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

Browse Search

�n=10 Statement of Purpose: This document frames the concepts and principles that have been identified by the Upper Neuse River Basin Association (UNRBA) members and watershed stakeholders as important in developing a revised Falls Lake Nutrient Management Strategy. This document supports the Consensus Principles II that will be submitted as part of the UNRBA's recommendations for a revised nutrient management strategy. This document includes the core concepts and principles that need to be evaluated during the readoption of the rules and addressed in the final version of the rules. This document was not developed to provide specific regulatory language or regulatory requirements. Executive Summary Background and Supporting Information Falls Lake Reservoir was constructed and filled in the late 1970s/early 1980s. Several pre--impoundment evaluations of the reservoir predicted that it would be eutrophic (overly productive biologically) but still meet its designated uses (DNER 1973, NCDEM 1983, USACE 1974): drinking water supply, recreational use, aquatic life use, and flood control. Based on information provided in the US Army Corps of Engineers (USACE) 2013 Falls Lake Master Plan and the NC Division of Water Resources (DWR) 2021 Falls Lake Status Report,the designated uses of the reservoir are being met, and the reservoir provides: • Flood control for downstream communities preventing over$600 million in cumulative flood damages from construction through 2012 • Water supply for over a half-million customers treating 41 million gallons per day • A regional recreation resource including swimming,fishing, and boating • Habitat to aquatic and terrestrial wildlife (no nutrient-related fish kills have been reported since the 1980s) Falls Lake was listed on the 303(d) list of impaired waters for exceedances of the North Carolina (NC) chlorophyll-a criterion of 40 micrograms per liter(pg/Q. Chlorophyll-a measures the green pigment in a water sample and is used as an indicator for algal growth. Monitoring by the Division of Water Resources (DWR) and other organizations show elevated chlorophyll-a levels at some locations and times of year in the lake, especially in shallow areas. However,these levels are lower than predicted, and they have not resulted in any demonstrated water quality conditions that impair designated uses. In 2005, the NC General Assembly passed a bill requiring the NC Environmental Management Commission (EMC)to develop a Nutrient Management Strategy for Falls Lake. To support this effort, DWR used predictive modeling of the watershed and the reservoir to develop the Falls Lake Rules which set two stages of nutrient reduction requirements for the lake. The two stages of nutrient reductions are relative to a "baseline" year of 2006. Both the monitoring and modeling were developed on a compressed time schedule with limited data. As a result, there is significant uncertainty in the nutrient load reduction targets and the ability of the lake to meet the chlorophyll--a criterion regardless of the nutrient load reductions achieved. Based on DWR's 2010 Fiscal Analysis of the Falls Lake Rules, the nutrient load reductions prescribed by the Rules were estimated to cost$604 million for Stage I and $946 million for Stage 11. In addition, a review by Cardno ENTRIX(2013) concluded that the required load reductions were not technically,financially, or logistically feasible. For example, each square foot of existing development would have to be treated by at least two stormwater control measures (SCMs) to meet i