Unveiling Aquifer Challenges: Dye Tracing Breakthroughs in Mining Impact Assessment

1. Understanding Our AquiferDye Tracing Challenges Conventional Wisdoms about Assessing Mining Impacts Todd R. Kincaid, Ph.D. H2H Associates, LLCwww.h2hmodeling.com Hydrogeology Consortiumwww.hydrogeologyconsortium.org

2. Mining Impacts: The Real Problem Topic Internet Hits • global water resources: 24,800,000 • aquifer protection: 1,350,000 • water shortage: 8,130,000 • water crisis: 27,900,000 • water pollution: 34,400,000 • bottled water: 10,100,000 • Florida springs: 40,900,000 • Quarry Impacts: 655,000 • Florida springs decline: 651,000 • Florida quarry impacts: 217,000 • Britney Spears: 49,800,000 • free porn: 188,000,000 • free sex: 366,000,000 Clean Water / Free Sex = < 10% Clean Water / Britney Spears = 68%

3. Purpose • Describe the basic hydrogeological principles on which mining impact assessments are based • Identify their assumptions and limitations • Describe why they often under-estimate impacts in karst aquifers • Provide examples of dye tracing in Florida • Show how tracer testing results are reshaping our understanding of the Floridan aquifer • Discuss the implications to mining impact assessments • Impacts can be classified broadly as water quality & water quantity

4. The Floridan Aquifer • 27 (>1/3) of the largest springs in North America discharge from the Floridan Aquifer • Average discharge from those springs > 6.5 billion gpd • All of those springs discharge from mapped underwater cave systems • >90% of inhabitants use groundwater from Floridan Aquifer • Conduit-dominated flow in unconfined sections • Less known under confining layer

5. Problem: More People – Less Water

6. Problem: More People – Less Water

7. Hydrologic Cycle How much groundwater do we have? • Water Budget • Sustainabletotal use = recharge • Surplus Storagetotal use < recharge • Declining Storagetotal use > recharge • Just like your check book • Water is in constant motion moving from rain to the sea. • Many different users (humans, plants, animals, rivers, streams, springs, estuaries, etc). • Groundwater withdrawals intercept part of that flow and return it along a different path (typically surface flow). • Quality & Quantity are impacted by how much we use, how we impact the quality of recharge, and how the water flows underground.

8. Aquifer make-up Most commonly assumed Most commonly true

9. Measuring Impacts - Quantity e.g. Mine Dewatering – most everywhere other than Florida Original Water Table Surface Cone of Depression Conditions that effect the shape of the COD Same for karst conduits Barrier Source

10. What is a karst aquifer? • A karst aquifer can be defined as any body of rock composed of soluble material through which groundwater flows and dissolves its own pathways. • Florida = karst • Rock is soluble • Lots of rain/recharge to dissolve rock • Springs • Sinkholes • Caves & conduits Indian Springs, Florida

11. Monitoring Impacts in Karst • Monitoring wells are most suited to porous media aquifers where flow is uniform through the rock. • Not as effective in karst aquifers where the bulk of the flow is carried by conduits because there is a low probability of intersecting them. • The data derived from monitoring wells is therefore not likely to reflect the “whole story.”

12. Well-Based Characterization Problems Wakulla Springs Basin – North Florida • Potentiometric surface map of the Woodville Karst Plain • Used to map groundwater flow directions and velocities • Produce very generalized estimations of groundwater flow directions • Under-estimate velocities • Misrepresent connections

13. What Gets Missed? • Swalletssinkholes that convey all or part of a streams flow into the aquifer • Springsthe largest concentration of the biggest springs in North America • Cavesthe longest underwater caves in North America • Connectionspredictions of slow velocities and broad diffusive flow patterns fail to map connections

14. Problem: Water Quality Declines Increasing nitrate & nutrient levels promote algae and bacterial growth Most probable source of nitrates: Septic systems & Tallahassee Spray Field

15. Dye Tracing – Mapping Connections • What is Dye Tracing?

16. Dye Tracing – Mapping Connections Emerald Sink - River Sink 1200 m – 5.74 hrs 5100 m/day River Sink – Turner Sink 2270 m – 33.7 hrs 1620 m/day

17. Dye Tracing – Mapping Connections • 2002: Fisher Creek • 1.2 miles / 56 hours • 0.51 miles/day • 2003: Black Creek • 1.6 miles / 76 hours • 0.50 miles/day • 2004: Leon Sinks • 10.6 miles / 7.1 days • 1.2 miles/day • 2004 & 2005: Ames Sink • Indian: 4.95 mi./16 days • Sally: 5.35 mi./17.5 days • Wakulla: 5.8 mi./22 days 2006: SESF – Wakulla B-Tunnel, Indian, Sally Ward & McBrides / about 1.5 months

18. Changing Perceptions – Gets Results $160,000,000.00 Breakthrough Curve Dye from Tallahassee Sprayfield reaches Wakulla Spring Tracer arrives at Wakulla: ~60 days City agrees to invest $160M in waste water treatment upgrades

19. Cooperation is the Key

20. Karst in my County? • No caves? • No big springs? • No sinking streams? • Can still have conduit flow! • Quarries located close to Northern Miami-Dade well field • Potential source of contamination to the wells • Conventional wisdoms “models” state that groundwater travel times are slow (many days) • Dye tracing – on the other hand – showed that travel times are hours: 1.5 orders of magnitude! • Problem was that the trace was designed assuming the slower rate and as a result the wells were flooded with red dyed water turning people’s underwear pink • Lesson: limestone + rain = karst • Adequate protection measures must be based on accurate conceptualizations “models”