H₂A’s Mike Hawthorne Coauthors NAPL Article in Ground Water Monitoring & Remediation on Identification of Confined and Perched NAPL

H₂A’s J. Michael (Mike) Hawthorne, PG, coauthored an article recently published in Ground Water Monitoring & Remediation titled “Identification and Assessment of Confined and Perched LNAPL Conditions.”  Coauthors include Andrew Kirkman and Mark Adamski of BP Americas.  The article presents powerful tools that use routinely collected data to identify confined or perched LNAPL.  Routinely collected data includes gauging data, boring logs, visual observations of soil cores, LNAPL baildown testing, and where available – laser induced fluorescence data.  Identification of the correct LNAPL hydrogeologic condition results in more accurate LNAPL conceptual site models, improved estimates of LNAPL recovery rates and volumes, more appropriate technology applications, and improved accuracy of LNAPL remediation metrics such as LNAPL transmissivity.  The article is available at the following link:  http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6592.2012.01412.x/abstract.

H₂A’s Dr. Rangaramanujam “Ranga” Muthu, co-author of the American Petroleum Institute’s (API’s) new Microsoft Excel^TM spreadsheet tool for estimating LNAPL transmissivity using baildown test data, will present the second part of a two-part training session on the spreadsheet on March 14, 2013, from 1:00 to 1:30 PM EST. This session is only available to National Ground Water Association members (free). Preregistration at the following link, http://www.ngwa.org/Events-Education/brownbag/Pages/bb031413.aspx, is required by 5:00 PM EST on February 25, 2013.

While the first training session provided a general overview of the spreadsheet tool and its use, this session will focus on specific examples showing how recharge data are used to estimate the transmissivity of LNAPL occurring in both confined and unconfined conditions. Assumptions and other considerations will also be discussed.

ASTM E-2856-11, Standard Guide for Estimation of LNAPL Transmissivity, identifies four primary methods to measure LNAPL transmissivity.  However, one of those four methods, recovery data analysis, has four sub-methods based upon the remediation technology used.  And one of those sub-methods, total fluids recovery data, can be further subdivided based on whether you plan to analyze long-term steady state data or instantaneous ratio test data.  The above chart graphically depicts the four primary methods and the associated sub-methods to create a clear visual picture of the multiple methods available under the ASTM standard.

H₂A’s Dr. Rangaramanujam “Ranga” Muthu, co-author of the American Petroleum Institute’s (API’s) new Microsoft Excel^TM spreadsheet tool for estimating LNAPL transmissivity using baildown test data, will present the first part of a two-part training session on the spreadsheet on February 27, 2013, from 1:00 to 1:30 PM EST.  This session is only available to National Ground Water Association members (free).  Preregistration at the following link, http://lnkd.in/Qz-nxr, is required by 5:00 PM EST on February 25, 2013.

The spreadsheet can be used to estimate LNAPL transmissivity in unconfined, confined, and perched conditions.  The tool does not automatically estimate transmissivity from recharge data, but requires varying degrees of user consideration with regard to the data and other input parameters.  The API spreadsheet tool and supporting documentation were developed to complement the new guide on LNAPL transmissivity published by ASTM (E2856-11).

Three-dimensional (3D) visualizations can provide powerful analytical capabilities in addition to “pretty pictures”.  3D visualization is particularly useful in conjunction with detailed microstratigraphic investigations (e.g., CPT), vertical Light Non-Aqueous Phase Liquid (LNAPL) impact profiles (e.g., laser induced fluorescence [LIF]), long-term equilibrium well gauging data, well construction data, and detailed topographic surveys.  While many factors control LNAPL distribution and migration potential, perhaps none is more important than microstratigraphy.

The capillary properties of thin stratigraphic horizons may be sufficient to either facilitate or inhibit LNAPL movement through the soil.  A microstratigraphic investigation (e.g., CPT) can identify such layers, and greatly facilitate understanding of the LNAPL conceptual site model (LCSM).  Macro-analysis of the microstratigraphic data can provide a broader understanding of critical stratigraphic geometries (e.g., LNAPL “traps” in high spots on the base of confining layers).  The addition of LNAPL impact profiles (e.g., LIF) can provide an understanding of the distribution and historical migration pathways of LNAPL through the soil profile within the microstratigraphic setting.  Long-term equilibrium gauging data provides a tool to evaluate the hydrogeologic conditions of the LNAPL (e.g., perched, confined, unconfined LNAPL), and data to identify critical surfaces (e.g., minimum historical NAPL/water interface elevation by well, which provides an estimated lower limit of the occurrence of mobile LNAPL).  Well construction and topographic data allow analysis of critical areas such as potential surface seeps.

All of this data can be combined into various types of 3D visualizations that can be rotated and sliced in any direction to better understand the 3D relationships of microstratigraphy, LNAPL distribution, and groundwater elevations.  Critical areas of the 3D blocks may be zoomed in to explore in detail the micro-scale stratigraphic variations critical to understanding LNAPL distribution and migration potential.  A stronger LCSM leads to better remediation design and optimization decisions.

H₂A Environmental, Ltd. is very pleased to welcome Dr. Rangaramanujam Muthu to our team of non-aqueous phase liquid (NAPL) experts.  Dr. Muthu is a co-author / co-developer of the forthcoming American Petroleum Institute software and guidance for the calculation of LNAPL transmissivity from LNAPL baildown tests for unconfined, confined, or perched LNAPL.  In addition, Dr. Muthu has assisted with the development of ASTM International guidance on estimation of LNAPL transmissivity and LNAPL conceptual site model development.  Among other project and technical tasks, he will be providing numerical analyses of NAPL nature, distribution, recoverability, and migration potential on various H₂A projects.

Dr. Muthu’s experience includes sites impacted with petroleum hydrocarbons and chlorinated solvents.  He has conducted NAPL nature and extent studies, NAPL mobility and recoverability field investigations and modeling, risk assessment and vapor intrusion analyses, statistical analysis and interpretation of a wide range of environmental data, guidance document development and training for software, and report preparation consistent with state and federal environmental regulations.

Dr. Muthu received his Bachelor of Science degree in Civil Engineering and his Doctorate in Environmental Engineering from the University of Houston.  His doctoral dissertation is entitled “Residual NAPL Saturations in Unsaturated Soils for Two- and Three-Fluid Phase Systems”, and dealt with analysis and evaluation of residual NAPL saturation in various media subject to various hydraulic head stress levels.  Dr. Muthu is an active member of ASTM International, the American Society of Civil Engineers, the Texas Association of Environmental Professionals, and the Society of Petroleum Engineers.

H₂A recently completed an evaluation of LNAPL transmissivity (T_n) at a major international airport in Texas.  The results are being used to further enhance the existing mobile dual-phase extraction (MDPE) remediation strategy for the site by focusing efforts on wells exhibiting the highest LNAPL transmissivity.  By doing so, H₂A has realized increases in product recovery of up to 20 percent over historic efforts of comparable duration.  H₂A also plans to utilize LNAPL transmissivity trends over time to gauge remediation efficacy and to establish active remediation endpoints.  It should be noted however, that although LNAPL transmissivities of between 0.1 to 0.8 square feet per day typically demonstrate the limit of practical LNAPL recovery, potential Texas Risk Reduction Program (TRRP)-32 (Risk-Based NAPL Management) triggers (as established by the Texas Commission on Environmental Quality) must also be considered.

The June 2011 issue of Applied NAPL Science Review (ANSR) was cited in the U.S. Environmental Protection Agency’s July 2011 issue of the TechDirect Newsletter, a publication that identifies new guidance resources related to the assessment and remediation of contaminated media.  ANSR was listed as a web resource that “provides technical insight into the science behind the characterization and remediation of light and dense NAPLs.”  You can sign up to receive the TechDirect newsletter at http://clu-in.org/techdirect, and current and historic issues of ANSR can be viewed/downloaded at http://www.h2altd.com/knowledge-center.

H₂A is currently performing a 12-day, mobile dual-phase extraction (MDPE) event at a former petroleum storage tank site located within TxDOT right-of-way in Angleton, Texas (the Site).  This is the latest of seven MDPE events performed by H₂A at the Site over the past several years.  During a 12-day event performed in March of this year, H₂A performed DPE on three wells located on the east side of the property (six days) and one well located on the west side of the property (six days).  Our system recovered 27.0 gallons of liquid-phase hydrocarbon and 73.9 gallons of vapor-phase hydrocarbon from the east side of the property, and 134.0 gallons of liquid-phase hydrocarbon and 388.1 gallons of vapor-phase hydrocarbon from the west side of the property, resulting in a total event recovery of over 600 gallons of hydrocarbon from the subsurface.

H₂A’s J. Michael Hawthorne, PG, Shannon Walker, PE, and Si Xu, EIT, recently completed an extensive redesign of the LNAPL Conceptual Site Model (LCSM) for a large-scale oil refinery located in southeast Texas. The analysis included a detailed review of all gauging and well construction data, fluid physical properties, aquifer properties, multiple LNAPL recovery and recoverability analyses, and detailed stratigraphic analyses (CPT/ROST and boring log data). The data were captured in LCSM update reports that included various Diagnostic Gauge Plots, Advanced (CPT) Hydrostratigraphs, and Production Hydrostratigraphs, as well as other analyses and cross-references. An initial goal of the LCSM updates was to identify areas of confined or perched LNAPL that result in exaggerated apparent NAPL thicknesses (ANTs) in gauged wells. Once wells exhibiting confined or perched conditions were identified, the mobile LNAPL interval in the formation was determined to remove the exaggeration. Subsequent tasks are to include analytical modeling to evaluate LNAPL specific and recoverable specific volumes, calculation of LNAPL transmissivity for multiple recovery wells based on LNAPL recovery and operational data, and capture analysis modeling of the active site remediation systems.