Erosion and Sediment Control: Plan Development
Erosion Control Devices and Installation Procedures
One of the most important factors for a successful erosion and sediment control plan is the timeliness of its installation. In order to contain sediment on-site, the timing of erosion control device installation must be coordinated with the progress of construction. Devices should be installed before the area draining to them is disturbed, if possible. As grading progresses and as drainage structures and inlets are installed, it is important that erosion control devices be constructed in intermediate phases to protect them from off-site sediment. This ensures that all new outlets and/or modified drainage patterns are protected from causing off-site sediment.
One of the most critical times for installing erosion control devices is at the clearing and grubbing stage. Clearing and grubbing erosion and sediment control plans should be available for most projects where clearing is necessary. These plans are designed to protect from off-site sediment by utilizing perimeter controls to intercept, divert, and/or address the first phase of construction and should be followed by installation of the final plans as construction permits.
A very critical location on these projects during this stage is at or around streams. Care should be taken to minimize disturbance to the natural stream bank. Diversions should be placed on both sides of the channel to intercept the runoff and divert it into devices to allow for entrapment of the sediment before discharging it into the stream. In addition, vegetative buffer zones (strips) adjacent to streams should be left in place until construction progresses in that particular area. This will provide protection to the stream from the cleared area until the work around the stream begins.
Location of Devices
The erosion control plans have been designed and drawn just like the roadway and structure plans and they must be given the same attention and importance. Many factors have been taken into account, such as topography, hydrology, desired trapping efficiency for a certain designed storm, sensitivity of the site, etc. Inspections of the site and knowledge of the erosion and sediment control devices and their uses make the designer and their advisers the most capable people to decide what measure is best for each location. The location and size of each device have been given careful consideration by the Roadside Environmental Unit and are designed to stop and/or control the anticipated erosion in the area.
The devices are designed to slow down the water flow in ditches and along roadway sections so that the silt will either settle out or it will be filtered out. This also reduces the cutting effect of fast moving water. The size of the devices is such that it will be able to handle the volume these devices are not normally placed in active streams because we do not want to restrict the flow of "clean" water.
For these reasons it is important that each device be placed as close as possible to the location shown on the plans and be built to the designed size. This is because we have a responsibility to keep the surrounding area clean and because the Land Quality representative will expect all of these erosion control measures to be installed as shown on the plans.