Environmental Stewardship – Dogwood Energy LLC

Storm-water erosion control project

Dogwood Energy LLC
Owned by Kelson Energy LLC
Operated by NAES Corp 

Challenge.  After construction of the plant there were two large areas that were used for laydown and parking. These areas were covered with gravel that had large amounts of small fines mixed in with the larger gravel (Fig 15). While this surface is considered as a permeable surface it created sheet flow during rain events that carried the small fines to one of the plants outfalls as suspended solids. The plant had trouble meeting the compliance requirements for total suspended solids (TSS) in its national pollution discharge elimination system (NPDES) permit.

   After completing several smaller projects to help lower the TSS levels for several years and even obtaining a sand filter permit from the Dept of Natural Resources, the lowering of permitted levels even further if the sand filter was installed, plus the maintenance aspects of the filter, the plant decided to look at other alternatives.

Solution.  The plant decided to take on a storm water erosion control project (SWECP). Instead of filtering the problem, the goal of this undertaking was to just remove the problem. The SWECP required the removal of nine inches of gravel which would then be replaced with nine inches of top soil to grow grass. The soil allows greater absorption while the grass breaks up the sheet flow across the areas that would carry TSS to the outfall (Figs 16, 17).

Results.  The plants permit requires <100 mg/l for a daily limit and <50 mg/l for a monthly average. The following results (table) are the yearly averages of the outfall since the current owner has been involved with the plant. The results trend down as different methods of control were attempted. The 2011 outcome represents the time period after grass was established.