Leeward Parties Stress Recharge Value Of Ditch, Discount Reuse of Effluent

posted in: August 1996, Water | 0

“But the figures, you know — we get all confused with it; it doesn’t add up.”

-Buddy Nobriga, Water Commissioner

One of the arguments mounted by the leeward parties in the Waiahole ditch contested case concerns the ability of Waiahole water to recharge the Pearl Harbor aquifer, the great basal lens of fresh water that serves as the primary source of drinking water for O`ahu. All but ignored in their case, however, was the potential for effluent reuse and other conservation measures to more than offset the possible loss of Waiahole water.

Several hydrology experts testified in the hearing that the 28 million gallons a day of Waiahole water used to irrigate sugar fields in the central plain added anywhere from 7.5 million gallons a day to 12 mgd to the aquifer. In other words, just as rain recharges the aquifer, so, too, does water used in irrigating fields. Of the 28 mgd delivered by the ditch, part was absorbed by the cane plant, part was evaporated, part ran off as surface flow, and part soaked into the ground where it eventually found its way into the aquifer.

Leeward parties argued strenuously, therefore, that not only would the leeward side lose 28 million gallons a day in fine fresh water, suitable for irrigation, but it would also experience a loss of up to 12 mgd in the sustainable yield of the Pearl Harbor aquifer. (Sustainable yield is the best estimate by hydrologists of the average amount of water that can be taken from an aquifer each day without the aquifer becoming saltier or without damaging the aquifer’s ability to support such withdrawals over the long term.)

Offsetting the loss from Waiahole recharge, however, is the fact that O`ahu Sugar is no longer pumping up to 115 mgd of groundwater from that same aquifer. Additionally, virtually all experts agreed that recharge rates would probably be lower on irrigated fields planted in diversified crops. Small farmers would generally tend to be stingier in their application of water to fields, making the amount available for percolation to the aquifer far less than it was in sugar’s prime.

The situation is further complicated, though, by the fact that some of the water formerly pumped was used to irrigate fields over the caprock aquifer, so that there was no recharge benefit to the Pearl Harbor basal lens.

Discussions at the hearing quickly deteriorated into hopeless confusion — not only owing to the myriad factors that come into play when determining the overall effect of removing Waiahole water from the leeward side, but also as a result of the less-than-transparent testimony of some of the witnesses. At one point, following some especially obfuscatory testimony from Chester Lao, an expert witness for the city Board of Water Supply, Water Commissioner Buddy Nobriga summed up the situation:

“You know, OSCo used to pump 60 [mgd], and you said, well, only 12 of that is potable, so 48 million would be nonpotable. The nonpotable would not be suitable to put into the basin because you probably could get your potable basin salty by using that. So you have 12 [mgd] that you could really use as far as potable water. I assume that 12 [mgd] is going to go to the caprock area [for urban development], so that’s not going to help recharge at all, right?…

“But the figures, you know — we all get confused with it; it doesn’t add up.”

A Little Clarity

The clouds parted slightly in the testimony of John Mink, a hydrologist who has studied the Pearl Harbor aquifer extensively. Here is a portion of his testimony in the case, first under questioning by Water Commissioner Lawrence Miike, director of the Department of Health, and then under cross-examination by Paul Achitoff, attorney for the Waiahole-Waikane Community Association:

Miike: Just to simplify it for me, it seems that what you’re saying is that if we use the Waiahole water on the leeward side in the ways that would recharge the Pearl Harbor aquifer, that would increase the sustainable yield of the Pearl Harbor aquifer by the recharge. That’s one way, right?

Mink: Yes….

Miike: The other way to replace Waiahole water is that the Pearl Harbor aquifer’s sustainable yield can be increased, but it comes at a cost of resiting wells —

Mink: That’s right.

Miike: — and possibly cessation of the [Pearl Harbor] springs, et cetera. So that the issue here is that sustainable yield is not some fixed number, it’s a managerial number and it comes with costs?

Mink: Absolutely….

Achitoff: … I want to ask you whether another way to increase the sustainable yield of the aquifer would be to increase the pumpage from the OSCo wells and use that water for irrigation over that aquifer.

Mink: Yes…

Achitoff: And wouldn’t another way to increase the sustainable yield be to use another source of water for irrigation over the aquifer that is not — that comes from outside the aquifer, such as reclaimed water?

Mink: Yes, because you’re adding a new component…

* * *
Reuse

“Let me just emphasize one point, if I could, and that is that wastewater reuse in this area would be a concern primarily because it hasn’t been used before.”

-Bruce Anderson,

Deputy Health Director

Reuse of treated sewage effluent for irrigation and other non-potable uses is a tried-and-true technology elsewhere. Yet time and again, witness after witness for the leeward parties described in dire tones the potential harm to the Pearl Harbor aquifer that might result should disease-carrying effluent reach the basal lens.

Erwin Kawata of the city Board of Water Supply, testified, for example, that he was concerned “about whether or not there’s biological substances that may be present inside of this reclaimed water.”

Under cross-examination, Kawata conceded that he had cited favorably in his testimony a study that had, in fact, found that “well operated and maintained treatment plants … will produce a quality of reclaimed water which can be used for non-restricted irrigation.” However, he said, the study may not be appropriate for Hawai`i: “the appropriateness of that risk level that was established for that place where the study was performed may or may not be appropriate here in Hawai`i. I think that’s where the Department of Health and their expertise should come in and do the evaluation.”

And so it did — in the testimony of Bruce Anderson, the deputy director of the Department of Health who testified on behalf of the state Department of Land and Natural Resources and the state Department of Agriculture.

Viewing with Alarm

Anderson described three levels of treated effluent: R-1, the highest quality, and also the most expensive to produce; R-2, which is effluent from secondary treatment plants that has been further disinfected; and R-3, which is effluent from secondary treatment plants without disinfection.

The state Department of Health, Anderson said, had developed guidelines to “specify how treated wastewater can be used in Hawai`i.” He continued:

“When evaluating how wastewater can be used, the department had a number of concerns. We are concerned about health risks associated with potential disease-causing organisms in the sewage. Viruses, bacteria, helminth worms, and other pathogens can be serious problems associated with contact with sewage effluents….

“Generally, it was felt that people are not willing to assume any additional risk without clear benefits. The risk of possible exposure to disease-causing organisms will be unacceptable in situations where there is an ample supply of good quality natural ground or surface water…

“Data in the Department of Health indicates that the Pearl Harbor aquifer is vulnerable to contamination from constituents in sewage effluent… Thus, while the Department of Health has no objections to the use of reclaimed water for irrigation below the H-1 freeway over the `Ewa caprock aquifer, which is used only for irrigation, we would be very concerned that water quality would be compromised in other areas where the Pearl Harbor aquifer has been shown to be vulnerable to contamination.”

In addition to concerns over pathogens, Anderson mentioned nutrients and total dissolved solids as other effluent constituents that could possibly damage the quality of water in the Pearl Harbor aquifer.

Yet Anderson readily acknowledged that for years, R-3 effluent from Wahiawa and Schofield Barracks had been used for irrigation of Waialua Sugar fields above Haleiwa. “We’ve been monitoring drinking water wells in that area, at least since the 1960s, for contaminants that would be of concern in the aquifer and have yet to see any impact that we’ve been able to measure,” he told his boss, Miike.

Under cross-examination, Anderson’s concerns migrated from pathogenic contamination to contamination by nitrates, chlorides, and total dissolved solids. Pathogens, he agreed, were pretty well filtered out as effluent percolated through the soil to the basal aquifer.

As it turns out, though, the Pearl Harbor aquifer already shows high levels of nitrate contamination, which Anderson attributed to use of fertilizers. Still, he continued, “what I’ve been urging throughout my testimony is to take a very cautious approach when we’re looking at wastewater reuse in this area because it would be new, it would be something else over and above what has been used before. And it’s for that reason we want to be scrutinizing its use to the point of preferring that its use be pursued in other areas where it’s not a potential problem.”

By the end of his testimony, Anderson appeared to have overcome his earlier concerns. “We think [reclaimed water] can be used over potable aquifers … throughout the state without compromising water quality,” he said.

No Harm

Several of the witnesses for the leeward parties said they had no objection in principle to the use of reclaimed water, but wanted to wait until additional studies had been done. Yet Alexis Strauss, the chief witness on this topic for the windward parties, had no such hesitation. Strauss, who is director of the Water Division of Region IX of the Environmental Protection Agency, informed the commission that she “would have no technical basis for recommending additional study” on the matter. “In California, irrigation with reclaimed water over potable aquifers is very commonplace and has not been considered a hazard to groundwater quality,” she testified. “Most of the reclaimed water uses in the Los Angeles region are over potable aquifers.”

Strauss also tackled head-on the qualms of some leeward witnesses about using reclaimed water on such crops as fresh vegetables or other foods traditionally eaten without extensive processing. She cited a five-year-long study in the Monterey, California area that involved monitoring groundwater, plant tissues, and soil, and which included “an extensive viral seeding program to see what the impact of viruses’ fate and transport in the soil would be.”

That study, Strauss testified, “concluded that the irrigation of foods that we eat raw, of raw-eaten vegetables, with filtered secondary municipal wastewater, was as safe as irrigation with well water.”

Volume 7, Number 2 August 1996