7.40 WATER POLLUTION CONTROL (SOIL EROSION)

While this section addresses soil erosion on all projects, Construction Manual 10.30 addresses the additional requirements of a storm water discharge permit. Coverage under the Iowa Department of Natural Resources permit is required for all projects which disturb more than 0.4 hectares (1 acre).

The primary objective is to control soil erosion during construction with reasonable and economical construction practices.

While the contract documents indicate locations of erosion control devices (silt fence, ditch checks, and silt basins), their actual location should be determined in the field in order to fit existing conditions.

The erosion control devices should not be limited to those which are included in the contract documents. The project engineer should authorize adding any device that will be most effective in controlling erosion.

The primary method for temporary erosion control is stabilizing crop seeding and fertilizing. The application of stabilizing crop seeding does not require inoculation, application of sticking agent or fungicide, except for hairy vetch and other legumes which require inoculation. After the fall seeding period, areas which are not seeded should be roughened and mulched.

Stabilizing crop seeding requires seedbed preparation as described in Specification 2601.04A and covering and compacting as described in Specification 2601.05C.

The installation of silt fence for ditch checks should be installed prior to any soil disturbing activities occurring on the project.

7.41 CONTRACTOR REQUIREMENTS

The contractor's responsibility is to insure that soil erosion is minimized and to prevent eroded soil from leaving the construction project onto adjacent property. Timely installation of silt control devices, such as silt fence and ditch checks, will help to prevent this damage from occurring. The most effective erosion control practice is stabilized crop seeding which shall be done as the grading progresses. This may require the erosion control contractor to mobilize and seed more than once.

The contractor's schedule (sequence of operation) and proposed method for accomplishing the required erosion control must be submitted to the project engineer and be approved before clearing and grubbing or excavation begins.

The contractor's erosion control work plan should include the following:

• Materials to be used
• Equipment to be used
• Location and timing of silt fence and silt basins and other temporary erosion control measures outlined on Standard Road Plans RL-9
• Schedule for placement of stabilizing crop seeding and fertilizing

If the temporary erosion control is to be performed by a subcontractor, the subcontractor should be involved in developing the work plan.

Damage due to siltation on private property shall be corrected by the contractor with no expense to the contracting authority.