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TCEQ-SY110501f � I For Public Comment May 2011 Two Total Maximum Daily Loads for Indicator Bacteria in Cottonwood Branch and Grapevine Creek Segments o822A & o822B Assessment Units: 0822A 02 and o822B Oi Prepared by the Office of Water, Water Quality Planning Division TEXAS COMMISSION ON ENVIRONMENTAL QUALITY l LOZ AeW 'luewwoO oilgnd BOA n A4!lenC leluewuaLnu3 uo uoissiwwoO sexal gapasag pluauzuoainug patlddd .zoj aln }ilsui sexas, aqj Sq paaedaad �,xaaa� auuaduao puu gaueag poonAu0110D ut upapug ao3 spUoq Kj ?UQ WnLuumw tujos oml l03 juawnao(l :poddnS uoi1moUV„ puu «xaaa� auznaduaf) — gzzso luaw2aS 29 gauuag poomuoPOD —Vzzso }uaw2aS :S-,Qya eua }aug .zo3 juawnoo(l :poddnS ILIDtugaay„ palitl spodaz aql uo .red ui paseq si:podaa zQML slU 'x3ua2V not ajoad IUjuauzuoainug wojj sjuuB g2noagi .red ui paauuuTj sem podaa stgl3o u011undaad aqj < /Iugq'L,ua }a ,oq adu,2uo}lo�S— 99 /ip }/ aa��n�/ uoi }e�uauzaiduzi /sn•x}'awis'baz)yA Am> ju alis qaM bgoZ aqj uo alquIleAu azu spodai iaofoad i(iw . Lso£ -TTLSL suxaZ `utlsnV Lso£T xog 'Q'd £OZ -Dw Tlenb IC}uauzuoatnua uo uotsstuiuz0 sexaZ UL,a1, pUo7 XIIV(l wnuzumy� It1os aq} Xq Pa}n9p}stQ Contents ExecutiveSummary .......................................................................................... ..............................1 Introduction.................................................................................................... ............................... 2 Problem Definition ..... ............................... Ambient Indicator Bacteria Concentrations .......................................... ............................... 3 WatershedOverview ....................................................................................... ............................... 3 EndpointIdentification .................................................................................... ..............................7 SourceAnalysis .............................. ............................... Permitted Sources ................ ............................... Domestic and Industrial Wastewater Facilities ............................... ............................... 8 Sanitary Sewer Overflows .......... ............................... TPDES - Regulated Storm Water ....................................................... ............................... 9 IllicitDischarges ............................................................................... ............................... 10 UnregulatedSources .............................................................................. ............................... 10 Wildlife and Unmanaged Animal Contributions .............................. .............................11 Unregulated Agricultural Activities and Domesticated Animals .... .............................11 Failing On -site Sewage Facilities ....................................................... .............................12 DomesticPets ...................................................................................... .............................12 Linkage Analysis ........................... ............................... Load and Flow Duration Curve Analyses ................................................ .............................13 LoadDuration Curve Results ................................................................... .............................15 SeasonalVariation ............................................................................................ .............................15 Marginof Safety ................................................... ............................... PollutantLoad Allocation ................................................................................ .............................18 WasteloadAllocation ................................................................................ .............................19 LoadAllocation ................................................................................................ .............................21 FutureGrowth ........................................................................................ ............................... 22 TMDLCalculations ................................................................................ ............................... 23 Public Participation .................. ............................... Implementation and Reasonable Assurances ............................................. ............................... 26 KeyElements of an I -Plan ..................................................................... ............................... 26 References............................................................................................... ............................... 27 Appendix A. Equations for Calculating . TMDL Allocations for Changed Contact Recreation Standard ........................................................ ............................... 29 VAdb wimnission on tnwronmental Quality iii For Public Comment, May 2011 i i ry Aew ivawwo,) oucim JO-A Ai A4!jenjD IquawuaLnu3 uo uoiSSiwwoO Sexal 5Z .................................... ............................... 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( Pa I /P l) P q q OT • sra.re as ;rM uuo�s lr n�aaun alr as a sza }uM aaa auunadra t aaat3 g ••• pags.ia}uM)laaiZ) auiAadu.zo aoj asn purl jo duW •E aaai3 9 •••••••••••••••• gaurig pOOMuO:4O3 jo zo VZzgo fIV paaiudwi ao; asn puul jo duw 'z aaai3 S.................................................................. .......................SUOIJUIS 2uuolluotu puu snV;O suo m MUo� Il gz a zn�i3 i saint i.1 List of Acronyms AU assessment unit AVMA American Veterinary Medical Association BMP best management practice CFR Code of Federal Regulations cfs cubic feet per second cros cubic meters per second DMR Discharge Monitoring Report E. coli Escherichia coli EPA Environmental Protection Agency FDC flow duration curve GIS geographic information system gpcd gallons per capita per day ha hectare I/I inflow and infiltration I -Plan implementation plan km kilometer LA load allocation LDC load duration curve MGD million gallons per day mm millimeter mL milliliter MOS margin of safety MPN most probable number MS4 municipal separate storm sewer system NCTCOG North Central Texas Council of Governments NDEP Nevada Division of Environmental Protection NETWPCC New England Interstate Water Pollution Control Commission NPDES National Pollutant Discharge Elimination System NWS National Weather Service OSSF on -site sewage facility SSO sanitary sewer overflow SWPPP Storm Water Pollution Prevention Plan SWQMIS Surface Water Quality Monitoring Information System TCEQ Texas Commission on Environmental Quality TIAER Texas Institute for Applied Environmental Research TMDL total maximum daily load TPDES Texas Pollutant Discharge Elimination System TRA Trinity River Authority USGS United States Geological Survey WLA wasteload allocation WQMP Water Quality Management Plan WWTF wastewater treatment facility Texas Commission on Environmental Quality v For Public Comment, May 2011 L LOZ AeW luawuaoo oilgnd aoJ in �4ijeno je;uawuainu3 uo uoissiwwOO se"i iff"M V AZ Two Total Maximum Daily Loads for �� Indicator Bacteria in Cottonwood �r `— Branch and Grapevine Creek Executive Summary This document describes total maximum daily loads (TMDLs) for Cottonwood Branch and Grapevine Creek, where concentrations of indicator bacteria exceed the criteria used to evaluate attainment of the contact recreation use. The Texas Commission on Environmental Quality (TCEQ) first identified the impairments in the 2006 version of the Texas Water Quality Inventory and 303(d) List. Cottonwood Branch and Grapevine Creek (Segments o822A and o822B) are urban creeks located in the north central portion of the Dallas-Fort Worth metroplex. Both are tributaries to the Elm Fork Trinity River below Lake Lewisville (Segment o822). Grapevine Creek (o822B) is the larger of the two creeks with a drainage area of 9,295 acres, while Cottonwood Branch (o822A) has a drainage area of 2,964 acres. Cottonwood Branch is divided into two assessment units (AUs) while Grapevine Creek consists of a single AU. The drainage area of both AUs for Cottonwood Branch and the sole AU for Grapevine Creek lie entirely within Dallas County with the exception of the upstream portion of the AU for Grapevine Creek that lies within Tarrant County. Escherichia coli (E. coh) are the preferred indicator bacteria for assessing the contact recreation use in freshwater, and were used for development of the TMDL. The criteria for assessing attainment of the contact recreation use are expressed as the number (or "counts ") of E. coli bacteria, typically given as the most probable number (MPN) per hundred milliliters (100 mL) of water. The contact recreation use is not supported when the geometric mean of all E. coli samples exceeds 126 MPN per loo mL, or if individual samples exceed 394 MPN per loo mL more than 25 percent of the time. Historical ambient water quality data for indicator bacteria (November 2001 - October 2004) were analyzed on select TCEQ monitoring stations in the Cottonwood Branch and Grapevine Creek watersheds. The geometric means of E. coli exceeded the standard in the upstream AU of Cottonwood Branch, o822A — 02, and in the single AU of Grapevine Creek, o822B_o1, with the geometric means calculated as 786 MPN /loo mL and 411 MPN /loo mL, respectively. The most probable sources of indicator bacteria within the watersheds of the impaired AUs are storm water runoff from permitted storm sewer sources, dry weather discharges (illicit discharges) from storm sewers, sanitary sewer overflows, and unregulated sources such as wildlife, unmanaged feral animals and pets. A load duration curve analysis was used to quantify allowable pollutant loads and specific TMDL allocations for point and nonpoint sources of indicator bacteria. The TMDL allocations are discussed in the section "TMDL Calculations." Compliance with these TMDLs is based on keeping the indicator bacteria concentrations in the selected waters below the geometric mean criterion of 126 MPN /loo mL. Future growth of existing or new point sources was determined using population projections. The TMDL calculations in this report will guide determination of the exas commission on tnwronmental Quality 1 For Public Comment, May 2011 L LOZ AeW `luawwoo oggnd J0=1 Z Al!lenD lelu9wuoa!nu3 uo u0!ss!ww00 sexal •(dwom) uuid }uauza2uuuw fqtiunb ialuM s,a}uls ag} o} alupdn uu awooaq Ulm s'Iava asaq} `iunoiddu Vdg uodn aouu inssv aiquuosuag puu uoi}ujuauiaiduiI uoijudioijiud oggnd uoi}uaollV PuoZ }uMngod Ala3us3o uddew uoiIuiaun iuuosuas sisXiuuv a2uxurl sisxiuuv aainos uoiluogijuapi iuiodpug uogtugaQ uiaigoad :podaa sig} Jo suoi}oas �?uiMOUoi aqj ui pagp3sap air XagZ •gQyu u 2uidoianap ui s}uauiaia uiuPao aapisuoo isnui bgoL aqj, •saugapia puu suoquiaaa asog} gjine aouupaoaau ui paauda.id uaaq suq juauinoop zQYiL sitU •(1661 `ddg) ssaaodd 7QyVd NJ : suors'aaQ pasng - dj ?1bn6 iajvAl jof aounpinD sii ui uoi}oaaip iaq:pnj sapinoid VjH aqL •slQya aiqujdaoou aoj sjuamwinbai Aum ii2aa puu Xiolnims aqj agpz)sap (OCT dAD ot,) OCT :Pud `WAD) suoiluiii�a-d ivaapa3 Jo ap03 ag} Jo op ai }is ui (�dg) �foua uoi�oa }oad iu }uauiuoainug .S-fl alp jo suoiluin2aa 2upuauiaidwi aq} puu 13V 131UM uualD atp Jo (p)£o£ uopoas •suxas, iva}uao -q:pou ui (ZZgo juaiu2as) aiiinsyAag axuq moiaq ianig nzuZ xao3 uzig aip of sauuingral on,q `xaa.iD ouinaduzf) puu gouuig poomuo:RoD ui uPallzo uua}ouq joluoipui 2uipaaoxa of anp asn uoi}uaaoaa lou}uoo aqj o} sluauuiuduii sassaappu -IGWI sign saipoq as }um paua }uaaT ao paiiuduii 3o- 2uigsij ao `afg oijunbu jo :poddns uolluaaoai Xlddns ialum 2ui4uiip su gons —sasn iuiogauaq aqj uiuiuiuui puu aaolsaa o} si uiva20 zd ZQML 01P Jo aniIoo fqo kimud aqj, suxal 3o aluls aqj uo 2uuap.ioq ao ui (saipoq ia}um) sauur4sa puu `sffuq `saxui `s iionaasaa `smua i }s paua4ua lqj io pa nuduii sassaappu uiva2oad aqj s zalun� am ns ski jo fqiiunb aqj 2ui2uuuui aoj ssaooid gu iano ,suxal jo juauoduioo iofuw u si u AO-ld -JUKL aqL •spjupuujs ,A4ijunb aaj-em anaigou of lap io ui sianai }uaaana mug paonpaa aq isnLu puoi IuMngod aqj gonui nog aluumsa osiu }snuff slQya •sxLm aaglo ui passa idxa aq XLw inq `pouad aunt} nd ssuuz jo sliun gjinn puoi u su passaadxa Xiuouxuzoo Si ZQya V •uoiivaaplsuoo aapun luulniiod u ioj Xpoq nium aqj ;o fqiouduo ani}uiiuzissu age 3o saluuipsa aigissod Isaq agi aau s,(,Wl •spiupuuls fqiiunb iajum aiquogddu sIi laaui iiiis puu antaoai um Xpoq aa}um u jug} luulnUod .zuin3wud u ;o junouiu ag} sauiui iajap }i— ja2pnq u axis si Z(Iy� L V •suxas ui sialum aoujins panuduii ao3 padoianap aau 9-JUML lugl 2uunsua aoj aigisuodsai si agZ)s aqL •Xpoq lalum palsii u jo juauuiuduii aqj o} sainquluoo jug} juLIniiod goua aoy j(jKj u doianap }snuz saiu }s •spaupuu }s X11iunb aalum aiquotiddu Iaaul o} pa}oadxa jou aau ao ` }aaui lou op lug} saa }um fqiluapi o} sa�uls iiu saatnba., 13V aa�uM uualD ivaapa3 aqj jo (p)£o£ uoi�oas uoilonpo.ajul •sisuq asuo- ,Kq -asuo u uo polonium aq gins sap!j!3uj a2aug3sip aalumNsuM -qlmo.i2 aiMnj 2uipnpui `suogpipuoa 2ui2uugo iopun umails goua jo 44pudm anpuituiissu Problem Definition TCEQ first identified the impairment to the contact recreation use for Cottonwood Branch (Segment o822A) and Grapevine Creek (Segment o822B) in the 20o6 Texas Water Quality Inventory and 303(d) List (TCEQ, 2oo8b). All or part of each water body was subsequently included on the 2oo8 and Draft 2010 §3o3(d) Lists under category 5a, indicating that they are a priority for developing a TMDL. The impaired AUs in Segments 0822A and o822B on the 303(d) list are o822A_02 and o822B—o1 (TCEQ, 2oo8b) (see Figure 1). An AU is the smallest geographic area of use support reported in the Texas Integrated Report. These AUs define the TMDL area addressed in this report. The standards for water quality are defined in the Texas Surface Water Quality Standards (TSWQS) (TCEQ 2000). Contact recreation is the presumed use in Cottonwood Branch and Grapevine Creek under the current TSWQS. E. coli are the preferred indicator bacteria for assessing the contact recreation use in freshwater, and were used for analysis and modeling to support TMDL development for the watershed. The criteria for assessing attainment of the contact recreation use are expressed as the number (or "counts ") of E. coli bacteria, typically given as the most probable number (MPN). For the E. coli indicator, if the minimum sample requirement is met, the contact recreation use is not supported when: • the geometric mean of all E. coli samples exceeds 126 MPN per loo mL; ■ and /or individual samples exceed 394 MPN per loo mL more than 25 percent of the time. Ambient Indicator Bacteria Concentrations Table 1 presents a historical summary of ambient indicator bacteria data from the TCEQ surface water database, Surface Water Quality Monitoring Information System (SWQMIS) for November 2001 through October 2004. All AUs in Segments o822A and o822B are included in the data summary. As indicated in Table 1, only the AUs associated with TCEQ stations 17165 and 17166 (in AU o822A_02) and 17531 and 17939 (in AU o822B_01) exceeded the geometric mean criterion of 126 MPN /loo mL. Watershed Overview Cottonwood Branch lies within the jurisdictional area of the City of Irving, Dallas County (Figure 1). The creek is defined in the Draft 2010 Texas Integrated Report for Clean Water Act Sections 305(b) and 303(d) (formerly the Water Quality Inventory and List) as starting at Valley View Lane, at the south end of Dallas -Fort Worth (DFW) International Airport and extending approximately six miles eastward to the confluence with Hackberry Creek. The creek consists of two AUs (see Figure 0 defined in the Draft 2010 Texas Integrated Report as follows. AU 0822A_01 is the downstream portion of Cottonwood Branch, from the confluence with Hackberry Creek at the downstream end to the upstream end at North Story Road. AU 0822A_02 is the upstream portion of Cottonwood Branch, from 0.5 miles downstream of North Story Road to the upstream end at Valley View Lane. AU o822A_02 is the focus of TMDL development. Texas Commission on Environmental Quality 3 For Public Comment, May 2011 L LOZ [%eW 'juawwoo oilgnd j03 b f4ilenc) Ie;u9wu0jlnu3 uo u0issiww00 sexal gloq jo an padsaad aqj uroij pags -1aWm xaa -1D 3u?nade -1'D aq} jo uo?lrod 2u?}nginuoa -uou e pa -1ap ?su03 a -1e e3-1e a2uure-1p s}1 pue a*1 gaaoN (T a -1a?3) pnjq -1nqjjWeyQ W TT£oZ uoge }s aU�s, jo ulea ilsdn s -1ajaur oo£ ffja�eurp o -1dde xaa -13 au?naduJD 01u? � ru�nq? r� paureuun uu ern sure-1p puu �aa� -a -1ae 000`LT XIaleur�o -1dde jo f4Iaedea ale -10 }s e seq `juejd iamod aaa e aol a?on-1asa-1 2u?Iooa a `a3ln gjjoN `Pagsaalum xaa -1D au? pasola xpua nadu -1� aq} ul -OD selleQ 66L 8£8`t — 8t ZZ / S£9-I3o weajlsdn 6£6L l W S£S •P^lfl 3ua2a-d .OD IueueL lZl 6It`Z <— I ZI / a$P!j93o weajlsdn 1£SLI IO 8ZZ80 lit gliOK Plag.nd -OD selleQ 991Lt 118 Ot8`t < -66 0£ / . 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Power company staff report that North Lake rarely releases into Grapevine Creek, with discharges typically occurring a few years apart (personal communication, John Mummert, TCEQ, December 1, 2009). Consequentially, for the remainder of this report the Grapevine Creek watershed will be defined to exclude the drainage area of North Lake resulting in a remaining watershed area of 3,x73 ha (about 12 Figure 1. Cottonwood Branch and Grapevine Creek study area showing locations of AUs and monitoring stations. exas kommission on environmental Quality 5 For Public Comment, May 2011 6 LOZ Aen `Iuawwo0 opgnd BOA 9 AIllenO leluewualnu3 uo uoisslwwo0 sexal (z algeZ `.£ a n2i3) aanoo puel @gljO /z asuduzoo sauo2aleo asn puel2ututeuzaa aqj, ( %t,i) 1,0!luapisaa pu>e ` sz) le ?.zlsnpul /leto.zawLuoo (%9z) padolanapun `(/££) aanpna}se.ijui apnlaui pagsaalene Aaaa0 auTnade.,D aql u1 sash puel }ueulwoQ •(sallw a unbs 60 8ZZ80(v Pdaleuual �looaJ aulAadeaE) pue 'Zp yZZ80 nv paaledwi 'goueje poomuopoo aol tiewwns asn puel Z algel (.Soot ao3 saleunlso aanoo /asn puel sluasaidag •< se elep> laui asno upealo uzoo•s euin p'MeeM�> allsgam asnogfuiaealo Uwa SI`) (9001:)N) s}uaww@Aoo jo liounoD sexaZ lealuaD quoN :aoinoS) goueje poomuogoo )o ZO dZZ80 nv paiiedwl ao) asn puel }o deal -Z ain6i j saaeloaq £LO`£ %001 saaeloaq £ZL sliviol %001 8Z' 8 19' b aaleM Z8'1 95 LI*9 Sb sIard SL'£l £Zb ZI'61 8£! o.mlon.Ase.yul 170'9Z OLL £S 1 Z 991 leulsnpul /leloiaw —D 89'SZ 68L 99'IZ 991 padolanapun cc LZO, I 10' 1 £ bZZ leuuopsa2l lelol ;o % I easy ( LO 8ZZ80) )laajo aulnadejLZ) lelol ;o % I easy (ZO `dZZ80) UoUeJB poomuolloo tio6aleo asn pue-i pa;eBeB6y 60 8ZZ80(v Pdaleuual �looaJ aulAadeaE) pue 'Zp yZZ80 nv paaledwi 'goueje poomuopoo aol tiewwns asn puel Z algel (.Soot ao3 saleunlso aanoo /asn puel sluasaidag •< se elep> laui asno upealo uzoo•s euin p'MeeM�> allsgam asnogfuiaealo Uwa SI`) (9001:)N) s}uaww@Aoo jo liounoD sexaZ lealuaD quoN :aoinoS) goueje poomuogoo )o ZO dZZ80 nv paiiedwl ao) asn puel }o deal -Z ain6i j In the Grapevine Creek watershed, North roxi ately 17,000 acre- feetrand drains viasan power plant, has a storage capacity of app stream of TCEQ unnamed tributary into Grapevine Creek approximately 300 meters up P station 20311 at MacArthur Blvd. (Figur Grapevine Creek Lake watershed nd its drainage area are from the perspective of considered a non - contributing portion of the bacteria loading and streamflow. Power company staff report that North Lake rarely releases typically occurring a few years apart (personal into Grapevine Creek, with discharges 09). Consequentially, for the communication, John Mummert, TCEQ, December 1, 20 remainder of this report the Grapevine Creek watershed will be defined to 3 ha(aboutl12 a remaining watershed area of 3 drainage area of North Lake resulting the Gra evine Creek watershed include infrastructure square miles). Dominant land uses p and residential (14 %). The (33 %), undeveloped (26 %), commercial/ industrial (25%), Table 2). remaining land use categories comprise 2% of the land cover (Figure 3; Texas, which has a Cottonwood Branch and Grapevine Creek s lie within m d wTenters, resulting in a wide subtropical climate characterized by ho Avera e high annual temperature range (National Weather Service (NWS), 2009). g August. Fair temperatures generally reach their epst to peratures obetween ummer, which are often bove 100° skies generally accompany the highest F; however, the low temperature rarely exceeds 8o o (NWS, During winter, F at night ad of extreme cold the average low temperature is 331 F in early to mid January d pert is 34.7 inches (881 generally do not last long (NWS, 2009). Annual average precipitation mm) of rain and 2.5 inches (64 mm) of snow. Endpoint Identification All TMDLs must identify a quantifiable water quality target that indicates the desired water endpoint serves quality condition and provides a measurable a and the criterion D gTMDWhich to evaluate to focus the technical work to be accomplished future conditions. The endpoint for the TMDLs in this report 00 mL Tin TCottonwood concentrations Branch (impaired AU geometric mean criterion of 126 MPN /10 o822A_O2) and Grapevine Creek (impaired AU o822B_01). Source Analysis Potential sources of indicator bacteria pollution can be divided into two primary categories: regulated and unregulated. Pollution sources that are regulated the National Pollution Texas Pollutant Discharge Elimination Sy Discharge Elimination System (NPDES). Examples of regulated sources in • municipal and private domestic wastewater treatment facility (WWWTF) discharges; • industrial facilities with individual storm water permits and /or discharging treated industrial wastewater and /or groundwater; and ■ storm water discharges from industries, construction, and municipal separate storm sewer systems (MS4s). Nonpoint source pollution originates from multiP under the TPDESIor y carried NP to surface waters by rainfall runoff. It is not regulated by permit For Public Comment, May 2011 Texas Commission on Environmental Quality L LOZ AeW 'luewwoo oilgnd X03 g A4!lent) lelu9wuoJinu3 uo uoissiwwoC) sexaj uanif) ''iu�aad JfM uuo ;S leaauOD II asugd SdQd,L aqi aapun paaanoa osle si :pod.,, aq4 `uoi4ippu ui •Iiutaad aq} ui paljpads si 4iuul mol; ou puu `(Jjouna pue not }u}idpaad o} 13afgns) aigeuun puu Jua:giuLaa}ui paaapisuoa si a2aegasip aqZ •suoi�uaado �utai- apuaaatu �uollo3 jjouna jo loaiuoa aq4 lu palaau4 si Iluuad aqZ auinaduaf) of sa2jugasip �eq (6So) IIe3ino auo sapnlaui }uq; (t t000aM) 1iumad as ;ent uilo }s lunpinipui ue suq aaodaiV Md(l (t aan2lA) 3ZMM luuol2ag lua4u@D (BIZ) X4poq;nV aanid X41up,L aq4 Xq panaas ua.iu utalsxs u0143alloa pajamas pue .iawma4sum aq4 uppm paluaol air snFr paaieduti qloq jo spagsaalem aai ua aqZ 'uivaa ;s aaq}ia jo pagsaalem aql uiglin� paleaol saa2.iugasip 3ZMM lepisnpui .io ai ;sawop pazaoglne Xllenpinipui ou aau aaaq} Xl ;uaaanD s014i113e=l .ialennOMM Jeulsnpul pue 311sawoa -To pue zo Vzzgo snV paaiudwi ui saaanos paI4iuzaad aq4 luasaadaa st w puu `saris uoi ;ana;suoa `saulsnpui woq sa�augasip aa}um LuiO4S 'SHQdN aT puu SHU U aq} aapun liuuad Xq paiuln2aa aau saaanos papiuuad sewnoS paUiwaad o ea pue/asn puel sluasaadaa pue <dse• a }epe}au/asnog2uvieali /tuoa•sde �"m3P-mmn> a s9 an asno Wupva I� 3 Q SI`J qOaL,)N) :aaanoS) paysJaleM XaaJO auinadejE) jo; asn puel ;o dew g ain6id !Mn- WOMinuo�.ua0rx� 60CLJ30] MWLL ` a m `w b << N - m m Sa4ad d lequapisaa m ialeM seq!Ign /ampnilsequl Y pedoleeapun M g a� s�l�ed m ,;�b� ��i leulsnpwAepjawwoo O sapW leuoileuiawl ti £ Z L 0 sjalawOMI L 9 5 b F z l 0 the circumstances of the permit, this outfall will be treated as part of the TPDES - permitted storm water discharge load. Sanitary Sewer Overflows Sanitary sewer overflows (SSOs) are unauthorized discharges that must be addressed by the responsible party, either the TPDES permittee or the owner of the collection system that is connected to a permitted system. SSOs in dry weather most often result from blockages in the sewer collection pipes caused by tree roots, grease, and other debris. Inflow and infiltration (I /I) are typical causes of SSOs under conditions of high flow in the WWTF system. Blockages in the line may exacerbate the I/I problem. Other causes, such as a collapsed sewer line, may occur under any condition. Determination of the importance of SSOs as a source of bacteria loadings is typically difficult to assess. A damaged sewer line near TCEQ station 17166 in Cottonwood Branch (Figure 1) is suspected of being a major source of high E. coli values determined for samples collected at this station in 2oo8 during TMDL bacteria data collection. The sewer line has since been repaired. The TCEQ - maintained database of SSO data reported by responsible entities in the Dallas-Fort Worth Metroplex was reviewed for the period September 2003 — February 2009. The database contains entries that appear to be within the Cottonwood Branch and Grapevine Creek watersheds, though most of these entries are the result of relatively minor line blockages. Based on available information it is concluded that SSOs are not a widespread source of bacteria to the two creeks; however, they may at times be a significant source in localized portions of either creek. TPDES - Regulated Storm Water When evaluating storm water for a TMDL allocation, a distinction must be made between storm water originating from an area under a TPDES - regulated discharge permit and storm water originating from areas not under a TPDES - regulated discharge permit. Storm water discharges fall into two categories: • storm water subject to regulation, which is any storm water originating from TPDES Phase I and Phase II MS4- permitted discharges (Table 3), permitted industrial storm water areas, and permitted construction site areas; and • storm water not subject to regulation. Table 3. Regulated storm water discharges in AUs 0822A_02 and 08226_01 Impaired AU Regulated Entity Name' NPDES Permit Number TPDES Permit Number 0822A02 North Texas Tollway Authority TXS000703 WQ0004400 0822A02 and 082213 01 City of Irving TXS001301 W00004691 0822B01 City of Coppell TXR040375 TXR040000 082213_01 City of Dallas TXS000701 WQ0004396 0822B01 DFW International Airport TXR040044 TXR040000 a Although the jurisdictional boundary of the City of Grapevine is within the Grapevine Creek watershed, that portion of the city boundary is not within the City of Grapevine MS4 and thus is not a permittee in the Grapevine Creek TMDL. Texas Commission on Environmental Quality 9 For Public Comment, May 2011 l 6OZ AeW 'juewwoo oilgnd JOJ M A4!lenp le;uawuoa'nu3 uo uoisslwwOO sexal 1 ogy alp ui pagtluapt sa2augoslp ll;)IUI jo salduzpxa sapinoad (DDdMIHN) uoissiTu oD loaluOD uollnllod aaluM alulsaalul puul2uH maN •suoilnquluoo laaatpul ao loaaip aaglla su pazpo2aluo aq upo sa2augosrp IioiiII « sailinilop �uilg�g aag �foua�aauza ujoaj 2utlinsaa sa2augos.p pup uoiluzuoglnp alpaudas p ao liuizad Ipaaua2 sigl of lupnsand sa2augosip ldaoxa `aalum uuols jo pasoduzoo Slaaqua lou si lugl camas uuols alpapdas ludynunuz u of a2apgosip Xuv„ `sp stsw II asegd aoj 0000tolM -oN Ilutaad luaauao SHQds ui paugap si «a2augos.p llz)!Ul„ uzaal aqZ •suoilipuoo aaglLam lane pup �fap gloq aapun savapgosip liol it? pup sllujlno palliuuad uzoaj suwuaals agl aalua um aalum uuols palulaw woaj spuol uzialoug sa6aeyosia imin xaaaD auinaduao ui io gzzgo nv aoj 2utprol tSw agl jo lapd sp paluaal aq UyA laodatd AA qQ ao3 liuzzad aalum umols lunptnipui agl ui 65o UpjIno `ffisnouaad palou sV •(t aaat3) sliuzaad tSW jo pan palupL2aa agl uigl�m si pagsaalum (to gzzgo fIV) xaaao auuaduao agl3o luaoaad g•tg pup `sliuuad tSW aapun palulaaa si (zo Vzzgo) gouuag poomuolloD jo ny paaiudurt agl jo pagsaaluni aailua au •(E alquy) Iluuad I aspgd u anuq f4!joglnV fun&lloZ suxaZ glaoN pup `2utnal jo ii4iD `sulluQ 3o X41D agl `spagsaalum oml agl ui sailtlua palltuuad tSW agl 3O •pa.V paziuugafl snsuaD 000z agl pup sliurtl ,Slio agl jo spaap 2utddulaano ao uopoasaalui agl su paugap si paap IpuopoipsLZnf agl `sliuraad II asuqd ao3 -sltunl A41a agl Xq paugap si paau feuoilotpsianf agl `sliuizad I asugd ao3 •Xltlua paluln2aa agl jo sa. jppunoq luuopotpsunf aql uigllm uaau �fpnis aql jo uoilaod lugs si sliuuad tSW II pup I asugd Xq paaanoo )laaaD auinaduao pup gouuag poomuolloD jo uoi2aa aigdua2oa2 aqZ (seaie jalem wools pajeInbojun/pa;efn6ai) paysaa;eM MaaJO auinadejo ,t7 am6i j t 1' Dam s3N ! 7 r iaflw jCUo!jPUlajUl b F F l n saajawo��}� ( 9 s b F 7 l 0 Discharge Detection and Elimination Manual: A Handbook for Municipalities (NEIWPCC, 2003) including: ■ Direct illicit discharges: • sanitary wastewater piping that is directly connected from a home to the storm sewer; • materials (e.g., used motor oil) that have been dumped illegally into a storm drain catch basin; • a shop floor drain that is connected to the storm sewer; and • a cross- connection between the municipal sewer and storm sewer systems. ■ Indirect illicit discharges: • an old and damaged sanitary sewer line that is leaking fluids into a cracked storm sewer line; and • a failing septic system that is leaking into a cracked storm sewer line or causing surface discharge into the storm sewer. Unregulated Sources Unregulated sources of indicator bacteria are generally nonpoint and can emanate from wildlife, various agricultural activities, agricultural animals, land application fields, urban runoff not covered by a permit, failing onsite sewage facilities (OSSFs), unmanaged feral animals, and domestic pets. Most of these unregulated sources are limited in scale in the TMDL study area because of the highly urban nature of the area. Wildlife and Unmanaged Animal Contributions E. coli bacteria are common inhabitants of the intestines of all warm- blooded animals, including wildlife such as mammals, birds, and unmanaged feral animals. In developing bacteria TMDU, it is important to identify by watershed the potential for bacteria contributions from wildlife, birds, and unmanaged feral animals. Wildlife are naturally attracted to riparian corridors of streams and rivers. With direct access to the stream channel, the direct deposition of wildlife waste can be a concentrated source of bacteria loading to a water body. Fecal bacteria from wildlife are also deposited onto land surfaces, where it may be washed into nearby streams by rainfall runoff. There are currently insufficient data available to estimate populations and spatial distribution of wildlife and avian species in the watershed. Consequently, it is difficult to assess the magnitude of bacteria contributions from wildlife species as a general category. Studies in other watersheds have found avian species to be important contributors to the bacteria load (e.g., Hussong et al., 1979; Hyer and Moyer, 2003). There is also little information available on contributions from feral animals in the watershed. Unregulated Agricultural Activities and Domesticated Animals A number of agricultural activities that do not require permits can also be sources of fecal bacteria loading. Given the fact that the Cottonwood Branch and Grapevine Creek watersheds are highly urbanized, livestock and other domesticated animals are either not found in the watershed or exist in very small numbers. Therefore, livestock and other domesticated animals are not considered a significant contributor of bacteria loads in the two impaired AUs. Texas Commission on Environmental Quality 11 For Public Comment, May 2011 6 LOZ AelN 'luewwoo ollgnd Jod Zl A4!lenlo lelu9wuoa'nu3 uo uolsslwwOO sexal •sanbiugoa} Jo ,'4aiaun u g2noagl pagsilqulsa aq Xuuu digsuoilulaa aU •}uiodpua paaisap alp anaigae Ulm }egg suol }do }uaLua2uueuu jo uoilunluna ag} ao3 smollu iI 'IQyQ.L e 2uidolanap ui luauoduuoo luu:poduui ue si s2uipuol jo aoanos ag} puu X4genb aalun� uueaaisui uaanaq digsuoi}ulaa aq} 2uigsilquisg SISAIBUV 36e )JU11 •uneoWn si )laaiD auinadua0 pue gouuag poomuolloZ) jo sagouaa paziedun ag} 2uigoeaa s }ad uzog spool uuaojiloo 1ma3 jo ao mUlu2is pue uou}ngi woo lunpu agZ loia }sip goua ui q}ine splogasnoq ;o uoi }ngialsip lui�uds uana pauunssu uu pue fIV goua apisui pa}uool joialsip gaea jo a2ujuaoaad aq} uo pasuq aluuupsa age gjim (g2gu600z `OODJ.DN) spiaisip uopulndod ffq saaquunu plogasnoq Sooz (OOo�N) s�uauuuaano0 jo liounoD suxaZ lualuao gaaoN 2uisn pauiuuaa}ap sung splogasnoq jo aaquunu aq,L •(600z `VWnV) plogasnoq aad (£><L•o) sieo pue (z£9•o) stop jo .zagwnu pawuui}sa (vwnv) not }uioossv luoip W �Saeuuajan uuz)uauiV uo paseq palulnoluo aaam saluuit }sa uoi�ulndod dad •(000z iajangoS) stop JOJ Ifup .gad 60ix£•£ pue �uo s ao3 �fup aad gotxt•S jo salua uoi}onpoad uuojiloo luoaj paiuwilsa uo pasuq aau s2uipuol pa}u -tupsa aq,L sleo 8oi x VS; pue stop 6ot x CT : Cup aad lewiue aad peol wao;iloo leoa; palewilsa (000z) salangaS, sleo EiL•o :sSop z£9•o :aluwilsa plogasnog -aad leuoileu vWAV 800z q alswilsa paseq- loialsip uoilelndod )ODIDN Sooz e b6b'b bb£`bZ £Z£`8 LL£`L £L9`II l0 UZZ80 LSl'Z £89`11 b66'£ obS`£ Z09`S Zo VZZ80 , sleO uo!lonPOJd Allea , s6oa uollonpoJd Alleo q sleO jegwnN q s6oa jegwnN esplogosnOH to jegwnN palewlls3 ny (601 x) uogonpald Apep wioploo leoal palewilse nagl pue pagsjalem eaae bawl agl ui sled jo sjegwnu palewlls3 elgel -Sim puu stop opsauuop uzoaJ pool uuao;iloo luoa3 aq} jo aluuipsa ue sapinoad puu pagsaalum eaae 'I(Iml aql jo snd alp ao3 s}uo puu stop jo aaqumu paluuui } a} sazuuuns p alge •2uipuol uiaapuq 3o aoanos lei }ualod u aq uuo puu suaau uugangns puu uugan uuoaj jjouna Xq suuuaa }s o} papodsuua} si sluo puu stop uuoaj aa:auw luoa3 •slad ou}sauuop ioj spuol 2upulnoleo ui paaapisuoo s }ad Xluo aq} aau squo pue stop `upp }uunalaa jo ,,�4iliqupunu aqp puu }oafoad sib jo aan}uu uugan aqj uo pasug sled 31}sewoa -fuussaoauun si euaajmq jo saoanos }uuogiu2us su s3SSO jo uoi }uaapisuoo iagpnj `siq} jo asnuoag •alouuaa si spagsaa;um onl asagj ui s3SSO Xuuuu jo Pooq ?laxil ag} s3SS0 Xq Paoinaas aq llps pinoo suaae }uauuuaa} pue not }oalloo pazulua}uao aqu ui papnloui suaau ag} jo suoi� uod lluuus juLp alq!ssod si }i g2nogllV •3�M luuoi2 lualuaD 4iaoglnV aanig 'CI!UuJL ag} Jo sula}sXs }uauuea11 puu uopoaum aalumalsum pazulua}uao Xq panaas air Aaaaz) auinadua0 puu gouuag poonjuo:RoD jo spagsaalum aailua aq} asnuoaq eaae Xpn }s ZQWZ aqp ui 2ulpuol Lua}ouq jo aoanos aofum u paaapisuoo iou an, s3SSO 2uuiiud saili1i3e=l 06yames ells -uo 6uiIie=l "Wo aulnade.ig pue goueje poomuolloz) ul el.ialoee Jolealpul aol speo-1 Allep wnwlxew lelol omi Generally, if high bacteria concentrations are measured in a water body at low to median flow in the absence of runoff events, the main contributing sources are likely to be point sources or direct deposition. During ambient flows, these constant inputs to the system will increase pollutant concentrations depending on the magnitude and concentration of the sources. As flows increase in magnitude, the impact of point sources is typically diluted, and is therefore a smaller part of the overall concentrations. Bacteria contributions from regulated and unregulated storm water sources are greatest during runoff events. Rainfall runoff, depending upon the severity of the storm, has the capacity to carry bacteria from the land surface into the receiving stream. Generally, this loading follows a pattern of low concentration in the water body just before the rain event, followed by a rapid increase in bacteria concentrations in the water body as the first flush of storm runoff enters the receiving stream. Over time, the concentrations diminish because the sources of bacteria are attenuated as runoff washes them from the land surface and the volume of runoff decreases following the rain event. Load and Flow Duration Curve Analyses Load duration curve (LDC) analyses were used to examine the relationship between instream water quality, the broad sources of bacteria loads (i.e., regulated point source and regulated /unregulated storm water), and are the basis of the TMDL allocations. The strength of this TMDL is the use of the LDC method to determine the TMDL allocations. - LDCs are a simple statistical method that provides a basic description of the water quality problem. This tool is easily developed and explained to stakeholders, and uses available water quality and flow data. The LDC method does not require any assumptions regarding loading rates, stream hydrology, land use conditions, and other conditions in the watershed. The U.S. EPA supports the use of this approach to characterize pollutant sources. The TCEQ and the Texas State Soil and Water Conservation Board, identified this method as a tool for TMDL development. In addition, many other states are using this method to develop TMDLs. The weaknesses of this method include the limited information it provides regarding the magnitude or specific origin of the various sources. Only limited information was gathered regarding point and nonpoint sources in the watershed. The general difficulty in analyzing and characterizing E. coli in the environment is also a weakness of this method. The LDC method provides a tool for estimation of existing and allowable loads by utilizing the cumulative frequency distribution of streamflow and measured pollutant concentration data (Cleland, 2003). In addition to estimating stream loads, this method allows for the determination of the hydrologic conditions under which impairments are typically occurring, can give indications of the broad origins of the bacteria (i.e., point source and storm water), and provides a means to allocate allowable loadings. Data requirements for the LDC are minimal, consisting of continuous daily streamflow records and historical bacteria data. While the number of observations required to develop a flow duration curve is not rigorously specified, the curves are usually based on more than five years of observations, and encompasses inter - annual and seasonal variation. Ideally, the drought of record and flood of record are included in the observations. Daily average stream flows over a period of 15 years (08 August 1993 — 07 August 2008) were used for this project. Texas Commission on Environmental Quality 13 For Public Comment, May 2011 6loZ AeW 'luawwoo oilgnd ao3 K Al!lenC) Ielu9wua[nu3 uo uoissiwwOO sexal pallold uaql sure pool gong •2uipuol yoo •g au} 2utllold jo sasodnnd aoj anlue „papaaoxa pool sXt,p jo Iuaoaad„ aql sauzooaq gatgne ,'papaaoxa neoll sffup luaa iad,, aoj anlun slt auiuualap of ulup DQ3 aql of paaudwoo sure 2u1puol up puq goua noj neollumaais paluioossu aqu -puol uualoug u of palaaeuoo puu Iuawanns w jo Sup atp uo neolJuzuaals atp gline paluioossu sure Iuawannsuaw iloo •g p?ouolsiq goug •(ZlgVlu) gaivasag luluauzuoatnug pagdd� 3o alnlilsul suxas, aql `aoloualuoo 'I(IKL aq1 Xq paloalloo ulup luuopippu snouun (z) puu `asuqulup SIWOAA S bgDZ aql uwaj pauiulgo puu wun2oad sn Ara uuaID suxau atI puu uzua20nd 2uuoliuoW �fltluna aaluM aou3anS bgDu aql aapun paloalloo ulup aullnoa (i) :saoinos oY4 uwozj pauiulgo aaane 800z Isn2nV — tooz aagwanoN uwon3 ulup 1loo •9 imiaolsill •D(I l uivalouq alquneollu atp uo posodwuadns uaql aaane ulup upalouq luoiaolslH •slxe -X atp uo puol olquneollu aql aeoqu ao lu sure pool uiaalouq aqI Imp sXup jo Iuaonad aql Iuasaadaa sm -x aql 2uolu sanlun aouupaaoxg •(stxu -x) anlue aouupaaoxa sli Isuiu2u (spcu-) anlue pool uinalouq goua slold anano 2uillnsan ago Sup /spuooas * Euz /'IW 001 000,0001,98 = (Sup /Nclw 01) aolouj uoisnanuoD Ci103 •a) -ITU oot /Ndw 9zi = uoualpo :aaagM aolouJ uoisnaeuoo , (suzo) Moll..), uoiaalino = (fop /NdW) 'IGKL :2uipuol alquneollu utninumuz jo anano 'IQLQU aql su DQg aql sSuldslp Slanlloaga situ -Xup aad satuoloo ui �utpuo, of Inanuoo of nolou3 uoisnanuoo aqI Xq puu (,Iw ooi /x(lw 9zt) uotaaltno yoo •g aql Xq sannna uoilunnp neoT1 aql 2uolu anlun neoU wuanls goua 2u!Xldtllnw Xq padolanap @nano SO(II •sanano uolluanp neolluzuaals aql uwoj ulup aql puu (-Iw ooi /INdw 9zi) uouallno X11junb nalum oivawnu Iuaaano aql uo pasuq padolanap uaql @Wane sDQrl upaloug •suotlipuoo poop ao neou g2lq 3o spotnad 2uunp nn000 /o 2uigouoaddu sanlun aligne suotlipuoo Iq2nonp ao neojl Wool 2uunp nn000 /ooi auau sanlun aouupaaoxg •sDw -X aLp uo anlue neop paluioossu aqI aeoqu no lu sum neop Imp sXup jo luaonad aqI Iuasaadan sum -x aqI 2uolu sanlun aouupaaoxg •(stxu -x) anlue aouupaaoxa slt Isuiu2u (stxu -X) anlue neoll goua 2up4old (£) puu `(t + sluiod ulup jo aagwnu aqI jo fqtluunb - �luun) papaaoxa sure neop goua sXup 3o luaonad aqI 2upulnoluo (z) `Isaneol of Isag2tq wotj ulup moU Xltup aql 2ut4uua (i) Xq polunaua2 sure DQq aqu •uolluls goua noj D(IA u dolaeap Isng of pasn anane (suzo) puooas gad snalaw oigno jo sliun ui ulup neog XItup aql, •(ii£oz puu `6E6Li `i£SLi) uanu Xpnls aqI ut suotluls 2uuoliuow OADI aangl aql noj padolanap aaane io gzzgo fly no3 sDQZ puu s�Q3 (9gjZi puu 991Li) uanu Xpnls aqI ui suotluls 2uuoltuow agDu onel aqI noj padolanap aaane zo vzz8o fIV aoI sOQrl puu (s3Q3) sanano uol np neolA sasuanoui uoilulndod aanlnj jo oI anp nn000 �fuuz sa�autosrp 3u� uzo t snoop luuotlippu lute f1t�?qugond aql noj lun000u Iug1 saluwllsa fIiouduo aaulnj loallaa of palsnfpu anane spnooan a12010npxq aql `suoilulndwoa puol luulnllod aqI jo sasodand ao3 •sollua uanu a2uum 3o uolluagddu uo pasuq to gzz8o puu zo vzzso SPIV uitltm paluurtlsa @Wane sneolq Aaano autnadunf) puu gouung pooneuolloo jo lugl of asn puul jo ,�4tauiiwis aql puu ,fltuzixond uo pasuq uasogo sure puu `uanu Xpnls 'I(IVU atp jo Isua aqI of sapw h Xjg2noa `sulluQ thou ui paluool Si 31aano situ •)laaao )too -d alight uo oozLSoSo a2u2 (SgSfI) faAznS iuoi2oioa`J -s-fl worj pautulgo anane smaX 8t, Isud atp woa3 snook a2unanu Xltu(l •suoiluool papaau lunaeas lu ulup neojl uual -2uol jo Aaul u si anatl aouis uanu -I(I j , alp uigline snoop. aluurtlsa of ,4Iussaoau sure 11 ME)OJO auinadejE) pue uoueag poomuolloo ui eualoeg @oleo pul aol speo-1 Ape(] wnwixeW jelol OMI on the load duration curve at its percent exceedance. This process was repeated for each E. coli measurement at each station. Points above a curve represent exceedances of the bacteria criterion and its associated allowable loadings. The flow exceedance frequency can be subdivided into hydrologic condition classes to facilitate the diagnostic and analytical uses of FDCs and LDCs. The hydrologic classification scheme utilized for the Cottonwood Branch and Grapevine Creek TMDLs is as follows: high flows (o — 10 %), mid -range flows (10 — 50 %), and low flows (50 — 100 %). These three flow regimes were based on hydrology (slope of the FDCs). Additional information explaining the LDC method may be found in Cleland (2003) and NDEP (2003). Load Duration Curve Results FDCs and LDCs were developed for the two TCEQ monitoring stations within AU o822A_02 and the three TCEQ monitoring stations within AU o822B_oi. LDCs and FDCs were developed for all stations for which adequate historical E. coli data existed in order to present a complete representation of conditions in each impaired AU. However, only the median loading of the high flow regime (5% exceedance) for the most downstream site within each impaired AU was used for the Cottonwood Branch and Grapevine Creek TMDL calculations. The most downstream station within AU o822A_02 was station 17166, and the most downstream station within AU 0822B_o1 was station 20311. The median loading of the high flow regime (or the 5% exceedance point) is used for the TMDL calculations, because it represents a reasonable yet high value for the allowable pollutant load allocation. At the TCEQ, monitoring station locations (Figure 1), load relationships and possible sources were defined through LDCs created with historical E. coli data and the associated daily average flow for the flow duration curves. Load duration curves developed for stations within impaired AU o822A_02 of Cottonwood Branch (Figures 5 and 6) indicate E. coli loadings often exceeded allowable loadings under all flow conditions, including those not influenced by rainfall runoff. Similar patterns were also found at stations on Grapevine Creek, for which exceedances were often reported under all flow conditions, and during both dry- and wet - weather conditions (Figures 7 — 9). Seasonal Variation Federal regulations (40 CFR §130.7(c)(1)) require that TMDLs account for seasonal variation in watershed conditions and pollutant loading. E. coli data were examined and no statistically significant seasonal variation was found in Cottonwood Branch and Grapevine Creek (Millican and Hauck, 2010). E. coli data are thus not considered in the TMDL calculations. Margin of Safety The margin of safety (MOS) is used to account for uncertainty in the analysis used to develop the TMDL and thus provide a higher level of assurance that the goal of the TMDL will be met. According to EPA guidance (EPA, 1991), the MOS can be incorporated into the TMDL using two methods: • Implicitly incorporating the MOS using conservative model assumptions to develop allocations; or • Explicitly specifying a portion of the TMDL as the MOS and using the remainder for allocations. Texas Commission on Environmental Quality 15 For Public Comment, May 2011 L lOZ AeW `;uawwoo oilgnd ao-� 9� A4ilena lelu9wuoa'nu3 uo uoissiwwOO sexal •(SUUO ozo•o) SP EoL•o = mo7 :(suua t go'o) s ;a 6s•T = a2uea -pry '(swD obE•o) s ;a 107T = 4!H :a u uo9MS s►ql W a2uul gDua ui snAol{ uetpay� sal�ue.4 se poleu�tsap aae Juana uopeltd aad e ;o sanog tz utgjFA pajoalloa saldwus goy g ,ZO vzzgo nv) 996L6 uoge ;s jol ammo uoi;emp peo-I -9 ain6id lu8n3 JaglBBAA laM v luan3 JayleGAA IOM -uoN + uoual!jo ueewoao le peol e!geMo!!y- papaaaxe peon sAep ;o;uaaaad %OOL %06 %08 %OL %09 %09 %04 ME %OZ %OL %0 80 +3' l 60 +3' L + + + + + * + 0 1+3 L m + +++ +v + O + n + + LL +3'L v Z v + v v + a v m $ + ZL +3 L + + v + £L +3'L v v SM01j MOB SMO!j 96uea -p!W SMO!j g61H VL +3'L (SUuz) Two) sp Eob•o =mo l !(suta Lzo•o) sp z96•0 = a2uez -p W !(swa z9T•o) sp TCS = q2!H :aae uoue }s sitl} lu a2uua gaua ut snoop ueipaw sal2ue.4 se paleu3isap aae Juana uollel►dtoaad a ;o sanog bz uigl>M paloalloo salduies }loa g (ZO vzzeo nv) 996L1 uoijels ao; emno uoi;emp peon •9 am6i.� lu8n3 JagleaM 1aM v luan3 J9glE8AA 19M -uoN + uopalpo ueawoaE) le peon elgeMoIIV- pepeeoxe peol sRep jo luaoaad %OOL %06 %OS %OL %09 %09 %04 ME %OZ %OL %0 v + v + v v v v VV v v v sM0 1=1 Mo'7 sM013 96uea -P!W SMOI� 46!H 90+31 60 +3'L m OL +3 L c 3 Z LL +3'L a N ZL +3'L L +3'L >l1a10 auinadejE) pue youejg pooMuolloo ui eualoee ioleoipul aol spe0-1 Aye(] wnwixepy jelol onnl 1.E +11 T A a Z a 2 1.E +10 0 U W 1.E+09 1.E+08 HAgh Flow Mid -Range Flows Low Flows e e ° e A e + + + 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of days load exceeded — Allowable Load at Geomean Criterion + Non -wet Weather Event a Wet Weather Event Figure 7. Load duration curve for station 17531 (AU 0822B_01) E. coli samples collected within 24 hours of a precipitation event are designated as triangles. Median flows in each range at this station are: High =14.35 cfs (0.406 cros); Mid -range = 2.38 cfs (o.o67 cros); Low = o.97o cfs (0.027 ems). 1.E +13 t4gh Flows Mid -Range Flows Low Flows e 1.E +12 T N 0 1.E +11 Z IL f u 1.E +10 4i 1.E+09 1.E+08 I I I I 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of days load exceeded — Allowable Load at Geomean Criterion + Non -wet Weather Event a Wet Weather Event Figure 8. Load duration curve for station 17939 (AU 0822B_01) E. coli samples collected within 24 hours of a precipitation event are designated as triangles. Median flows in each range at this station are: High = 22.34 cfs (o.632 cros); Mid -range = 3.56 cfs (o.1ol cros); Low = 1.35 cfs (0.038 cros). l exas Uommission on Environmental Quality 17 For Public Comment, May 2011 L LOZ AeW `luawwoo opgnd JOJ 9L A!Ienl9 Ielu9wu0Jlnu3 Uo u0issiww00 sexaj SON + 033 + VTK + V'IM3 = 'I(IML :uotiunba 2upmoll03 aql 2uisn palulttoluo ajam sot tuuao lo s paalas aqi aoI suoiluoollu pool luelnllod ails 'sprepuuis ,flilunb aalum 2uipaaoxa inotlipA Ap al2uis u ut antaoaa uuo utuaals aql leip luelnllod u jo lunoutu utnwixuut aqi sivasaadaa -IQKI atU uoile3olld peO-1 jue4nll0d pool algumollu utnwixuw luloi = 'I(Ivu :azaqm ,lava. 50.0 = SON :uotlenba �?upAolloj aui ui passaadxa st siLIL •IlV tloua �?uualua 2utpuol alguneollu app luaouad S su palndutoo si SON Itoildxa ails, •paonpaa Xpq2ils si Xpoq aalum goua jo 2uipuol luelnllod alqumollu ao X4pvduo antlultutissu aql leul si SOW ulim IQLU atli jo loapa lau aU .!loo •g jo Zuz ooi /NdW ort jo la2lui uuauz oulautoa2 u of salunba still `uotluaaoaa louluoo and •uoualiso uuauz oulauioa2 aui uutli aamol luawad 5 si luLp spool uualouq aoluoipui aoj la2aul u 2ull4as Xq SOLI lioildxa uu alutodaoout podw stgi Xq paaanoo s-I(IKL a%L -SOW u 2uiu2issu .to3 sisuq aqj si `algissod lualxa atll of `i,4umpaoun still jo uoiluotspuunb •Xlilunb aalum loagu luui sassaooad luluautuoainua xaldutoo atll aoI sai2alwis loaluoo �flilunb aalum 2up44pads ut asuu Moot lugj fqutulaaoun Xuu aoj lun000u of pau2isap si SOLI aq,L •(sw3 Mo•o) slip �e a2 U.1 uaea s ;o z£•£ = moZ '(sLuo bLz-o) s ;o L9'6 = aSuea -P!W :(sulo zog*t) sP 59'£9 = q2ig :aae uoe ;s d � ui snoop usiPOW •saftru n su paluu2isap aau Juana uoq i0aid L, jo sinoq ft uigp!m papallo0 salduws 1100 •g (60 8ZZ80 nv) 6lCOZ uoi ;els jol aNno uoileinp peo-I -6 ain6i j luan3 JayleaM LeM v lu9n3 JayleaM lam -uON + uopelpo ueawoaE) le peol algemollV— papaeoxe peon step JO IU83J8d %OOL %06 %08 %OL %09 %09 %04 %0£ %OZ %M %0 v v v v V sMOU Mot �I_q a6uea -pin smOlj LAH 80 +3'L 60 +3' L m OL +3'L o 3 v z_ L L +3 L n w ZL +3'L EL +3'L AaaJo OUlnadeJo pue UoUeje pooMU0ll0Z) UI eUaj0ee JoIe3IPuI JO; spe01 Aflea wnwlxeW Jejoj OMj 1 Where: WLA = wasteload allocation, the amount of pollutant allowed by permitted or regulated dischargers LA = load allocation, the amount of pollutant allowed by unregulated sources FG = loadings associated with future growth from potential permitted facilities MOS = margin of safety load As stated in 40 CFR, 130.2(i), TMDLs can be expressed in terms of mass per time, toxicity, or other appropriate measures. For E. coli, TMDLs are expressed as MPN /day, and represent the maximum one -day load the stream can assimilate while still attaining the standards for surface water quality. Wasteload Allocation TPDES- permitted wastewater treatment facilities are allocated a daily wasteload (WLAwwrF) calculated as their full permitted discharge flow rate multiplied by one -half of the instream geometric mean criterion. One -half of the water quality criterion (63 MPN /ioomL) is used as the WWTF target to provide instream and downstream load capacity. This is expressed in the following equation: WLAwwrF = Criterion /2 * flow (MGD) * conversion factor Where: Criterion = 126 MPN /loo mL Flow (MGD) = full permitted flow Conversion factor = 37,854,000 loo mL / MGD As previously discussed, there are currently no permitted wastewater treatment facilities within the TMDL study area. DFW Airport is the only facility with an individual permit; however, that permit authorizes the discharge of only storm water during periods of de -icing activity and will be treated as part of the waste load allocation for TPDES - permitted storm water discharges (discussed below). The Airport is also covered under the TPDES Phase II General Permit. No individual WLAwwrF was calculated for the DFW Airport permit, and the total WLAwwrF is set to zero. In the event that the permitting process for a new WWTF is initiated in either watershed, a future growth component has been included in this TMDL that will allow for the allocation of loads based on an estimate of the future WWTF discharge requirements for both watersheds. Additional storm water dischargers represent additional flow that is not accounted for in the current allocations. In urbanized areas currently regulated by an MS4 permit, development and /or re- development of land in urbanized areas must implement the control measures /programs outlined in an approved Storm Water Pollution Prevention Plan (SWPPP). Although additional flow may occur from development or re- development, loading of the pollutant of concern should be controlled and /or reduced through the implementation of best management practices (BMPs) as specified in both the NPDES permit and the SWPPP. An iterative, adaptive management approach will be used to address storm water discharges. This approach encourages the implementation of structural or non - structural controls, implementation of mechanisms to evaluate the performance of the controls, and finally, Texas Commission on Environmental Quality 19 For Public Comment, May 2011 6 60Z AeW ';uawwoo oilgnd io3 oz A4ilenC) leluewuainu3 uo uoissiwwOO sexal auatunu su uugl iaglea `sluauiaambaa auluuts daglo ao sdwq se passaidxa aq Menu aalune uuols ioj V-IM agl luauialduut lugl slitutl luanlja pasug- ffltlenb aalune `sa2aegasip ialum uuols Ieialsnpui pue `sa2aegasip aalene uuols uoilanalsuoa `ludiaiunui paleln2ai -SdQdZ /SHudN ao3 •suoiluaollu peolalsune agl jo suoilduunsse pue sluauiadinbaa agl gline lualsisuoa suoilipuoa aainbaa Illnn sliuuaad SdQdZ 31.MM atlsauiop `panoaddu uaaq sug'IQW.I, e aiagM •Ittuad Wean e ao3 paneollu lou aae salnpagas aauutlduuoa asneaaq skull luanlja uuualui uueluoa lou Mine sluuuad neaN •aauenssi -ai lluuad ;o alep aql uuo4 sauaX aaagl uugl aa2uol Xue aq lou Xeuu sliuuM luanlja uuiaalui Xuu 3o uoileanp aU •suoileaolle -IUVU panoidde VdH pue aHDs aq} laauu of faessaaau slituil Iuanlja luuid agl um o} aapao ui lilunb lunl a i poTu of mull aalluuuad a molle M?M sltunI uuaaluu asagZ •leneauaa luuuad ao luauupuauuu Iluuad u le sluauiaainbad ffluo- 2uuoliuouu ao /pue sliuuil luanUja tuaalut gsilqulsa Menu uoissiuuuuoa ao iolaa iip antinaaxa ails, •'IQY�i.L agl gline aauuilduuoa alualsuouiap Mine suoilae 2uilliuuad Ile `ss3lpa03g •uuld Iuauua2uuuw f4llunb aaleM s,alels aql of alupdn uu jo uoiluauda id anlonui Xetu gatgne `uoilau 2uilliuuaad SdQdZ, aluaudas e tin paluauialduu jtlun �uupuiq -uou aae `I L'm uuols ao� svqM agl su Mane su `sV-IM IunplAlpm agl `adojaaaU •paldope si 'I(ImL sigl ia4e sV"IM Iunpinipui ui s32ue113 luuddune tutu saauulsuunaaia pue Xlilunb aalune panoaduui jo leo2 agl 2utnaug3u jo sueauu algiseaj XIleatugaal ao Iuattuouoaa aaouu u aq Muni aaagl `aananeoH •ssaaoad leneauad liuuaad ouilnoa agl 2uunp paluatualdun aq Min,+ sluauuaambaa liuuad aqZ •6.6i£§ ui palsll aau pue salua neoll palliuuad uo pasug aae sluatuaainbaa 2uuoliuoW --JUK , agl uo pasuq luuul luanlja ue pau2isse aq Mu" snd luat gas 'I(IWI agl of 2ui2degasip s31 MM 600z 19z aagwanoN anulaajja auueaag gaigne 61£ iajdugD apoD anulualsiuuuipv suxal o£ 30 luauupuauiu agl Xq padinbaa se suolleliuuil luanUja io /puu sluauuaii i 2uuoliuouu su ssaaoad 2ui }liuuad agl g2noagl sVIM IunpinipUl agl luawaldiul of spualui OaD j, aU sltuuad aalene uuols jo uoilaips�znf aapun uaau a2uum jo uoiadodo id leuoilaedj _ dmsdQ3 ,lava . 50.0 = puol fflajus jo ui2auui = SOW saililtauj papluuad letlualod uuod3 spool glneoa2 aimnj jo wins = Od3 o = spuol 31.MM Ile 3o tuns = �u"v'IM3 peol algeneolle uununxeuu lulol = rIuva speol aalene uuols popluuad lle jo nuns = Msv -IM3 :aaagm dmsvcu . (SOLI — J33 — -,""v im:K — 'I(IKL) _ msv IM3 :sneolloj se palelnalua si pue saadnos aalene uuols (palltuuad ao) paluln2aa uwoaj speol jo tuns agl si Msv i AN `snU •uoulnqualuoa aalune uuols palliuuad agl su msvIM agl ut paluaolie aq pinogs leg} pool jjouna Iledano alp jo lunouie agl aluuulsa of pasn su (dmsVQ3) suoileln2ai liuuad VSW gllm Alduuoa of padmbaa �flulua ue 3o uoiplpsunf agl aapun si lugl pagsaalune gaua Io a2uluaaaad aql •2uipeol aalune uuols jo ffltligetaen agl pue `jjound Mejuiud 2upulnuuls gline paluiaosse sapixalduuoa agl `algelrene elep ;o lunouue paliutil agl of anp s I(IKL asagl jo luatudolanap agl ui pasn sere wade asagl ioj H-IM agl 2uputui4sa ioj gaeoadde paidilduns v •(MSv-LM) sa2dug3sup ialune uuols paplumd doh uopuaoUu ue apnlaui oslu Isnui suoulelnalea AIM agl `ado�adag� saaanos luuod palliuuad paaapisuoa aau seaau uoilanalsuoa pue `luulsnpui `tSW uuoaj sa2dugasip aalene uuols •Xlilunb aalune laaload of f essaaau su (sdWq aidiaads ao slodluoa lua2uLils adoui 1•2•a) sluauilsnCpe aVtu of aoueneolle MaaaO auinadejE:) pue Uoueag poomuouuoo ui eua;oeg aoleoipul ao} speo-1 Al!ea wnwixeW je;ol omi Two Total Maximum Daily Loads for Indicator Bacteria in Cottonwood Branch and Grapevine Creek effluent limits (November 12, 2010, memorandum from EPA relating to establishing WLAs for storm water sources). The EPA memo states that: "The CWA provides that storm water permits for MS4 discharges shall contain controls to reduce the discharge of pollutants to the "maximum extent practicable" and such other provisions as the Administrator or the State determines appropriate for the control of such pollutants. CWA section 402(p)(3)(8)(iii ). Under this provision, the NPDES permitting authority has the discretion to include requirements for reducing pollutants in storm water discharges as necessary for compliance with water quality standards. Defenders of Wildlife v. Browner, 191 F.3d 1159,1166 (9th Cir.1999)• The permitting authority's decision as to how to express the WQBEL(s), either as numeric effluent limitations or BMPs, including BMPs accompanied by numeric benchmarks, should be based on an analysis of the specific facts and circumstances surrounding the permit, and /or the underlying WLA, including the nature of the storm water discharge, available data, modeling results or other relevant information. As discussed in the 2002 memorandum, the permit's administrative record needs to provide an adequate demonstration that, where a BMP -based approach to permit limitations is selected, the BMPs required by the permit will be sufficient to implement applicable WLAs. Improved knowledge of BMP effectiveness gained since 2002 should be reflected in the demonstration and supporting rationale that implementation of the BMPs will attain water quality standards and WLAs." A November 22, 2002, memorandum from EPA relating to establishing WLAs for storm water sources states that: "...the Interim Permitting Approach Policy recognizes the need for an iterative approach to control pollutants in storm water discharges ... [s]pecifically, the policy anticipates that a suite of BMPs will be used in the initial rounds of permits and that these BMPs will be tailored in subsequent rounds." Using this iterative adaptive approach to the maximum extent practicable is appropriate to address the storm water component of this TMDL. This TMDL is, by definition, the total of the sum of the WLA, the sum of the LA, and the MOS. Changes to individual WLAs may be necessary in the future in order to accommodate changing conditions within the watershed. These changes to individual WLAs do not ordinarily require a revision of the TMDL document; instead, changes will be made through updates to the TCEQ's WQMP. Any future changes to effluent limitations will be addressed through the permitting process and by updating the WQMP. Load Allocation The LA is the sum of loads from unregulated sources. Nonpoint sources within the Cottonwood Branch and Grapevine Creek watersheds include unregulated storm water runoff and direct deposition from warm- blooded animals. The LA term is calculated as: Texas Commission on Environmental Quality 21 For Public Comment, May 2011 6lOZ AeW ';uawwoo oggnd JOJ ZZ f4ilenC) lelu9wuaUu3 uo uoissiwwoO sexal goua jo a2uluaoaad uo pasuq pauiuu lop uagl sure pagsaalune goua jo uoilulndod aill `loialsip goea ui notingia }sip uana 2utuznssV o£oz puu Sooz ao3 ulup uopulndod puu sloialsip uoilulndod OOD.IDN aql puu pagsaalune goua jo salg adults SI0 agl 2uisn paluunlsa aaane )Iaaao auinadua0 puu gouuag pooneuolloD jo spagsaalune aailua aql jo uoilulndod agl `IxaN •podgy Lot 3o neoU aalunealsune u 2uind uoilulndod a3Luas sli Xq a2augosip Xliop lunuuu Sooz 3ZMM IuuoiJ a2l lealuaD VZ aql 2uipinip Xq pautuzaalap uagl sure uliduo aad neog aaluneals'em aqZ ppIsIp goua uigline uoi }ngia ;sip uoilulndod uana �utuznssu aaglanj `uaau a3Luas agl ui lo?alsip goua jo a2uluaoaad aql puu saluuxpsa loin }sip uoilulndod OODiLz)N Sooz aql uo pasuq paluunlsa sure uaau aoLuas AIMM leuol ald lualuaD VHJL agl utgline uoRulndod agZ •(g2gu600z `OODJLDN) lo?alsip uoilulndod Kq saluwnlsa uoilulndod OODZDN puu `sloialsip uopulndod OOo.L7N puu uaau a;)Luas 3ZMM agl jo saaXul SIO alquliunu 2uisn pauiuu3jap sere Sooz auaX agl io3 3ZMM V-dZ agl jo uoilulndod wLuas aq} IxaN auaX lugl aoj (600a `Vdg) alisgane uzals fs aouugduzoo Iluuad Vdg agl woq pauiulgo (sdW(I) slaodaa 2uuoltuow a2aug3sip sli uo paseq 3JMM luuoj2ag lualuaD VdZ aql ao3 a %ugosrp Xliup Auaanu Sooz auaX aql auiuualap o} sere uaVI gouoaddu aqZ •pagsaalune goma ioj uosaad sad uolluaaua2 aalunealsune a2uaanu auiuualap Xltpuaa o} algisua ui si li `.3j mm iuuoi2ag IualuaD V-dj agl ao3 uaau anuas uoiloalloo aalunealsune aa2aul gonuz agl uigline ail spagsaalune paaiudun gloq aouis -(It So luaui2aS) aanig ,,liuiaZ )1.103 IsaM aamM agl uo paluool 31,MM Iuuop -d Iualuao V-dZ agl of spagsaalune gloq jo Ino papodsuual si )IaaaD auinadua0 puu gouuag pooneuolloZ) utgline paluaau32 aalunealsuM gzz8o puu �zzgo sluaui2aS olui a2augosip s31,MM palltuzaad ou `�flluaaanZ) •(pod2) Xup aad ulldm aad suolle2 ao Xup aad uosaad aad paluaaua2 aalunealsune jo lunouxu aql jo aluunlsa up puu suotloaload o£oz auaX of saluunlsa Sooz auax T1104 asuaaoui uollulndod aql uo pasuq suopulnoluo ZQKI agl ui papnloui sere glneoa2 aanlnj aoj uoisinoad u `snV gloq ui in000 Xuua sa2augosip ADAM wzoaj snoop. neau Will fIiligugoad aqlioj lun000u oZ gjmojE) aanln=l •,4biiod uotlupuaapiluu s,suxaZ o} uuojuoo puu sasn luiagauaq 2uilsixa jo uoiloaload ui Ilnsaa Ul m luawnoop sigj ui sZQya aqZ •flilunb aalune apua�ap Mine �Slinilou aq} 3i auiwIaalap of suoilou pasodoad lunpintpui 2uineainaa ao3 ssaooad u gsilqulsa saanpaooad uotlupua2apiluu `Iuaaua2 uI •sa2augosip Iuulnllod aoanos lutoduou puu luiod gloq of satlddu �fogod uoilupua2apiluu aU •asn 2ullsixa uu jo u0pupuBap of aingialuoo ao asnua phone lugl 2uipuol III asuaaoui uu sligigoad spaupuuls agl ui Xoiiod uotlupua�aptluu paaap -aaagl aql `uoilrppu uI sow+ 033 + VI + ",Sv IM3 + crane VIM3 = 'I(Iwl :V-1 puu V-lM3o sluauodwoo aql moils of popuudxa aq sngl uuo uollunba -I(ImL alts, -iuv I .* So•o = puol'flajus jo ut2auuz = sow saililioe3 Pa14iuuad legualod woaj spool glneoB aanlnl3o wins = 033 spool aalune uuols polliuuad Iiu jo wins = nest" IM3 o = spuol 3J,MM Ile 3o wins = ALIAM 'IM3 pool alquneollu wnu Draw Ielol = 'IQva fld aql 2uualua saoanos palulawun uwoaj pool alquneoliu = yI :aaagm sow — 033 — 'IUKI = VII population district in each watershed, the 2005 and 2030 population estimates for each district, and summing the computed populations by watershed. With this information, the future growth (FG) of each watershed is calculated as follows: Where: FG = criterion /2 * Flow2005 * (Pop3o - Pop05) Criterion = 126 MPN /loo mL Flow2005 =107 gallons per capita per day (gpcd) based on the average daily discharge of TRA W WTF from year 2005 DMR data divided by year 2005 TRA WWTF wastewater collection area population estimate Pop3o = estimated watershed population for year 2030 POP 05 = estimated watershed population for year 2005 Conversion factor =10-6 MGD /gpcd * 37,854,000 loo mL / MGD = 37.8541oomL /gpcd Additional storm water dischargers represent additional flow that is not accounted for in the current allocations. Changes in MS4 jurisdiction or additional development associated with population increases in the watershed can be accommodated by shifting allotments between the WLA and the LA. This can be done without the need to reserve future- capacity WLAs for storm water. In non - urbanized areas, growth can be accommodated by shifting loads between the LA and the WLA (for storm water). TMDL Calculations The TMDL was calculated based on the median flow in the o -10 percentile range (high flow regime) from the LDC developed for the most downstream station within each AU, which is station 17166 in AU o822A_02 and station 20311 in AU o822B_o1(Figure 1). Each term in the TMDL equation was determined based on the equations provided previously. Table 5 summarizes the calculation of the TMDL for each AU. Table 6 summarizes the computation of future growth for the combined AUs. The entire drainage area of AU o822A 02 is located within jurisdictional areas regulated by storm water permits, and 84.8% of the drainage area of AU o822B_o1 is located within the jurisdictional areas regulated by storm water permits (2,605 ha out of 3,073 ha are under storm water permit regulation). Table 7 summarizes the computation of term WLAsw. Since the entire drainage of AU 0822A_02 is within the jurisdictional areas regulated by storm water permits, the LA associated with this AU is zero. For AU o822B_01, 468 ha or 15.2% of its drainage area is not regulated by storm water permits, and LA was computed from the value of terms in Table 7 (see Table 8). Table 9 summarizes the TMDL calculations for AUs o822A 02 and o822B_o1. The final TMDL allocations needed to comply with the requirements of 4o CFR 130.7 are presented in Table 1o. The final TMDL allocations include the future growth component designated as WLAwwrF while allocations to permitted MS4 entities are designated as WLAsw. The allocations are based on the current geometric mean criterion for E. coli in freshwater of 126 MPN /loo mL, with the exception of the Future Growth component. The Future Growth component is based on 1/2 the current geometric mean criterion (63 MPN /loo mL) to account to provide instream and downstream capacity. In the event that the criteria change due to future revisions in the state's surface water quality standards, Appendix A provides guidance for recalculating the allocations in Table Texas Commission on Environmental Quality 23 vor vumic GommenL, rviay —1 L LOZ AeIN '}uewwoo oilgnd Jod bZ AlllenC) leluawualnu3 uo uolsslwwoo sexal 17£'8Z IO OZZ80 0 ZO VZZ80 (ABP /NdW UO11118) V-1 nv ( LO 8zz90 nv) �99JO auinadejE) PUe (zO vzzgo nv) 4ouej8 poomuouoo jo; uol;elndwoo jajem wiols paleln69a -uoN g elgel 09'L91 8178'0 18'6 917'0 00'0 ZZ'961 to —OZZ80 L617 £ 000'1 98'1 1Z'0 00'0 170'L£ ZO `dZZ80 msd-1M dmsvQ j sow 41moig ainln j mm1/lM laWl nv (SLIP /NdW u01II 18 se possaadxa speol IIV) (LO ezz90 nv) N99JO aulnadeaE) PUe (zO vzzgo nv) gouej8 poomuouoo jol uollelndwoo jajem wiols paleln698 ,L algel %9 jo SOJAZ so; uoi;onpai a sapnloui glmoB ainlnd .. 17917' 961'0 9l8`l ZZ9`ZZ L08`OZ amnadwq EIZZ80 Z1Z' 680'0 6Z8 8Z£`OZ 6617`61 pumEl dZZ80 luawoes PooMuouoD . (AeP /NdW (aoW) OSOZ o; uollelndod uollelndod aweN luawfiaS u0!II!8) uollonpo�d SOOZ esee�oul 0£OZ SOOZ weailS 4lmoj0 aininj JalemelseM uollelndod Ieuo!3!PP1l N99JO aulnadejE) pue gouej8 poonnuouoo jol suolle;ndwoo gymoaE) aanlnd *9 algel ZZ'961 (sia 99'£9) swo Z08,1 11 £OZ N33JD aulnadulD 10 OZZ80 170'L£ (sla IO'ZI) swa Z017£'0 991L1 g3ue18 PooMuolloD ZO `dZZ80 (AeP /NdW uoIIIIS) "IOWl awl6aa mold 46IH ;o enleq ue1PaW uollelS aweN weaJlS luawoes N99JO aulnadejE) pue gouej8 poomuouoo jo; uollelnoleo -1allNl ;o luewwnS .5 elgel •ijoa •g aoj uoraalpo fq! jenb aajum neau jupualod Auu uo pasuq suoiltDolle peol lue}nUod pue s7UKL mau jo uol�iulnolm mollu `z -V pue t -V sam2IA 1pYA 2uole 'papinoad suoq;enba aiU •tjoa •g aoj eualuo Xignb .tjvm leoppagjoclxq jo saquznu >L, o} uopelaa ui a2mgo suoi�eoolle peol }uulnllod pue Isuoi P,lnaleo Z(IWI `,�}iaL'dm aAIJU WISSe MOO alea}suouzap of padolanap aaam V xlpuaddV jo z -V pue t -V sawajA •ol< Table 9. TMDL allocation summary for Cottonwood Branch and Grapevine Creek (all units in Billion MPN per day) AU Stream Name TMDL' WLA,,,,F' WLAgW` LA° MOS' Future Growth' 0822A02 Cottonwood Branch 37.04 0.00 34.97 0 1.85 0.21 0822B_01 Grapevine Creek 196.22 0.00 157.60 28.34 9.81 0.46 a TMDL = Median flow (high flow regime) * 126 MPN /loo mL * Conversion Factor; where the Conversion Factor = 8.64E +o8 loo mL /m3 * seconds /day; Median Flow from Table 5 b No WWTF discharges into AUs o822A_02 and o822B_oi ` WLAsw = (TMDL - WLAwwTF - FG - MOS) * FDAswF; (see Table 7 for equation values) d LA = TMDL - WLAwwTF - MOS - WLAsw - FG; because the entire drainage area of o822A_02 is covered by MS4 permits its LA = o.000 e MOS = 0.05 * TMDL f Future Growth = Criterion /2 (63 MPN /day) *Flowzoos * (Pop30 — Pop05) * Conversion Factor; where FlOW2005 = 107 gpcd, Pop30 is the estimated population within the watershed for year 203o and POP05 is the estimated population within the watershed for year 2005; and Conversion Factor = 37.854100 ml /gpcd; (see Table 6 for population estimates) Table 10. Final TMDL allocations for Cottonwood Branch (AU 0822A_02) and Grapevine Creek (AU 0822_01) (all units in Billion MPN per day) AU Stream Name TMDL WLAwwTE* WLAsw LA MOs 0822A02 Grapevine Creek 37.04 0.21 34.97 0 1.85 08221_01 Cottonwood Branch 196.22 0.46 157.60 28.34 9.81 * WLAwwTF = WLAwwTF + Future Growth Public Participation The TCEQ maintains an inclusive public participation process. From the inception of the investigation, the project team sought to ensure that stakeholders were informed and involved. Communication and comments from the stakeholders in the watershed strengthen TMDL projects and their implementation. TCEQ and TIAER are jointly providing coordination for public participation in this project. A series of public meetings have been conducted over recent years to keep the public aware of the TMDL process and to engage public participation. Public meetings were held at the Valley Ranch Library in Irving on June 10, 2008, September 24, 20og, and April 22, 2010. The meetings introduced the TMDL process, identified the impaired AUs and reason for the impairment, reviewed historical data, described potential sources of bacteria within the watershed, and presented the TMDL allocations. In addition, the meetings gave TCEQ the opportunity to solicit input from all interested parties within the study area. Information on past and future meetings for the Cottonwood Branch and Grapevine Creek TMDLs can be found on the TCEQ website at: <www.tceq.state.tx.us /implementation /water /tmdl/ 66_cottongrape_bacteria.html >. i exas Commission on Environmental Quality 25 For Public Comment, May 2011 6 60Z AeW ';uawwoo oilgnd god 9Z f4ilenC) IMu8wuaLnu3 uo uoissiwwOO sexal •Iuauutudun up of 2utingtaluoo Aitiva palulaaa u Jo uotiou anuloaaaoo aaunbaa of Xpauuaa luauuaoaojua up 3o uotlulmso pup `siutulduuoo oggnd of l000load asuodsaa U ao Xouanbaa3 uopoadsui up jo luauuisn[pu `spuaal 2utpuol Ajtaan puu alunlpna oI f4llunb a2apgostp ivanlpa jo 2utlaodaa pup 2utaoltuouu juuotluppu apnlout Xuuu sai2aluals eons ,faussaoau uaigm uuld -I up ui pagtivapt air Itl$tsaano pup aouptldmoo amundo of sai2alualS •sZQya suxaZ aoj suuld -I anoaddU lou saop Vdg ssaa2oad 3o uotlunluna oipouad ioj upld u pup `saanseatu Iuauua2muuu Ino 2ut�.uuo ioj algisuodsaz suoilezmajo aqI f4lluapt oslu suuld -I •awil alquuoseaa U uugllm s'I(IKL aulnoulapd jo sV j pup svim aql Iuauualdiuu of saansuaw Iuauua2utuuuu ,�iulunlon pup 4Liojujn2ai agi jo alnpaulos pup uoliduosap paptulap u sapnlout uull -I and UBld -1 uB 10 SIUGW013 AG),i •ssaa2oad jo suotlunluna ui pagtluapt spaau loallaa of faussaoau su pnidupu aq UFA suuld-I - Aauatou a aspaaouu of paijlPouu aq pinogs saoanos 2uotuu 2uipuol jo uoilnqulsip luui2uo aqi lugs molts Xuuu pup 12up in000 si ssaa2oad iaglz)gm utepamu spoglauu uotlpivauualduut jo ssauanuloajja aql to suopunluna paluadaa `otpou d paluawalduut aq Illm suoulonpaa Iuulnllod anatgou of saritntlou XaujunjoA pup Ximulaw f uussaoau ails Iugl saanssu Xlquuosuaa ulopoaddu antidupu sags •sluo2 luluauuuoainua anaiulou of spoglauu 3o uoiltppu ao luauuaugaa aoj smollu Iut l gouoaddu Iuauua2uuuuu antidupu up asn srlQyu suxaZ aoj supld -I •uoussiuutuoa aqi Sq paldopu s-l(lp L Ile 3o uoppivauualdtuu 2uliaoddns of pallluutuoo si agZ)Z agjL •uuld -I up jo asn s,aluls aql Xq paansse Xlquuospaa aau samnos lutoduou pup Iutod qloq tuoaj srlaWjL ui spuol luuinllod 2utnatgou ioj sai2alwlS uuid -I paldopu up glyA aouupa000p ui saa2apgasip aalum uuaois 2utioajju suoistnaa optoads aaglo Iuatualduut so `uuid uo M a u mbaa `iutaad aalun . l t uuols u astnaa Ig2utu ORDL aqI `aaglug alupdn uoulpiutuul ivanlpa up q2noagl luuuad aaium uuols SHQdZ ogtoads u of algpoulddu sluamaainbaa uotlpluawalduui ogtoads Xjpuapt lou Illm bHoi aql `Ituuzad VSW up ui pagstlquisa an saotlopad Bons uagm •(saoanos aalum uuaols ioj sV"IM I(Iya $utgstIquisa of 2utlulai VdH uuoa3 uunpupaouuauu `zooz `za aaquuanoN aas) alglsuajut am suollultuutl Iuanjpa ouauunu aaagm `salsa Ipaapaj Xq p Mollu sp `suoilpittutl luanlpa aoj alnitlsgns u aap sdWq •sdWg gstlqulsa XUruuou Iltm bgoi aql `sitttuad pSyQ ao3 •sltuuad a2augosjp aalumalsum SHQds ogtoads .ioj fbussaoau suopull -L utl Iuanlpa paspq- Xltlpnb -aalum paambaa gstlquisa of salupdn dWom Xjl:pao pup asodoad ti?m baDi atp `(uuld -I) uuld uolluluauualdwl pup rlQyU aqi uo pasug •alupdn dWOM palutoosse aqi jo uotlpogtiaao s,aluls aqi si rlQyU u jo uotldom uoissiuuuuoD •((0)9•o£t -dAD oV suoululn2aa luaapaj ut pagtluapt su `sivatuala uuld pasnooj Xlluagtoads aaotu `nlkau giyA palupdn XUunuiluoo su IW?)M aqZ •suxas inog2noagl sasn paluu2isap aaoisaa ao ululututu pup ,4!lunb aalum a2mutu of sVoja s,aluis aql sioaatp pup saluutpa000 dWOM s,a 'AD.L aul.L •dyVaM ,sexaZ of alupdn up jo luauuala ueld u si rlQyL qma `sivatuaamboa luaapaj gllm lualstsuoo •panatgou aq Iltne laodaa rlQyL si gl ut suoulpoollp puolalspm lugl aoupansse alquuosuaa saptnoad SH(I(U g2noatp srl(IyL gltm lualsisuoo sinuaad jo aouunssi aq 1, � OWZ) auinadeaE) pue 14ouea8 poonnuouoZ) ui eua10e9 aole3lpuj JOI speo-j Al!ea wnwixeW lejoi omi The TCEQ works with stakeholders and interested governmental agencies to develop and support I -Plans and track their progress. Work on the I -Plan begins during development of TMDLs, but the plan is not completed until sometime after the EPA approves the TMDLs. The cooperation required to develop an I -Plan for approval by the commission becomes a cornerstone for the shared responsibility necessary for carrying out the plan. Ultimately, the I -Plan will identify the commitments and requirements to be implemented through specific permit actions and other means. For these reasons, the I -Plan that is adopted may not approximate the predicted loadings identified category -by- category in the TMDL and its underlying assessment. However, with certain exceptions, the I -Plan must nonetheless meet the overall loading goal established by the EPA - approved TMDL. NCTCOG is working with the TCEQ to lead development of the I -Plan. Through the stakeholder group led by the NCI'COG, the resources and expertise of the local organizations and individuals will be brought together to set priorities, provide flexibility, and consider appropriate social and economic factors. References AVMA. 2009. U.S. Pet Ownership -2007. <www.avma.org/ reference /marketstats /ownership.asp >. Accessed 28 October 2009. Cleland, B. 2003. TMDL Development from the "Bottom Up" —Part III: Duration Curves and Wet - Weather Assessments. America's Clean Water Foundation, Washington, DC. EPA. 1991. Guidance for Water Quality -Based Decisions: The TMDL Process. <www.epa.gov /OWOW /tmdl /decisions / >. Accessed 28 October 2009. EPA. 2002. Memorandum: Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs. November 22, 2002 (Robert H. Wayland, III to Water Division Directors). EPA. 2oo6. Memorandum: Clarification Regarding "Phased" Total Maximum Daily Loads. August 2, 2oo6 (Benita Best -Wong to Water Division Directors). EPA 2009. (United States Environmental Protection Agency). 2009. <www.epa.gov /enviro /html /pcs /adhoc.html> Accessed December 8, 2009. Millican, J. and L. Hauck. 201o. Allocation Support Document For Two Total Maximum Daily Loads for Bacteria in Cottonwood Branch and Grapevine Creek. Prepared for: Texas Commission on Environmental Quality, Prepared by: Texas Institute for Applied Environmental Research, Tarleton State University, Stephenville, TX. Millican, J. and L. Hauck. 2010. Technical Support Document For Bacteria TMDLs Segments o822A Cottonwood Branch and o822B Grapevine Creek. Prepared for: Texas Commission on Environmental Quality, Prepared by: Texas Institute for Applied Environmental Research, Tarleton State University, Stephenville, TX. NDEP (Nevada Division of Environmental Protection). 2003. Load duration curve methodology for assessment and TMDL development. <ndep.nv.gov /bwqp/ loadcurv.pdf >. Accessed o8 December 2009. i exas Uommission on Environmental Quality 27 For Public Comment, May 2011 l 60Z AeW '}uawwoo oilgnd Jo=l gZ fq!lenC) Iqu9wua'nu3 uo uoissiwwOO sexal •oioz 19T kiurugaq passaoov <Jpd • p£ o£— oioz/ ibAgoi/ aalum/ sdouout/ aouutidutoo/ oggnd /slassu /sn•xi•alels•baol-AVA M> •(oioz `9,faenaga3) Isi l (p)£o£ suxaJ, oioz IJPJQ •otoz •baoJ. •600z iagoioO gz passaooV •< iutlg• gotbmi/ ibnqgo/ uiep/, fitjunb /.talum /2upoituout /aouutidutoo /sn•xi•aluis•baoi•nv m> (p)£o£ pup ftoluanul Xitiunb aaluM suxas ggooz b��i •600z .zagopo ga passaood • <sluautnoop #puliq- 2muVwbMs / ulup/, fltienb/ aaium/ 2upoiiuout/ aouutidutoo /sn•xi•aluis•baoi•mmm> (800z 16T tl3jLw) sexas ui fIttunb aapM aoujanS Vuypodag pup Vutssassd ioj aouupinO goon •egooz bHDi •600z .tagoloO gz passaoov •<iutiq•000z spaupuuls bM /spaupuuls /luauzssasse bm/ Xlt tunb—a alL, m/ Vutii tuuad /sn•xl•alt?ls•baol•mmm> •Lo£ Z)VZ o£ `aiupdn 000z `spat?puujS ,,litunb ialuM aouj tnS suxaZ •000z bRDJ. '(JW `fl?Z) llootgR `uotioalotd pagszaluM aoj ialuao -spa `pueitoH ?I•H pup aaiangoS g Z `uotloalotd pagsaalt?M Jo aotloutd ags uI •sXumglud pup `sooinoS `suoputivaouoD :spagsialuM uugan put' sagoaoilN `.tajangoS £ooz ftunuer iunuuW uopuutuzgg pup uo�ioalaQ aVaugosiQ IID!Uj •£ooz •(uotsstutuzoo toziuoD uotiniiod .1aluM alelsaalul pueiVuH maN) DDdMIHN •600z Xlnr 6z passaooV •< antlutat?up= uz /pyq /eoV-uLou•gts•m mm> •600z (aotntaS aatPPOM p?uopt'N) SMN •600z .taquzanoN gi passaoov •< /asnogVupuaio /uzoo•sduuim p-mmm> asnoq�uttuaj� uleQ SI`J 'g600z (sluauzuaanoO3o pounoZ) suxaZ Iuaivao glaoN) OODJDN 600z `9i iagopo passaoDV •< dse• ist?3ato3/ sotgdu jVoutap /sp /Vto•Vo3l3u•mmm> o£oz lsToaao3 otgduiVowa(I suxaZ iutluaD q:poN •e600z (sluauzu.tanof) jo iiounoo suxas ieiluaD q:poN) ` oDiaN Appendix A. Equations for Calculating TMDL Allocations for Changed Contact Recreation Standard VAa� l,V[IIfIII55IUn on tnwronmentai Uuality 29 For Public Comment, May 2011 i ro Aew ivawwo7 olgnd and 0£ Alpena lelu9wuatnu3 uo u0issiww03 sexal t%ajus jO U12JEW = soli piupuu }S uoileanag }aeIu03 pasina-d = PIS ((19W) 92auil3sip 3J.MM paIltumad ainin3 tutlualod = qlmOaD aanInA palum uLlols pa:giuuad -uou) uopmollu PuO7 = Yl uotleooliu pool a2.zugoslp 31.MM pa:atuuad admnl lupuaiod = A' AWIM palum uuo }s pagtumad) uoppollu pool alsuM = MsVqM :aaaqm ,iuv L.50'0 = sow o =V-1 aztz'o — PIS , z6Lz'0 = msV'IM zziz'o = (90'0 — z) * £g JOIDU3 uOISIanuOD , loaf) aanln3 = ADAM " IM PIS , 6£6z 'o = 'I(IVU SOIL + V-1 + MsvqM + Aj"vgM = ,I(Iv L :zo �zzgo nd sO� soot }uaollu pue ZQy�, mau 2ui }ulnalea joj suotlenba eua}�ao Al!lenb jaleM Io uoi;oun; a se z `dzz8o nv `uoUeJB Poomuo:400 col speo-i uoileoolly * � -y aanbi j OOZ' l MM /SHIM SOW- IOWl- epoluo 0 OFnL tft til (1W00NNdW) euejuo 009 004 0£9 0 04- 90Z 9Z6 0 04 COE 09 r 0 m a OZl 0 to 09l Z a ON ObZ O9Z OZ£ 1,81 1,61 1,4( 1,2( �a 1,0( z a. 8( 0 0 6( J 4( 2C 0 -200 0 400 800 1,200 Criteria (MPN /100n -L) A Criteria—TMDL— MOS— LA —WLAsw WLAwwtf Figure A -2. Allocation Loads for Grapevine Creek, AU 0822B_01, as a function of water quality criteria Equations for calculating new TMDL and allocations for AU o822B o1: TMDL = WLAwwrF + WLAsw + LA + MOS TMDL = 1.5573 * Std WLAwwrF = Future Growth * Conversion Factor * 63 = 0.4643 WLASW = 1.2540 * Std — 0.3935 LA = 0.2255 * Std — 0.07o8 MOS = 0.05 * TMDL Where: WLAwwn, = Potential future permitted WWTF discharge load allocation WI.AS,.,, = Waste load allocation (permitted storm water) LA = Load allocation (non - permitted storm water) Future Growth = Potential future permitted WWTF discharge (MGD) Std = Revised Contact Recreation Standard MOS = Margin of Safety i exas Commission on Environmental Quality 31 For Public Comment, May 2011