Field-based monitoring of sediment runoff from natural gas well sites in Denton County, Texas, USAAbstractIntroductionStudy areaMethodsResultsSediment from weirs and bed load trapsDebris lobesDiscussionSummary and conclusionsAcknowledgmentsReferencesORIGINAL ARTICLEField-based monitoring of sediment runoff from natural gaswell sites in Denton County, Texas, USAH. F. L. Williams Æ D. L. Havens Æ K. E. Banks ÆD. J. WachalReceived: 18 September 2007 / Accepted: 12 October 2007 / Published online: 30 October 2007Ó Springer-Verlag 2007Abstract This study evaluates sediment runoff from gaswell development sites in Denton County, Texas. Themagnitude of sediment runoff was investigated by inter-cepting sediment in traps and weirs at the periphery of eachgas well site and by measuring the growth of debris lobesthat formed down slope from two sites. Four debris lobesformed at one gas well site and one formed at a second site.Debris lobes ranged in size from 30 to 306 square meters.Sediment from one site entered local creek channels, eitheras a component of storm water runoff or, in one case, as adebris lobe that flowed into a channel. The study findingssuggest that sediment movement is significantly dimin-ished once areas disturbed by gas well construction becomenaturally re-vegetated. Based on estimates of debris lobevolumes, sediment loading rates of about 54 metric tonnesper hectare per year were calculated for one site. It isconcluded that gas well development sites in areas similarto those studied, especially where vegetation has beenremoved and terrain has relatively steep slopes (greaterthan 6%), generate sediment runoff comparable to smallconstruction sites and should therefore be considered forregulations requiring erosion and sediment controlmeasures.Keywords Gas well  Land disturbance  Storm runoff Erosion  SedimentIntroductionMaintaining and improving waters within the United Stateshas been one of the main objectives of the United StatesEnvironmental Protection Agency (USEPA) since its crea-tion in 1970. To meet water quality goals, the USEPAregulates and encourages the study, monitoring, andimprovement of watersheds, streams, rivers, and otherreceiving water bodies by city, county, and state govern-ments. Numerous studies have documented sedimentimpacts on aquatic habitats from construction sites. Con-struction activities can raise soil erosion rates up to 40,000times greater than pre-construction levels (Harbor 1999)and resulting sediment runoff can alter the morphology ofnearby channels (Wolman and Schick 1967; Simons andSenturk 1992; Schueler 1997; Nelson and Booth 2002).Increased sedimentation can also affect aquatic life. Sedi-ment pollution has numerous detrimental impacts on fishpopulations (Newcombe and Jensen 1996) and aquaticplants (Brookes 1986; Wood and Armitage 1997). Otherproblems associated with sediments include decreasedwater transparency, diminished channel depths in navigablewater ways, decreased recreational use of water bodieswhen they become aesthetically undesirable (Ryding andThornton 1999; Holmes 1988; Novotny and Chesters 1981),and eutrophication of aquatic systems when nutrients, suchas nitrogen and phosphorus, are carried by sediments intowater bodies (Wetzel 2001). In a study completed by theH. F. L. Williams (&)Department of Geography, University of North Texas,P.O. Box 305279, Denton, TX 76203, USAe-mail: [email protected]. L. Havens3520-G Victorine Lane, Del Valle, TX 78617, USAK. E. BanksDivision of Environmental Quality, City of Denton,901-A Texas Street, Denton, TX 76209, USAD. J. WachalInstitute of Applied Sciences, University of North Texas,P.O. Box 305279, Denton, TX 76203, USA123Environ Geol (2008) 55:1463–1471DOI 10.1007/s00254-007-1096-9United State Environmental Protection Agency (USEPA) in2004, sedimentation was found to be one of the majorcontributors to poor stream health amongst small U.S.streams (USEPA 2006). Excessive sedimentation is com-monly caused by anthropogenic activities that increasestorm water runoff, such as removing natural vegetation,increasing slopes, or decreasing permeability of surfaces.Currently, small construction sites (larger than 0.4 ha)are subject to USEPA regulations designed to minimizesediment movement from disturbed areas into nearby waterbodies (USEPA 2005). Unlike construction sites, oil, andgas well development sites in Texas are not regulated andhave not been extensively studied for storm water runoffeffects. Recent advances in natural gas recovery, specifi-cally fracturing and horizontal drilling techniques (Durham2005), have dramatically increased exploration andrecovery of natural gas in the North Central Texas regionand thousands of gas wells have been drilled in the pastdecade (Devon Energy 2004) (Fig. 1).Because relatively little is known about storm waterrunoff from gas well sites, this study is designed to answersome basic questions about sediment runoff from thesesites. The questions the study attempts to answer are: (1)How much sediment is eroded from gas well sites? (2)Where and how does sediment runoff occur? (3) Howfrequently does sediment runoff occur in response tostorms? (4) How far does sediment travel beyond theperimeters of gas well sites (in short time frames)? (5) Issediment transported into local stream channels? (6) Isthere a relationship between slope, rainfall volume andintensity, and erosion? Results of this research shouldbenefit local, state, and federal policy makers in deter-mining if storm water runoff regulations similar to thosecurrently applied to construction sites should also beapplied to gas well development sites.Study areaThe study area includes three gas well sites and twoundisturbed reference sites located southwest of the City ofDenton, in Denton County, Texas (Fig. 1). Reference sitesare in undisturbed areas located close to the gas well sitesand within the same physiographic region. Many of thewells being drilled or planned for future recovery activitieslie within the Hickory Creek watershed, which drains intoLake Lewisville (Fig. 1). Soils of two major physiographicareas exist within this watershed: black, heavily organicclay soils of the Grand Prairie physiographic region andsandier, well drained soils typical of the Eastern CrossTimbers physiographic area.The five sites used for this study are located in the GrandPrairie physiographic region, on lands currently used asmixed rangeland. Clay, clay loam, and stony clay soilspredominate