7.60 SPECIAL DITCH CONTROL
Special ditch control is to be placed in conjunction with seedbed preparation and planting times as specified in Specification 2601.03, B.
The limits of ditches should be staked with flats or flags, and markers should be placed to one side of the ditch to remain visible during construction. The centerline of the ditch is determined by the low point of the ditch. It may be necessary to shift the ditch in order to maintain the best possible alignment and to avoid sharp turns in sod ditches.
The suggested sequence of work for special ditch control is as follows:
Shape the ditch and prepare the seedbed approximately 20 mm (3/4 inch) deep. If ditches are unstable and equipment leaves them in a rough condition, the seedbed must be prepared by hand. The ditches should be shaped so that the ditch drains without water ponding and has a minimum depth of 150 mm (6 inches). Minor irregularities in ditch alignment must be corrected so the completed ditch will follow the ditch line constructed during the grading operation. This may not be possible in cases of severe washing of the ditch bottom. All rocks and clods 40 mm (1 1/2 inches) in diameter, and all sticks and other materials, which prevent contact of the special ditch control materials with the seedbed, shall be removed.
Install check slots as required. Take care that all check slots are carefully and properly installed. The success of the ditch may be dependent on proper installation of the check slots.
Smooth disturbed areas adjacent to ditch control. Make sure that no ridge of dirt remains alongside the ditch, and that material excavated from the ditch channel is properly shaped and sloped to allow water to run onto the special ditch control material. This area should be raked.
Fertilizer should be applied at the proper rate with a mechanical spreader. A cyclone seeder may be used to secure a uniform rate of application.
Seed mixture and rate of application are specified. Seed must be applied in the same manner as fertilizer. Make sure that the required legumes are properly inoculated.
Special Ditch Control Material
Special ditch control materials must be applied without tension and in the direction of the flow of water since there may be some settling of low or filled portions of the ditch and some shrinkage of the material. Do not stretch the material. Install staples as specified in the Design Standards.
Special ditch control should be watered
initially by the end of the day following installation. Water should saturate
the soil to a depth of approximately 50
(2 inches) with the maximum of 20 L/m2 (50 gallons of water per 100 square feet). This is roughly equivalent to a ¾ inch rainfall but depends on soils conditions, rate of rainfall, and topography of land. Three additional waterings are required at one week intervals, depending on weather conditions. The scheduled waterings may be deleted if precipitation has moistened the soil to a depth of 75 mm (2 inches).
The specifications provide for a price adjustment per calendar day if the Contractor does not complete the watering.
Payment for the special ditch control item will not be made until the watering has been completed.
Per Standard Specification 2601.05, A, 11, when there is a large area to be watered, the contract documents will include an item for Watering and payment will be based on the predetermined contract unit price per 1000 gallons (kiloliter). When an item for Watering is not included, then the cost of watering is included in the amount paid for the item to be watered.
Typically, projects that have a contract item for Watering should also include a contract item for Mobilization for Watering, unless they are identified as erosion control or landscaping. Initial watering required at installation will not be counted for payment of Mobilization for Watering.