In this article, we continue our discussion of the Top 10 most frequently cited significant deficiencies and violations to raise awareness and help operators identify and correct issues before they become a potential health threat or citations in a sanitary survey. Coming in at #1 in the Top 10, storage tank significant deficiencies (F310 and T310) were the most common findings cited during sanitary surveys for the 2022 inspection year. Storage tanks can be used for treatment to achieve log inactivation by providing contact time, or in the distribution system to help with water demand and pressure (tanks in distribution are subject to the Storage Tank Rule). The most commonly discovered significant deficiencies with tanks are related to access hatches and vents.
Access Hatches:
All water storage tanks must have at least one access opening to allow for routine inspections and, if applicable, inspections required under the Storage Tank Rule (Section 11.28 of Regulation 11). The access opening must be designed to protect the tank from contaminants such as: surface water infiltration, stormwater runoff, insects, rodents, and birds.
Access Hatches - Common Significant Deficiencies to check for and correct if found:
- Improper use of gasketing or lack of gasket on the hatch lid
- Infiltration of water, debris or dirt from the hatch
- Degrading or corroding hatch lids with pathway(s) for contamination
- Hatches with unsealed penetrations (bolts missing, unsealed openings for level sensors, etc.)
- Hatches flush with the ground or surface of the tank that can allow water, dirt or debris to enter the tank.
It is important to note that access hatches located outdoors or exposed to the elements must be fitted with a solid, water and insect tight, gasketed cover. It is recommended that the hatch overlap the framed opening, extend down around the frame, be hinged on one side, and have a locking device.
Below is a photo of an unsealed access hatch followed by a set of photos of a newly installed gasket. The supplier created a water and insect tight seal, effectively resolving the significant deficiency.
Below is a photo of a flush mounted hatch, which allows for potential contamination due to the lack of an overlapping framed opening. Note the channel on the interior of the hatch that can allow for water accumulation that can seep into the tank. These hatches are vulnerable to extreme weather conditions and contain potential points of failure.
For additional discussion about flush mounted hatches - see our September, 2022 article.
Flush mounted hatches often contain drains, which frequently clog with debris, dust, dirt and insects. During heavy weather events, these clogged drains can cause water to pass through the gasket and leak into the storage tank, as seen below.
The hatches above and below allow for insect activity and debris buildup close to or on the gasket, creating a potential for contamination. In the photo below, there are substantial spider webs surrounding the gasketed area of the hatch.
Vents:
Vents must be designed to protect the tank from contaminants such as: surface water, stormwater runoff, insects, rodents, birds, etc. All openings must be protected by a non-corrodible screen. Screens may not have openings that exceed 0.07 inches (typically 12 or 16 mesh screen). The screen must be installed within the vent at a location least susceptible to vandalism. The screen must be accessible for replacement. Vents must be designed for unobstructed air flow into and out of the tank.
Common Significant Deficiency to check for and correct if found (the following air vent conditions are not allowed):
- Storage tanks with unscreened, open construction between the sidewall and the roof
- Air vents that are not screened or that have damaged or blocked screens
- Air vents with screens with openings that exceed 0.07 inches (typically 12 or 16 mesh screen)
- Outdoor tanks with air vents that do not open downward or are not fully covered to protect from rainwater
Please keep in mind, the use of steel wool and/or stuffing steel wool into vents is not accepted as a proper form of screening a vent.
Below are photos of an interior tank lid that is improperly vented. The venting for these commonly found tanks function as a labyrinth preventing potential contaminants; however, the vent does not contain a mesh screen with openings that do not exceed 0.07 inches. With the addition of the mesh screen, the supplier now meets the requirement. Please note that indoor tanks must be vented and must be located at or above the highest point of the tank.
Vents on outdoor tanks must open downward. Downturned vents can be candy cane, mushroom style, or where no portion of the vent screen is visible from a horizontal position (e.g. vent in the side of a hatch assembly with louver protecting the vent). Any vent cover must overlap so that no horizontal pathway exists. Candy cane or downturned vents are allowed to have a visible screen (i.e. not covered) below the bottom of the vent opening as long as no direct horizontal pathway exists between the vent opening and the tank. When a mushroom type vent is used, the minimum opening distance must be measured from the lowest point on the vent cap to allow for air flow to enter the screened area. Integral vents on tanks (e.g., threaded cap on a polyethylene tank access lid) that do not have downturned screening are not allowed outdoors.
For outdoor elevated tanks, the vent elevation from the top of the roof should be a minimum of 24-inches above the top of the roof to prevent snow from clogging vents. The photos below show air vents on an outdoor tank that are screened but not downturned or fully covered to protect contamination from rainwater.
Please note there are resource online to assist water systems in the operation and maintenance of storage tanks:
- Section 11.28 (Storage Tank Rule) of Regulation 11 outlines the requirements for the proper operation of storage tanks.
- The Storage Tank Rule webpage provides templates and instructions for both periodic and comprehensive tank inspections.
- Drinking Water Policy DW010 provides general definitions of basic drinking water terms, as well as common findings defined as sanitary defects.
- Chapter 7 of the State of Colorado Design Criteria for Potable Water Systems contains specific requirements for the design, construction and amendments of water storage tanks.
The supplier is responsible for complying with Section 11.28 (Storage Tank Rule) of Regulation 11. Please note that if an inspector identifies any of these issues during a sanitary survey and they have not been previously identified as sanitary defects with a written corrective action schedule, they will be cited as significant deficiencies. If sanitary defects were identified by the supplier during a Storage Tank Rule periodic or comprehensive inspection but are not under a corrective action schedule or were not fixed in accordance with a corrective action schedule, a violation of the Storage Tank Rule may be cited during the sanitary survey. It is highly recommended that the supplier’s inspection documentation include pictures of the “before” and “after” corrections for each sanitary defect.
Prior to making any alterations to tank venting the department recommends that the supplier consult with an engineer or a professional with expertise in potable water storage tanks to ensure that the tank’s venting capability is not compromised. Alternatively, the supplier can check with the manufacturer of the storage tank to see if any limitations exist for the component in need of alteration or repair.
➽ Connor Clarke, CWP, Field Services Section
