1 Session 3 LNAPL Assessment and LCSM Development

1 Session 3 – LNAPL Assessment and LCSM Development Part 4: LNAPL Transmissivity

2 LCSM: Key Components Of The ‘Source’ • Source Delineation: LCSM where and what • Residual Saturation and impacts • LNAPL migration potential/ stability • LNAPL transmissivity – to assess recoverability Source

3 Roadmap for LCSM Section (continued) LNAPL Transmissivity u LNAPL Migration Potential/Stability • Darcy’s Law • Pore Entry Pressure • Lines of Evidence for LNAPL Stability u Parameter to understand LNAPL conditions and assess LNAPL Recoverability • LNAPL Transmissivity • Tomorrow to discuss how LNAPL transmissivity can be applied

4 LNAPL Transmissivity Learning Objectives: LNAPL Transmissivity u Discuss LNAPL Transmissivity as a parameter, and how it is measured LNAPL Transmissivity ?

5 Discussion Points u LNAPL Transmissivity u u u Introduce the LNAPL transmissivity (Tn) parameter Demonstrate its analogy & relation to other flow parameters Demonstrate Tn as a function of soil properties, LNAPL properties, formation thickness and saturation Introduce Tn measurement methods Tn values for different soil and LNAPL types and in-well thicknesses Explain why Tn is important to LCSM

6 Definition and Context u LNAPL Transmissivity (Tn) • Definition: proportionality coefficient describing the LNAPL Transmissivity ability of a permeable medium to transmit LNAPL § Units: length 2/time • A coarse-textured aquifer (coarse sand) will deliver more LNAPL than a fine-textured aquifer (clay) for similar LNAPL well thickness/gradient u Assumptions inherent in Tn • Vertical (hydrostatic) equilibrium • Aquifer type (horizontal) flow

7 LNAPL Transmissivity u Discussed LNAPL conductivity (Kn) in Darcy’s Law for LNAPL flow • Kn is a point parameter; i. e. , varies in three dimensions • Has limited practical utility in site characterization and evaluating LNAPL recoverability u LNAPL Transmissivity (Tn): will be discussed for evaluating LNAPL flow and recovery potential • Tn is a vertically integrated parameter; i. e. , varies in the horizontal dimensions only • Much more practical in site characterization/LCSM development (need one Tn per monitoring well/time)

8 Relationship to LNAPL Conductivity (Kn) LNAPL Transmissivity u Tn is proportionality coefficient like LNAPL conductivity (Kn); i. e. , no gradient, no flow qn = K n i n qn b n = K n b n in Qn = T n in qn = LNAPL flow per unit area perpendicular to flow/gradient Qn = LNAPL discharge per unit width perpendicular to flow/gradient in = LNAPL gradient bn = LNAPL formation thickness Key Point: Higher Tn, higher Qn potential

9 LNAPL Transmissivity (Tn) Analogous to Hydraulic Transmissivity (Tw) u Tn analogous to Tw LNAPL Transmissivity • Tw hydraulic transmissivity • Tn LNAPL transmissivity u Correct terms: aquifer transmissivity to water/LNAPL • Aquifer that is transmissive; not the fluids LNAPL /Hydraulic Transmissivity or Aquifer Transmissivity?

10 Analogous to Water Transmissivity (Tw) LNAPL Transmissivity u Transmissivity - proportionality coefficient describing the ability of a permeable medium to Hydraulic Gradient = 1 ft/ft transmit water ce a rf u S c ri et m io nt te o P d e g. B in Tw =Kw∙b K = hydraulic conductivity b = aquifer thickness T K fin n Co 1 ft “b” 1 ft Modified from Driscoll (1989)

11 Water Transmissivity (Tw) LNAPL Transmissivity Tw integrates hydraulic conductivity (Kw) over entire water column (bw)

12 LNAPL Transmissivity (Tn) Tn integrates Kn over the formation LNAPL thickness (bn) Ta Conductivity i Comprehensive Summary Metric Ko value for specific stream line ρn = LNAPL density g = acceleration due to gravity k = soil permeability krn = LNAPL relative permeability µn = LNAPL viscosity Sn = LNAPL saturation 1 krn LNAPL Transmissivity rn ·g ·k ·krn Kn = mn 0 100% Sn 0

13 Relation to LNAPL Saturation LNAPL Transmissivity Significance u u Zone of highest LNAPL saturation has highest LNAPL conductivity Low LNAPL saturation results in low LNAPL conductivity VEQ conditions in a sand tank MW LNAPL Tn = ∑ Kn over bn u u Hydraulic recovery rate proportional to Tn for given technology Well thickness does not dictate relative recoverability Kn(Sn) varies over shark fin Residual LNAPL From Andrew Kirkman

14 Formation Thicknesses for Confined/Perched Conditions Confined LNAPL Perched LNAPL bn Clay LNAPL Water bn bn = lower elevation of confining layer – elevation of LNAPL water interface bn = elevation of LNAPL-air interface – upper elevation of low permeability layer

15 LNAPL Flow Through Contrasting Media LNAPL Transmissivity Significance LNAPL Δ Hn Two contrasting media (sand & clay), same LNAPL gradient, same time period Sand ΔL Clay LNAPL in = ΔHn/ΔL LNAPL Tnsand >> Tnclay Qnsand >> Qnclay Key Point: LNAPL Tn is much greater in sand, thus LNAPL discharge much greater through sand Tn – LNAPL transmissivity Qn – LNAPL discharge in – LNAPL gradient

16 The Name Game & Tn Measurement Tn Tn not measurable Tn measureable LNAPL present, but cannot flow into wells LNAPL can flow into wells Sr > Sr Csat LNAPL Terminology Changes Csat, Residual, Mobile, Migrating >Sr= Mobile

17 LNAPL Transmissivity Learning Objectives: LNAPL Transmissivity u Discuss LNAPL Transmissivity field measurement methods How do we measure Tn?

18 Tn Tests Methods LNAPL Transmissivity Estimation u Short-term Tn estimation methods • Instantaneous applied stress • LNAPL baildown, LNAPL slug and LNAPL manual skimmer tests u Long-term Tn estimation methods • Relatively long-term stress • LNAPL recovery data analysis, and LNAPL tracer test

19 Short-Term Tn Tests Methods LNAPL Transmissivity Estimation u LNAPL baildown test • Default method for determining Tn • Most common, relatively inexpensive, easy to conduct and analyze • Standard aquifer test software can analyze data • Yields Tn in the vicinity of test well u LNAPL slug test • Analogous to baildown test • Not widely used • Yields Tn in the vicinity of test well

20 Short-Term Tn Tests Methods (continued) LNAPL Transmissivity Estimation u LNAPL manual skimming test • Done where well thickness is too small for baildown test • Yields Tn in the vicinity of test well

21 Long-Term Tn Tests Methods LNAPL Transmissivity Estimation u LNAPL recovery data analysis • Gaining traction • Can be done by numerical model or by hand calculations/spreadsheet • Yields Tn over the capture zone of the system • Requires a recovery system u LNAPL tracer test • New, not widely used, relatively expensive to conduct • In-well LNAPL thickness > 0. 2 ft • Yield Tn over a large area compared to baildown test

22 Details of Tn Methods/Analyses Will Not Be Discussed LNAPL Transmissivity Estimation u References • Huntley 2000 • Lundy and Zimmerman, 1996 • ASTM, 2011 (updated as of April 2013); http: //www. astm. org/Standards/E 2856. htm • API 2012; www. api. org search for LNAPL Tn Tool

23 Baildown Testing u Qn Vn • >0. 5 feet Borehole volume – adjusted for filter pack volume and NAPL saturation Vadose LNAPL rw Filter Pack sn Baildown Test LNAPL Transmissivity Estimation u Groundwater LNAPL thickness bn u u LNAPL conditions: confined, unconfined, perched Developed monitoring well Test method: • Remove borehole LNAPL (i. e. well plus sand pack) • Monitor LNAPL layer recovery u Analytical options: • Huntley, 2000 • Lundy and Zimmerman, 1996 • ASTM, 2011 (updated 2013) • API spreadsheet; www. api. org search for LNAPL Tn Tool

24 Comparability of Short and Long Term Tn Tests u Estimated Tn values not comparable LNAPL Transmissivity Estimation • Different temporal and spatial scales § Short term: instantaneous stress, point Tn § Long term: prolonged stress, area Tn • Spatial and temporal trends are comparable

25 Tn Values for Gasoline/Diesel Medium Sand Fine Sandy Loam Silt Loam Saturated LNAPL Tn Hydraulic Thickness gasoline Conductivity (ft) (ft 2/day) (ft/day) 100 21 1. 25 0. 6 Tn diesel (ft 2/day) 1 8. 5 0. 2 2 58 2. 4 5* 335 38 1 1. 6 0. 03 2 11 0. 4 5* 67 7. 4 1 0. 3 0. 03 2 1. 0 0. 1 5 4. 4 0. 6 1 0. 006 0. 0 2 0. 05 0. 005 5 0. 05 Tech. Reg = 0. 1 - 0. 8 ft 2/day Tn modeled assuming homogenous soils 1 Relative Permeability USDA Soil Type 0 0 100% LNAPL Saturation *5 ft formation thickness unlikely at old sites

26 Importance of Tn to LCSM Take Aways u Tn measurement integral to LNAPL body assessment • Determines LNAPL mobility/recoverability across the LNAPL body • Can generate LNAPL Tn isopleths to show distribution • Determines how recoverability varies temporally with LNAPL thickness and potentiometric surface. • Identify areas for saturation reduction technologies (later) • Gives insight into how implemented technology can be managed (later)

27 What Did You Learn? u u Take Aways u u Defined LNAPL transmissivity (Tn) parameter Tn’s analogy/relation to other flow parameters (Kn and Tw ) That Tn is a function of soil properties, LNAPL properties, thickness and saturation That LNAPL Tn and flow rate higher under coarse textured material relative to fines About Tn measurement methods What Tn values may be expected for different soil types, LNAPL thickness and types

28 Knowledge Check In LNAPL containing wells, the Tn is greater in the well with the greater thickness (true/false/it depends). Why? Tn is greater for one foot of in-well LNAPL thickness for a sand than for a gravel aquifer (true/false). Why? Tn is greater for one ft. of in-well LNAPL thickness for fresh diesel oil than for fresh gasoline in similar materials (true/false)? Why?

29 Knowledge Check In LNAPL containing wells, the Tn is greater in the well with the greater thickness (true/false/it depends). Why? It depends. Tn is a function of the aquifer and fluid properties, and LNAPL thickness is not a reliable indicator of relative Tn. Tn is greater for one foot of in-well LNAPL thickness for a sand than for a gravel aquifer (true/false). Why? False. Gravel aquifer is coarser grained, easier for it to transmit LNAPL than for sand. Tn is greater for one ft. of in-well LNAPL thickness for fresh diesel oil than for fresh gasoline in similar materials (true/false)? Why? False, diesel is more viscous than gasoline and doesn’t flow as easily as gasoline.

30 Illinois Guest Speaker Hernando Albarracin Illinois EPA Springfield, IL 217 -524 -2448 Hernando. Albarracin@illinois. gov