Transcript Integrating Hydrology, Economics, and Policy

Is Deep Injection a Disposal
Option in Arizona?
GATEKEEPER REGULATORY ROUNDUP 2011
February 16, 2011
Michele Robertson, PG
Topics for Discussion
• Sources of TDS and concentrate
• Concentrate disposal options
• Cost comparison of concentrate disposal options
• Programs that regulate injection wells in Arizona
• Policy implications
• Conclusions
Sources of Salt (Total Dissolved Solids)
• Water sources – Colorado River, Salt
River, groundwater
• Expanded use of home water softeners
• Additional TDS increase during
wastewater treatment (100 – 150 mg/L)
• Brine from salt cavern development for
natural gas or compressed air storage
Concentrate Sources (Treatment Residuals)
• Advanced wastewater treatment options (RO, EDR, MF)
• RO reject waters discharged to sewers concentrated in
WWTP
• Water treatment for arsenic removal, etc.
• Desalination of brackish water
sources resulting from
development of poorer
quality water
Conventional Concentrate Disposal Options

Impoundments

Surface water discharges

Sewers

Land disposal (dust control)

Injection wells
Future Concentrate Disposal Options

Pipeline to Sea of Cortez

Remote location of
evaporation ponds

High recovery and Zero
Liquid Discharge

Alternative uses of
concentrate
Relative Cost of Concentrate Disposal Options
Evaporation
Pond
Brine
Concentrator
ZLD
Spray
Irrigation
Capital
Cost
Deep Well
Injection
Surface
Water
Sewer
Concentrate
Flow Rate
From Mickley, M., 2006
Regulatory Programs – Injection Wells
• Underground Injection Control Program –
implemented by EPA
• Aquifer Protection Permit Program – implemented
by ADEQ
Regulatory Programs
• Underground Injection Control Program (EPA)

6 classes of injection wells

Underground source of drinking water is ≤10,000 mg/l TDS

Numerous permits issued nationwide – 7 Class I permits
issued in CA for wastewater disposal
• Aquifer Protection Permit Program (ADEQ)

Injection wells are discharging facilities

All aquifers are protected for drinking water use

Permits for injection of reclaimed water, solution mining, LPG
storage, CO2 sequestration
Arizona Policy Issues
• Can disposal by injection be permitted in AZ?
• Does injection require reclassification of the receiving
aquifer?
• Assuming TDS is pollutant of concern, can narrative
standards policy be applied?
Reclassification of an Aquifer
• Reclassification of aquifer requires public process
• Consultation with local GUAC if in AMA
• Demonstration:

Hydrologic isolation

Water not being used as drinking water

Benefits of degradation outweigh costs to the public of
reclassification
Reclassification Process
• Reclassification petition to ADEQ must include:

Proposed use and pollutant for reclassification

Hydrogeologic report that demonstrates hydrologic isolation

Documentation that aquifer is not used for drinking water

Cost-benefit analysis

ADEQ review of complete petition within 120 days

ADEQ must initiate rulemaking to adopt new AWQS

Lengthy process

What standard for TDS?
The Use of Narrative AWQS to Develop Permit
Conditions for APPs (Policy 3010.000)
• Narrative AWQS rule states that pollutant:

Cannot endanger human health

Cause or contribute to violation of SWQS

Impair existing or foreseeable future uses of water
• Establish a UPL at nearest point of use downgradient
of discharge
• Set AL at point of compliance to protect UPL and
establish contingency plan
Technical Issues
• Finding right hydrogeologic setting:

Injection zone with sufficient porosity,
permeability and thickness to accept
volume and rate of injection

Lateral extent of geologic conditions

Upper confining layer of sufficient
thickness to ensure protection of
drinking water uses, lower confining
layer

No faulting, fractures or seismic activity

Location close to concentrate source
Concentrate Management Research:
• Reduce volume
• Improved recovery does not solve disposal problem
• Reduce energy and other costs

Conventional ZLD is very energy intensive
• Provide for beneficial reuse
• Find new uses for concentrate
• Overcome/address institutional barriers
Conclusions
• Regulatory framework exists to permit injection wells
for wastewater disposal:

Reclassification of aquifers process is likely to be difficult and
time intensive

Narrative standards policy provides a reasonable permitting
approach
• To date, no injection tests in AZ have demonstrated
the suitable geologic conditions needed for injection
Questions?