Storage Tank Rule
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
