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Gorgas Wetlands Revitalization Alabama Power Company Environmental Affairs Field Services Gerson Pickett.

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Presentation on theme: "Gorgas Wetlands Revitalization Alabama Power Company Environmental Affairs Field Services Gerson Pickett."— Presentation transcript:

1 Gorgas Wetlands Revitalization Alabama Power Company Environmental Affairs Field Services Gerson Pickett

2 Background Recirculating Reducing and Alkalinity Producing System (ReRAPS) ReRAPS was designed and built by APC as a EPRI TC in the late 1990’s Purpose is to treat acidic coal pile runoff Treatment system is a series of constructed wetland cells

3 Where it Begins Chemical process begins at the coal pile Pyrite oxidation process occurs: Pyrite + Bacteria + Moisture acid 2FeS 2(s) +7O 2 +2H 2 O 2Fe 2+ +4SO H + Water produced is high in dissolved metals Aluminum Iron Acidic CPR is harmful to aquatic life Runoff is routed to a detention basin Coal pile runoff pH ranges between 2.5 and 5.5

4 ReRAPS ReRAPS (Recirculating Reducing and Alkalinity Producing System) Treats runoff using an alternative constructed wetland design Provides improved wetland performance Based on partial recirculation of treated water into detention pond (pH >4.25) Set to 20 to 40 gpm, <6”- 24hr rain Semi-passive RAPS based system Combined pump/gravity generated system Recirculation moderate pH in detention pond Minimize potential Al hydroxide plugging (armoring) of RAPS substrate 11 acre coal pile Constructed Wetland

5 Coal Pile Runoff Collection Detention Basin Cattail Filter Oxidation Precipitation Basin RAPS & Stilling Basin Wetland Storage Basin Aeration Vegetative Cell Flow Diagram River Discharge

6 Coal Pile Runoff Collection Detention Basin Cattail Filter Oxidation Precipitation Basin RAPS & Stilling Basin Wetland Storage Basin Aeration Vegetative Cell Flow Diagram River Discharge

7 RAPS or Vertical Flow Component Organic matter is composed of wood chips, also cow, horse, and chicken manure. Pooled Water Coal Pile Runoff Low pH D-Fe D-Al (avoided) Neutral pH Low ORP D-Fe passes through Organic Matter Pooled Water Alkalinity production Metal sulfide precipitation Limestone

8 RAPS Chemistry Alkalinity Production Limestone Dissolution CaCO 3 (s) +H + Ca 2+ +HCO 3 - Organic Decomposition 2CH 2 O+SO 4 2- H 2 S+2HCO 3- Metal sulfide precipitation Me 2+ (ag) +S - (ag) MeS 2(s)

9 Background 2 acre ReRAPS has successfully treated coal pile runoff for over 10 yrs. Neutralize acidity Reduce toxicity to aquatic life 0.1 acre RAPS or vertical flow component (VFC) RAPS cell is the heart of the wetland Performance has diminished due to decomposition and reduced porosity (plugging).

10 Waste Characteristics and Disposal Toxicity Characteristics Leaching Potential (TCLP) TCLP results determined that the materials were non hazardous Disposal option chosen was off-site landfill Greenhouse Gas (GHG) Rule reporting avoided Cost effectiveness Hazardous Waste Identification Test Results Found (mg/l) TCLP Regulatory Level (mg/L) SilverND (<0.006)5.0 ArsenicND (<0.009)5.0 Barium Cadmium ChromiumND (<0.01)5.0 MercuryND (<0.0002)0.2 LeadND (<0.01)5.0 SeleniumND (<0.02)1.0

11 Majority of the decomposed materials was replaced Through joint efforts between EA Field Services and Plant Gorgas, the old organics/limestone have been removed and replaced Process was accomplished by allowing the system to completely dry Material was removed in layers to assure thorough drying Dried product then hauled to a off-site landfill. Waste removal process

12 Quantity of Material Removed/Replaced- “Revitalizing” the Wetland Organic Material 220 tons 4 ft in depth 125 ft long wood chip/manure mixture Limestone 30 tons 1 ft of the original 3 ft 3 to 4 inch stone

13 Back In Business The wetland is in full operation mode. With recent rain events, there is now CPR water to be treated Testing and pH monitoring has confirmed optimal performance Annual compliance test are TSS, pH and oil & grease

14 Questions?


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