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Wastewater Injection Wells

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1. Why are wastewater injection wells used?

Every day, residents, businesses and visitors in our county send over 14.6 million gallons of
wastewater down drains that lead to our sewer systems. This is a substantial amount for our sewer infrastructure to manage.

An excess of approximately 11.4 million gallons per day of reclaimed water is produced at County of Maui
treatment facilities. Since the County of Maui does not have sufficient storage and distribution capability to utilize all of the reclaimed wastewater produced on our islands, the excess is sent to the injection wells.

The County of Maui wastewater treatment plants and injection wells reduce the impact of human waste on the environment.

2. What is an injection well?

An injection well is a deeper-than-wide pipe that is placed vertically into the ground. Injection wells are located downstream of any potable water sources. The County of Maui uses Class V injection wells as a means of disposing the treated domestic, commercial and industrial wastewater that has been processed at County of Maui sewage treatment plants. The EPA estimates that there are over 1.7 million injection wells throughout the United States.

3. What happens in an underground injection well?

Only highly-treated wastewater goes into all of the County of Maui’s underground injection wells. The County of Maui processes this water to remove solids and contaminates to dramatically improve the water quality so that it can be reintroduced into our environment with minimal effect.

Wastewater discharged into wells is absorbed by natural geologic formations, which complete the treatment by natural filtering through rock and sand layers. When properly sited, constructed and operated, injection wells are an economical, environmentally responsible and effective tool for safe wastewater management.

4. How many underground wastewater injection wells are owned and operated by the County of Maui?

The County of Maui owns and operates 18 wells: eight in Kahului, four in Lahaina, three in Kihei and three in Kaunakakai on Molokai. Seventeen of the injection wells in Maui County range in depth from 180 to 385 feet; Molokai has one that is 29 feet deep.

5. Where are the County of Maui’s injection wells located?

Except for one well on Molokai, which is located less than a mile from the Kaunakakai Wastewater Treatment Plant and monitored on a regular basis, County of Maui wells are located within our wastewater treatment plant sites to allow close monitoring of use and performance and avoid potential pumping costs that would otherwise be passed on to sewer users.

6. Are there privately-owned and operated wastewater injection wells in the county?

Yes. There are numerous privately-owned and operated injection wells in our county. Many
privately-owned condominiums and businesses in areas that were built outside of existing County of Maui sewer service have their own injection well(s). Single-family homes built outside sewer service areas use cesspools or septic systems discharging minimally treated waste directly into the ground.

7. Does the County of Maui own or operate any wastewater injection wells in Maalaea?

No. The injection wells adjacent to Maalaea are privately-owned and operated by the condominiums in the area. They are shallow compared to the County of Maui’s injection wells, and do not undergo the same level of treatment as is done in County of Maui treatment facilities.

8. How long has the County of Maui operated underground wastewater injection wells?

In the mid-1970s, the County of Maui began switching over to treatment plants and injection wells, replacing pipes that discharged sewage into the ocean, in order to comply with the Clean Water Act created by the federal government to protect near-shore ocean waters.

9. What happened prior to the mid-1970s before the County of Maui put in injection wells to comply with the federal Clean Water Act?

Raw, untreated sewage was discharged directly into near-shore ocean waters.

10. Are algae blooms and coral reef damage caused by the reclaimed water sent down the injection wells?

Studies do not prove that nutrients (including nitrogen) from these wells are the sole or most
significant source of blooms or reef damage. While independent studies detected injection well discharge in some areas of algae blooms, other sources from rainfall runoff, reef siltation, agricultural fertilizer, over-fishing and human interaction must also be analyzed as contributing causes. It is important to thoroughly consider and identify all sources so that efforts to eliminate damage are successful.

11. Who regulates (controls) wastewater injections wells?

The United States Environmental Protection Agency (EPA) and the state Department of Health (DOH) are the regulating agencies responsible for overseeing health and safety requirements. The EPA and DOH approve well construction and issue permits. Industry standards for type, volume and quality of discharge into the wells are set by the federal and state government agencies.

12. Do the underground injection wells operated by the County of Maui meet standard requirements?

Yes. All of the County of Maui’s 18 underground injection wells go through regular testing and reporting in order to verify proper well operations and maintenance. The County of Maui’s injection wells are approved by the EPA and the DOH as an environmentally sound, effective and safe disposal method.

13. What is the quality of the water discharged into the wells?

The water sent to the injection wells at the County of Maui treatment plants looks no different than your tap water at home. In producing this water, the County of Maui goes beyond the minimum requirements set by state and federal regulators.

Our permits require that the water consist of no more than 30 mg/l of Biochemical Oxygen Demand (BOD5), 30 mg/l Total Suspended Solids (TSS) and 10mg/l of Total Nitrogen. Nevertheless, our plants typically deliver water far cleaner than required. The County of Maui’s treatment plants normally produce effluent with less than 5mg/l BOD5 and TSS.

Our treatment plants use an aerobic biological process, nutrient removal and filtration. Because the water contains between 4 and 10 mg/l of Total Nitrogen (the regulatory limit is 10mg/l) - the effluent that our treatment facilities produce actually meets federal and state drinking water standards for Total Nitrogen.

14. How much of our wastewater is recycled?

Currently, 22% of our wastewater is recycled and reused for landscape, golf course and
agricultural irrigation, fire control and construction dust control. It is important to note that during rainy periods less recycled wastewater is needed and therefore less utilized – resulting in a larger percentage disposed of through injection wells.

By making use of recycled water that comes from treated wastewater, potable water can be
conserved.

15. Why can’t the County of Maui reuse all of the recycled water its treatment facilities produce instead of routing it through underground injection wells?

More wastewater could be reused if there were additional pipeline infrastructure available. Because distributing recycled water requires a separate and dedicated pipeline, additional pipeline systems will need to be built and put in throughout the county in order to increase the amount of wastewater that is recycled. Any costs to plan, build and install new systems would be shouldered by county taxpayers.

16. What are the alternatives to using injection wells?

Alternatives being considered around the world include expanding R-1-quality water recycling
systems for landscape irrigation, agriculture or recreational facilities; constructing deep ocean
outfalls; directly discharging to the ocean, waterways or streams; recycling to R-0 standards for reintroduction into drinking water; developing huge ponds for natural evaporation; applying to the ground; or a combination of several of these methods. Technology for these methods exists today; however, each alternative carries varying economic, social and environmental costs that need to be considered; in most cases, the alternatives incur significant costs that must be supported by taxpayers.

17. If the counties are required to improve existing standards and increase the use of recycled water, are federal funds available to fulfill such mandates?

Probably not. It is likely that any federal mandate will NOT be accompanied by federal funding support. Improvements and construction of additional pipelines can be expected to come from local County government through increased sewer and water usage fees.

18. Would my sewer rate be affected by any improvements or infrastructure needs?

Yes. Since the early 1990s, federal grant funding for wastewater treatment plants throughout the nation stopped, placing the burden on local governments to assess user fees to pay for operations, maintenance and replacement costs.

Wastewater facilities depend entirely on user fees and do not receive funding from the County of Maui’s general fund. Thus, any unfunded federal mandate would result in increased costs paid for by sewer system customers.