Texas Transportation Institute

Since the inception of the Texas Transportation Institute (TTI) in 1993, the facility has conducted extensive testing on various North American Green products to determine acceptance for the Texas Department of Transportation (TXDOT).

Testing conducted by TTI is driven by the conversion of TXDOT from a material-type specification to an approved-products specification, based on the performance of erosion control materials from TTI’s erosion control research.

TXDOT has defined specific performance factors that must be met prior to acceptance of an erosion control product for use in DOT construction or maintenance activities.

TTI evaluates two primary performance factors:

Effectiveness of an erosion control product at protecting the seedbed of an embankment from soil loss during simulated rainfall and runoff
Effectiveness of an erosion control product at promoting vegetation establishment in a single growing season (March through December)

Slope Protection Testing Protocol

Products are tested on either a 1:2 or 1:3 (vertical:horizontal) embankment, as selected by the manufacturer. The slope testing for each steepness of slope is conducted on two soil types, including one composed of a clay-type soil, and one of a sand-type soil.

The slopes are seeded and products are installed per manufacturer installation instructions. Vegetation is allowed to establish through one growing season (March – December).

Beginning two weeks after installation, each application is exposed to six simulated rainfall events consisting of two repetitions of each of the following, ten (10)-minute duration storm events.

1-Year Design Storm – 30.2 mm/hr (1.2 inches per hour)
2-Year Design Storm Event – 145.5 mm/hr (5.7 inches per hour)
5-Year Design Storm Event – 183.6 mm/hr (7.2 inches per hour)

The average sediment loss from each event is collected, dried, weighed, and recorded.

Each product application site is measured for vegetation density after the appropriate grow-in period has occurred.

Test Results

2 Horizontal: 1 Vertical Category

Soil Loss (kg/10m²)

Soil Loss (kg/10m²)

Veg. Density (%)

Veg. Density (%)

3 Horizontal: 1 Vertical Category

Soil Loss (kg/10m²)

Veg. Density (%)

Notes:
All content in this section is derived from the publication Final Performance Analysis Through the 2000 Evaluation Cycle Slope Protection Products, Flexible Channel Liner Products & Hydraulic Mulches, co-authored by Paul Northcutt and Jett McFalls.

For additional information on slope testing conducted at TTI, contact North American Green.

We are a proud participant in AASHTO's National Transportation Product Evaluation Program for RECPs.

GSA Contract Number GS-07F-8870D : 04/01/2004-03/31/2009

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