Bid Package 08 North Well Field - Garney Construction

Colorado River Municipal Water District
Raw Water Supply Well Sites
Ward County North Well Field
1. Contractor shall verify that the well casing, screen, and sump are free of
sediment. If sediment has accumulated, clean by bailing or other Engineerapproved
method.
2. Prior to installation of pumping equipment, Contractor to ensure pump outside
diameter is at least one (1) inch less than the inside diameter of the well casing to
the pump installation depth.
D. Power cable: supported on the column pipe by means of cable clamps and stainless steel
bands. Cable clamps shall be suitable for continuous submergence and carry an NSF seal
if not stainless steel. Place cable clamps every 20 feet, minimum.
E. Column check valves: Install less than 20 feet above the pump and thereafter in
conformance with manufacturer suggested spacing. In no case shall the distance between
valves and the surface plate be equal. Unequal distances are essential to prevent harmonic
valve hammer.
F. Surface plate: Install per manufacturer’s installation instructions and as indicated on the
drawings.
3.2 DISINFECTION
A. Disinfection of Wells: per AWWA C654.
B. 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. However, disinfection will be required following
submersible pump installation.
C. Contractor shall disinfect each well to satisfy the requirements of TCEQ Water Hygiene
(Drinking Water) rules (TAC Chapter 290). 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.
D. Forms of Chlorine: Disinfectant used for the wells shall be in liquid form. Solid tablets or
powders will not be allowed. A simple chlorine solution will not be satisfactory.
E. Well chlorination:
1. Water in the well casing shall be treated with chlorine so that an average chlorine
residual of 50 milligrams per liter (mg/L) is in the entire volume of water in the
well casing. Chlorinated water shall rest in the well casing for at least 12 hours,
but no more than 24 hours.
2. 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. 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.
3. Testing for chlorine residual shall be performed by the Contractor or his
approved testing laboratory.
May 18, 2012
Submersible Pumps and Installation
Revision 0 11 97 00 - 4