2021-10-27 EMC Agenda item 5-b(i) Identifying wastewater management tradeoffs ... in Kona, Hawaii (RG)

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PLOS ONE Identifying wastewater management tradeoffs in Kona, Hawai'i takeaway from this analysis might be that concentrating exclusively on the cesspool conver- sions (per the language in Act 125) without concurrently improving the WWTP where all future permitted development will likely flow through may lead to suboptimal nutrient reduc- tions and marine habitat outcomes. Although the focus on the benefit side is largely on the environmental changes associated with each management action evaluated, additional co -benefits may be generated such as job creation and other economic impacts in the wastewater management industry. Providing an exhaustive list of co -benefits and quantitative estimates for each is beyond the scope of this study. However, impacts to Hawai`i's economy, defined as the direct, indirect, and induced economic activities generated by the local expenditures required to support each wastewater management action are likely to be in the millions of dollars and thousands of jobs. When type II multipliers generated from the State's input-output model [6 i ] for the waste management and remediation services industry are applied to the costs of each scenario, estimated eco- nomic impacts range from $206-919 million in business sales, $55-247 million in earnings, $11-51 million in state tax revenue, and 980-4,371 jobs, depending on the management action and the share of total cost that is counted as local expenditures. Including such co -benefits help to provide a more holistic picture of the wastewater management problem, but it should be noted that while costlier management options tend to generate higher economic impacts, more is not necessarily better; if such co -benefits are more rigorously estimated to inform the evaluation of the management actions under consideration, the opportunity cost or alternative use of funds for each action should also be evaluated. Not all possible combinations of wastewater treatment technologies are considered here, as current Hawaii OSDS procedures, design criteria, standards, and restrictions are limited to septic tanks, ATUs, and absorption trenches/beds. More cost-effective and efficient alterna- tives have been implemented in other areas of the country and beyond, but such systems must be approved on a case -by -case basis by the State Department of Health. For example, layered soil treatment systems are a low maintenance disposal option with expected nitrogen removal in the range of 50 to 90 percent [24] . If paired with a standard septic tank, nutrient removal efficiency could be on par with an ATU system at a fraction of the cost in certain areas. In some instances, decentralized cluster wastewater systems may also be a more cost-effective alternative than individual OSDS upgrades. However, there are several factors to consider: the number of (current) cesspool owners in the cluster that would connect to the decentralized wastewater system, terrain, land availability, and the funding mechanism [24]. Because the optimal solution would likely require a portfolio of treatment technologies, one might inter- pret the results of this analysis as a base case that can be expanded upon in the future to con- sider emerging technologies as knowledge of such systems improve and as the state's OSDS technology approval procedures continue to evolve. When a suboptimal choice is selected among the kinds of scenarios presented here, there can be tangible costs associated with reductions in coastal water and habitat quality, such as lower occupancy rates for areas like our study site in Hawaii that are highly dependent on tourism. Perhaps more significant for local residents are the intangible costs such as unpleas- ant odors, unappealing windrows of invasive species biomass that are costly nuisances and bio- logical threats to native marine biota. Such costs can be on the order of tens of millions of dollars or more. For example, results from a study of the Kihei coast on Maui (Hawai`i) suggest that a failure to undertake nutrient abatement measures at the study site will eventually reduce current annual benefits derived from coral reefs by nearly $15 million [62]. The study further suggests that reducing nutrient levels will not only avoid losses but will also eventually increase annual benefits above the current level to nearly $30 million more than what would be realized in the absence of nutrient management. However, because of the delay between the time of PLOSONE IIhu�tlps://doaa.oirg/n0.t:171/�OLuirirualll,lpoine,0257125 September8,2021 20/26