Agenda - 09-16-1986 - Laserfiche WebLink

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3 northern Orange County in terms of some of the stream losses below Lake Orange before it gets to Corporation Lake. During extreme drought periods a significant percent of the water is lost from evaporation and transpiration and other means from Lake Orange to Corporation Lake. He noted that the OWASA operating scheme is not set forth in detail in terms of how they operate their system when pumping is done from Cane Creek and the quarry. Based on the model done by the Division of Water Resources the yield from the OWASA system during the critical drought of records is 6.2mgd. It means that both north and south Orange County without system modifications or outside water import would have problems in a very severe drought. In terms of comparison, without modifications to the northern Orange or a drawdown system with the percentage of time above 30% storage, the Eno system would be about 93% in October and 82% in December. He further explained that 82% of the time it would be greater than 30% full and 18% of the time less than 30% full. This does not include the steam loss. The OWASA system would be 94% for October and 88% for December on a 30% basis. With the modifications in the Eno system the percentage would increase to 99% for October and 96% for December. Because OWASA can bring in 2mgd from Durham, the stress would be in the northern end of the County without any water supplement. He mentioned that all ordinances should be reviewed and modified with serious consideration given to the optimization of the OWASA system in terms of fine tuning their operation and determining how best yields could be operated from that system. To date, this has not been done but should be as soon as possible. There are some problems experienced on the Eno River downstream which need to be resolved. In summation Mr. Wray asked that consideration be given to balancing the increased growth with the increased yield so that the systems can be improved. There is the need for a consensus to resolve a number of things and in particular in the northern part of the County in terms of water resources. Commissioner Marshall asked about the stage one triggering level of 90% and John Wray indicated that this triggering point is addressed in the revised table that will be voted upon later in the meeting. He will continue to work with the County Administrators especially in terms of operating the system. Commissioner Lloyd asked Wray to explain his statement about problems in the northern end of the County. Wray explained the problem had to do with the stream gauge showing the water at a lower level than the Ordinance recommended. His office had received several letters of complaint about the situation. Based on past experience and studies, he would suspect some damage to aquatic life during this period. Commissioner Lloyd asked Wray to comment on the possibility of not using Lake Orange as the sole triggering point for enacting the various stages of the Water Ordinance. Wray indicated there had been times, particularly before Lake Ben Johnston and Corporation Lake were drawn down, where a spilling took place and where the rules could have been relaxed. However, as soon as the spilling stopped, the optimum water yield would be that it would have to go back to that specified in the Ordinance. Commissioner Lloyd explained the spillage that took place at both Lake Ben Johnston and Corporation Lake in August. John Wray noted that the average flow is 4mgd. In answer to a question from Chair Willhoit Wray explained that any system has downstream and upstream users. Some release would provide for some utilization for upstream and downstream users. G. WATER RELATED MATTERS 4 . WATER SUPPLY STATUS AND ORDINANCE REVISIONS Chair Willhoit explained that the proposed revisions to the Water