Sodding

From Massachusetts Erosion and Sediment Control Guidelines for Urban and Suburban Areas

Definition

Stabilizing fine-graded disturbed areas by establishing permanent grass stands with sod. To provide immediate erosion protection or to stabilize drainageways where concentrated overland flow will occur.

Where Practice Applies

• Disturbed areas which require immediate vegetative cover.
• Areas adjacent to Outstanding Resources Waters (ORW ) of the Common- wealth.
• Waterways carrying intermittent flow: where immediate stabilization or aesthetics are factors; where velocities will not exceed that specified for a grass lining; and other locations which are particularly suited to stabilization with sod.

Disturbed areas requiring immediate and permanent vegetative cover. Locations best suited to stabilization with sod are:

• Areas around drop inlets, when the drainage area has been stabilized.
• Steep critical areas.
• If mowing is required, do not use grass sod on slopes steeper than 3:1 (Use minimum maintenance ground covers.)

Advantages

• Sod gives an immediate vegetative cover, which is both effective in checking erosion and is aesthetically pleasing.
• Provides more stabilizing protection than initial seeding through dense cover formed by sod.
• Produces lower weed growth than seeded vegetation. Can be used for site activities within a shorter time than can seeded vegetation. Can be placed at any time of the year as long as moisture conditions in the soil are favorable and the ground is not frozen.

Disadvantages/Problems

• Sod is expensive.
• Sod is heavy and handling costs are high.
• Good quality sod, free from weed species, may be difficult to obtain.
• If laid in an unfavorable season, midsummer irrigation may be required.
• Grass species in the sod may not be suitable for site conditions.
• If not anchored or drained properly, sod will "roll up" in grassed waterways.

Planning Considerations

• Sod requires careful handling and is sensitive to transport and storage conditions. Soil preparation, installation, and proper maintenance are as important with sod as with seed.
• Choosing the appropriate type of sod for site conditions and intended use is of the utmost importance.

Installation

Sod should be free of weeds and be of uniform thickness (approximately 1 inch) and should have a dense root mat for mechanical strength. Sodding is a very expensive method of establishing a grass-type cover but it has the benefit of giving "instant" protection for critical areas. This value may be well worth the higher expense.

Site Preparation:

Rake or harrow to achieve a smooth, final grade. Roll or culti- pack to create a smooth, firm surface on which to lay the sod. Do not install on compacted clay or pesticide-treated soil. Apply topsoil if needed.

Lime and Fertilizer

Lime according to soil test to pH 6.5, or in the absence of a soil test, apply lime at the rate of 2 to 3 tons of ground limestone per acre (10-15 lbs. per 100 sq. feet). Fertilize according to soil test or at the rate of 500-1,000 lbs. per acre (1 1/4 to 2 1/2 pounds per 100 sq. feet) of 10-5-5 or similar fertilizer.

Fertilizer with 40% or more of the nitrogen in organic form is preferred. Work the lime and fertilizer into the soil 1 or 2 inches deep, and smooth.

Sod

• Select high-quality, healthy, vigorous certified-class sod which is at least one year old but not older than three years. It should be a variety that is well-adapted to the region and expected level of maintenance. Common sod types include: Kentucky bluegrass blends, Kentucky bluegrass/Fine fescue mixes and Tall fescue/ Kentucky bluegrass mixture.
• Sod should be machine cut to a uniform thickness of 3/4 inch, plus or minus 1/4 inch, at the time of cutting. Measurement of thickness should exclude top growth or thatch.
• Standard size sections of sod should be strong enough to support their own weight and retain their size and shape when suspended vertically with a firm grasp of the upper 10% of the section.
• Individual pieces of sod should be cut to supplier’s width and length. Maximum allowable deviation from the standard widths and lengths should be 5 percent. Broken pads or torn or uneven ends will not be accepted.
• If sod is not purchased and local sod is used, cut the sod in strips 12 to 24 inches wide, 6 to 10 feet long, and approximately 1- 1/4 inches thick. Roll with roots out to facilitate handling. Sod should not be harvested or transplanted when the moisture content (excessively wet or dry) may adversely affect its survival.
• Sod should be harvested, delivered, and installed within a period of 36 hours. Store rolls of sod in shade during installation. Sod not transplanted within this period should be inspected and approved prior to its installation.
• Sod labels should be made available to the job foreman or inspector.

Sod Placement

• Rake soil surface to break crust just before laying sod. During periods of high temperature, lightly irrigate the soil immediately prior to placement. Do not install on hot, dry soil, compacted clay, frozen soil, gravel, or soil that has been treated with pesticides.
• Sod strips should be laid on the contour, never up and down the slope, starting at the bottom of the slope and working up. Install strips of sod with their longest dimension perpendicular to the slope, and stagger in a brick-like pattern with snug even joints. Do not stretch or overlap. All joints should be butted tightly in order to prevent voids which would cause drying of the roots. Also, open spaces invite erosion.
• On slopes greater than 3 to 1, secure sod to surface soil with wood pegs, wire staples, or split shingles (8 to 10 inches long by 3/4 inch wide). The use of ladders will facilitate work on steep slopes, and prevent damage to the sod.
• Wedge strips securely into place. Square the ends of each strip to provide for a close tight bond. Stagger joints at least 12 inches.
• Match angled ends correctly to prevent voids. Use a knife or mason’s trowel to trim and fit irregularly shaped areas.
• Trim all areas where water enters or leaves the sodded area so that a smooth, flush joint is secured.
• Roll or tamp sod immediately following placement to insure solid contact of root mat and soil surface.
• Immediately following installation, sod should be watered until moisture pen- etrates the soil layer beneath sod to a depth of 4 inches. Maintain optimum moisture for at least two weeks.
• When sodding is carried out in alternating strips, or other patterns the areas between the sod should be seeded as soon after the sodding as possible.
• Surface water cannot always be diverted from flowing over the face of the slope, but a capping strip of heavy jute or plastic netting, properly secured, along the crown of the slope and edges will provide extra protection against lifting and undercutting of sod. The same technique can be used to anchor sod in water-carrying channels and other critical areas. Wire staples must be used to anchor netting in channel work.

Sodded Waterways

• Sod provides quicker protection than seeding and may reduce the risk of early washout.
• When installing sod in waterways, use the type of sod specified in the channel design. Lay sod strips perpendicular to the direction of waterflow and stagger in a brick-like pattern. Staple firmly at the corners and middle of each strip. Jute or plastic netting may be pegged over the sod for further protection against washout during establishment.

Common Trouble Points

• Sod laid on poorly prepared soil or unsuitable surface.
• Grass dies because it is unable to root.
• Sod not adequately irrigated after installation.
• May cause root dieback; grass does not root rapidly and is subject to drying out.
• Sod not anchored properly.
• May be loosened by runoff.

Maintenance

• Keep sod moist until it is fully rooted.
• Inspect sodded areas regularly, especially after large storm events. Re-tack, re-sod, or re-seed as necessary.
• Mow to a height of 2-3 inches after sod is well-rooted. Do not remove more than one-third of the shoot in any mowing.
• Permanent, fine turf areas require yearly maintenance fertilization. Fertilize warm-season grass in late spring to early summer, cool-season grass in late winter and again in early fall.

References

Massachusetts Department of Environmental Protection, Office of Watershed Management, Nonpoint Source Program, Massachusetts Nonpoint Source Management Manual, Boston, Massachusetts, June, 1993.

North Carolina Department of Environment, Health, and Natural Resources, Erosion and Sediment Control Field Manual, Raleigh, NC, February 1991.

U.S. Environmental Protection Agency, Storm Water Management For Construction Activities , EPA-832-R-92-005,Washington,DC,September,1992.