The interior and exterior of water storage facilities
serving public water systems shall be regularly inspected and maintained.
Inspections of storage facilities 10,000 gallons or greater shall be by a
professional tank inspection firm or by a registered professional engineer.
Maintenance shall include removal of sediment and biofilm prior to evaluation
of structural, mechanical and coating systems. Repairs shall be provided as
necessary to ensure good working condition. Interior and exterior paint
coatings for steel elevated water storage tanks or treatment structures shall
be inspected by a person trained to evaluate the integrity of the paint system
and repainted as necessary to maintain structural integrity. The water supplier
may perform the inspection if experienced in paint inspection.
(1) FREQUENCY. All storage facilities shall
be inspected a minimum of every 5 years and as required in sub. (2) (a) unless
otherwise approved by the department. Repairs or welding on the exterior of a
tank may make a special interior inspection necessary. Exterior inspections of
vent and overflow screens and hatches shall be conducted once per year by the
water supplier.
(2) METHODS. Any of
the following methods are acceptable for the required 5-year interior tank/
water storage facility inspection:
(a)
Drain down inspections. Drain down inspections include completely
draining the tank. Rigging and ladders may be necessary to access all surfaces.
The tank shall be cleaned of all sediment prior to inspecting. Unless an
alternative schedule is approved by the department, a drain down inspection
shall be utilized a minimum of every ten years or every other inspection.
1. Following all drain down inspections and
painting, the interior of the tank shall be disinfected in accordance with one
of the methods in AWWA Standard C652-02. A minimum of 2 successive safe
samples, taken at 24-hour intervals, shall be obtained which indicate
bacteriologically safe water; or one safe sample shall be obtained only if a
free chlorine residual of at least 0.1 mg/l is remaining when the results of
the safe sample are reported.
2.
For all concrete ground reservoirs with cracks or signs of leakage, the top
shall be soaked with water and the interior shall be checked for
leaks.
(b)
Float
down or partial drain inspections. Float down inspections involve the
use of a disinfected inflatable raft and allow access to all levels of the
tank. The water level shall be lowered below the normal low operating level to
expose the sidewalls of the tank. If the tank is to remain in service during
the inspection or the water will be sent to the distribution system following
the inspection, all of the following requirements apply:
1. A minimum 0.5 mg/l chlorine residual shall
be maintained in the tank throughout the inspection.
2. All equipment shall be dedicated for
potable water use and is disinfected with a 200 ppm chlorine
solution.
3. For all concrete
ground reservoirs with cracks or signs of leakage, the top shall be soaked with
water and the interior shall be checked for leaks.
4. A minimum of 2 bacteriologically safe
samples shall be obtained from the tank after the inspection, one following the
inspection and one 24 hours later.
5. A minimum pressure of 35 psi shall be
maintained throughout the distribution system during the inspection.
(c)
Diver
inspections. Diver inspections shall involve the use of a commercial
diver tethered to, and in communication with, the outside. Procedures shall be
done in accordance with Section 4.4 of AWWA Standard C652-02 and Section 12.0
of the Consensus Standards for Commercial Diving and Underwater Inspection. The
department recommends that the tank be removed from service during the
inspection. If the tank is to remain in service during the inspection or if the
water will be sent to the distribution system following the inspection, all of
the following requirements apply:
1. A
minimum 0.5 mg/l chlorine residual shall be maintained in the tank throughout
the inspection.
2. All equipment
shall be dedicated for potable water use and shall be disinfected with a 200
ppm chlorine solution. The inspector shall also be disinfected.
3. The inspection of the tank shall be done
after the sediment is removed from the bottom of tank and shall include a
visual inspection of any expansion joints.
4. For all concrete ground reservoirs with
cracks or signs of leakage, the top shall be soaked with water and the interior
shall be checked for leaks.
5. A
minimum of 2 bacteriologically safe samples shall be obtained from the tank
after the inspection, one following the inspection and one 24 hours
later.
(d)
Robotic inspections. Robotic inspections shall involve a rover
unit with a fiber optic tether and video camera and shall include cleaning
capabilities. If the tank is to remain in service during the inspection or if
the water will be sent to the distribution system following the inspection, all
of the following requirements apply:
1. A
minimum 0.5 mg/l chlorine residual shall be maintained in the tank throughout
the inspection.
2. All equipment
entering the tank shall be dedicated for potable water use and be disinfected
with a 200 ppm chlorine solution.
3. For all concrete ground reservoirs with
cracks or signs of leakage, the top shall be soaked with water and the interior
shall be checked for leaks.
4. A
minimum of 2 bacteriologically safe samples shall be obtained from the tank
after the inspection, one immediately following the inspection and one 24 hours
later.
(3)
DEPARTMENT NOTIFICATION. The department's regional drinking water staff person
shall be given 48 hours prior notice of the date and time of the
inspection.
(4) INSPECTION REPORT
SUBMITTAL. Upon completion of the water storage facility inspection, a
completed department report form shall be submitted to the department's
regional drinking water staff person documenting the condition of the storage
facility. The water supplier shall submit copies of any additional reports and
videos prepared by the inspector.
Note: The report forms are available from the department's
regional or central office drinking water program staff.
(5) MANHOLE COVER GASKET. Following all
inspections and maintenance, the integrity of the gasket between the access
manhole cover and curbing shall be checked and replaced if necessary to prevent
the entrance of dust and insects. If no gasket is present, one meeting s.
NR 811.64(7) requirements shall be
provided to prevent the entrance of dust and insects.
