Fence line after hardwood removal from a ditch, in ST. Petersburg, Fla. The ditch is located behind a retention pond which had a lot of vegetative growth. This vegetative growth impacts the natural flow of stormwater, preventing the water to properly permeate through the soil. The trees also caused damage to the privacy fence around the retention pond. DGC Environmental Services went into the ditch and removed all the hardwood.
There are many types of stormwater assets and even more methods for maintaining and repairing them. A Detention Pond is our main focus in this blog post and we will discuss how to remediate a detention pond that is not functioning properly. During and after a storm event, a detention pond collects stormwater that is conveyed to it from somewhere else (usually an impermeable surface close-by). Generally, the water that collects is supposed to drain - or percolate - back into the aquifer within a 72 hour time period. An easy way to remember the difference between a detention pond and a retention pond is after school detention ended and you were let go, whereas retention is a more long term scenario, holding water permanently.
There are a number of reasons why the stormwater in a detention pond might not percolate properly, including improper design and construction, incorrect fill media, and sedimentation - a build up of sediment transported by stormwater. Rectifying all of these issues is very important for the simple fact of safety and flood control. In addition, most regulatory agencies have compliance standards and consistently look for these non-compliant systems to issue Notice of Violations - NOVs. Ensuring your detention pond functions properly will save you money on maintenance and maintaining compliance.
Our case study is an excellent representation of a non-percolating detention pond that totals approximately 4,000 square feet and includes a concrete retention wall. The pond did not drain within the allotted 72hr period, at times became an eyesore due to algal blooms and unwanted vegetation was difficult to maintain for the contractor as they could not mow sod under water. On top of all that, this site was out of compliance and an NOV could have been right around the corner, literally - there is a regional field office for the local water management district less than two miles away from this location.
The processes involved in a project of this scope extend way beyond what one might think and various specialists are involved throughout the entire project. Geotechnical experts are occasionally consulted to provide geological surveys and soil analysis. Engineers and their assessments are consistently relied upon ranging from as-built drawings to any modifications that may need to occur. In the event of a modification to originally designed systems, additional permitting is ALWAYS required and opens the door for regulatory agencies and their involvement. Proper equipment and experienced operators are vital to the success of a project of this nature. Fences and gates are also a common piece of the puzzle that need to be handled accordingly. Unforeseen obstacles such as electric conduit or irrigation systems are always a concern; while ensuring proper trees and sod/seed are specified. Seed is usually preferred to sod due to the sedimentation that naturally collects in the sod at the sod farms.
Once the geotechnical items are handled, excavation can begin. The equipment operators will have been instructed on exactly how much earthwork needs to be done to satisfy the geo-parameters. A specific, predetermined depth is achieved and the foundation is scarified. Again, pre-determined choice of fill is brought in and distributed evenly across the area that has been excavated, careful not to impact the newly laid fill material. Trees are planted, grass seed is distributed and we wait for a rain event to see our handiwork in action!!
In conclusion, it is important to know what kind of stormwater assets you have and how best to maintain them. Detention ponds are meant to percolate back into the earth over a short period of time, and when that process is stagnated the pond needs to be repaired. There are many variables that can comprise the process and a proper plan of action is fundamental in a successful project. In the event that it needs remediating, having knowledgeable, experienced contractors is a very important aspect of the process. DGC Environmental is that knowledgeable, experienced contractor.
Let’s Work Together!
DGC Environmental is the solution to your stormwater problem.