Retention ponds are often as simple as holes dug in low lying dirt areas but can also reach high levels of complexity with multiple compartments, advanced filtration systems, and extensive overtopping protection for floods. Regardless of how basic or complex the pond, the same principles apply to the creation and management of all retention areas.
Storm Water Storage
In general, retention ponds are only used for gathering, storing, and processing storm water. Similar drainage ponds and basins are used for managing irrigation water runoff and industrial processing wastewater, but these structures require different designs. Rural retention ponds may receive runoff from surrounding farms and livestock fields, requiring a comprehensive approach to processing the high nutrient load. Storm water ponds in all settings are prone to silt build-up and rapidly changing water conditions, requiring routine management to maintain steady performance.
Treating Polluted Water
The majority of well-built retention ponds also serve as treatment systems to condense dissolved solids and to process high levels of nutrients and contaminants before the water reaches other natural waterways. When a retention pond is undersized or lacks vegetation and other living features, it tends to discharge water that causes algae blooms or fish kills in nearby streams, lakes, and ponds. Filters, skimmers, and routine chemical treatments are only necessary for the most intensive treatment ponds. Most retention basins simply need a thriving water-based ecosystem and appropriate holding time to transform contaminated runoff into relatively clean discharge water.
Flood Protection
Properly sized ponds and basins redirect excess storm water to prevent flooding in streets and around homes and businesses. Flooded streets can lead to accidents and injuries, while flooded structures cost tens of thousands of dollars to repair. Retention ponds should play an essential role in a city or town’s flood control system for both immediate and long-term storm water management.
Flexible Design and Sizing
With many options for storm water management, some municipal managers question the need for seemingly old-fashioned retention ponds. However, these installations remain popular around the world because of the sheer flexibility in sizing and design to handle practically any amount of water. Some retention ponds are as large as many man-made lakes, allowing for recreation and even power generation options if the water quality is high enough.
Gradual Discharge
These ponds are designed to release storm water slowly rather than allowing it to stand on the surface of saturated soil. Since paved areas like parking lots and ground covered by structures can’t absorb water, it’s necessary to gather all those gallons in a central location for gradual discharge. A controlled rate of release is essential for both settling out silt and processing nutrients and chemical contaminants.
Connection to Water Sources
Water can travel to the retention pond through dozens of different paths, including:
- French drains and gutter downspouts connected to storm drains
- Open street-side drains and large culverts at the lowest points of an area
- Flat surfaces like parking lots that gradually slope towards drainage ditches
- Surface runoff that accumulates from paved surfaces or surrounding open fields and slopes.
Retention ponds are installed at the lowest point of a particular area to accumulate as much runoff as possible. Some ponds are installed in chains to capture any runoff or excess water from previous basins for extra flood protection.
Potential Secondary Benefits
Healthy and useful retention ponds offer a wide range of secondary benefits to the community or neighborhood around them. Many subdivisions and gated communities have designed their ponds to serve as a recreational or aesthetic feature to attract new buyers. Ponds fed by clean runoff that may contain silt or nutrients from nearby farms are often clean enough for growing fish to catch for fun or consumption.
Regardless of the capacity of the pond, it should be lined with an impermeable geomembrane like those from BTL Liners. Our expert team members, specifically recommend the PP-45, RPEL-30 or BTL-40; all part of our AquaArmor product line. Our flexible and durable liners can withstand the most challenging runoff and storm water storage applications to prevent rapid discharge and saturated soil conditions that can lead to collapsed banks.
