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As estimated 35% of resident wastewater ends up in nearshore injection wells.
On average, about 35% of resident wastewater is discharged into nearshore injection wells at the Kihei Wastewater Reclamation Facility, while about 65% is used for irrigation reuse. Detailed UIC water quality and County of Maui plant flow reports here.
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Kihei WWRF injected Total Nitrogen & Total Phosphorus 1999 - 2021
Injected nutrient concentrations in Kihei from 1999-2021 showed a strong upward trend in Total Nitrogen, starting around 3 mg/L TN in 1999 and ending up more than 300% higher above 10 mg/L in 2021. Total Phosphorus trends are steady over the years around 2 mg/L. Detailed UIC water quality and County of Maui plant flow reports here.
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Kihei WWRF total Plant Flow, Injection Well Flow and Reuse Flow
Flow data in Kihei from 1999-2021 show a steady decline in total plant flow and injection flowrates, due presumably to successful conservation efforts, with a slow increase in reuse flowrates. Injection rates dipped very significantly below reuse rates due to decreases in system loading associated with COVID-19. Detailed UIC water quality and County of Maui plant flow reports here.
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Kihei WWRF Total Plant, Injected and Reuse Nutrient Total Nitrogen + Total Phosphorus mass loading (lbs/year)
During 1999-2021 dissolved nutrients discharged in Kihei is trending up, presently around 140,000 pounds or 70 tons per year in Kihei municipal wastewater. For the first time, in 2020 nutrient mass discharged to reuse was greater than mass injected, due to a decline in overall plant flow rates associated with COVID. Detailed UIC water quality and County of Maui plant flow reports here.
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Kihei WWRF injected coliform (MPN/100mL) 1999 - 2021
An analysis of fecal coliform cell counts from 1999-2021 shows that injected municipal wastewater has rarely been disinfected in Kihei, and fecal coliform counts have been steadily increasing over the decades, which recently have been measured as above the detection limit for the test of 2419.6 Most Probable Number of colony-forming (or infection forming) units of bacteria per 100mL of wastewater. Detailed UIC water quality and County of Maui plant flow reports here.
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Hawaii Department of Health measurements at Cove Park of indicator bacteria enterococcus (MPN/gallon) 2021 - 2023
An analysis of indicator bacteria enterococcus Most Probable Number of Colony Forming Units per gallon from sea water samples taken from nearshore recreation areas at Cove Park in Kihei shows 4 out of 72 samples or 5.6% of readings exceed the Beach Action Value with the highest of 13,779 colony forming units of indicator bacteria per gallon of seawater measured on 8/17/22 (this is off the charts as shown). That’s greater than 1 out of 20 chance that the water is deemed unsafe by the Clean Water Branch on any given day at Cove Park. Also, 22 out of 72 or 30.6% of measurements had greater than 700 Colony Forming Units of indicator bacteria per gallon sea water, almost one out of 3 days sampled.
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Kihei Wastewater Reclamation Facility By The Numbers
Kihei Wastewater Reclamation Facility Flow Summary
April 2020 total flow
Ave. 2020 reuse flow Est. April 2020 injection flow 2020 injected TN 2020 injected TP (MGD) (MGD) (MGD) (mg/L) (mg/L) 2.60 1.70 0.90 8.54 3.49 The average daily plant flow at the Kihei Wastewater Reclamation Facility in April 2020 was over 2.5 MGD, average reuse in 2020 was about 1.7 MGD, so estimated injection was about 0.9 MGD. Total Nitrogen in the same period was over 8.5 mg/L and Total Phosphorous was about 3.5 mg/L. Detailed UIC water quality and County of Maui plant flow reports here.
Injected Flow and Nutrients Per Census Resident
inj. nutrients / census resident / year inj. wastewater / census resident / year inj. wastewater / census resident / day (lbs/year) gallons/year (gallons/day) 1.0 9,818 27 The total estimated nutrient mass injected per census resident per year at the Kihei Wastewater Reclamation Facility is about 1 pound of dissolved nutrients per year. Each resident contributes about 10K gallons to injection per year in Kihei, averaging about 27 gallons per resident per day. 1
Injected Fecal Coliform Cell Counts Per Census Resident
injected coliform cell counts (MPN/100ML) total inj. coliform cell counts / resident (MPN/year) 248.9 92,506,220 Injected fecal coliform Most Probable Number of colony forming (infection forming) units injected at the Kihei WWRF was recently measured at 248.9 per 100 mL. Total injected fecal coliform colony forming units per census resident is over 92 million cells per year. Detailed UIC water quality and County of Maui plant flow reports here.
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Kihei Municipal Wastewater Reclamation Facility Water Quality History
Underground Injection Control compliance monitoring report summary
Date Total Flow (MGD) Reuse Flow (MGD) Injection Flow (MGD) Total Nitrogen (mg/L) Total Phosphorus (mg/L) Coliform (MPN/100mL) 8/17/99 4.265 1.678 2.587 4.9 2.3 < 2 1/31/00 4.806 1.191 3.615 1.7 2.2 < 2 7/17/00 4.654 1.859 2.795 1.201 1.63 < 2 1/17/01 4.953 1.329 3.624 4 0.85 2 7/25/01 4.843 1.935 2.908 5.486 0.993 < 2 2/14/02 4.797 1.379 3.418 3.11 1.32 < 2 7/19/02 4.751 1.807 2.944 4.35 1.78 130 2/4/03 4.711 1.319 3.392 6.11 2.31 < 2 7/21/03 4.768 1.842 2.926 7.18 1 1600 2/6/04 4.891 1.183 3.708 6.16 0.29 17 7/19/04 4.504 1.707 2.797 3.38 1.73 < 2 2/7/05 4.671 1.02 3.651 2.84 2.27 < 2 8/9/05 5.144 1.837 3.307 5.03 1 < 2 1/27/06 4.894 1.017 3.877 2.91 4.19 900 8/15/06 4.758 1.761 2.997 7.17 3.2 30 2/1/07 5.316 1.176 4.14 3.05 2.66 80 7/16/07 4.807 1.783 3.024 1.96 8.95 4 2/7/08 4.111 1.076 3.035 6.66 0.35 90 8/14/08 3.799 1.755 2.044 2.72 0.34 130 2/4/09 3.758 1.215 2.543 6.37 1.57 > 1600 7/10/09 3.487 1.588 1.899 7.33 1.64 > 1600 01/15/10 3.644 1.358 2.286 7.48 0.38 > 1600 07/19/10 3.306 1.691 1.615 10.27 2 > 1600 01/11/11 3.628 0.851 2.777 9.3 3.1 > 1600 07/25/11 3.306 1.771 1.535 5.74 0.7 > 1600 01/23/12 3.638 1.302 2.336 11.79 0.36 79 07/27/12 3.335 1.887 1.448 7.6 0.39 2 01/17/13 3.849 1.322 2.527 7.52 1.51 > 1600 04/17/13 3.581 1.588 1.993 9.6 1.7 > 1600 07/15/13 3.624 1.816 1.808 7.14 1.25 < 1.8 01/24/14 3.799 0.934 2.865 6.35 0.7 79 06/27/14 3.389 1.782 1.607 6.49 3.3 < 1.8 01/12/15 3.781 1.365 2.416 8.85 1.6 540 07/17/15 3.625 1.918 1.707 8.03 3.4 540 01/15/16 3.766 1.332 2.434 13.5 3.2 920 07/27/16 3.6 1.745 1.855 6.79 2.6 < 1 01/27/17 3.873 1.516 2.357 7.88 2 < 1 08/17/17 3.712 1.934 1.778 4.23 0.43 16 01/11/18 3.849 1.407 2.442 6.78 1.01 290.9 07/25/18 3.776 1.802 1.974 9 0.48 > 2419.6 01/19/19 3.823 1.589 2.234 8.84 2.4 133.4 07/24/19 3.821 2.025 1.796 7.58 0.306 > 2419.6 01/17/20 3.919 1.473 2.446 7.794 0.302 > 2419.6 07/28/20 2.678 1.929 0.749 9.288 6.68 > 2419.6 01/05/21 3.267 1.45 1.817 11.55 2.41 > 2419.6 07/14/21 3.968
2.186
1.782
11.35 0.864 248.9 01/19/22 3.721
1.579
2.142
10.01 1.50 > 2419.6 06/29/22 3.755
2.416
1.339
7.65 0.351 > 2419.6 12/06/22 - - - 4.437 1.05 1400 This data summary table shows nutrient concentration, fecal coliform cell counts, and flowrates for the total plant, reuse and injection for the Kihei Wastewater Reclamation Facility, during the biannual months when the Underground Injection Control Program with the Safe Drinking Water Branch requires testing. Detailed UIC water quality and County of Maui plant flow reports here.