Water Resources in The

AN EVALUATION OF

WATER RESOURCES IN THE

KOHALA RANCH AREA

By Kelly Pomeroy

October 2005

Acknowledgements

The information in this paper was drawn from many sources, but I owe a special debt of gratitude to the following four geologists, who gave freely of their professional time in responding to the many issues of this study:

· John Mink of Mink & Yuen, Inc., Honolulu

· Bill Meyer, Hawai'i District Chief (now retired), U.S. Geological Survey.

· Dr. Steven Spengler of Environet, Inc., Honolulu

· Glenn Bauer of the Hawai'i State Commission on Water Resource Management

Additional Water Commission staff members were very helpful in providing data useful for this paper.

Gordon Tribble, USGS District Chief and Director of the Pacific Islands Water Science Center, has been very accessible and helpful.

I am also grateful for information about TDEM technology from Scott Urquhart of Zonge Engineering in Tucson and Dave Hart of the Wisconsin Geological and Natural History Survey, University of Wisconsin Extension.

Very special thanks go to Chris Gabriele of Kohala Estates and to my husband, John Broussard, for their multiple readings of the manuscript and their many invaluable suggestions for improving it. Thanks also to several other homeowners in the area who read the paper and made useful comments.

If there are any errors or emissions in my compilation of the opinions of these experts, or if I have drawn any undue conclusions from them, I take full responsibility.

TABLE OF CONTENTS

Executive Summary ......

Introduction ......

The Study Area ......

Nance’s Recharge Calculations ......

Other Recharge Calculations ......

Sustainable Yield ......

Other Possible Sources of Water ......

System Capacity ......

Demand ......

Results of Shortages ......

Current Consumption ......

Taking Stock ......

Government’s Role ......

Summary ......

Appendix I: Summary of Existing Water Supply ......

Appendix II: Table of Consultants' Opinions ......

Appendix III: Kohala Ranch Water Demand Projection, in Gallons per Day. .

Appendix IV: Kohala Ranch Water Commitment of 5000 Gallons per Day . .

References ......

Figure 1. Map of the Kohala Ranch Study Area, from Nance 1994 . . . .

AN EVALUATION OF WATER RESOURCES IN THE KOHALA RANCH AREA

Executive Summary

Kohala Ranch covers some 4000 acres between the mountain and coast roads on the leeward side of the Big Island, just inside the North Kohala boundary. The middle third of the Ranch has urban classification, with approvals for 1490 lots and condos - beyond an earlier 478 lots - plus a golf course and substantial shopping center. The upper and lower two-thirds of the Ranch have agricultural zoning, as do most of the surrounding subdivisions. The Kohala Ranch Water Company, owned by the Kohala Ranch developer, supplies water to all these subdivisions.

The hydrology report done for the original developer after testing of Well 4 estimated the water supply under Kohala Ranch as "up to" 3.7 mgd (million gallons per day)*. Yet an application by the current developer in 2000 gave the projected water demand as 3.82 to 4.68 mgd.

This paper will show that the actual shortfall may be much greater than the above figures suggest, because it appears both that the groundwater estimate is inflated and that the projected demand is understated. More wells will be needed in order to maximize retrieval of the limited groundwater available, yet the developer is not being required to drill them or to find other sources.

There could be a shortfall without any further subdivision, yet the Project IV urban area will likely increase demand by another 1½ to 2½ mgd of fresh water, plus roughly one mgd of brackish water for irrigating the golf course. According to its PUC tariff, the water company may not provide service to new subdivisions unless it can do so without detriment to the subdivisions it already serves. It is incumbent upon the developer to pay for adequate system capacity, and those costs are to be reimbursed through land sales, not water sales.

But if the developer is not held accountable in a timely way, the burden is likely to fall upon the consumers, with possible price increases, fines, rationing, improvement district assessments...

conceivably even water cutoffs. All of these, in turn, could affect property values. Because of this, it is crucial that public agencies step in to ensure that subdivision not continue to take place within the water service area until these issues have been satisfactorily resolved.

Some of the evidence that will be presented includes the fact that the developer's water consultant assumed a large area of impounded water that probably does not exist as shown; that his cal-culations were based on yearly averages, which generally yield figures that overstate the resource; that he used a groundwater recharge rate that more recent studies suggest is too high; and that he assumed a greater percentage of the groundwater is retrievable than state standards support.

The developer has understated eventual demand by using average consumption (thus ignoring fluctuations in demand), by not allowing for system losses (which could be as high as 5-10%), and by making some estimates that seem unrealistically low. For example the demand estimate referred to in paragraph 2 above is based on single-family homes in Project IV averaging 750 gallons per day; yet the design guidelines for the first increment there budget 2000 gallons a day per home, a figure that is still only two-third of the historical average for other Kohala Ranch lots.

* It actually said 3.8 mgd, but this was due to a math or print error.

Figure 1. Map of the Kohala Ranch Study Area, from Nance 1994.

Introduction

In the absence of extensive exploratory drilling, an accurate groundwater modeling study and/or long-term production data, the developer's claim of water sufficiency is based upon a relatively crude water budget calculation presented by hydrologist Tom Nance in his Evaluation of Well No. 4 of the Kohala Ranch Water System, 1994. This water budget attempts to account for what happens to rainfall in the study area by allocating it to 1: runoff; 2: evaporation from ground, water and plant surfaces (evapotranspiration); and 3: replenishment of the aquifer (recharge). Sustain-able yield is the volume of groundwater that can be extracted on an ongoing basis without harming the resource. It is actually a range of values, but it's assumed that there is an optimal safe one.

The study area

Nance defines a 10.2 sq. mi. study area, as shown on the map on page 2. It's the wedge-shaped area that encompasses roughly the southeastern third of Kohala Ranch, and a much larger area above it, as well as a sliver to the south of it. The wells in this zone and below it are shown as small squares, and a description of them appears in Appendix I. This is a portion of the Mahukona Aquifer, which stretches approximately seventeen miles along the western flank of Kohala Mountain from the northern tip of the Big Island to the vicinity of the Waimea-Kawaihae Road in South Kohala.

The boundary of the 10.2 square miles is based upon a 1990 geophysical survey by Blackhawk Geosciences, Inc. of Golden, Colorado, using time domain electromagnetic (TDEM) technology. TDEM studies use magnetic pulses, and the ground currents they generate, to determine subsurface geology. The Blackhawk results defined the lower portion of what became Nance's study area.

Scott Urquhart of Zonge Engineering in Tucson, Arizona, which does TDEM surveys, says that the resolution obtained by each sounding is the same as the length of one side of the square of wire that is placed on the ground in order to make it. This is because each sounding sees only beneath the outline of the square, and an average value is then calculated and extrapolated to the entire area under the square. [9/9/05 phone conversation] Thus, the Kohala Ranch soundings, using squares of a thousand feet per side, would have obtained broad-brush readings that represented an assumed average for the million square feet involved in each layout. Individual structures within that area would not be discernable.

Bill Meyer, retired Hawai'i District Chief of the U.S. Geological Survey, and Glenn Bauer of the State Commission on Water Resource Management (CWRM) are not enthusiastic about the use of TDEM in this context. Apparently it has been used in Hawai'i only by Nance, and not since the early 1990's. [personal communications]

Hydrologist John Mink says "TDEM is an inferential, not direct, gatherer of information about the subsurface. It is subject to interpretation and thus the conclusions depend on the interpreter. It gives some data on which all interpreters can agree, but much data may prove controversial.

On page 25 of his 2001 South Kohala report, Nance himself points out several incorrect TDEM predictions. In his Kohala Ranch report, he includes a contour map from the Blackhawk report showing depth to the salt water body that infiltrates the island. Because this salt water is overlain by a floating lens of fresh and brackish water, called a basal lens, salt water is encountered at some distance below sea level, depending on which part of the lens one looks at. It shows the second Hawaiian Homes well next to the contour where salt water occurs at a depth of 700 ft. below sea level. Since this is in the area of basal water, the Ghyben-Herzberg principle should apply and, if the map is accurate, that well should have a water level on the order of 17-20 feet. In actuality, the level is only a little over six feet.

According to Blackhawk's Kohala Ranch study (p. 8), "[w]ithin the area interpreted to be controlled by geologic structures, the hydrologic parameters such as static head [natural water level] and volume of the ground water resource, cannot be inferred from the geophysical data. This is due to the fact that the presence or absence of fresh water has little effect upon the electrical resistivity measured by the TDEM method. In areas with comparable TDEM results . . . it can be assumed that similar hydrologic parameters may exist. For example, soundings 1, 8 and 13 near well #3 all display similar results, and therefore likely outline the extent of the structure which creates the anomalous head at well #3 . . . .Geologic structures are inferred between separate groups of soundings with similar results . . . "

The original developer, relying on what seemed like a sure bet, drilled Well 4 just 900 ft. from Well 3, at a 94-foot lower elevation, and with a lateral displacement that looks like about 600 feet. According to the Blackhawk report, this should put it in the same structure as Well 3; yet the much lower water level in Well 4 clearly indicates a barrier between it and Well 3 which Blackhawk didn't predict, or didn't locate exactly enough.

In a letter dated 11/5/01, Cary Kondo of Belt Collins & Associates told the County Dept. of Water Supply that Well 4 was backup to Well 3. If backup was the sole consideration, its placement may have made sense. But it could also have served the goal of obtaining better coverage of the aquifer if the developer had aimed for a location further to the side across the slope.

On page 5, the Blackhawk report says that resistivity characteristics of the rock below Wells 1 and 2 "did not detect salt water saturated volcanics below sea level." Yet those wells have water levels and chloride contents typical of basal wells. Nance is the only hydrologist cited in this paper who has indicated that these wells are anything other than basal.

Dave Hart, of the Wisconsin Geological and Natural History Survey, University of Wisconsin Extension, considers TDEM a useful technology, but cautions that it should be used in combination with other information or techniques. [personal communication dated 8-11-05] In this case, the other information points in a different direction, but Nance ignores it.

Dr. Steven Spengler of the hydrology consulting firm Environet, Inc. reviewed Nance's report, and it was his observation that the shape of the designated 10.2 square mile area "is not consistent with the orientation of the underlying rift zone - based on gravity measurements and the orientation of post-shield volcanism - and the spatial distribution of rainfall and, presumably, recharge in the area." Spengler's opinions should be given considerable weight because of his detailed study of Kohala Mountain, which was the topic of his master's thesis.

Certainly Nance's extrapolation of an ever-widening high-level groundwater area above the 2000-foot contour is unwarranted. At higher elevations there is a rift zone, but it tends to divert water parallel to the coastline. There could be areas of perched water, as Mink has suggested. But, so far, the boundaries of the high level water are speculative.

Meyer says "[t]he altitude that ground water is normally encountered at in the more permeable aquifers in Hawai'i is about 50 feet or less above sea level. If the water level in a well is above this, the aquifer that the well is located in is generally considered high level. Based on this definition, the only well that can be said to be located in a high level aquifer in your area is Kohala Ranch No. 3". Leakage from the nearby upgradient compartment could be contributing to the water level in Well 4, but Mink and Spengler doubt that it is basal, even though the chlorides are higher than in Well 3.

[There's some confusion as to what the chlorides actually are. Nance says in his report that they rose from 33 to 34 mg/L during the pump test, yet the field notes attached to the report show that they actually rose from 45 to 50. This compares to a reported 35 mg/L in Well 3. (The 1983 Belt Collins report on Well 1 gave a chloride count for the original wells of about 60 mg/L, but the water analysis attached to it says 51.8. Because of pumping, it now reaches into the 70's.)]

If the Blackhawk report does truly reflect subsurface structures, the most striking thing it shows is that the study area is segmented into at least six different groupings of similar characteristics in its lower tip - the portion below 2,000 feet. No soundings were made above that level. If these areas shown on the Blackhawk map represent confining structures, then a proliferation of wells will undoubtedly be required in order to maximize harvest of the groundwater under Kohala Ranch.