Designing an ISCO Remedy for a Wood Treating Site Using Hydrogeologic Testing, High-Resolution Site Characterization, and 3D Modeling Joseph Ivanowski, P.G. Shanna Thompson, P.E.
Presentation Outline Site Background Treatability Testing High-Resolution Site Characterization Aquifer Testing 3-D Visualization Remedial Design (ISCO) Results and Path Forward 2
Site Background 3 Former creosote and PCP use for wood treating Primary COCs in groundwater are PCP and naphthalene Operations from 1947 1991 Creosote Pentachlorophenol (PCP) City drinking water supply well located 1,000 ft away Remedial Design Barrier wall installation was performed by others Geosyntec performed groundwater treatment outside barrier wall
Site Background: 1970s Operations Black & Veatch 2010 Basis of Design Report 4
Site Background: Geology Dissolution features Sinkholes 5
Treatability Testing ISCO and ISEB treatability testing completed in May 2012 ISCO evaluate permanganate and persulfate (matrix, alkaline, and iron activation) ISEB evaluate aerobic and anaerobic (nitrate and lactate amended) conditions Permanganate PCP Reduction = 96% Naphthalene = 85% Reduction Persulfate PCP Reduction = 99% Naphthalene = 97% Reduction 6
Treatability Testing: ISCO Oxidant demand for permanganate was ~ 2 g/kg Recommended potassium permanganate: Longer persistence in subsurface Easier to measure in the field (look for purple color) No activation chemistry required 7
8 Treatability Testing: ISEB
Treatability Testing ISEB PCP No degradation after 83 days ~65% reduction after bioaugmentation with KB-1 Plus Naphthalene Aerobic degradation was most rapid and greatest reduction (280 ug/l to < 12 ug/l) Nitrate-amended showed some degradation (285 ug/l to 57 ug/l) Lactate-amended showed limited degradation (355 ug/l to 330 ug/l) Conclusion: ISCO performed better than ISEB (particularly with PCP) 9
High-Resolution Site Characterization Iso-Flow drilling and sampling performed to collect depth discrete bedrock groundwater data On-site mobile lab for quick TAT and data evaluation Data used to generate cross-sections and 3D model
11 High-Resolution Site Characterization
Aquifer Testing: Objectives 1. Estimate the hydraulic conductivity (K), storage (S) of the bedrock aquifer and evaluate potential anisotropy; 2. Evaluate preferential groundwater flowpaths; 3. Evaluate ROI to support injection/extraction well spacing; 4. Aid in well design; and 5. Evaluate injectate travel time to support ISCO remedy. 12
Aquifer Testing: Approach Pneumatic slug testing Preliminary testing of extraction well and pumping system Step drawdown test Evaluate drawdown and yield Tested four discharge rates (10, 15, 20, 25 gpm) for selecting rate for long-term test Constant rate/dye tracer test Evaluate T, S, hydraulic ROI, tracer travel time, porosity Potentially gain insight on mass recovery 13
Aquifer Testing: Layout One extraction well (80-95 ft bgs) 13 observation wells Two injection wells 15 ft and 25 ft distance 80-95 ft bgs 14
Aquifer Testing: Layout Extraction and sampling system layout Sample Port Totalizer Carbon Filter Extraction Well Digital Flowmeter 15
Slug Test Results Bouwer-Rice Butler (1998) method for high k aquifers Well Screen Interval K (ft/day) (ft bgs) EW-01 80-95 71 EW MW-30D MW-35D MW-36D 01 MW-26A 64-69 40 MW-30D 127-137 5 MW-31I 87-97 40 MW-35D 80-95 95 MW-36D 80-95 350 Mean 100 Geometric Mean 52 16
Step Drawdown Results 0 Step 1 = 10 gpm 5 Step 2 = 15 gpm 10 Step 3 = 20 gpm Drawdown (ft) 15 20 Step 4 = 25 gpm 25 30 Step Drawdown Data Pump Intake 17 35 1 10 Elapsed Time (min) 100 1000 Pumping conducted in 90 minute steps Evidence for well inefficiency Selected 20 gpm for constant rate pumping for 72 hrs
Constant Rate Test Results Time Elapsed (min) 0.01 0.1 1 10 100 1000 10000 46.5 47 MW36D (80 95 ft bgs) MW30D (127 137 ft bgs) MW26A (64 69 ft bgs) MW35D (80 95 ft bgs) 47.5 CMW01I (110 120 ft bgs) Depth to Water (ft) 48 48.5 49 49.5 50 Well MW31I (87 97 ft bgs) Pump Off Distance to EW01 (ft) MW36D 25 MW30D 40 MW26A 45 MW35D 15 CMW01I 47 MW31I 43 18
Constant Rate Test: Analytical Methods Time-drawdown plots per MW (Leaky solution, Hantush-Jacob) Best curve matches among solutions evaluated Ks are higher to account for leakage from overlying residuum Drawdown (in) 19 0 1 2 3 4 5 6 7 8 9 10 r 0 = 595 ds = 9.00 1 10 100 Distance (in) 1000 10000 Distance drawdown (Jacob) Match drawdown with straight line at selected elapsed time Meets steady-state time requirements Areal averages K, S
Aquifer Testing: Results Hydraulic Conductivity (ft/d) by Well and Method Well Pumping Test Drawdown (ft) Slug Tests -- Confined Aquifer (Bouwer-Rice/Butler Methods) Constant Rate -- Leaky Confined Aquifer (Hantush-Jacob Method) EW01 26.48 71 37* MW35D 0.42 95 36* Constant Rate -- Confined Aquifer (Distance Drawdown Method All locations) A 23* MW36D 0.12 350 196* Average Hydraulic Conductivity Constant Rate Values* (ft/d) Geometric Mean 50 * Used to calculate geometric mean since slug test stress is limited to radius of well. A average of analyses using pumping data and recovery data 20
Dye Tracer Test Can we achieve a measurable ROI? What is the actual travel time of the tracer (oxidant)? Would the tracer be recoverable? Lost? Turner Designs AquaFluor field fluorometer
Dye Tracer Test Injected two dye tracers Fluorescein MW-35D Rhodamine MW-36D Rhodamine injection at MW-36D Fluorescein injection at MW-35D
Dye Tracer Test Results 1200 20 Fluorescein (ppb) 1000 800 600 400 200 15 10 5 Rhodamine (ppb) Fluorescein (ppb = ug/l) Rhodamine (ppb = ug/l) 0 0 0 1000 2000 3000 4000 Time (min) Dye Distance Time to Break Through Break Through Velocity Time to Peak Dye Peak Velocity Fluorescein 15 ft 10.58 hrs 34.02 ft/day 45.58 hrs 7.90 ft/day Rhodamine 25 ft 16.58 hrs 36.18 ft/day 42.58 hrs 14.10 ft/day 23
Aquifer Testing: Objectives Met 1. Aquifer Parameters a. Range of K = 32 to 350 ft/d b. Mean K = 117 ft/d; Geometric Mean K = 79 ft/d 2. Preferential Flow Paths Identified a. MW36D high K = 350 ft/d, and low concentration of Rhodamine dye 3. Travel Time a. Break Through Velocity of 34 to 36 ft/d b. Peak velocity of 8 to 14 ft/d 4. Radius of Influence (ROI) a. Maximum = 50 ft (20 gpm); <1 inch drawdown at distance b. Effectively 25 ft
ISCO Design: 3D Model Environmental Visualization System (EVS Pro) used to generate plume model and geometry PCP > 100 ug/l PCP > 500 ug/l PCP > 1,000 ug/l 25
ISCO Design: 3D Model Well depth targeted using 3D model to guide placement Min. inj. depth 65 bgs Max. inj. depth 110 bgs Max. treatment thickness 55 ft. Clustered Wells Maximum 15 ft screen interval Possible vertical separation of 5 to 10 feet 26
ISCO Design: Well Network Clustered wells on 17 nodes that fall on 40-foot grid spacing One 4 diameter well in the apparent source zone to use as extraction well Two additional 2 diameter injection wells along building edge Proposed Injection Well Cluster Proposed 4 Well, use TBD after initial 9-mths of operation Additional Injection Well for better distribution under building 27
ISCO Injection Initial injection completed in Fall 2014 8 week field event 188,363 gallons of 4% KMnO 4 solution mixed onsite and injected Geosyntec self-performed the entire injection event 28
ISCO Injection Injection pressures generally less than 10 psi Flow rates generally 6 to 8 gpm Target volumes were delivered successfully to each interval 29
ISCO Performance Plume footprint reduced Plume volume significantly reduced Pre-Injection Baseline Three Months After Injection Estimated Plume Reduction Volume 29,000 CY 17,000 CY 42 % plume volume reduction in three months Mass 28.1 lb PCP 11.8 lb PCP 58% PCP mass reduction in three months 30
ISCO Path Forward Path Forward Additional injection event planned for Fall 2015 Event 2 will include extraction and re-injection to enhance oxidant distribution (existing KMnO 4 in aquifer) Additional oxidant will be injected into target areas with persistent PCP concentrations 31
ISCO Path Forward Targeted injection where PCP exceeds 500 ug/l Use extraction from EWs and IWs and reinjection to enhance distribution 32
Lessons Learned Take home message? Large-scale remedies are expensive Better conceptual site model allows for more focused and targeted remediation with less uncertainty Spend a little more up front, save a lot of your client s money! 33
34 Questions?