be possible with the permanent pumping equipment as the
column pipe will be fitted with a check valve. It may be necessary for the Contractor to
utilize his own auxiliary pumping equipment to achieve the required surging of the wells.
The chlorinated water shall rest in the casing for at least 12 hours, but no more than
24 hours.
D. Following the rest period, circulate the chlorinated water by pumping, wasting some of
the water and returning some to the well, periodically testing for chlorine residual.
Testing for chlorine residual shall be performed by the Contractor or his approved testing
laboratory. When zero chlorine residual is measured, continue pumping the well to waste
for at least 15 minutes or 10 casing diameters, whichever is greater. The Contractor shall
then sample the well for bacteriological evaluation. Samples shall be submitted to a
Texas Department of Health approved laboratory for chemical analysis until three
successive daily raw water samples are free of coliform organisms.
E. The bacteriological evaluation shall be tested by a Texas Department of Health approved
laboratory for the presence of coliform in accordance with Standard Methods of the
January 2012
Submersible Vertical Turbine Pumping Units
Revision 0 11210 - 12