Wailuku Well Proposed in Anticipation of Shaft Closure

By Wendy Osher

Wailuku Exploratory Well Site. (Click image to enlarge) Map prepared for Maui DWS courtesy Munekiyo & Hiraga, Inc.

The Maui County Department of Water Supply plans to construct an exploratory well in Wailuku, in an effort to spread out pumping within the Iao Aquifer System. The well is being developed within the Kehalani Mauka subdivision on an undeveloped parcel that will be used as part of a future park.

The Wailuku Exploratory Well is being proposed as one of four replacement wells, in anticipation of the closure of Shaft 33, which is slated for retirement. Shaft 33 has been in operation since 1948, as an irrigation source for operations at Wailuku Sugar Company.

The four wells are designed to disperse pumping instead of concentrating pumping at one site, as is presently the case at Shaft 33. Today, the County DWS pumps an average of 5 MGD at Shaft 33 under an agreement with the landowner. The total anticipated capacity for the four planned wells is 5.2 MGD, slightly less than the 5.491 MGD allocated for the County at Shaft 33.

In addition to the Shaft 33, seven other wells pump from the Iao Aquifer where the estimated sustainable yield is 20 MGD, according to the State Commission on Water Resource Management. According to the Final Environmental Assessment for the new well site, current spacing of existing wells and their depths may be detrimental to the sustainability of the Iao Aquifer System.

A Final Environmental Assessment has been filed for the replacement well with a finding of No Significant Impact.