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CI & VA TMDLs 0258 . hup:/Iwww.kdhe.state.ks.usltmdlluastrearl. . Wasteload Allocation is improved over the quality of the underlying ground water and should mark a gradual improvement. Non-Point Sources: The primary cause of elevated sulfate throughout these strcam reaches is the natural contribution from the geology and soils of the drainage area in the valley aggravated by the historic pattern of irrigation retUl11 flow along the river, a non-point source. A majority of the retum flow emanates from thc watcr usc pattern in Colorado since little tailwatcr occurs within Kansas, The Load Allocation will be to reduce the average sulfate content of flows over 200 cfs over the next ten years, This allocation will be documented through the plotting of future sampled loads below thc TMDL curve, indicative of a 1875 mg/I average, Activities to reduce sulfate in this flow range would benefit from more direct delivery of some flow between John Martin and the stateline and a sequence of higher quality water at high flows over the long term to reduce sulfate loads entering the stream system, These practices must adhere to the protocols and procedures of the Arkansas Rivcr Compact between Kansas and Colorado and any subsequent rulings relative to litigation involving the Compact. Defined Margin of Safety: The margin of safety will be defined where direct allocations may influence watcr quality at flows below 10 cfs which is subject to the influencc of point sourcc discharges, The margin of safety for this TMDL and its Wasteload Allocation will be implicit based on the conservative assumptions used in detennining the wasteload allocation, These assumptions include the use of coincidental design nows. the dominance of Garden City wastewater which tends to have sulfate levels lower than the presumed 400 mg/llevel and the sevcre (70%) loss of water through evaporation for flow between Garden City and Pierceville, State Water Plan Implementation Priority: This TMDL will be a Medium Priority for implementation because of the need to establish background levels given high ambient concentrations. time is needed to establish any new operating procedures for the delivery of water under the Arkansas River Compact by Colorado to Kansas; review of alternative delivery operations will need to be explored between the two states duting Compact discussions; and the two states will need to collaborate on a comprehensive plan for reduction of irrigation return flow constituents. particularly sclenium, which is also e1cvatcd at thc stateline, Unified Watershed Assessment Priority Ranking: This watershed lies within the Middle Arkansas-Lake McKinney Subbasin (HUC 8: 11030001) with a priOlity ranking of 31 (Medium Plionty for restoration work), Priority HlIe lIs and Stream Segments: Because the sulfate impairment is confined to the mainstem of the Arkansas River, priority will be given to Segment 9 as the entry point of high sulfate within water coming from Colorado and Segment I where potcntial return flows and point source discharges influence water quality (Figure I). 5. IMPLEMENTATION Desired I mplementation Activities Short term I, Renew necessary state and federal permits and monitor pcrmitted facilities for permit compliance with approptiate eflluentlimits .111'"1101,.0'