Texas generates about 4 million tons of yard trimmings (leaves, grass, weeds, and tree limbs) each year. Rather than dispose of these materials in landfills, many cities and private enterprises turn these materials into compost or mulch.
Compost is an effective soil amendment and erosion-control material. It retains water in sandy soil, maintains even moisture in clay soils, and adds nutrients to soil to be passed though plants. Similarly, shredded brush mulch is useful in controlling erosion. It retains moisture, reduces soil temperature, and prevents erosion during heavy rains.
TxDOT uses several hundred cubic yards of compost and mulch each year to establish vegetation and control erosion on highway roadsides. Using project-generated shredded brush mulch increases the benefits.
During the final phase of most roadway construction projects, the contractor blades topsoil over subgrade material, hydroseeds the area with grass seed, applies a mulch or erosion-control blanket over the seedbed, and irrigates the area to re-establish vegetation.
Establishing vegetation after roadway construction is completed is extremely critical. If grass fails to grow, soil washes away and erosion begins to threaten the paved surface of the roadway. The Environmental Protection Agency (EPA) mandates stiff penalties for noncompliance. Delays are expensive to the contractor and inconvenient for the traveling public.
Quality topsoil is essential to adequate grass cover. Unfortunately, soil is often void of the organic matter needed for proper grass establishment, whether stockpiled on site or obtained from other sources. Research found that adding compost improves topsoil quality.
Consequently, TxDOT worked with the Texas Commission on Environmental Quality (TCEQ), the Texas Transportation Institute (TTI) and the compost industry to develop a specification for compost. This specification has enabled TxDOT to enhance the environmental sensitivity of its transportation system while providing a much-needed market for organic materials.
Research and Reports
|Characteristics of Composts: Moisture Holding and Water Quality Improvement|
|Comparison of Alternative Seed Mixes to Standard TxDOT Specifications|
|Effects of Using Compost as a Preventive Measure to Mitigate Shoulder Cracking: Laboratory and Field Studies|
|Evaluation of Highway Runoff Filtration Systems|
|Research Summary: Use of Compost and Shredded Wood on ROWs|
|Use of Compost and Shredded Brush on Rights-of-Way for Erosion Control: Final Report|
|Water Quality Characteristics and Performance of Compost Filter Berms|
|Item 161 Compost|
|Item 161 Special Provisions|
|Special Specification 1122 Temporary Erosion, Sedimentation, and Environmental Control|
|Erosion Control Log|
Material Use and Availability
|Construction and Material Tips|
|Material Supplier Mapping System|
|Seal of Testing Assurance, Texas Participants|