If digging and lining a pond sounds like a lot of work, it’s also possible to choose pre-formed vaults and tanks to hold fresh water or waste products. These ready to install structures or custom-built designs may seem like a faster way to add storage. Unfortunately, they often take just as long as a pond to construct or install and have a similar cost for the same volume of storage. Here are a few other reasons that in-ground ponds with floating covers tend to win out over buried one-piece vaults or above-ground tanks with solid covers.
Total Volume
Whether pre-cast or built in place, tanks and vaults have a much more limited storage volume than in-ground ponds or basins. When you need to store millions of gallons of waste, or water at a time, a pond quickly becomes more economical to build and maintain than dozens of individual tanks or vaults. Don’t forget to consider long-term costs of ownership when comparing prices for two different methods of water storage.
Corrosion Resistance
The concrete and steel used for vaults and tanks, respectively, both lack the chemical resistance offered by high quality pond liners and covers. Geomembranes are easily formulated to maximize resistance to specific chemicals, ensuring that high concentrations of chlorine or other water treatment chemicals won’t cause the liner or cover to break down. For concrete and steel fixtures, this necessitates special coatings and routine inspections to ensure corrosion isn’t about to rupture a holding tank or vault.
Overflow Control
Fixed, above-ground tanks with rigid covers and in-ground vaults are all capable of holding only a specific amount of liquid. As soon as one gallon over the total volume enters the system, overflow conditions will begin and may damage the vessel itself. Ponds are much more flexible in their ability to handle extra water and re-route overflow liquid so it’s not damaging to anyone or anything. Thanks to the large surface area and the use of impermeable liners that can stretch, it’s easier to deal with slight fluctuations in flow without immediately experiencing flooding issues.
Installation Difficulty
Pre-cast concrete vaults and assembled steel tanks are popular in water holding projects because they are quick to install once they’re on site. With no curing times and few welding requirements, they’re ready to use soon after installation. However, actually getting them on site is a different story. The difficulty of moving a heavy and oversized piece of equipment can inflate the cost of the project tremendously. Heavy equipment for excavating ponds is easy to source locally, and the geomembranes used for both liners and covers are surprisingly lightweight and easy to fold compactly for shipping.
Scum Submergence
Maintaining proper scum submergence is an essential feature of a flexible floating pond cover. Since the floats and weights work together to keep the cover right at the surface of the water, it’s not surprising that this helps push the scum layer underneath where it can decompose rapidly. This is an essential task in both wastewater treatment and manure digestion for biogas production. Solid, single-piece tanks and rigid covers don’t rise or fall with the water level, eliminating the chance they’ll help with scum submergence.
In almost all cases, custom ponds with covers to fit make more sense than a collection of tanks or vaults. For an advanced wastewater treatment center, you may need to combine all three to divert sludge and direct cleaner water to further polishing steps. If you plan to use concrete or steel sides, to increase pond volume, make sure to extend the liner over these additions before re-attaching the cover. BTL Liners cover and liner products will work well for these applications and more. Their expert team is readily available to help you select the best product for your project and answer any questions you might have.
