Agenda 11-02-23; 4-a - Resolution Endorsing Consensus Principles II for Revised Falls Lake Rules

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=21 Quality Certification required for permitting of a "fill" under Section 404). Evaluations conducted as part of the reexamination process have demonstrated that the lake is meeting its designated uses. There have not been nutrient-related fish kills since the lake was filled. The City of Raleigh is able to use Falls Lake to provide drinking water to over 500,000 customers and was awarded 3rd place in the 2023 American Water Works Association's international ""Best of the Best" Water Taste Test." Dissolved oxygen levels are sufficient to provide aquatic habitat to many species, and the lake supports recreational activities throughout the year. Monitoring by DWR and other organizations show elevated chlorophyll-a levels at some locations and times of year in the lake. However, these levels are lower than predicted, and they have not resulted in any demonstrated water quality or use-related conditions that impair designated uses. For example, the earlier studies predicted summer average chlorophyll-a concentrations of 110 pg/L in the upper part of the lake while data collected from August 2014 to October 2018 show a summer average concentration of 41 pg/L.These data are summarized in the UNRBA 2019 Monitoring Report. The decade-long evaluation process by the UNRBA and the 4-year study period funded by the NC Collaboratory have provided exceptional scientific information and knowledge about conditions in the lake and its watershed. Falls Lake is at risk of increasing eutrophication, but data and analyses indicate a relatively stable trophic condition at this time. Falls Lake is eutrophic, but it is not increasing in the level of enrichment. The lake currently meets its intended uses. Nutrient reduction efforts in the watershed and changes in environmental conditions have resulted in significant reductions in nutrient loading to the lake since the designated "baseline" year of 2006. These conditions have not yet reflected significant and demonstrative reductions in chlorophyll-a in the lake. Due to the slow response of nutrient cycling processes in the lake and its sediments, the full implications of reduced loading over the last 17 years may not have fully manifested. However, lake water quality has stabilized since the Rules were enacted, and the lake is continuing to meet its designated uses. The revised strategy should include a long-term water quality review process to track water quality in Falls Lake and the other water supply impoundments in the basin. Other watersheds in the country face similar challenges. The Chesapeake Bay Program Scientific and Technical Advisory Committee (STAC) released a Comprehensive Evaluation of System Response in May 2023. Similar to the Falls Lake watershed,the report concludes that"current efforts to reduce nutrient loads will not meet the TMDL targets" and that "estuary water quality has been slow to respond to realized nutrient and sediment reductions in many regions of the Bay" This report focuses on an estuary that drains a much larger watershed with more opportunities for implementation given the relative amount of agricultural land and urban land in the watershed. Even with additional opportunities for implementation in the Chesapeake Bay watershed,the report concludes that "additional nutrient reductions will improve water quality, but water quality criteria may be unattainable in some regions of the Bay under existing technologies." Falls Lake was sited and constructed within a hydrologic, geologic, and nutrient balance environment that produced a unique morphological configuration and a reservoir environment that was destined to be eutrophic. All reservoirs in Piedmont NC strongly demonstrate a eutrophic nature, and this condition is unavoidable. Previous monitoring and evaluation as well as study, research, and assessment efforts over the last 11 years document this condition in Falls Lake. While all Piedmont reservoirs have different characteristics, site-specific water quality factors, and management challenges, the level of understanding of these factors and challenges are well understood for Falls Lake and its watershed. A revised Nutrient Management Strategy for Falls Lake needs to be based on the available science and sound management principles. While it is impossible to change the fundamental characteristics of this watershed and reservoir, a regulatory framework for nutrient 2