by Jane Porter
On the feasibility of in lake (“in-situ”) technologies:Will the EMC's new Water Quality committee chair challenge the watered down report? We'll find out on Wednesday. Meanwhile, you can read both the original and revised report below.
Original report, (Executive Summary, p.3):
“After reviewing the available scientific evidence, no single in-situ technology or combination of technologies appears to be feasible for restoring North Carolina’s large waterbodies, including the piedmont reservoirs and estuaries subject to nutrient management strategies.”
Revised report, (Executive Summary, p. 3):
“In general, the potential utility of these measures to treat the types of large waterbodies that have been the subject of nutrient strategies to date in North Carolina appears either presently uncertain (including one under evaluation) or unlikely, depending on the measure.”
Recommendation to use nutrient management strategies
(such as the Jordan Lake Rules):
“A comprehensive, adaptive, and science-based approach to reducing nutrient inputs to the watershed remains the most viable option for recovering these waterbodies from impairment.” (Executive Summary, p. 3)
“Finally, efficacy of in-situ and lakeside technologies are generally predicated on first reducing upstream nutrient inputs to the maximum extent practicable. Nutrient management approaches that rely heavily on these technologies instead of reducing nutrient inputs to the watershed would appear to disregard the fundamental premise of the Clean Water Act, which seeks reduction of pollutants to waters of the United States. The US EPA notes in their guidance ‘… it is clear that nearly all (in-lake) restoration procedures will be quickly overwhelmed by continued high incomes of silt, organic matter and nutrients.’ ” (Executive Summary, p. 3)
“When considering in-lake measures for mitigation or control of nutrient related impairments, there are multiple factors that must be recognized before attempting to evaluate their potential efficacy. Initially, there is an assumption that control of watershed nutrient sources have been established. Guidance documents emphasize the importance of first addressing watershed nutrient sources to the greatest extent possible. This is especially true for reservoirs given their large drainage-to-lake area ratios. Guidance from US Environmental Protection Agency states“…it is clear that nearly all (in-lake) restoration procedures will be quickly overwhelmed by continued high incomes of silt, organic matter and nutrients. Protection and watershed management are therefore paramount to restoration.” (p.5)
The above language is not included in the revised report. Further, it does not reference keeping nutrients out of the water as a control technology.
Further, the two substantive references to the EPA and purpose of the Clean Water Act are stricken from the final report.
Cost of scaling up in-lake technologies, such as
SolarBees, for large water bodies:
Original report: (Executive Summary, p. 3):
“Many technologies were developed for and tested in small scale applications, including stormwater ponds, wastewater basins, and small natural lakes. Scaling these approaches to larger waterbodies will likely pose serious operational and financial challenges. Importantly, independent research regarding the efficacy of these technologies at larger scales remains to be done. Where independent evaluations have been conducted in larger systems, specifically for epilimnetic mixers in Jordan Lake, improvements are not evident.”
Another reference to nutrient management and another warning about the high cost of in-situ projects appears in the original report, (Conclusions, p. 16):
“Furthermore, nutrient sources from watersheds should continue to be addressed. All potential in-situ and lakeside approaches have only been proven feasible in relatively small natural lakes. In some cases, applying in-situ measures to reservoirs in North Carolina will only address symptoms created by watershed scale issues. The scale to which these options would need to be expanded to can lead to extremely expensive projects when applied to entire reservoirs. These options are all long term scenarios that require multiple treatments or continuous operation and provide unproven results in flowing systems.
The sections referenced above do not appear in the final report.
Water mixers’ aesthetics and potential to be boating
“These create aesthetic issues as they float on the surface of the water, and are continually visible. They have the potential to create other user conflicts such as hazards to boating due to the density and amount of machines required to circulate large open waterbodies.”
Does not include the above language. No references to aesthetic or safety issues appear in the revised report.
So when will we know if the SolarBees are working?
The original report appears to find the data collected as conclusive that SolarBees aren’t feasible.
The revised report suggests waiting until late 2018 to revisit the efficacy of SolarBees.
“In terms of scale evaluations, a proprietary epilimnetic mixing device, SolarBee®, is currently under evaluation in Jordan Lake. It is being monitored by both the Division and researchers at North Carolina State University, and results may be available in late 2018. Other practices reviewed would appear to face prohibitive challenges in this state’s reservoirs.” (Executive Summary, p. 3)