Assessment:

 

At this site, a bentonite cap started to erode and exposing the coal ash underneath. This created a potentially harmful situation, as rainfall would carry the exposed coal ash into a creek, which emptied into a major lake nearby. An earlier design build project utilized undersized riprap in the flumes, which resulted in a project failure at the first rainfall. D2 aided in the design to create a site-specific solution and to provide effective, durable erosion control measures to stabilize the area and prevent future releases of coal ash.

 

Solution:

 

Because of the immediate need to stop pollutant releases, a phased approach was instituted. Initially, GeoRidge, a temporary sediment control device was utilized to mitigate the erosion and reduce the flow of contaminated water into the creek and lake. The second phase of the project utilized grade control structures to decrease the speed of the water before it reached the down slope flumes. Articulated concrete block mats in the high flow areas and turf reinforcement mats with native vegetation in the lower flow areas were incorporated in the down slope flumes. At the bottom of the hill, a splash pad of articulated concrete block was used and the water was diverted via a weir structure. A step down system was incorporated using GeoWeb, turf reinforcement mats and native vegetation.  The stairstep portion of the project was constructed using gabion structures, and baffles and settling ponds were added below to clean the water prior to releasing it to normal flow situations.

 

Summary:

 

D2 aided in the design, supplied the materials and provided on-site support to the contractor in during construction of the project. The combination of design, products and on-site assistance lead to the resolution of the erosion issue and the elimination of contaminated water reaching important waterways.

 

Products Used:

 

Articulated concrete block mats

Gabions

GeoWeb

Turf reinforcement mats

Native seeds