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NOAA / USGS Cooperative Program
Simulation of Coastal Wastewater Injection in
Hawaii using SUTRA and the Value of Compelling
Visualizations in Conveying Results to the
Non-Specialist Public

• Chip Hunt
• U.S. Geological Survey, Honolulu, HI
• cdhunt_at_usgs.gov

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Maui Municipal Wastewater Injection Sites
Kahului
Lahaina
3000 m
1500 m
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Photo Jennifer Smith
Nuisance algal blooms are land-derived
nutrients a contributing factor ?
Funding by NOAA ECOHAB (Ecology and Oceanography
of Harmful Algae Blooms)
Hypnea musciformis
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Objectives

• Estimate ground-water nutrient loads
• Identify useful wastewater tracers
• Answer injection-plume questions
• Where does it go?
• We inject this stuff, and if it gets to the
  coast
• - Plume width at coast?

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Sugar cane (fertilizers)
Resort / urban coastal strip
Dryland forest, low-intensity ranching
Some small farms on upper road
3000 m
1500 m
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Sugar cane
Condominiums
Photo Univ. of Hawaii Coastal Geology Group
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Dryland scrub-forest in uplands
Suburban residential
Resorts / condos
Photo Univ. of Hawaii Coastal Geology Group
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Approximate plume extent ?
Kalama Park
Shallow fringing reef /-1m
Basalt promontory ?
Photo NOAA Coastal Habitat Atlas
No fringing reef ?
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Sand beach no fringing reef ?
Basalt promontory ?
Basalt promontory ?
Photo NOAA Coastal Habitat Atlas
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N7.3 mg/L 6x Background conc P1.7 mg/L 26x
Background conc
13 km coast
11,400 m3/d injected effluent
Ambient GW flow 6,600 m3/d per km coast
Plume 1.5 km wide
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3-D Ground-Water Model

• Code SUTRA (Voss Provost, 2002, USGS)
• Variable-density flow solute transport
• Solute Salt (freshwater-saltwater flow)
• DID NOT simulate nutrient transport
• Post-processing to visualize plume, GW age
• Kh 3000 m/d KhKv anisotropy2001
• aL 76 m aT .022 m

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Model Mesh
74,592 elements
? 63 ?
? 32 ?
x 37 vertical
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Freshwater Lens (Natural flow)
Recharge nodes v
Freshwater
Mixing zone
Saltwater
Brackish water
Saltwater circulation
lt Constant pressure nodes
Visualizations via Model Viewer (Hsieh and
Winston, 2002, USGS)
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Injection Plume is Buoyant
3 ledge
Salinity Visualization
(fluid fresher than 3 removed)
- looking northwest
Upstream shoulder
3 ledge
Percent seawater
? Shoreline
3
Effluent 1 salinity (buoyant)
20
40
60
80
Injection interval -14 to -58
m within mixing zone and saltwater)
100
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Velocity vectors show regional flow diverging
around plume
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Salinity Visualization
Salinity
100
Upstream shoulder
0
3 ledge
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Effluent-Tracer Visualization
Percent effluent
100
? fluid more than 90 effluent removed
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Plume internal structure, 20 shells
Percent effluent
100
80
60
40
20
0
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Plume width1.5 km at shore
Percent effluent
100
5
60 effluent at shore (yellow)
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Lipoa St
Lipoa St algae site
Superimpose over tax map and landmarks
Welekahao Rd
Halama St algae site
Kalama Park ?
Cove Park ?
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Ground-Water Ageat Water Table
Years
? fluid younger than 1 year removed
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Downgradient well in plume was anoxic, with
wastewater tracers, denitrification, and heavy
d15N
Percent effluent
100
0
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Algal tissue d15N highest near plume
C. Smith, J. Smith, Univ. of Hawaii
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Nutrient load per kilometer coast(kg / day km
coast)
Upland background N7.8P.44
13 km
1.5km
Injected N 55 ( 7xB)P 13 (30xB)
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Attenuated wastewater nutrient load(kg / day
km coast)
13 km
Attenuated N 273.5xB was 7x. P1.53.4xB
was 30x.
1.5km
very speculative, based on just 1
well in plume
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Urban Nutrient Load? Dont know.
Fertilizers
Background
Injection
Houses on cess- pools
?
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rough work but somebodys gotta do it
Enough modeling, lets go look Wading survey for
wastewater tracers
Water-quality meter and GPS
Funding Hawaii Dept. of Health, USEPA
Photo Joshua Marvit, Hawaii Dept. of Health
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Smaller platform coolers strapped together
GPS unit
Multiparameter water-quality meter
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Even better
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Wading Salinity (redfreshest)
Injection wells
Approximate plume extent
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Fabric-Brightener Fluorescence
(water-column samples)

• Also
• - Caffeine
• Carbamazepine
• NO3 2-4 mg/L
• Algal 15N 18
• ( Meghan Dailer)

Injection wells
Approximate plume extent
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Funding by NOAA ECOHAB (Ecology and Oceanography
of Harmful Algae Blooms)
Online report