For temporary or permanent planting on a construction site, Bowers recommends using hydroseeders. This equipment mixes together seed, mulch and additives such as fertilizers to create a slurry substance.
“When you spray the slurry on the ground, the mulch fibers hold your seed and additives on top of the soil, effectively creating a cap,” Bowers explains.
“This does a couple things. It keeps the soil underneath from getting direct water runoff. It keeps the soil from taking a direct water hit. And it also holds the nutrients the seed needs to get started right there where the seed is. It can hold them in suspension until it gets regular water. But as soon as you start watering it, several weeks later you’re going to need to mow it. It starts growing quickly, and as soon as you have root, it’s the root that you’re counting on to hold the soil in place. Also, because you are planting from seed, when you hydroseed with the proper soil amendments and additives, you get a healthier root structure than with sod.”
Options For Runoff Control
Stopping all erosion and eliminating all chances of runoff is a high order. You have to expect some sediment to collect in storm water during a heavy storm. Retention ponds, sediment basins or traps and protection of existing water-flow channels on site can help control this runoff.
Silt fencing is a very common method for temporarily containing runoff. The fabric that makes up the fence is permeable, allowing water to slowly drain through while capturing sediment. Silt fence can be installed manually. A trencher is used to create a trench, workers place the fabric into the hole, secure it with posts, then backfill and compact the soil around the trench.
Compacting the soil after manual installation is a critical factor often left undone, notes Tom Carpenter, a certified professional in erosion and sediment control, and owner of Carpenter Erosion Control, developer of the Tommy Silt Fence Machine. He cites an EPA study, co-sponsored by his company, which found that compaction is the key to ensuring silt fence remains firmly in place.
Equipment specifically designed for silt fence installation serves as an alternative to manual methods. The equipment slices through the ground with minimal soil disturbance, then a wheel following the slicing mechanism pushes the fabric into the ground. Workers later come through and attach the fence to either wooden or metal posts and compact the soil next to the fence.
“A machine installation is the same every time,” Carpenter points out. “You’re not excavating any soil, so you can slice it in and all the soil is still on either side of the fence. Then you compact it with the wheel of your vehicle and you have a silt fence that won’t wash out on the bottom.”
Installation time is also greatly reduced, says Carpenter. “You eliminate soil excavation and consequent backfilling,” he explains. “And a silt fence machine is more maneuverable on construction sites, saving double to triple the installation time.”
Like all other BMPs, a silt fence needs to be inspected and maintained, with intervals more dependent on weather than on time. “If it rains an inch every day, you might have to replace the silt fence every day because it’s full of sediment,” Carpenter says. “But if it doesn’t rain for three months, then one silt fence might last a long time.”
Whether you’re working on a 50-acre development project or a 1-acre parking lot, adherence to the EPA’s storm water runoff rules can help save your company from facing steep fines, and help save our nation’s waterways for the enjoyment of generations to come.