If you are managing several stormwater ponds, it may have crossed your mind that dredging will be needed at some point. Hopefully your community has had a professional reserve study performed which includes funds allocated to a future dredging project. If you have reviewed this line item, you may see that it is one of the costliest projects that a community will ever undergo. Still, you may find that even though funds have been allocated, these funds may not be adequate to cover the scope of work needed. In order to prepare for the “big dig out” that may be around the corner, here are a couple of tips to prolong the time needed between dredging projects:
Sediment Surveying: Your lake is a dynamic and unique ecosystem. Bathymetry allows you to better understand the changes that are going on in your lake. Sediment Surveying is the science of three dimensional lake mapping where surface area is shown with the corresponding depths. It shows the underwater mountains and valleys. Specifically, it shows the very shallow parts of your pond. It also gives information on the quantity, location, and types of sediments sitting at the bottom of your pond. When compared to original plans, it will also allow you to calculate the rate at which your pond is filling in with sediment. This information allows you to tailor your dredging planning and budgeting to be more site and cost specific, reducing the unknown and taking the guess work out of your long-term reserve planning and budgeting.
Aeration: Stormwater Pond aeration is an important part to any pond management strategy but specifically it can help prolong the amount of time before dredging is required. The movement of water generated by aeration keeps sediments in a suspended stated not allowing them to settle out and add layers to the bottom of your pond. By adding oxygen and movement to the water, you can slow the accumulation of organic sediment and even help to break down a vast majority of sediments through the microbial processes that are enhanced by the aeration. Minimisation of organic sediment accumulation on the bottom of the pond will greatly extend the life of your pond and push back the timeline for dredging.
Fish Stocking (Grass Carp): Fish stocking can be another effective way of increasing time before dredging is required. Stocking your pond with fish, specifically sterile grass carp, is a biological control against nuisance aquatic vegetation and algae. These fish are herbivores and only go after the vegetation in your pond. Removing harmful vegetation improves the “look” of your pond and has the added benefit of removing organic matter that can build up and increase the “filling” of your pond. By consuming these plants, the fish are effectively removing any of the nutrients that might be recycled and used for growth of new plants.
Biological Augmentation: Another way to decrease the nutrient build up in your pond is through biological augmentation which is the addition of natural bacteria and enzymes to your pond or lake, also known as “biologicals.” Biologicals are naturally occurring bacteria that utilise excess nutrients in the water for their own growth. This means that they remove the food source that algae and other nuisance vegetation need to grow. These bacteria are also responsible for helping to break down the “organic sludge” sitting on the bottom of your pond. Coupled with aeration, biologicals effectively remove nutrients and break down the organic layer slowing the “filling” of your pond.
Overall there are multiple ways to prolong the time before you need to dredge your pond. These are just a few of the more effective strategies to help your pond from filling up. Through proper pond management you can have a pond that looks great and gives you adequate time to plan for the “big dig out.”