Opinion ID: 2629221
Heading Depth: 4
Heading Rank: 2

Heading: DHHL's existing uses in the Kualapu'u aquifer

Text: Notwithstanding the Commission's conclusion that the proposed water use did not interfere with DHHL's reservation in the Kualapu'u aquifer system, the Commission addressed, in accordance with the mandate of HRS § 174C-49(a)(3), whether the proposed water use would interfere with DHHL's existing uses in Kualapu'u. In so doing, the Commission considered two case studies, the McNulty Model and the United States Geological Survey (USGS) Model, submitted by the parties to assist in evaluating the effect of the proposed well on DHHL's wells located in the Kualapu'u aquifer, as well as the impact of the proposed well on the nearshore environment. Both models predicted a small degree of water-level decline at the Kualapu'u well field and an insignificant reduction of groundwater discharge to the nearshore area.
The McNulty Model, proffered by MR, studied the effect of pumping 1.25 mgd from the Kamiloloa aquifer on the existing wells in Kualapu'u. The McNulty Model predicted that pumping 1.25 mgd from the proposed well in Kamiloloa would result in a water-level decline of 0.17 to 0.32 feet at the existing Kualapu'u well field and a decline of 0.09 to 0.11 feet at the nearshore well. The testimony adduced at the contested case hearing revealed that the foregoing water-level declines were conservative for Kualapu'u and Kawela, because the model did not include the effect of intrusive structures, which could limit water-level declines to the Kamiloloa aquifer system. The McNulty Model essentially predicted the worst case response incident to the proposed pumping and, in fact, predicted a more extreme effect on the existing Kualapu`u wells than the USGS Model. In sum, the McNulty Model concluded that the water-level declines at the predicted levels would have no measurable effect on the quality or quantity of water drawn from the existing wells. With respect to the nearshore environment, the McNulty Model predicted that, by pumping 1.25 mgd of groundwater from the proposed Kamiloloa well, the flux of groundwater at the Kamiloloa shoreline would be reduced by approximately fifteen percent.
The USGS Model, proffered by DHHL, analyzed the long-term effects of current and additional withdrawals on groundwater levels on the entirety of Moloka'i. The USGS Model predicted that pumping 1.326 mgd from the proposed well would cause a drawdown at the Kualapu'u wells of up to 0.5 foot and approximately 1.0 foot in the vicinity of the Kamiloloa well itself. In this connection, the study opined that the largest effects occur in areas nearest the well and effects diminish with distance from the well. The resulting water-level decline was likely to be less than normal seasonal fluctuations of the groundwater level and of the same order of magnitude of normal semi-diurnal water level fluctuations created by varying barometric pressure. In other words, the impact is relatively small. With respect to the nearshore environment, the USGS Model predicted that pumping 1.326 mgd from the proposed well would result in a reduction of coastal discharge by three percent over a thirteen-mile stretch of coastline. Based on the foregoing studies and the actual pumping levels permitted by the Commission ( i.e., 655,928 gpd), the Commission concluded that the proposed use would have a minimal impact, if any, upon DHHL's wells in Kualapu'u and, therefore, would not interfere with any existing legal uses in the Kualapu'u aquifer system.