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Feb
19

ASTM Standard References Multiple Methods for Estimating LNAPL Transmissivity

written by Andrea

ASTM Tn Methoods Basic

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.

Feb
12

H2A’s Dr. Ranga Muthu to Provide Training on API’s LNAPL Transmissivity Spreadsheet

written by Andrea

Tn Spreadsheet PicH2A’s Dr. Rangaramanujam “Ranga” Muthu, co-author of the American Petroleum Institute’s (API’s) new Microsoft ExcelTM 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).

Apr
2

LNAPL Conceptual Site Model Three-Dimensional Visualizations

written by Andrea

LCSM 3D Visualization

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.

Mar
13

H2A Welcomes Dr. Rangaramanujam Muthu to Our Team

written by Andrea

Ranga MuthuH2A 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.

Aug
15

H2A is Using LNAPL Transmissivity to Make MDPE More Efficient and Cost Effective

written by Shannon

Tn DeclineH2A recently completed an evaluation of LNAPL transmissivity (Tn) 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.

Jul
8

ANSR Listed as Resource in USEPA’s TechDirect Newsletter

written by Shannon

EPA LogoThe 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.

Jun
16

H2A Performs 12-Day MDPE Event in Angleton, Texas

written by Shannon

Angleton MDPEH2A 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.

Jun
3

H2A Completes LNAPL Conceptual Site Model (LCSM) Updates for a Large-Scale Refinery

written by Shannon

Adv. HSGH2A’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.

May
25

LNAPL – It’s Not Just Unconfined

written by Andrea

LNAPL-Not Just UnconfinedAbstract of presentation to be given by Mike Hawthorne of H2A (coauthors Andrew Kirkman of AECOM and Mark Adamski of BP America) at the LNAPL Site Management Strategies Session of the 2011 Battelle Bioremediation and Sustainable Environmental Technologies Conference, Reno, Nevada, June 27-30, 2011.

Background. Existing LNAPL distribution literature is heavily biased towards ideal unconfined conditions representing static water-table elevations.  Mobile LNAPL has been documented at multiple sites to be submerged below the water-table as well as existing perched above the water-table.  Given the substantially exaggerated apparent NAPL thicknesses (ANT) that can occur in wells under these conditions, the identification of confined or perched LNAPL at a site is critical to correctly characterize the mobile LNAPL interval thickness and stratigraphic occurrence in the LNAPL Conceptual Site Model (LCSM).  A more accurate LCSM will lead to better metrics for both LNAPL characterization and remediation.  For example, ANT in wells is a poor metric for remediation because the ANT represents LNAPL confining pressure rather than recoverability or thickness of the mobile LNAPL interval.  The presence of confined or perched LNAPL may also have a profound effect on LNAPL remediation technology selection.

Approach. LNAPL flow vertically is inhibited due to non-wetting phase capillary pressure limitations rather than soil permeability limits.  However, LNAPL confining capillary pressures typically coincide with reduced grain size in unconsolidated sediments.  Therefore, an improved understanding of microstratigraphy results in more precise identification of potential confining or perching layers.  Improved characterization tools (e.g., laser induced fluorescence or LIF, baildown testing, soil core analyses) simplify identification of confined or perched mobile LNAPL intervals.  By combining microstratigraphic characterization tools (e.g., soil core analyses) with mobile LNAPL interval identification tools (e.g., baildown testing, diagnostic gauge plots), stratigraphic intervals containing mobile LNAPL may be identified even under confined, perched or interbedded conditions.

Results. This presentation will discuss methods to identify confined and perched LNAPL, and will include a review of site-specific examples of both simple and complex confined and perched LNAPL sites.  The tools discussed include hydrostratigraphs, diagnostic gauge plots, visual soil boring data, CPT and laser induced fluorescence borings, soil core photography and core analyses, and baildown test data.

May
6

LNAPL Remediation Drivers

written by Andrea

LNAPL DriversOne way to look at light non-aqueous phase liquid (LNAPL) drivers for remediation is to break them down into: (1) physical science issues and (2) human science issues.  Physical science drivers include saturation and composition risks.  Saturation risks are primarily related to migration of LNAPL, if the LNAPL mass present is great enough for migration to occur.  Composition risks are the classic human health and ecological risk-based evaluation pathways that typically address exposure to dissolved-phase or vapor-phase hydrocarbon chemicals of concern (COCs).  The primary drivers governing evaluation of remediation need and design of selected remedies should be the physical science drivers, which govern both risk and technical feasibility.

Human science drivers include regulatory requirements, legal issues, business issues, and perception concerns.  The primary regulatory requirement of concern is the requirement to “recover to the maximum extent practicable (MEP)”, which has historically resulted in LNAPL remediation goals ranging from no measurable LNAPL to some arbitrary thickness of LNAPL in wells.  These MEP requirements are not grounded in multi-phase fluid science and are often unattainable with current remediation technologies.  Similarly, the perception that the mere presence of LNAPL requires remediation does not recognize that the LNAPL may pose no risk (if saturations are too low for migration and compositionally the LNAPL contains COCs at concentrations below risk-based thresholds).

Frequently these human science drivers are important, but they may primarily serve as secondary drivers that modify or adjust the selected approach rather than controlling the technology selection or design.  For example, attempting to design to an arbitrary MEP (e.g., 1/8 inch measured LNAPL in wells) may result in endless operation of costly remediation systems that achieve little to no improvement in human health or environmental protection.  By focusing on the physical science drivers that govern risk and technical feasibility, LNAPL remedies can be designed to efficiently achieve meaningful and lasting protection of human health and the environment.

Some states have already begun to implement this approach (e.g., Texas, Minnesota).  For other agencies with arbitrary LNAPL thickness goals, reasonable remedy selection and endpoint metrics may be attainable by demonstrating the “Technical Impracticability” of the arbitrary thickness standard through pilot testing and modeling or analysis of operational remediation data for your site.

Remember – “Have a Plan, Don’t Pump Because You Can.”

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H2A Environmental, Ltd.
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Keller, TX 76248

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