Article 16
Sec 20.16.004
Temporary Berms

A. A temporary berm is a temporary ridge of compacted soil, with or without a shallow ditch, constructed at the top of fill slopes or transverse to centerline on fills.

B. The purpose of these ridges is to divert storm runoff from small areas away from steep slopes and direct this water to temporary outlets where the water can be discharged with minimum erosion.

C. These temporary ridges are used at the top of newly constructed slopes to prevent excessive erosion until permanent controls are installed and/or slopes are stabilized, as well as transverse to grade to divert runoff to stabilized slope drains. Two types of temporary berms will be utilized under conditions listed below, unless directed otherwise by the Engineer:

Type "A" berms will be constructed at the end of each day's operations on embankments.

Type "B" berms will be constructed when embankment operations are shut down over the winter season or discontinued at the direction of or with the concurrence of the Engineer.

D. Interceptor berms transverse to centerline may be used when temporary berms are installed on all grades in excess of one percent (1%) and at all locations where water is to be carried down the fill slope by temporary or permanent slope drains.

Sec 20.16.005
Construction Requirements

Type "A" Berms shall be constructed in accordance with the Standard Drawings as shown in Article 4. These berms will be machine compacted with a minimum of one pass over the entire width of the berm with a dozer tread, grader wheel, or other compaction device.

Type "B" Berms will be constructed in accordance with the Standard Detail as shown in Article 4. These berms will be machine compacted with a minimum of 3 passes over the entire width of the berm with a dozer tread, grader wheel, or other compaction device.

Temporary berms must drain to a compacted outlet at a slope drain. The top width of these berms may be wider and the side slopes flatter on transverse berms to allow equipment to pass over these berms with minimal disruption.

Sec 20.16.006
Temporary Slope Drains

A. A temporary slope drain is a temporary facility consisting of stone, concrete or asphalt gutters, half-round pipe, metal pipe, plastic pipe, or flexible rubber pipe, used to carry water down slopes to reduce erosion. The method selected shall meet the approval of the Engineer.

Temporary slope drains shall be required to carry water flowing from cut sections down the fill slopes prior to the time permanent facilities are installed. Temporary slope drains shall also be required on fill slopes at approximately five hundred foot (500') intervals or as directed by the Engineer.

All temporary slope drains will be adequately anchored to the slope to prevent disruption by the force of the water flowing in these drains. The inlet end will be properly constructed to channel water into the temporary drain. The outlet ends of these temporary slope drains will have some means of dissipating the energy of this water to reduce erosion downstream. Unless otherwise specified by the Engineer all temporary slope drains will be removed when no longer necessary and the site restored.

Sec 20.16.007
Ditch Checks

Ditch Checks shall be constructed in accordance with the detail shown in Article 4.

1. Rock Ditch Checks shall be constructed of 2 to 3 inch (2"-3") clean gravel or limestone placed according to the configuration show on the plans. Hand or mechanical placement will be necessary to achieve complete coverage of the ditch or swale and to insure that the center of the check is lower than the edges.

2. Straw Bale Ditch Checks shall be constructed according to the plans and specifications for the ditch application of the straw bale ditch check as shown on the plans.

3. Silt Fence Ditch Checks shall be constructed according to the plans and specifications for the ditch application of the silt fence ditch check as shown on the plans.

Sec 20.16.008
Maintenance of Ditch Checks

A. Rock Ditch Checks shall be checked for sediment accumulation after each significant rainfall. Sediment shall be removed when it reaches one-half of the original height. Regular inspections shall be made to insure that the center of the check is lower than the edges. Erosion caused by high flows around the edges of the check shall be corrected immediately.

B. Straw Bale Ditch Checks shall have sediment deposits removed after each storm event. Deposits shall be removed when approximately one-half the height of the barrier is reached.

C. Silt Fence Ditch Checks shall have sediment deposits removed after each storm event. Sediment must be removed when deposits reach approximately one-half the height of the barrier.

Sec 20.16.009
Sediment Basins

Sediment Basins as required herein shall be constructed in accordance with the details shown in Article 4. A sediment basin can be an excavated or dammed storage area with rock riprap placed in inlet and outlet areas with defined side slopes.

Sediment basins are constructed to trap and store sediment from erodible areas in order to protect properties and stream channels below the installation from excessive siltation. These structures trap and store sediment that unavoidably occurs in spite of temporary erosion control measures in use.

The area where a sediment basin is to be constructed shall be cleared of vegetation to enable removal of sediment.

The inlets of these sediment basins shall be constructed with a wide cross-section and a minimum grade to prevent turbulence and allow deposition of the soil particles. When the depth of sediment reaches 1/3 of the depth of structures in any part of the pool, all accumulation shall be removed.

Sediment basins shall normally remain in service until all disturbed areas draining into the structure have been satisfactorily stabilized. When use of temporary sediment basins is to be discontinued, all excavations are to be backfilled and properly compacted. Any fill material shall be removed and the existing ground restored to its natural or intended condition.

Removed accumulated sediment and excavated material during construction shall be disposed of in such locations that the sediment will not again erode into the construction areas or into natural waterways.

Sec 20.16.010
Temporary Seeding and Mulching

Temporary seeding and mulching required herein shall be preferred in accordance with applicable provisions in Article 10.

Temporary seeding and mulching is to produce a quick ground cover to reduce erosion in disturbed areas that are expected to be redisturbed at a later date.

Seeding and/or mulching will be a continuous operation on all cut and fill slopes, waste sites, and borrow pits during the construction process, as directed by the Engineer. All disturbed areas shall be seeded and mulched when and where necessary to eliminate erosion, as directed by the Engineer.

Temporary seeding mixtures according to the planting season shall be as follows:

December 1 to March 1 - Per Acre

50 lbs. Oat Grain

March 1 to December 1 - Per Acre

50 lbs. (cereal rye or wheat)

Temporary Mulch and Fertilizer for seeding shall meet applicable provisions of Article 10 of the Public Works Manual.

Sec 20.16.011
Straw Bales

Bales of straw used as a means of controlling pollution and erosion as required herein, are to be placed in accordance with the plans and as approved by the Engineer. Straw may be used to obstruct the flow of water to allow deposit of sediment and/or to divert water. Straw may be used at the bottom of embankment slopes to divert runoff from sheet flow and also catch some of the sediment picked up in the sheet flow, and as ditch checks in small ditches and drainage areas. Straw may also be used on the lower side of the cleared area to catch sediment from sheet flow.

Bales of straw will be utilized to control erosion, trap sediment, and divert runoff as directed and approved by the Engineer. When used to trap sediment or divert runoff, the bales must be adequately braced from behind.

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