WRRCSR No.01:31:92 Wellhead Protection Methodology for Hawaii

Abstract

Development of a wellhead protection strategy for Hawaii is technically difficult due to the wide range of aquifer types and groundwater extraction units which exist in the state. Three approaches were identified to meet wellhead protection needs in Hawaii. The first approach involves the delineation of wellhead protection areas (WHPAs) around individual extraction units. This is the approach originally envisioned by the U. S. Environmental Protection Agency (EPA) in its guidelines for delineation of WHPAs. In most instances, lack of detailed hydrogeological information precludes the use of sophisticated delineation techniques. Thus, simple delineation methods have been identified for the principal extraction units in Hawaii. The second approach involves delineation of aquifer protection areas (APAs), which are based on aquifer boundaries. The APA approach is conceptually superior to the WHPA approach by virtue of its comprehensiveness since the entire aquifer is protected rather than just isolated areas surrounding the wellheads. The third is a phased approach which involves the initial delineation of WHPAs followed by delineation of an APA. That is, WHPAs can be delineated during the early stage of groundwater exploitation, and then an APA can be delineated at a later stage of exploitation near the sustainable yield of the aquifer. Selection of protection approach will be dependent on the importance of the aquifer and the degree of groundwater development.