Using ASR as a Component of Managing Water

Using ASR as a Component of Managing Water Supply & Growth, City of Dallas, OR Presented By: Phil Brown, Golder Associates

Presentation Outline • • • What is ASR? Why Use ASR? Benefits to City of Dallas

What is ASR? Be Careful What You Ask For ü ü ü ü Alkali Silica Reaction (ASR) ("concrete cancer”) Asian Soybean Rust (ASR) Automotive Shredder Residue (ASR) (or "fluff“) Americans for Secure Retirement (ASR) Architects for Social Responsibility (ASR) Artificial Surf Reefs (ASR) Australian Seabird Rescue (ASR) Answer Seizure Ratio (ASR) (website operation) Annual Security Report (ASR) (SEC requirement) Articular Surface Replacement' (ASR) (new hip joint) Acceleration Slip Regulation (ASR) Answer Supervision Ratio (ASR) (telemarketing) American Systems Registrar (ASR) (ISO 9000) Artificial Silicon Retina (ASR) (microchip implants) Accredited Seller Representative (ASR®) (real estate)

Aquifer Storage and Recovery • • • Water is Treated to Applicable Standards Stored in the Subsurface Recovered for Later Use Water Typically Stored and Recovered from the Same Well

Why Use ASR? • New Supply Sources are Limited – Minimum instream flow – Over-allocation – Conjunctive use policies • Water can be available during winter months: high-flow/low-demand • Subsurface storage less expensive • WTP Efficiency

What Does ASR Do? • Re-distributes surface water supply profile • Expands capacity through increased storage • Provides emergency/second source • Makes existing infrastructure and new construction more efficient

Technical Issues • • • Source Water Availability Source Water Quality Aquifer Storage Capacity Geochemical Compatibility Recovery Efficiency – where native groundwater quality is poor

City of Dallas Water Supply Ø Mercer Reservoir Stores Water on Rickreall Creek (designed for 1550 AF) Ø 10 cfs summer releases from Mercer Reservoir Ø 5. 9 cfs Diverted to WTP During Summer Months Rickreall Creek Dallas

City of Dallas 2007 Water System • 842 MG Delivered • 5643 Connections • 81 new

City of Dallas Demand Profile 3 to 4 MGD Summer Average

Water Supply Situation: Decreasing Storage Capacity and Increasing Demand ØMercer Reservoir loses 10 AF/year due to sedimentation ~1% annually ØApprox. 500 AF lost since 1973 ØGrowth is increasing demand ØAdditional supply required by 2010

Storage Options: Ø Flashboards at Mercer Reservoir to Create an Additional 170 AF Ø ASR Ø Construct New Reservoir Ø Off-Stream Storage Ø Develop Regional Supply

Storage Plan: Ø Install Flashboards at Mercer Reservoir Ø Implement an ASR system designed to recover 1 MGD during peak demand periods Ø These actions will extend system capacity by 10 years

ASR Project Overview 2003: Completed ASR Feasibility Studies 2004: Drilled and tested the ASR test well (ASR No. 1) 2005: Design/Construction of ASR No. 1

Technical Challenges for Dallas • • • Low permeability fractured rock Aquifer (? ) not well defined Fresh water shallow - Saline water deep Need to develop fresh storage zone Advective dispersion, density driven mixing Recovery efficiency starts low, then improves RE% = (VR / VS) X 100

ASR Project Overview 2006: ü Received ASR testing permit ü Facility construction ü 1 st year of testing Ø 6 short cycles Winter 2006/2007: ü 2 nd year of pilot testing Ø 1 st operational-scale cycle

3 rd Year, Winter 2007/2008 • Well performance has improved, less buildup • Suggests higher density saline water is being displaced • 50 MG Target Storage Volume 2006/2007/2008

ASR Pilot Testing Results To-Date Ø Single-Well System: 0. 35 MGD and store 50+ MG/year, Ø 3 -well system: 1+ MGD and store 120 MG/year Ø Aquifer can support ASR, though at limited rates/volumes Ø Project Will Develop Fresh. Water Storage Zone: how much? 1 MGD = 25% summer demand 120 MG = 14% annual volume

Flow Benefit to Rickreall Creek Ø Excess capacity at WTP allows the City to manage flows in Rickreall Creek Ø Higher flows: Ø Increase velocity ØLimit warming ØIncrease DO

Other Benefits ØASR costs do not require rate increase ØIncreased supply supports growth Rickreall Creek WTP and ASR Site

The City of Dallas ASR Program Will Ø Benefit Rate Payers Ø Result in a Cost Effective Source Expansion Option Ø Provide Watershed-Scale Benefit Rickreall Creek, and Downstream Users

Questions? Thank you for your time!