Designing a quality brine pond, that functions as desired, takes a lot more work than just picking a liner. Design steps vary depending on whether the pond is intended for storage or evaporation use. Surface area plays a large role in the evaporation rate of a body of water since anything below the surface isn’t exposed enough to air to turn into vapor. If storage is the goal, a deeper brine pond with a smaller surface area slows evaporation. Alternatively, ponds used for brine mining and salt production tend to be shallow with large surface areas to aid evaporation as much as possible. Aside from the consideration of evaporation, most of the steps for designing a durable brine pond are relatively the same for all types.
Selecting the Right Location
The brine pond works best when located as close to the source of wastewater as possible, to minimize trucking or pipelines needed for delivery. If the brine will be reused or requires further processing, the pond should also be close to those facilities when feasible. Keeping brine away from sensitive areas, like agricultural fields and land with high water tables, reduces the impact of spills or floods that releases concentrated brine. Don’t forget to factor in drainage and wind trends that can cause spray or wave risks. Full sun exposure is also recommended if you’re designing an evaporation brine pond, since sunlight dramatically speeds up the process and can help control unwanted bacterial growth.
Calculating the Total Size Based on Evaporation Rates
Evaporation rates are never steady, but liquid reduction times can be estimated based upon brine type and pond design. These estimates can then be used to determine the time needed to reach the desired impoundment level. Evaporation slows down as the brine concentration rises. So, there’s a steady curve to consider when aiming to remove as much water as possible while leaving behind valuable solids. The formulas for modeling evaporation rates require information such as surface area, daily solar radiation, average wind speeds, and the chemical composition of the brine in question. If you don’t have all of this information yet, you may need to use commonly assumed values for your initial designs and rework the plans after securing the necessary data. State environmental protection agencies are often great resources for finding local data on wind speed and sun exposure. The agency may even be able to supply you with designs for brine ponds already installed in your area to give you more ideas on how to manage your wastewater.
Double Lining the Pond for Contamination Control
The most toxic, contaminated, and concentrated brine mixtures need a little more protection than a single layer of liner material. If there are serious health or environmental risks posed by every spill or leak, double lining is the best option for securing the pond. This isn’t simply a method of laying two sets of liners right on top of each other or pouring concrete over a geomembrane. Double liners for brine ponds tend to be installed with a thick layer of soil in between them to create an absorption cushion that can hold spilled or leaked brine before it reaches the secondary liner. This interim space should be monitored continuously with leak detection sensors. These sensors are usually installed under brine pond liners anyway so leaks are caught early, but they’re essential and can’t be skipped when handling brine dangerous enough to require a double liner system.
Choosing a Liner Material
Geomembrane liner selection is outlined above, but many brine ponds need more than just a flexible plastic barrier at the bottom to protect them. Brine ponds that cover an acre or more of ground, and that are designed for long-term storage, tend to also feature a concrete liner to keep the soil stable. This also protects the impermeable material by blocking water loss through seepage. Concrete alone has limited value for seepage control because it’s surprisingly porous. Thanks to tiny tunnels that run through the concrete, it also creates capillary action like a sponge sucking up a puddle of water. This can introduce outside water into the brine pond unless there’s an impermeable barrier like a geomembrane installed between the concrete and soil. No matter the lining method, a quality RPE liner, like those fabricated by BTL Liners will likely play an essential role in protecting the bottom and sides of the brine pond.
Considering Wave Risks from Wind
Surface area, depth, and overall volume of the brine pond all affect more than just the evaporation rate and the total storage capacity. Without factoring in the highest possible wind speeds for the area, serious wave risks develop that can send thousands of gallons of brine where you least expected it. Ignoring or overlooking wave risks has led to many brine pond bank and berm collapses. These failures have created major spills with expensive remediation processes. To avoiding overfilling, allow an extra 10-20% above needed pond capacity. Then, you can manage any waves that might arise during a heavy storm without having to significantly alter your brine pond design.
Planning for Makeup Water
Unless the brine pond is completely sealed with a water-tight cover, makeup water is going to get into the pond and mingle with the brine. With proper design, this has no effect on desired evaporation rates or storage concerns. For example, a brine pond that receives a makeup water rate of 1% of its volume every year could have its surface volume increased slightly to compensate for that extra water by speeding up evaporation. Designers analyze 25-year storm record levels that show the highest amount of rainfall, both at once and over the course of a year. This helps ensure that brine ponds will hold and perform as expected even during years when there are record-breaking amounts of rainfall. Using a basic average, that doesn’t take into account unusual spikes in rainfall, dramatically increases the chances of a flood or bank breach, in addition to interfering with the normal operation of evaporation.
Preventing Spills and Leaching
Brine that is hazardous enough to warrant double lining of the holding pond most likely requires additional above-ground spill containment as well. Additional sets of berms, dikes, and other water control structures around the perimeter of the pond can make all the difference between a successful weathering of a storm and a breach that costs millions to clean up. Don’t skimp on secondary safety features just because they’re unlikely to be used on a regular basis. It only takes one failure of a brine pond’s sides or bottom to lead to major losses. Even if the spill prevention features you work into your never actually used, they’re still providing a valuable service that was worth the extra cost for design and installation.
Conclusion
Brine ponds may be tricky to design and build, but they’re absolutely necessary for handling salty water that would otherwise have a detrimental effect on the environment. They should be designed with care to extend their lifespans and minimize the need for replacement as much as possible. By choosing AquaArmor from BTL Liners as your brine pond lining material, you’re ensuring the best longevity and greatest spill and leak protection. Don’t let seepage suck up any of your valuable brine products when you have plenty of flexible, affordable, and impermeable liners to choose from. For help with product selection, please reach out to our highly trained team; we’d love to assist you!
