Reuse of Treated water for Aquifer Recharge in the East Snake River Plain

1
Reuse of Treated water for Aquifer
Recharge in theEast Snake River Plain
Waste
Eric Collins, R.G. GSI Water Solutions, Inc. May
1, 2008
2
Reuse and Aquifer Recharge

• News headlines and public awareness
• Nationally most reuse projects in four states
• Idaho Reuse Conferences and new DEQ guidance
  documents
• ESPA Comprehensive Aquifer Management Plan
  includes aquifer recharge alternatives

3
Presentation Topics

• Wendell, Idaho project
• Other related reuse and recharge projects in the
  region

Boise
?
?
Wendell
?
Twin Falls
4
Wendell Project Setting

• Groundwater is sole source water supply
• Regional water level declines in ESPA
• Potential curtailment of water rights for
  groundwater users - uncertain long-term water
  availability
• City WWTP planned upgrades

5
Wendell Project Objectives

• Mitigate potential reductions in the Citys water
  supply by reuse of treated wastewater for aquifer
  recharge
• GSI invited by J-U-B Engineering to help the City
  assess the feasibility of two aquifer recharge
  options
• 1) Injection Wells
• 2) Infiltration Basins

6
Wendell WWTP Overview

• Current facilities
• Wastewater Facilities Plan (2007)
• Target discharge rate 1.5 AF/day

Wendell
Lagoons
7
Wendell Conceptual Model

• Geology
• Thin soil mantle overlying Snake River Group
  Basalts

8
Wendell Conceptual Model

• Shallow Soil
• Soil generally consists of loam, clay, silt, and
  sand
• Caliche within soil profile and/or at soil basalt
  interface
• Permeability estimates moderately slow to rapid
• Infiltration Tests
• Infiltrometer test near lagoon 1.5
  inches/hr (JUB 2007)
• Small scale pilot tests 1 - 3 inches/day (JUB
  2008)
• State W-Canal Recharge Site 1 foot/day (Blew
  2007)
• State X1 Recharge Site 3.6 feet/day (DEQ 2006)

9
Wendell Conceptual Model
Wendell
Lagoons
10
Wendell Conceptual Model

• Snake River Basalt
• Series of basalt flows about 20-25 feet thick
• Interbeds with unconsolidated sediments
• Hosts the ESPA and is relatively transmissive
• Groundwater about 125 -150 feet deep discharging
  to the west and south as springs next to the
  Snake River
• Perched water possible from fined-grained
  sediments in the interbeds

11
Wendell Conceptual Model

• Particle Tracking
• Flow Model
• Snake River Basalts

12
W-Canal Recharge Project
Wendell
Lagoons
13
Wendell Hydrogeologic Considerations

• Injection Wells Option
• Specific capacity about 150 gpm/ft
• One potential injection well could easily
  accommodate the target recharge rate of 1.5
  AF/day
• Direct recharge to the aquifer timing control
• High density of wells and water rights in study
  area means a small buffer zone

14
Wendell Hydrogeologic Considerations

• Infiltration Basins
• Dependent on the vadose zone above aquifer
• Shallow soil has high percentage of fines and
  limited infiltration capacity
• Snake River basalts are highly transmissive in
  the lateral direction but water is expected to
  travel slower in the vertical direction

15
Wendell DEQ Considerations

• Injection Wells Option
• Injection wells not allowed under new reuse rules
  (RO treatment prior to injection was acceptable)
• Vadose zone injection wells also not allowed

16
Wendell DEQ Considerations

• Infiltration Basins
• Allowed if Rapid Infiltration Land Treatment (RI)
  is incorporated in treatment process
• (IDAPA 58.01.16 and 58.01.17)
• Groundwater Quality Rule (IDAPA 58.01.11)
• Buffer zone (Well Location Acceptability
  Analysis) - potential groundwater monitoring
• New DEQ guidance available
• (Guidance for Reclamation and Reuse of Municipal
  and Industrial Wastewater Rapid Infiltration Land
  Treatment, April 2008)

17
Wendell Water Rights Considerations

• Does DWR allow reuse aquifer recharge as
  mitigation for out-of-priority diversions from
  groundwater?

• There are no projects in Idaho where DWR has
  approved this concept. However, Idaho may follow
  the trend set by other states.

18
Wendell Project Summary

• No injection wells
• RI basins for aquifer recharge may be feasible
  but a few issues still need to be addressed
• Shallow soil infiltration capacity
• Understanding of flow path through basalts
• Securing mitigation credit from DWR
• The City is currently conducting small-scale
  pilot testing to further assess infiltration
  rates
• Also consulting with DWR regarding mitigation
  credit

19
Other Projects in the Region

• State W-Canal project
• Wendell area
• ASR projects
• Boise area
• Reuse projects
• Mountain Home AFB
• Reuse and aquifer recharge
• Boise area planned community developments

20
Closing Remarks

• With increasing stresses on the water supply in
  this region of Idaho, treated water reuse and
  managed aquifer recharge will likely develop as
  it has in other states.
• Legislative funding, regulatory attention, and
  community perceptions are positive indicators.