Katie Walton-Day

Biography

Katie obtained M.S. and Ph.D. degrees in geology from the Colorado School of Mines. She is a research hydrologist and has worked at the U.S. Geological Survey located in Denver, Colorado for over 30 years. During this time her research has primily focused on understading the sources and mobility of trace metals associated with hard rock and uranium mineral deposits primariy in the western United States.  A primary goal of her research is to provide science-based information to facilitate decisions about remediation in areas contaminated by historic mining practices.  

 

Publications

1. Day, K.W., Filipek, L.H. and Papp, C.S.E., 1986, Processes controlling the vertical distribution of selected trace metals in Filson Creek bog, Lake County, Minnesota, in Averett, R.C., and McKnight, D.M., eds., Chemical quality of water and the hydrologic cycle:  Chelsea, Mich., Lewis Publishers, p. 367-372.

2. Day, K.W., 1986, Determination of processes controlling vertical trace element distribution in Filson Creek bog, Lake County, Minnesota:  Golden, Colorado School of Mines, M.S. thesis # 3149, 236 p.

3. Ficklin, W.H., Smith, K.S. and Walton-Day, Katherine, 1987, Some effects of acid mine drainage on Clear Creek, Colorado, in Reimann, Martha, ed., A view of water supply, water quality and geotechnical engineering in Denver, Jefferson, Gilpin, and Clear Creek Counties, Colorado:  Colorado Groundwater Association, 6th annual field trip, July 25, 1987, Guidebook, p. 4-12. 

4. Walton-Day, Katherine, and Briggs, P.H, 1989, Preliminary assessment of the effects of acid mine drainage on ground water beneath a wetland near Leadville, Colorado, in Mallard, G.E., and Ragone, S.E., eds., U.S. Geological Survey Toxic Substances Hydrology Program, proceedings of the technical meeting, Phoenix, Arizona, September 26-30, 1988:  U.S. Geological Survey Water-Resources Investigations Report 88-4220, p. 119-124. http://pubs.er.usgs.gov/publication/wri884220

5. Walton-Day, Katherine, Filipek, L.H., and Papp, C.S.E., 1990a, Mechanisms controlling Cu, Fe, Mn, and Co profiles in peat of the Filson Creek fen, northeastern Minnesota:  Geochimica et Cosmochimica Acta, v. 54, no. 11, p. 2933-2946.  http://dx.doi.org/10.1016%2F0016-7037%2890%2990111-W

6. Walton-Day, Katherine, Macalady, D.L., Brooks, M.H., and Tate, V.T., 1990b,  Field methods for the determination of ground-water redox parameters:  Ground Water Monitoring Review, v. 10, no. 4, p. 81-90.   http://dx.doi.org/10.1111%2Fj.1745-6592.1990.tb00024.x

7. Walton-Day, Katherine, 1991, Hydrology and geochemistry of a natural wetland affected by acid mine drainage, St. Kevin Gulch, Lake County, Colorado:  Golden, Colorado School of Mines, Ph.D. dissertation # 4033, 299 p.

8. Walton-Day, Katherine, Briggs, P.H., and Romberger, S.B., 1991, Use of mass-flow calculations to identify processes controlling water quality in a subalpine wetland receiving acid mine drainage, St. Kevin Gulch, Colo., in Mallard, G.E., and Aronson, D.A., eds., U.S. Geological Survey Toxic Substances Hydrology Program, proceedings of the technical meeting, Monterey, California, March 11-15, 1991:  U.S. Geological Survey Water-Resources Investigations Report 91-4034, p. 371-376. http://pubs.er.usgs.gov/publication/wri914034

9. Leventhal, J.S., Jackson, L.L., Smith, K.S., Walton-Day, Katherine, Balistrieri, L.S., Foote, Lee, and Guntenspergen, Glen, 1993, Biogeochemistry along an estuarine salinity gradient: a proxy for sea level rise due to global change, in Landin, M.C. (ed.) Wetlands:  Proceedings of the 13th annual conference of the Society of Wetland Scientists, New Orleans, La., May 31-June 6, 1992, South central chapter, Society of Wetland Scientists, Utica, Miss., p. 95-100. 

10. Jackson, L.L., Balistrieri, L.S., Smith, K.S., Walton-Day, Katherine, Kirschenman, D.L, Briggs, P.S., Fey, D.L., and Sutley, S.J., 1995, Geochemistry of sediments from coastal marshes of Louisiana:  I.  Sampling and analysis methods and chemical analysis results: U.S. Geological Survey Open-File Report 95-251, 146 p. http://pubs.er.usgs.gov/publication/ofr95251

11. Ortiz, R.F., von Guerard, P. B., and Walton-Day, Katherine, 1995, Effect of a localized rainstorm on the water quality of the Alamosa River upstream from Terrace Reservoir, south-central Colorado, August 9-10, 1993, in Posey, H.H., Pendleton, J.A., and Van Zyl, Dirk (eds.) Proceedings, Summitville Forum '95: Colorado Geological Survey Special Publication 38, p. 178-182. 

12. Walton-Day, Katherine, Ortiz, R.F., and von Guerard, P.B., 1995a, Sources of water having low pH and elevated metal concentrations in the upper Alamosa River from the headwaters to the outlet of Terrace Reservoir, south-central Colorado, April-September, 1993, in Posey, H.H., Pendleton, J.A., and Van Zyl, Dirk (eds.) Proceedings, Summitville Forum '95: Colorado Geological Survey Special Publication 38, p. 160-170.

13. Walton-Day, Katherine, von Guerard, P.B., and Ortiz, R.F., 1995b, Water transport--a powerful way to move metals, in King, T.V.V. (ed.), Environmental Considerations of Active and Abandoned Mine Lands--Lessons from Summitville, Colorado: U.S. Geological Survey Bulletin 2220, p. 20-23.  http://pubs.er.usgs.gov/publication/b2220

14. Ward, E.C., and Walton-Day, Katherine, 1995, Seasonal variations in water quality on Wightman Fork of the Alamosa River, 1993, in Posey, H.H., Pendleton, J.A., and Van Zyl, Dirk (eds.) Proceedings, Summitville Forum '95: Colorado Geological Survey Special Publication 38, p. 183-190. 

15. Walton-Day, Katherine, 1996a, Colorado wetland resources, in National Water Summary 1992-93---Hydrologic events and wetland resources:  U.S. Geological Survey Water-Supply Paper 2425, p. 135-140. http://pubs.er.usgs.gov/publication/wsp2425

16. Walton-Day, Katherine, 1996b, Iron and zinc budgets in surface water for a natural wetland affected by acidic mine drainage, St. Kevin Gulch, Lake County, Colorado, in Morganwalp, D.W., and Aronson, D.A., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colo., Sept. 20-24, 1993:  U.S. Geological Survey Water-Resources Investigations Report 94-4015, vol. 2, p. 759-764. http://pubs.er.usgs.gov/publication/wri944015

17. Stogner, R.W., Edelmann, Patrick, and Walton-Day, Katherine, 1997, Physical and chemical characteristics of Terrace Reservoir, Conejos County, Colorado, May 1994 through May 1995: U.S. Geological Survey Water-Resources Investigations Report 96-4150, 34 p. http://pubs.er.usgs.gov/publication/wri964150

18. Smith, K.S., Sutley, S.J., Briggs, P.H., Meier, A.L., Walton-Day, Katherine, Ranville, J.F., and Jerz, J.K., 1998, Trends in water-leachable lead from a fluvial tailings deposit along the upper Arkansas River, Colorado, in Tailings and Mine Waste '98--Proceedings of the Fifth International Conference on Tailings and Mine Waste '98, Fort Collins, Colorado, January 26-28, 1998: Rotterdam, A.A. Balkema, p. 763-768. 

19. Kimball, B.A., Runkel, T.L., Bencala, K.E., and Walton-Day, Katherine, 1999, Use of tracer-injection and synoptic-sampling studies to quantify effects of metal loading from mine drainage, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999--Volume 1 of 3--Contamination from Hardrock Mining: U.S. Geological Survey Water-Resources Investigations Report 99-4018A, p. 31-36.  http://pubs.er.usgs.gov/publication/wri994018A

20. Peiffer, Stefan, Walton-Day, Katherine, Macalady, D.L., 1999, The interaction of natural organic matter with ferric iron colloids in a natural wetland (Tennessee Park, Colorado) receiving acid mine drainage: Aquatic Geochemistry, v. 5, p. 207-223. http://dx.doi.org/10.1023%2FA%3A1009617925959

21. Smith, K.S., Ranville, J.F., Lamothe, P.J., Meier, A.L., and Walton-Day, Katherine, 1999, Metal leaching through a fluvial tailings deposit along the upper Arkansas River, Colorado, in Tailings and Mine Waste '99--Proceedings of the Sixth International Conference on Tailings and Mine Waste '99, Fort Collins, Colorado, January 24-27, 1999: Rotterdam, A.A. Balkema, p. 627-632. 

22. Smith, K.S., Walton-Day, Katherine, Ranville, J.F., 1999, Considerations of observational scale when evaluating the effect of and remediation strategies for fluvial tailings deposits in the upper Arkansas River Basin, Colorado, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999--Volume 1 of 3--Contamination from Hardrock Mining: U.S. Geological Survey Water-Resources Investigations Report 99-4018A, p. 131-138.  http://pubs.er.usgs.gov/publication/wri994018A

23. Walton-Day, Katherine, 1999, Geochemistry of the processes that attenuate acid mine drainage in wetlands:  in Plumlee, G.S., and Logsdon, M.J. (eds.), The Environmental Geochemistry of Mineral Deposits, Reviews in Economic Geology, Volume 6A:  Society of Economic Geologists, p. 215-228.

25. Walton-Day, Katherine, Runkel, R.L., Kimball, B.A., and Bencala, K.E., 1999, Application of the solute-transport models OTIS and OTEQ and implications for remediation in a watershed affected by acid mine drainage, Cement Creek, Animas River Basin, Colorado, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999--Volume 1 of 3--Contamination from Hardrock Mining: U.S. Geological Survey Water-Resources Investigations Report 99-4018A, p. 37-46.http://pubs.er.usgs.gov/publication/wri994018A

26. Smith, K.S., Walton-Day, Katherine, and Ranville, J.F., 2000, Evaluating the effects of fluvial tailings deposits on water quality in the upper Arkansas River basin, Colorado--observational scale considerations, in Proceedings from the Fifth International Conference on Acid Rock Drainage, Denver, Colorado, May 21-24, 2000: Littleton, Colorado, Society for Mining, Metallurgy, and Exploration, p. 1415-1424. 

27. Walton-Day, Katherine, Healy, R.W., Maestas, F.B., and Ranalli, A.J., 2000a, Effects of remediation on geochem­istry and hydrology of the unsaturated zone of fluvial tailings deposits in the flood plain of the upper Arkansas River, Colorado, in ICARD 2000, Proceedings of the Fifth International Conference on Acid Rock Drainage, Volume 2: Littleton, Colo., Society for Mining, Metallurgy, and Exploration, p. 1443-1450.

28. Walton-Day, Katherine, Rossi, F.J., Gerner, L.J., Evans, J.B., Yager, T.J., Ranville, J.F., and Smith, K.S., 2000b, Effects of fluvial tailings deposits on soils and surface- and ground-water quality, and implications for remedi­ation--Upper Arkansas River, Colorado, 1992-1996: U.S. Geological Survey Water-Resources Investigations Report 99-4273, 100 p. http://pubs.er.usgs.gov/publication/wri994273

29. Walton-Day, Katherine, Runkel, R.L., Kimball, B.A., and Bencala, K.E., 2000c, Application of the solute-transport models OTIS and OTEQ and implications for remediation in a watershed affected by acid mine drainage, Cement Creek, Animas River basin, Colorado, in ICARD 2000, Proceedings of the Fifth International Conference on Acid Rock Drainage, Volume 2: Littleton, Colo., Society for Mining, Metallurgy, and Exploration, p. 389-399.

30. Paschke, S.S., Harrison, W.J., and Walton-Day, Katherine, 2001, Effects of acidic recharge on groundwater at the St. Kevin Gulch site, Leadville, Colorado: Geochemistry: Exploration, Environment, Analysis, vol. 1, p. 3-14. http://geea.lyellcollection.org/content/1/1/3.full.pdf+html

31. Kelley, K.D., Eppinger, R.G., and Walton-Day, Katherine, 2002, Selected geochemical studies related to mineral deposits by the U.S. Geological Survey: Explore Newsletter, Association of Exploration Geochemists, number 116, p. 1-24. 

32. Kimball, B.A., Runkel, R.L., Walton-Day, Katherine, and Bencala, K.E., 2002, Assessment of metal loads in watersheds affected by acid mine drainage by using tracer injection and synoptic sampling--Cement Creek, Colorado, USA: Applied Geochemistry, v. 17, no. 9, p. 1183-1207. http://pubs.er.usgs.gov/publication/70024356

33. Walton-Day, Katherine, Kimball, B. K., and Runkel, Robert L., 2002, The use of mass-loading studies and solute-transport modeling to assist in the development of TMDL’s for streams affected by mine drainage: Workshop notebook, 10th National Nonpoint Source Monitoring Workshop, September 8-12, Breckenridge, Colorado, 5 p.

34. Ranville, J.F., Smith, K.S., Lamothe, P.J., Jackson, B.P., and Walton-Day, Katherine, 2003, Use of an intact core and stable-metal isotopes to examine leaching characteristics of a fluvial tailings deposit: in Proceedings, Acid Rock Drainage 6th International Conference (ICARD 6), Cairns, Australia, July 14-17, 2003, p. 1101-1104.  

35. Kimball, B.A., Runkel, R.L., and Walton-Day, Katherine, 2003, Use of field-scale experiments and reactive transport modeling to evaluate remediation alternatives in streams affected by acid mine drainage, in Jambor, J.L., Blowes, D.W., and Ritchie, A.I.M., eds., Environmental Aspects of Mine Wastes: Mineralogical Association of Canada, Short Course Series, v. 31, p. 261-282. 

36. Walton-Day, Katherine, 2003, Geochemistry of active and passive treatment processes used to treat mine drainage, in Jambor, J.L., Blowes, D.W., and Ritchie, A.I.M., eds., Environmental Aspects of Mine Wastes: Mineralogical Association of Canada, Short Course Series, v. 31, p. 335-359. 

37. Kimball, B.A., Runkel, R.L., and  Walton-Day, Katherine, 2004, Evaluation of remediation alternatives in streams affected by acidic, metal-rich drainage, in Wanty, R.B., and Seal III, R.R., eds., Proceedings of the Eleventh International Symposium on Water-Rock Interaction WRI-II, Saratoga Springs, New York, June 27-July 2, 2004: A.A. Balkema, p. 1551-1555.  

38. Runkel, R.L., Kimball, B.A., Walton-Day, Katherine, and Verplanck, P.L., 2005, Geochemistry of Red Mountain Creek, Colorado, under low-flow conditions, August 2002: U.S. Geological Survey Scientific Investigations Report 2005-5101, 78 p. http://pubs.er.usgs.gov/publication/sir20055101

39. Kimball, B.A., Runkel, R.L., Walton-Day, Katherine, and Stover, B.K., 2006, Evaluation of metal loading to streams near Creede, Colorado, August and September 2000: U.S. Geological Survey Scientific Investigations Report 2004-5143, 64 p. http://pubs.er.usgs.gov/publication/sir20045143

40. Walton-Day, Katherine, Flynn, J.L., Kimball, B.A., and Runkel, R.L., 2005, Mass loading of selected major and trace elements in Lake Fork Creek near Leadville, Colorado, September-October 2001: U.S. Geological Survey Scientific Investigations Report 2005-5151, 46 p. http://pubs.er.usgs.gov/publication/sir20055151

41. Kimball, B.A., Runkel, R.L., Walton-Day, Katherine, and Williamson, J.E., 2006, Quantification of mass loading to Strawberry Creek near the Gilt Edge mine, South Dakota: U.S. Geological Survey Scientific Investigations Report 2006-5006, 41 p. http://pubs.er.usgs.gov/publication/sir20065006

42. Herring, J.R. and Walton-Day, Katherine, 2007, Selenium and other elements in water and adjacent rock and sediment of Toll Gate Creek, Aurora, Arapahoe County, Colorado, December 2003 through March 2004: U.S. Geological Survey Scientific Investigations Report 2007—5018, 58 p.  http://pubs.er.usgs.gov/publication/sir20075018

43. Kimball, B.A., Bianchi, F., Walton-Day, K., Runkel, R.L., Nannucci, M., and Salvadori, A., 2007, Quantification of changes in metal loading from storm runoff, Merse River (Tuscany, Italy), in Cidu, R., and Frau, F., eds., Water in Mining Environments, Proceedings of the International Mine Water Association Symposium 2007, University of Cagliari, Cagliari, Sardinia, Italy, May 27-31, 2007: p. 83-87.  http://www.imwa.info/docs/imwa_2007/IMWA2007_Kimball.pdf

44. Kimball, B.A., Bianchi, F., Walton-Day, K., Runkel, R.L., Nannucci, M., and Salvadori, A., 2007, Quantification of changes in metal loading from storm runoff, Merse River (Tuscany, Italy): Mine Water and Environment, v. 26, no. 4, p. 209-216. doi:10.1007/s10230-007-0020-6.  http://www.springerlink.com/content/e840g2674l3g0x09/?p=cc13d79d7848463cb99d48b09e643ef8&pi=2

45. Kimball, B.A., Runkel, R.L., and Walton-Day, K., 2007, Principal locations of metal loading from flood-plain tailings, lower Silver Creek, Utah, April 2004: U.S. Geological Survey Scientific Investigations Report 2007-5248, 33 p. http://pubs.er.usgs.gov/publication/sir20075248

46. Kimball, B.A., Walton-Day, K., and Runkel, R.L., 2007, Quantification of metal loading by tracer injection and synoptic sampling, 1996-2000, in Church, S. E., von Guerard, P. B., and Finger, S. E., eds., Integrated investigations of environmental effects of historical mining in the Animas River watershed, San Juan County, Colorado, U.S. Geological Survey Professional Paper 1651, p. 417-495.  http://pubs.usgs.gov/pp/1651/downloads/Vol1_combinedChapters/vol1_chapE9.pdf

47. Runkel, R.L., Kimball, B.A., Walton-Day, K., and Verplanck, P.L., 2007, A simulation-based approach for estimating pre-mining water quality: Red Mountain Creek, Colorado: Applied Geochemistry, v. 22, no. 9, p. 1899-1918. http://pubs.er.usgs.gov/publication/70030743

48. Walton-Day, K., Paschke, S.S., Runkel, R.L., and Kimball, B.A., 2007, Using the OTIS solute transport model to evaluate remediation scenarios in Cement Creek and the upper Animas River, in Church, S. E., von Guerard, P. B., and Finger, S. E., eds., Integrated investigations of environmental effects of historical mining in the Animas River watershed, San Juan County, Colorado, U.S. Geological Survey Professional Paper, p. 973-1028. http://pubs.usgs.gov/pp/1651/downloads/Vol2_combinedChapters/vol2_chapE24.pdf

49. Kimball, B.A., Runkel, R.L., and Walton-Day, K., 2008, Principal locations of major-ion, trace-element, nitrate, and Escherichia coli loading to Emigration Creek, Salt Lake County, Utah, October 2005: U.S. Geological Survey Scientific Investigations Report 2008-5043, 33 p.  http://pubs.er.usgs.gov/publication/sir20085043

50. Bove, D.J., Walton-Day, Katherine, Kimball, B.A., 2009, The use of fluoride as a natural tracer and the relationship to geologic features: examples from the Animas River Watershed, San Juan Mountains, Colorado: Geochemistry, Exploration, Environment, and Analysis, v. 9, p. 125-138.  http://dx.doi.org/10.1144%2F1467-7873%2F09-197

51. Hoal, K.O., Smith, K.S., Russell, C.C., Walton-Day, K., and Stammer, J.G., 2009, Application of quantitative micro-mineralogy to tailings and mining waste, in D. Sego, Alostaz, M., and Beier, N., eds., Proceedings of the Thirteenth International Conference on Tailings and Mine Waste (Tailings and Mine Waste ‘09), Banff, Alberta, Canada, November 1-4, 2009: University of Alberta, Canada, Department of Civil and Environmental Engineering, p. 703-709, ISBN:978-1-55195-225-0.  

52. Runkel, R.L., Bencala, K.E., Kimball, B.A., Walton-Day, Katherine, and Verplanck, P.L., 2009,  A Comparison of Pre- and Post-Remediation Water Quality, Mineral Creek, Colorado, Hydrological Processes, v. 23, p. 3319-3333. http://dx.doi.org/10.1002/hyp.7427

53. Runkel, R.L., Kimball, B.A., Steiger, J.I., and Walton-Day, Katherine, 2009, Geochemical data for upper Mineral Creek, Colorado, under existing ambient conditions and during an experimental pH modification, August 2005 : U.S. Geological Survey Data Series 442, 41p.   http://pubs.usgs.gov/ds/442/

54. Macalady, D.L. and Walton-Day, Katherine, 2009, New light on a dark subject: On the use of fluorescence data to deduce redox states of natural organic matter (NOM):  Aquatic Sciences, v. 71, p. 135-143.  http://dx.doi.org/10.1007%2Fs00027-009-9174-6

55. Walton-Day, Katherine and Poeter, E., 2009, Investigating hydraulic connections and the origin of water in a mine tunnel using stable isotopes and hydrographs: Applied Geochemistry, v. 24, no. 12, p. 2266-2282. http://dx.doi.org/10.1016/j.apgeochem.2009.09.015

56. Kimball, B.A., Runkel, R.L., and Walton-Day, K., 2010,  An approach to quantify sources, seasonal change, and biogeochemical processes affecting metal loading in streams—Facilitating decisions for remediation of mine drainage: Applied Geochemistry, v. 25, no. 5, p. 728-740.  http://dx.doi.org/10.1016/j.apgeochem.2010.02.005

57.  Macalady, D.L., and Walton-Day, Katherine, 2011, Redox chemistry and natural organic matter (NOM): Geochemists’ dream, analytical chemists’ nightmare, inTratnyek, P.G., Grundl, T.J., and Haderlein, S.B., eds.  Aquatic Redox Chemistry ACS Symposium Series (1071): Washington, D.C., America Chemical Society, p. 85-111.  http://pubs.er.usgs.gov/publication/70037903

58.  Runkel, R.L., Kimball, B.A., Walton-Day, Katherine, Verplanck, P.L., Broshears, R.E., 2012, Evaluating remedial alternatives for an acid mine drainage stream: a model post audit: Environmental Science and Technology, v. 46, p. 340-347. http://pubs.er.usgs.gov/publication/70005928

59.  Smith, K.S., Walton-Day, K., Hoal, K.O., Driscoll, R.L., and Pietersen, K., 2012, Pre- and post-remediation characterization of acid-generating fluvial tailings material, in Proceedings of the 9th International Conference on Acid Rock Drainage (ICARD9), Ottawa, Ontario, Canada, May 20–26, 2012, 10 p., http://www.mend-nedem.org/icard-e.aspx.

60. Walton-Day, Katherine, Runkel, R.L., and Kimball, B.A., 2012, Using spatially detailed water-quality data and solute-transport modeling to improve total maximum daily load development:  Journal of the American Water Resources Association, v. 48, p. 949-969.  http://pubs.er.usgs.gov/publication/70042073

61.  Haines, S.S., Diffendorfer, James, Balistrieri, L.S., Berger, B.R., Cook, T.A., Gautier, D.L., Gallegos, T.J., Gerritsen, Margot, Graffy, Elisabeth, Hawkins, Sarah, Johnson, Kathleen, Macknick, Jordan, McMahon, Peter, Modde, Tim, Pierce, Brenda, Schuenemeyer, Semmens, Darius, Simon, Benjamin, Taylor, Jason, and Walton-Day, Katie, 2013, A framework for quantitative assessment of impacts related to energy and mineral resource development: Natural Resources Research, v. 23, p. 2-17. http://pubs.er.usgs.gov/publication/70072108

62.  Paschke, S.S., Runkel, R.L., Walton-Day, Katherine, Kimball, B.A., Schaffrath, K.R., 2013, Streamflow and water-quality conditions including geologic sources and processes affecting selenium loading in the Toll Gate Creek watershed, Aurora, Arapahoe County, Colorado 2007: U.S. Geological Survey Scientific Investigations Report 2012-5280. http://pubs.er.usgs.gov/publication/sir20125280

63.  Runkel. R.L., Walton-Day, Katherine, Kimball, B.A., Verplanck, P.L., and Nimick, D.A., 2013, Estimating instream constituent loads using replicate synoptic sampling, Peru Creek, Colorado: Journal of Hydrology, v. 489, p. 26-41. http://dx.doi.org/10.1016/j.jhydrol.2013.02.031 

64. Walton-Day, Katherine, Mills, T.J., Amundson, Adolph, Dee, K.T., Relego, M.R., and Borbely, Caitlyn, 2013, The water-quality effects of a bulkhead installed in the Dinero mine tunnel, near Leadville, Colorado, in, Brown, Adrian, Figueroa, Linda, and Wolkersdorfer, Christian, eds.,  International Mine Water Association AnnualConference  in Golden, Colorado, August 5-9, 2013, p. 163-169   

65.  Paschke, S.S., Walton-Day, Katie, Beck, J.A., Webbers, Ank, Dupree, J.A., 2014, Geologic sources and concentrations of selenium in the West-Central Denver Basin, including the Toll Gate Creek watershed, Aurora, Colorado, 2003-2007:  U.S. Geological Survey Scientific Investigations Report 2013-5099, 30 p. http://pubs.er.usgs.gov/publication/sir20135099

66.  Walton-Day, Katherine and Mills, T.J., in press, Hydrogeochemical effects of a bulkhead in the Dinero mine tunnel Sugar Loaf mining district, near Leadville, Colorado:  Applied Geochemistry, 15 p.  http://dx.doi.org/10.1016/j.apgeochem.2015.03.002