ITEM 671  TEMPORARY EROSION CONTROL MATS

671.01   Description
671.02   Materials
671.03   Construction
671.04   Maintenance
671.05   Method of Measurement
671.06   Basis of Payment

671.01  Description.  This work consists of furnishing, placing, and maintaining Types A through I temporary erosion control mats.  This work also consists of furnishing, placing, and maintaining seeding and mulching when the seeding and mulching is to be held in place with temporary erosion control mats.

671.02  Materials.  Furnish materials conforming to:

If the mat type is not specifically itemized, furnish any mat type listed in 712.11.

Furnish staples consisting of 12-inch (0.3 m) lengths of No. 11 gage steel wire bent into narrow U-shape with the ends of the staples approximately 1 inch (25 mm) apart.  For clay, shale, and other heavy soils, furnish 3-inch (75 mm) steel staples, at least No. 9 gage with points approximately 1 inch (25 mm) apart, as required by the Engineer.

671.03  Construction.  Before placing any type of temporary erosion control mats, prepare the surface, apply the fertilizer and lime if specified, and seed as specified in Item 659 or as shown on the plans.  Place the temporary erosion control mat in the locations shown on the plans.

A.     Types A, B, C, D E, F, and I.  Construct temporary erosion control mat Types A, B, C, D, E, F, and I as follows:

1.      Within 48 hours after seeding and before placing the mat, evenly place mulch over the specified area at the following rates:

a.      For straw mulch, use 30 percent of the rate specified in 659.14.
b.      For wood fiber mulch, use 30 percent of the rate specified in 659.15.
c.      For compost, use the same rate as specified in 659.16.
d.      Asphalt emulsion tack or tackifier is not required.

2.      Immediately after mulching, lay the mat strips flat, loose, parallel to the flow of water, and with the mat contacting the ground at all points.  For mats placed in ditches, start the construction at the down stream end.

3.      Where more than one strip is required to cover the area, overlap the strips at least 4 inches (100 mm).  Overlap the ends at least 6 inches (150 mm) with the upgrade strip on top.

4.      Bury the up grade end of each strip of mat in 6-inch (150 mm) slots and firmly tamp the soil against the ends.  If directed by the Engineer, bury other edges exposed to more than normal flow in a similar manner.

5.      Place check slots between the ends of strips by placing a tight fold of the mat at least 6 inches (150 mm) vertically into the soil.  Tamp the soil and staple the mat the same as up grade ends.  Space check slots so that one check slot or one end occurs within each 50 feet (15 m) of slope.

6.      Bury the edges of the mat where the mat abuts catch basins and other structures.

7.      Secure the mat in place with staples driven vertically into the soil.  Do not stretch or draw the mat taut during the stapling operation.  Install three rows of staples for each strip of mat, with one row along each edge and one row alternately spaced in the middle.  Space stables not more than 3 feet (1 m) apart in each row.  Staple all ends of the mat and all check slots across the width, with staples spaced not more than 6 inches (150 mm) apart.

8.      After completing the mat installation, seed over top of the mat in areas that the Engineer identifies as disturbed.  Use a seed mixture conforming to Item 659 at the rate of 1 pound per 1000 square feet (5 g/m²) or with a mixture or rate shown on the plans.

B.     Type G.  Construct temporary erosion control mat Type G according to 671.03.A, with the following exceptions.

1.      Do not use mulch under the mat.
2.      Overlap edges and ends by 1 1/2 inches (40 mm).
3.      Do not bury the up grade end or top edge of each strip unless required by the Engineer due to special conditions in the field.
4.      The Contractor may elect not to provide check slots.
5.      Place the mat in contact with the soil.

C.     Type H.  Construct temporary erosion control mat Type H according to 671.03.A, with the following exceptions.

1.      Clear the surface of rock, clods, or foreign material 1 1/2 inches (38 mm) or greater in size.
2.      Do not use mulch under the mat.

671.04  Maintenance.  Maintain the specified areas until all work in the Contract has been completed and the Engineer issues the final acceptance.  Restore damaged areas to the condition and grade existing just before placing the mat.  Relime, refertilize, and reseed restored areas according to Item 659.  Replace all damaged mats.

671.05  Method of Measurement.  The Department will measure Erosion Control Mat, Type ___ by the number of square yards (square meters) completed and accepted.  The Department will determine the area based on the surface area covered by the erosion control mat.

671.06  Basis of Payment.  The Department will not pay for maintenance as detailed in 671.04 that is required due to the Contractor’s negligence, carelessness, or failure to install permanent or temporary erosion controls.

If temporary and permanent erosion control items in the Contract are properly placed according to the Contract Documents, the Department will pay for maintenance detailed in 671.04 or according to 109.05.

The Department will pay for liming and fertilizing of areas covered by the mats under Item 659.  The Department will not pay for the seeding and mulching performed under or over the mats.

The Department will pay for accepted quantities at the contract prices as follows: