Storage Tank Rule
Questions around wetwells are now included in the sanitary survey. If you haven’t seen a question during your most recent sanitary survey, you’ll probably hear it during your next one.
Why are we interested in wetwells?
A wetwell is a specifically designed system that pumps water from one place to another, usually against gravity forces (e.g. pumping water upwards or uphill). We are interested in wetwells because some wetwells fall under the definition of a finished water storage tank. Regulation 11 (11.28(1)(c)) states that any “tank or vessel owned by the supplier that is located downstream of the entry point and is not pressurized at the air water interface” is subject to the storage tank rule. Additionally, chapter 7 of the design criteria states “All tanks storing finished water including distribution pump station wetwells must meet the requirements of Chapter 7.” Unpressurized wetwells are an important part of the storage tank rule that the state is looking to improve on identifying in order to protect public health.
Starting this year we’ve begun a three year process to discuss and identify unpressurized wetwells during sanitary surveys. If the inspector finds a wetwell that meets the definition of a storage tank it will be added to the supplier’s Safe Drinking Water Information System inventory and the storage tank plan.
Having wetwells in the storage tank plan will necessitate quarterly inspection, unless there is an alternative inspection plan in place. Since the department hasn’t previously required that wetwells be included in the storage tank plan, we will not be issuing any violations for failing to perform periodic inspections of previously unidentified, unpressurized wetwells until 2022.
However, we will be looking for any sanitary defects and significant deficiencies associated with wetwells, especially those associated with any existing hatches, vents and overflows. Recent sanitary surveys have found debris, foliage, spiders and even a chipmunk carcass in wetwells. Unpressurized wetwells, like all storage tanks, need properly screened vents, water tight hatches and protected overflows to protect the quality of the finished water.
The department encourages suppliers to be proactive in addressing the addition of unpressurized wetwells to storage tanks plans. If you have unpressurized wetwells, contact your compliance officer and update your inventory. Add any unpressurized wetwells to your storage tank plan and begin conducting and documenting periodic inspections.
Now when the inspector asks about vertical turbine wetwells during your next sanitary survey, you’ll know why.
➽ Greg Naugle, Field Services Section Manager
Storage Tank Inspections
The Storage Tank Rule (Section 11.28 of Regulation 11) requires all public suppliers of water with finished water distribution system storage tanks to conduct comprehensive storage tank inspections every five years or on a department accepted alternative schedule. Suppliers operating such tanks must complete their first comprehensive inspection on or by April 1, 2021 and subsequently every five years thereafter. Finished water storage tanks that are not inspected and maintained can present a pathway for microbial contamination into the tank, which constitutes a sanitary defect.
While inspection of water tanks should be a priority, please be aware that operator safety is of paramount importance when conducting tank inspections, especially comprehensive inspections. Never inspect a tank if there is any question about the safety of the personnel involved.
Comprehensive tank inspections are more robust than periodic inspections and include a thorough inspection of all external and internal components of the storage tank. As with periodic inspections, the goal of completing comprehensive tank inspections is to identify any sanitary defects that could be present. These defects cover all aspects of the condition of the storage tank including but not limited to sanitary, structural, and coating systems conditions, as well as security and safety concerns.
Common examples of tank sanitary defects identified during inspections include, but are not limited to, the following:
- Access opening with no sanitary seal (i.e., metal on metal hatch) or a damaged gasket.
- Unscreened tank vent or overflow.
- Blistering of interior coating to the degree where it is peeling into the water.
- Greater than one inch of sediment on the tank floor.
- Unsealed or inadequately sealed tank penetrations.
- Visible contamination inside the tank.
The inspection method that the supplier chooses to complete a comprehensive inspection largely depends on the type of storage tank being operated and whether the tank can be pulled off line. In some cases, the supplier may choose to contract with a company that dives into the tank to inspect it internally with the use of both video and still photos.
At the conclusion of the inspection, the contractor will typically provide the supplier with a written inspection report. The department has reviewed numerous comprehensive tank inspection reports and has frequently found that the reports have identified what the department deems a sanitary defect but the report states the defect as a recommendation or in some cases there is no mention of any needed follow-up action. If the inspection report includes any finding that constitutes a sanitary defect as a recommendation or does not mention that any action is needed, the supplier must respond to it as a sanitary defect. The supplier needs to include and complete a corrective action schedule for any sanitary defect in the written inspection plan. Failing to do so results in a treatment technique violation of Regulation 11 that requires notification to the department no later than 48 hours after the violation occurs and completion of a Tier 2 public notice.
Please keep in mind that it is the responsibility of the supplier to understand what constitutes a storage tank sanitary defect and to correct it. The department’s tank inspection checklists highlight in bold which questions are sanitary defects depending on a Yes or No answer. These checklists are available on our website.
In addition, the department has a Sanitary Defect Applicability Policy (Safe Drinking Water Program Policy # DW-010) that outlines what constitutes a sanitary defect in water distribution systems including storage tanks. This policy is available on the drinking water policies webpage.
For questions concerning finished water storage tank inspections and what constitutes a sanitary defect, please call the department at 303-692-3500.
➽ Cathy Heald, Non-Community Groundwater Unit Manager
