Products. Evaluation of an Engineered Fill. Using Recycled Coal Combustion

Transcription

1 Evaluation of an Engineered Fill Using Recycled Coal Combustion Products Dr. John D. Pugh 1, Georgene S. Geary 2, Jim McNamara 3 1 Southern Company Services, Birmingham, AL 35242; 2 GA DOT, 15 Kennedy Drive, Forest Park, GA 30297; 3 Georgia Environmental Protection Division, 2 MLK Junior Dr, Suite 1054, Atlanta, GA 30334

2 Project History Siting Construction Monitoring Results Path Forward Topics LT MW-12 MW-12 MW-11 MW-11 MW-8 MW-8 MW-7 MW LT RT MW-6 MW-6 MW-5 MW-5 MW-10 MW-10 MW-9 MW RT

3 Project History Beneficial use of coal combustion products requires demonstration of engineering and environmental acceptability. As part of an effort to foster the beneficial reuse of coal fly ash, a demonstration project was developed in coordination with the Environmental Protection Agency, Georgia Power Company, the Georgia Environmental Protection Division, and the Georgia Department of Transportation (GDOT). Short term goals: Generate data to demonstrate the safety and effectiveness of using coal combustion products (ash) in a large highway fill application Long term goals: Support regulatory or statutory changes in GA to allow ash use in fill applications Facilitate future commercial fill applications, thereby reducing the need for landfills, land consumption, and depletion of natural resources The demonstration project consisted of constructing a research test section of a coal combustion engineered fill on a new highway construction project in north Georgia in 2008.

4 Project Location Rome, GA Site Site

5 Site Rome, GA Site Location

6 Construction Ash (31,000 tons) was rolled and compacted to DOT standard specifications for roadway fill application. The compacted ash height extends from 10 to 12 feet across the section. Normal fill (sand, silt, clay, rock) material was placed above the ash. The material was placed in lifts and compacted to at least 95 percent of the maximum laboratory dry density. Material within one foot of the pavement was also required to be free of rock fragments and compacted to 100 percent of maximum laboratory dry density.

7 Commenced Hauling October 2008 Ready! Go!

8 Placement and Compaction

9 Placement and Compaction, cont.

10 GDOT conducted tests to confirm that compacted fly ash would meet specifications required for roadway fill application prior to the project. These tests included soils classification in accordance with GDOT and AASHTO classification systems, and remolded, unconsolidated, undrained triaxial compression testing. Also, tests were performed on the in place material, including classification and in place density using the sand cone method and nuclear gauge. The following results were obtained: GDOT Soils Classification: IIIC4, AASHTO Soils Classification: A 4, UU triaxial results: δ (deg) = 22.3, c = GDOT Testing

11 To monitor any settlement, dipping, rutting, etc. in the roadway and along the median and shoulders of the fly ash fill section, high definition laser scanning equipment was utilized. The scanning was first done in July 19, 2011, and a scan was completed every 3 months over the next year. The High Definition Laser Scanner (HDLS) operates by taking many shots (scans) very quickly, forming the same framework as a digital camera image, only in 3 dimensions, made up of millions of dot pixels in order to form a 3 dimensional point cloud. We also conducted the HDLS lidar scan along an area with normal fill. There were no abnormalities noted in the test section based on the HDLS HDLS Lidar Scan

12 Well Installations

13 Lysimeter Installations

14 Monitoring Locations MW-8 MW-8 Upgradient: MW s 4* & 5 Beneath Section: MW s 6 & 7 Downgradient wells: MW s 8-12 MW-12 MW-12 MW-11 MW LT MW-7 MW RT MW-6 MW-6 MW-10 MW-10 MW-9 MW RT LT MW-5 MW-5 *Background MW-4 not shown

15 Monitoring System Soil Porewater Shallow Groundwater Ash Porewater LY-5A MW-5 LY-5B LY-6A Overburden Rock MW-6 LY-6B Fill Ash LY-7A MW-7 LY-7B MW Horizontal Distance (ft.) LY = Lysimeter MW = Monitoring Well

16 Arsenic Post Construction Max baseline conc.

17 Barium Post Construction Max baseline conc.

18 Lead Post Construction Max baseline conc.

19 Beryllium Post Construction Max baseline conc.

20 Mercury Post Construction Max baseline conc.

21 Iron Post Construction Max baseline conc.

22 Manganese Post Construction Max baseline conc.

23 Statistical Evaluation Interwell Methods Results compared to Upper prediction limit based on background BG: MW 4, MW 5 Detection: All other Statistical Exceedances: Cr, Cu, Hg, Ni, Tl, V, Zn MW-12 MW-12 MW-11 MW LT MW-8 MW-7 MW LT RT MW-6 MW-6 MW-5 MW-5 MW-10 MW-10 MW-9 MW RT

24 Characterization of Naturally Occurring Constituents SPLP Total Metals Element Ash Ash Normal Fill Soil LY-7B LY-6B LY-5B LY-5A Al < Sb <0.05 <0.05 <0.05 <0.05 As <2.5 <2.5 <2.5 <2.5 Ba <0.1 <0.1 <0.1 <0.1 Be <0.01 <0.01 <0.01 <0.01 B Cd <0.01 <0.01 <0.01 <0.01 Ca Cr <0.01 <0.01 <0.01 <0.01 Co <0.04 <0.04 <0.04 <0.04 Cu <0.02 <0.02 <0.02 <0.02 Fe <0.04 < Pb <0.1 <0.1 <0.1 <0.1 Mg Mn <0.04 < Ni <0.02 <0.02 <0.02 <0.02 K Se <0.5 <0.5 <0.5 <0.5 Ag <0.01 <0.01 <0.01 <0.01 Tl <0.2 <0.2 <0.2 <0.2 V < <0.02 <0.02 Zn <0.02 <0.02 < *All results in mg/l Concentration (mg/kg) Cd Ag Be Tl Sb Se Co Pb B Ni Cr Zn Cu V As Mn Ba Na Mg K Ca Al Fe Initial Screening Yates Ash Test Section Yates Ash Soil and Rock Element Ranges shown as minima and maxima *Fe and B are leached from natural soils Many metals naturally present

25 Boron Post Construction Upgradient well

26 Iron Post Construction

27 Fe vs As

28 Fe vs Pb

29 Fe vs Cr

30 Fe vs Cu

31 Fe vs Hg BG Well

32 Fe vs Ni

33 Fe vs Tl

34 Fe vs V

35 Fe vs Zn

36 Conclusions Geotechnical evaluations conducted so far have shown that fly ash is an acceptable substitute for commercial fill applications such as a roadbase fill; No discernible differences from a geotechnical standpoint were noted in tests conducted on the fly ash section and normal fill sections; Soils and rock in the area contain overlapping concentration ranges in some cases, higher concentrations for many trace elements compared to the fly ash used in the test; Statistical exceedances above background concentrations tend to be rare and isolated events that do not represent trends, and tend to show good correlation with total iron concentrations suggesting a naturally occurring souce.