EROSION & SEDIMENT CONTROL
7.00 GENERAL INSPECTION
Inspection personnel assigned to erosion control work should review project plans, specifications, special provisions, and road standards pertaining to erosion control. The right‑of‑way contracts should be reviewed for special treated areas not mentioned on the plans. For seeding, fertilizing, and mulching, a pre‑measurement using slope distances of the project is needed before the contractor starts. Both the contractor and inspector should know the quantities of seed, fertilizer, and mulch required on the project.
Attention should be given to the erosion control plan and proposal notes for the special items and conditions involved with each individual project. This will include seed mixtures, seed variety, fertilizer type and rate, and required watering.
Material delivered to the project and damaged due to improper storage or handling should be rejected, even though it may have been previously accepted.
Specification 4169 should be referred to for material requirements.
The testing requirements for seed and fertilizer are outlined in Materials I.M. 469.02 and 469.03.
If possible, the inspector should observe the application of seed, fertilizer, and mulch. If the inspector is not present, the contractor should collect and provide tags/tickets for the seed, fertilizer, and mulch applied so the inspector can verify quantities placed.
Record the quantities of these materials used in the project records.
Witnessing the mixing of seed for Native Grass, Wildflower and Wetland Grass seeding mixtures is no longer required by the specifications. Instead, these mixes and urban and permanent rural seed mixes shall be mixed off-site by a seed conditioner approved by the Iowa Crop Improvement Association or other state’s crop improvement association.
All revisions made to the seed mixtures, fertilizer, or rate of fertilizer should be approved by the Construction and Materials Bureau or the Design Bureau (Roadside Development Section).
Current seed supply issues and recommended substitutions are provided at: https://iowadot.gov/construction_materials/Earthwork-and-erosion-control
7.01 EQUIPMENT
Proper equipment in good working condition and operated at a reasonable speed must be used to get the best results. Where possible, the equipment should be operated on the contour or parallel to the slope.
Equipment for preparation of the seedbed includes a disc, cultipacker, spike tooth harrow, spring tooth harrow, slope harrow, and a rotary tiller. Other equipment may be approved for use provided that it achieves the desired results.
A heavy disc, such as a Rome disc, may be required in areas of heavy vegetation. A slope harrow may be required in areas of light soil, where equipment tracks damage the appearance of the seedbed.
Equipment for applying seed and fertilizer consists of a hydro‑seeder, gravity seeder, end gate cyclone seeder, cyclone seeder, slit seeder, drop seeder, and a seed drill. The cyclone seeder (hand seeder) is usually used to spread seed and fertilizer in small areas or areas inaccessible to field equipment. If allowed by the contract documents, aerial equipment may be used for the application of seed and fertilizer. Contract documents may also specify where seeding must be done with a seed drill with a no‑till attachment.
Equipment should be checked for proper rate of application of seed and fertilizer by measuring a representative area and weighing the required amount of seed to be applied. All seeders must be cleaned when changing seed mixtures, particularly when changing from rural seeding to urban seeding.
7.02 CONTRACT ADMINISTRATION
Both the project engineer and the inspector should review the construction period shown on the proposal form. On most projects, the contract will have a late start date with a specified number of work days.
For overseeding, the work is to be done during February and March when the soil is friable from frost action. Working days are not to be charged until April 1, unless winter work is required in the contract documents.
The placement of special ditch control for the spring planting period should be done as soon as weather and soil will allow. After April 1, working days should be charged whenever it is possible to perform the controlling operation.