Produced water pits have a tough job; holding back thousands to millions of gallons of wastewater. Considering that most mixtures also include abrasives sands and sludges that wear away at the liner over time, it’s a wonder that there aren’t more leaks and losses. It’s the development of durable and chemical resistant liners that have made it possible to store produced water in such large volumes, even for long periods of time. Yet, the design of the produced water pit itself often makes it difficult to keep lined and contained over time. Discover what’s so challenging about designing and lining produced water pits.
Rocky Soil
Many of the country’s most productive hydraulic fracturing areas, including the Permian and Appalachian Basins, are also highly rocky. Larger rocks are easier to remove from soil during grading and site preparation, but small bits of stone and abrasive soils remain in place no matter how much the surface is smoothed. Bringing in layers of smooth sand or clay can help, but in many cases choosing a tougher liner is all that’s needed to overcome this challenge. Reinforced liners like RPE and RPP are a good choice for these areas to ensure that a stray rock or root won’t cause a hard-to-spot tear during installation.
Movement and Slumping
Produced water pit design recommendations, or requirements, from various states tend to call for steep sides and deep designs to minimize unwanted evaporation while encouraging settling of solids. This makes it harder to attach the liner to the sides of the pit or pond in particular. Even after a successful attachment during the installation process, it’s possible for the liner to move and slump under the weight of the produced water. Soil shifting over time also leaves the liner less supported and can cause stretching until it tears or slumps. Extra reinforcement and careful pit design, with the soil and liner’s preferred angles of repose in mind, will prevent these problems.
High Water Table
A high, water table causes issues with produced water ponds in two different ways. First, rising water from below causes the liner to bubble up and rise as well. No amount of water pressing down from above can counteract a similar pressure from below. Second, high water tables also tend to mingle with any minor seepage or leaks occurring right below the liner surface. A rising and falling water table can carry traces of produced water long distances and create the appearance of bigger leaks than you’re actually experiencing. Avoid areas with high water tables or maintain pumping equipment to keep seasonal changes from affecting the liner.
Mechanical Damage During Installation
It’s necessary to pull, spread, and stretch the liner across the ground during installation to get a perfect fit and to eliminate as many wrinkles as possible. Leaving the liner wrinkled, when it’s not necessary, results in a higher chance of cracks and leaks later. Material that’s folded together without being sealed at a seam tends to split under the weight of the water. Straightening and smoothing the liner can damage it too, so there’s a fine balance between getting a good adherence to the soil and moving on to the seam sealing step. Use equipment designed to spread and stretch liners to avoid mechanical damage. Don’t skimp on site and soil preparation since a rocky surface adds a lot of unnecessary wear and tear to the new liner material.
Fixed Lifespans
All liners, and therefore the pits and ponds lined with them, have fixed expected lifespans. It’s impossible to perfectly predict how long a liner can last, but the warranty offered by the manufacturer is a good indicator of what to expect. If a supplier can’t guarantee at least a few decades of use in a challenging environment like produced water storage, it’s likely not a good option for this kind of facility. It’s inevitable that the liner will need replacement, which may be difficult if the produced water pit is designed for long-term storage after a mining operation has shut down. Designing access and storage space for pumping processed water out during the repair and liner replacement stages will only make it easier to maintain a pit as it ages.
Chemical Reactions
Finally, the high chance of reactivity between the produced water and the liner makes it hard to prevent leaks over time. Damage from chemical reactions, triggered by hydrocarbons mixed into the produced water, tends to shorten the lifespan of all but the best pond liners. Spending a little more on oil-compatible liners will pay off in the long run by helping each liner last decades rather than just a few years.
Despite all of these challenges, using a reliable pit liner will protect the environment and limit losses. Selecting the right liner material and installing it with care are the two most valuable tricks for preventing damage and getting a long life from the pit. BTL Liners has all the hydrocarbon-compatible liner materials you need for building ponds, pits, wells, and other produced water storage structures.
