Environmental

Tricolored Bat: USFWS Announces 90-Day Finding to Determine if Listing is Warranted

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On December 20, 2017, the U.S. Fish and Wildlife Service (USFWS) announced its affirmative 90-Day Finding for the tricolored bat (Perimyotis subflavus), formerly known as the eastern pipistrelle. Upon publication in the Federal Register, the USFWS will begin evaluating whether to propose to list the species or not.

The Center for Biological Diversity (CBD) and Defenders of Wildlife submitted a petition on June 14, 2016, requesting that the tricolored bat be listed as endangered or threatened, and that critical habitat be designated for this species under the Endangered Species Act.

The 90-Day Finding means that USFWS has determined that the CBD and Defenders of Wildlife petition presented substantial information that warranted a review. It does not mean the USFWS will list the species, it means that USFWS will spend time officially evaluating the species for listing as threatened or endangered or not listing the species at all. After completing a 12-month status review, the USFWS will issue a finding on the petition, and, after that, there will be a public comment period.

The tricolored bat has a very broad range covering 38 states; from Alabama to Maine, North Carolina to New Mexico. It is the only member of the genus Perimyotis. White Nose Syndrome, a fungal disease that affects bats during hibernation, has been determined to be responsible for the significant decline of this species.

CEC will continue to track the progress of USFWS in relation to the tricolored bat and the potential listing under the Endangered Species Act. Should you have any questions, please contact Dan Maltese (412-249-3158; dmaltese@cecinc.com) or Ryan Slack (317-655-7777; rslack@cecinc.com). Additional information can be found at https://www.federalregister.gov/documents/2017/12/20/2017-27389/endangered-and-threatened-wildlife-and-plants-90-day-findings-for-five-species

A New Respirable Crystalline Silica Rule for the Construction, General Industry, and Maritime Sectors

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On March 25, 2016, OSHA issued a new Respirable Crystalline Silica Rule that will ultimately impact nearly one million workers in the construction, general industry, and maritime sectors. The Rule reduced the permissible exposure level (PEL) for respirable crystalline silica from 100 to 50 micrograms of silica per cubic meter of air (µg/m3) and established a new action level of 25 µg/m3. Other provisions were included to protect employees, such as requirements for exposure assessment, exposure control methods, respiratory protection, medical surveillance, hazard communication, and recordkeeping.

The Rule included two standards: one for construction (29 CFR 1926.1153) and one for general industry and maritime (29 CFR 1910.1053), both of which became effective on June 23, 2016. OSHA’s new Respirable Crystalline Silica Rule will be implemented over a period of five years (starting on the abovementioned effective date), with enforcement coming most quickly to the construction industry. OSHA has been enforcing the Respirable Crystalline Silica in Construction standard since September 23, 2017. However, for the first 30 days, OSHA offered compliance assistance in lieu of enforcement for those employers who were making good faith efforts to comply with the new construction standard. Effective October 23, 2017, OSHA commenced enforcement of all appropriate provisions of the Respirable Crystalline Silica in Construction standard, except for requirements for sample analysis,1 which will commence on June 23, 2018. OSHA will begin enforcing most provisions of the standard for general industry and maritime on June 23, 2018. This article provides an overview of OSHA’s Respirable Crystalline Silica Rule and its applicability to the construction, general industry, and maritime business sectors.

Introduction

Crystalline silica is a basic component of soil, sand, granite, and many minerals. Quartz is the most common form of crystalline silica. Respirable size2 particles can be created as a result of activities such as cutting, drilling, and grinding of materials that contain crystalline silica. Crystalline silica has been classified as a human carcinogen. Silica exposure is a concern for nearly two million U.S. workers, including more than 100,000 workers in higher-risk jobs for this matter, such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work, and tunneling. Exposure to respirable crystalline silica can cause silicosis, lung cancer, and other respiratory and kidney diseases. There is no cure for silicosis, which in severe cases can lead to death in a few months.

OSHA has a newly established PEL (50 µg/m3), which is the maximum amount of crystalline silica to which workers may be exposed during an eight-hour work shift. OSHA also requires hazard communication training for workers exposed to crystalline silica, and a respirator protection program until engineering controls are implemented. OSHA estimates that more than 840,000 workers are exposed to silica levels that exceed the new PEL.

General industry sectors that will be affected by the new Rule include asphalt roofing materials, concrete products, cut stone, foundries, railroads, ready-mix concrete, shipyards, structure clay products, support activities for oil & gas operations, dental laboratories, jewelry, porcelain enameling, and pottery.

For construction, the most severe exposures generally occur during abrasive blasting with sand to remove paint and rust from bridges, tanks, concrete structures, and other surfaces. Other construction activities that may result in severe exposure include: jack hammering, rock/well drilling, concrete mixing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing, tunneling, operating crushing machines, and milling.

Based on OSHA’s Respirable Crystalline Silica Rule, employers are required to:

  • Establish and implement a written exposure control plan that identifies tasks that involve exposure and methods used to protect workers, including procedures to restrict access to work areas where high exposures may occur.
  • Designate a competent person to implement the written exposure control plan.
  • Restrict housekeeping practices that expose workers to silica where feasible alternatives are available.
  • Offer medical exams including chest X-rays and lung function tests every three years for workers who are required by the standard to wear a respirator for 30 or more days per year.
  • Train workers on work operations that result in silica exposure and ways to limit exposure.
  • Keep records of workers’ silica exposure and medical exams.

OSHA provides a table that contains dust control methods for 18 common task groups for the construction industry. Employers can either use the control methods laid out by OSHA, or they can measure workers’ exposure to silica and independently decide which dust controls work best to limit exposures to the PEL in their workplaces. Employers who do not use OSHA’s recommended control methods must:

  • Measure the amount of silica that workers are exposed to if it may be at or above an action level of 25 μg/m3, averaged over an eight-hour day.
  • Protect workers from respirable crystalline silica exposures above the permissible exposure limit of 50 μg/m3, averaged over an eight-hour day.
  • Use dust controls to protect workers from silica exposures above the PEL.
  • Provide respirators to workers when dust controls cannot limit exposures to the PEL.

OSHA prepared the following flowcharts to provide assistance to employers that are working to comply with the new Respirable Crystalline Silica Rule. For more information regarding the enforcement guidance, please visit OSHA’s enforcement guidance for the Respirable Crystalline Silica standard for construction activities.

On December 19, 2017, OSHA released 18 fact sheets that provide guidance on the respirable crystalline silica standard for construction. These fact sheets provide employers with information on how to fully and properly implement controls, work practices, and, if needed, respiratory protection for each of the 18 task groups identified by OSHA.

The Mine Safety and Health Administration (MSHA) published its own proposed rule to address miners’ exposure to respirable crystalline silica. MSHA has mentioned that it had “looked at the OSHA Rule” to establish a new PEL for work activities subject to MSHA regulation. Please contact CEC’s Ali Lashgari (alashgari@cecinc.com; 412-249-1558) with any questions or comments. CEC will make updates on respirable silica-related rules via this blog.

Note 1: Compliance Safety and Health Officers (CSHOs) should repeat Flowchart A for each employee engaged in a Table 1 task.

Note 2: To determine whether the engineering controls, work practices, and respiratory protection specified in Table 1 are fully and properly implemented, CSHOs should consult 29 CFR 1926.1153(c)(2), which contains additional requirements for tasks performed indoors or in an enclosed area, and for control measures involving wet methods or an enclosed cab or booth.

Note 3: Table 1 at 29 CFR 1926.1153(c)(1): Specified Exposure Control Methods When Working With Materials Containing Crystalline Silica

Note 4: Please click here to find details on each compliance guidance paragraph.

 

1 29 CFR 1926.1153(d)(2)(v)
2 Particles with a diameter equal or less than 10 μm

BUSTR Rule Revisions Effective September 1, 2017

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This is an update to CEC’s blog posting of February 27, 2017, that described upcoming changes to Ohio’s Bureau of Underground Storage Tank Regulations’ (BUSTR’s) rules in the Ohio Administrative Code (OAC) 1301: 7-9-01 et. seq. (https://blog.cecinc.com/2017/02/27/bustr-proposes-rule-revisions-for-ohio-usts/). Since then, the draft rules underwent additional revision and have been through review and approval of the Joint Committee on Agency Rule Review (JCARR).

The new rules were issued final on July 31, 2017, and became effective September 1, 2017. Most of the changes described in our February blog were maintained; however, there were some changes to the proposed rules – some minor, some more significant – that were incorporated into the final rules. The more significant changes include:

  • Rule 02, Definitions: BUSTR did not include work on spill prevention equipment and cathodic protection in the definition of a “modification.” These activities are included under “routine maintenance or normal operational upkeep.” The definition of “free product” as used in prior rules was retained in the new 2017 rule.
  • Rule 04, System Registration: A 10% late fee was added to UST registrations that are filed after June 30 of each year.
  • Rule 06, Design, Construction, Installation and O&M: BUSTR retained requirements from previous rule sets pertaining to internal linings added in the field to USTs and containment systems for new dispensers. October 13, 2018, was established as the final compliance date for performing spill and overspill prevention equipment testing and walkthrough inspections. BUSTR removed the requirement to obtain a modification permit to perform a change of product, and clarified the acceptable “codes of practice” that apply to installation, modification, and repair of UST systems.
  • Rule 07, Release Detection: Rule language was modified to allow owners and operators of UST systems that store fuel for use by emergency power generators to request approval of an alternative method of release detection in lieu of installing automatic line leak detectors on pressure lines. BUSTR removed requirements for a “qualified person” to evaluate automatic tank gauging equipment. Language was added that pertains to manufacturers who are no longer in business. Record retention requirements were reduced from the proposed three years to one year for sampling, testing, or monitoring, and reduced from five years to three years for calibrations, maintenance, and repair of release detection equipment.
  • Rule 12, Closure Rule: The time period for actions required for UST systems that are out-of-service for more than twelve months was relaxed from 30 days to 90 days. Specifications were added for inert material used to fill a UST to have a density that is greater than the density of water. They also specified that the installation of monitoring wells was only required if groundwater is encountered around a UST system or portion of a UST system that was permanently removed, closed-in-place, or underwent a change-of-service on or after September 1, 1992, where a closure assessment was not conducted in accordance with the rules effective at that time.
  • Rule 13, Corrective Action Rule: The previous definition of “free product” was retained consistent with the Rule 2 definition.
  • Rule 15, Delegated Authority: A provision was added to allow a certified inspector to be employed by the owner or operator.

In our opinion, one of the more significant shifts from the 2012 rules to the 2017 rules occurred in the Corrective Action Rule (OAC 1301:7-9-13, or Rule 13) with the inclusion of additional chemicals of concern (COCs) for Analytical Group 1 – Light Distillates. Naphthalene and 1,2,4-Trimethylbenzene (1,2,4-TMB) were added to the list of aromatic hydrocarbon analyses for all release investigations. Two other chemicals, 1,2-Dibromoethane (ethylene dibromide, or EDB) and 1,2-Dichloroethane (ethylene dichloride, or EDC), were added to the list of additives. These constituents are to be analyzed only for release sites where the USTs were in service prior to January 1, 1996, and where the USTs contained aviation gasoline (“av-gas”), racing fuel, and used oil. This change in COCs will not only have implications for UST owners currently performing corrective actions, but also for former UST sites undergoing Phase II Environmental Site Assessments for property transfers.

If you would like to learn more about how the new BUSTR rules may impact your operations or if you would simply like further information, contact Brent Smith (brsmith@cecinc.com) or Andy McCorkle (amccorkle@cecinc.com) at (614) 540-6633.

Requirements for the Final TSCA Inventory Notification (Active/Inactive) Rule – (40 CFR Part 710), published August 11, 2017

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On June 22, 2016, the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amends the Toxic Substances Control Act (TSCA), was signed into law, making it the nation’s new primary chemicals management law.

According to the EPA, the new law, which received bipartisan support in both the U.S. House of Representatives and the U.S. Senate, includes much needed improvements such as:

  • Mandatory requirement for EPA to evaluate existing chemicals with clear and enforceable deadlines;
  • New risk-based safety standard;
  • Increased public transparency for chemical information; and
  • Consistent source of funding for EPA to carry out the responsibilities under the new law.

One year later, on June 22, 2017, EPA announced the required implementation activities. Those activities included finalization of a rule to require industry to report chemicals manufactured, imported, or processed in the U.S. over the past 10 years. This reporting will be used to identify which chemical substances on the TSCA Inventory are active in U.S. commerce and will help determine the chemicals EPA prioritizes for risk evaluation. Read more: https://www.epa.gov/tsca-inventory/tsca-inventory-notification-active-inactive-rule.

The Final Rule (TSCA Inventory Notification (Active/Inactive) Rule) was published on August 11, 2017. Supplier companies will have 180 days to report all chemicals manufactured or imported during the past 10-year period. (See further below for specifics applying to processing companies.) A number of chemical substances are excluded, such as naturally occurring substances, mixtures, exempt polymers, articles, R&D substances, etc.  There is a section of the standard 40 CFR 710.26 outlining Chemical substances for which information is not required: https://www.epa.gov/tsca-inventory/list-active-substances-exempt-tsca-inventory-notifications-active-inactive-rule#download.

EPA has published the interim Active TSCA Inventory using reporting from the 2012 and 2016 Chemical Data Reporting cycles: https://www.epa.gov/tsca-inventory/how-access-tsca-inventory.

The regulated community is required to add all other active Chemical Abstract Service (CAS) registration numbers that were manufactured or imported during the 10-year retrospective period to the active list. Companies are responsible for identifying all chemical substances that are known or reasonably ascertainable.

Companies that are only chemical processors have an additional 240 days to review the interim Active TSCA Inventory and report any additional chemicals that may have been overlooked by their suppliers. The Notice of Activity Form A will be used for retrospective reporting and the Notice of Activity Form B will be used for forward-looking reporting. Forms will need to be submitted via the EPA’s Central Data Exchange (CDX).

Companies that fail to report are in violation of TSCA Section 15 and may be subject to penalties (40 CFR 711.1(c)).

If you would benefit from having someone examine this new Rule and how it may affect your reporting requirements for the substances you manufacture, import, or process, please contact the author, Scott K. Wilson, MS, CIH, CSP, CHMM, at swilson@cecinc.com; 630-963-6026.

PADEP’s New (and Improved) Vapor Intrusion Guidance

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Are you buying a property in the city? Have you been informed that the property is being sold at a reduced rate, but were not given a reason why? Is it possible that there was a release from a facility near your property? Depending on the concentrations and site conditions, volatile substances in the subsurface could potentially result in vapor-phase intrusion of these substances into inhabited buildings at a level that poses a threat to human health.

PADEP’s updated Vapor Intrusion (VI) Guidance, entitled “Land Recycling Program Technical Guidance Manual (TGM) for Vapor Intrusion into Buildings from Groundwater and Soil under Act 2,” became effective January 18, 2017. The TGM provides guidance for implementing the Pennsylvania Code Chapter 250 regulations (Pennsylvania’s Voluntary Cleanup Program, commonly known as Act 2). As a property owner (referred to as “remediator” in the TGM), you will be expected to implement the new VI Guidance in order to satisfy the requirements of Act 2 for any Act 2 reports submitted after January 18,2017.

The VI Guidance outlines significant changes to the process for addressing VI that include new/clarified key terms and more options to comply with the Act 2 Statewide Health and Site-Specific Standards. Some benefits of the new VI Guidance include separate approaches for petroleum versus non-petroleum constituents, additional alternative assessment options (near-source and sub-slab soil gas screenings), and details regarding addressing VI under the Act 2 Site-Specific Standard.

In general, the VI assessment process under the new VI Guidance initially includes development of a Conceptual Site Model (CSM) and delineation of concentrations of soil and groundwater constituents, followed by screening of potential VI sources via identification of preferential pathways and application of proximity distances as described in the TGM.

Mitigation (elimination of the complete pathway between the contamination source and the receptor) may be used at any time during the process, and it can be used in lieu of a complete evaluation of the VI pathway.

The remediator chooses from the following options if potential VI sources are identified: (1) alternative VI assessment options (near-source soil gas screening, sub-slab soil gas screening, indoor air screening, or VI modeling); (2) mitigation with an Environmental Covenant; (3) remediation and re-evaluation of the VI pathway; or (4) selection of the Act 2 Site-Specific Standard.

Some of the new/clarified terminology in the VI Guidance that may be important to consider during your building design phase and/or when evaluating existing on-site buildings include Potential VI Source, Preferential Pathway, External Preferential Pathway, Significant Foundation Opening (SFO), Point of Application (POA), and Proximity Distance.

Preferential pathways considered in consort with POA and proximity distance as it relates to the horizontal and vertical location of the potential VI source could be utilized to address potential VI when siting and designing future buildings at the site. When identified, SFOs in existing buildings at the site could be sealed to inhibit vapor entry. Depending on your proposed plans, mitigation may be a more favorable option for your particular scenario with regards to schedule.

Summary

PADEP’s new VI Guidance provides a more-detailed process for satisfying Act 2 requirements and additional options for addressing VI to those who wish to obtain a release of environmental liability from the PADEP. Understanding how to apply the process and evaluate options could possibly save you time and/or money.

Please contact Jennifer A. Ewing, P.G., (jewing@cecinc.com) or Mary A. King, P.G., (mking@cecinc.com) at 800-365-2324 if you have any questions about the new VI Guidance and how it may influence an upcoming project, or about Act 2 in general.

Sixth-Generation Ohio Multi-Sector General Permit for Stormwater Issued Final

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Ohio EPA’s new Multi-Sector General Permit (MSGP) for Industrial Stormwater Discharges (Ohio EPA (OEPA) General Permit Number OHR000006) was issued final on May 8, 2017. The effective date of the permit is June 1, 2017. OEPA’s fifth-generation MSGP (OHR000005) expired on December 31, 2016, and its replacement has incorporated changes that clarify allowances and exceptions and ensure that Ohio’s MSGP is consistent with its U.S. EPA counterpart. This post describes some important dates for associated submittals and summarizes new provisions of the permit.

Companies with facilities currently covered by OHR000005 should expect to receive a letter from OEPA in the next few weeks. No action is required of current permit holders until this letter is received.

Important dates to keep in mind:

  • Effective permit date: June 1, 2017
  • Permit expiration date: May 31, 2022
  • Notice of Intent (NOI) submittal deadline date for existing permit holders: within 90 days of the OEPA’s written instructions (letter) to re-notify. Per Jason Fyffe, Supervisor, OEPA Central Office Stormwater Permitting, renewal letters will be mailed late the week of May 22, at the earliest.
  • Stormwater Pollution Prevention Plan (SWPPP) update timeframe for existing permit holders: within 180 days of the effective date of the permit (i.e., November 28, 2017)
  • Facilities not covered under a prior NPDES permit (new dischargers) must prepare a SWPPP prior to submitting an NOI. NOIs for new dischargers are to be submitted at least 180 days prior to discharge.

It is important to note that as of February 1, 2017, OEPA has instituted an all-electronic NOI filing policy, and facilities must use eBusiness to prepare and submit the form. If you prefer, the NPDES application utility (Surface Water Tracking, Reporting, and Electronic Application Management System or STREAMS) allows consultants to prepare the NOIs on behalf of their clients and delegate the forms to the appropriate individual for electronic signature and final submittal. CEC can assist you with this matter. Online payment is also available.

Notable changes to the current MSGP compared to OHR000005 include the following:

  • Clarifying language was added that defines conditions when pavement wash waters and routine external building washdown are an allowable non-stormwater discharge authorized by the permit. MSGP Part 1.1.3.
  • A list of the stormwater discharges subject to effluent limitation guidelines under 40 CFR, Subchapter N that are not eligible for coverage under the general permit and would require authorization to discharge under an individual NPDES permit is now included in MSGP Part 1.1.4.4.
  • A reduction in required frequency for routine facility inspections and quarterly visual assessments is now allowed for facilities recognized under the Gold and Platinum levels by OEPA’s Encouraging Environmental Excellence (E3) Program. MSGP Parts 4.1.3 and 4.2.3.
  • The requirement for a comprehensive annual site inspection has been eliminated in order to match the U.S. MSGP and to “eliminate redundancies and reduce burden” on facilities. The requirement for routine facility inspection remains, and required procedures are listed in MSGP Part 4.1.1 (no change from OHR000005).
  • Language has been added to clarify that documents incorporated into the SWPPP by reference may be maintained on site electronically (i.e., satisfies “available on site” requirement). MSGP Part 5.1.5.1.
  • Permittees are now required to make their SWPPP available to the public when requested, excluding any confidential or restricted business information. MSGP Part 5.3.
  • Language has been added to clarify that, for monitoring purposes, an outfall can include a discrete conveyance (i.e., pipe, ditch, channel, tunnel, or conduit) or a location where sheet flow leaves the facility property. MSGP Part 6.1.1.
  • Language has been added to clarify that permittees obtaining coverage in years 4 and 5 of the general permit must complete benchmark monitoring requirements to the extent of remaining monitoring periods available before the general permit expires. (Permittees obtaining coverage before this time are to complete the benchmark monitoring requirements within the first three years of permit coverage. This has not changed from OHR000005.) MSGP Part 6.2.1.2.
  • Provisions have been added for permittees who are exceeding a benchmark due to neighboring facility run-on to account for this situation. MSGP Part 6.2.1.2.
  • Provisions have been added for a facility to default to a different benchmark value if a parameter’s water quality standard is less restrictive than the permit benchmark value. MSGP Part 6.2.1.2.
  • Provisions have been added for permittees to consider pollutant concentrations (contributions) from the facility structures (roofs, walls, fencing, etc.) when determining whether it is available, practical, and achievable to implement additional control measures when a benchmark has been exceeded. MSGP Part 6.2.1.2.
  • The annual report requirements have been revised to be consistent with the federal MSGP. (The frequency and recordkeeping requirements have remained the same.) MSGP Part 7.2 and Appendix I.
  • Language has been added to clarify that the discharge of leachate (defined in OAC 3745-27-01(L)(1)) is not authorized under the MSGP. MSGP Part 8.C.2.1.
  • Composting fertilizer mixing facilities (SIC 2875) have been removed from Subsector C1 and located in a newly created Subsector C6, which provides more appropriate benchmark monitoring parameters for this industry. Table 8.C-1 and Appendix D to Sector C have been revised to specify that SIC 2875 (non-composting fertilizer mixing facilities) will be subject to Subsector C1 and SIC 2875 (composting fertilizer mixing facilities) will be subject to Subsector C6.
  • Language was added to Sector N (Scrap Recycling Facilities) to clarify that references to secondary containment under this part are referencing stationary outdoor equipment and not mobile equipment. MSGP Part 8.N.3.1.7.
  • Marinas have been added to Sector Q (Water Transportation) of the MSGP. The current OEPA Marina stormwater general permit (OHRM00002) expires on January 21, 2018, and will not be renewed. Marinas with coverage under OHRM00002 will remain covered under that general permit until it expires, and at that time, will be instructed to renew their coverage under OHR000006. NOTE: the current Marina Stormwater general permit authorizes the discharge of boat wash water if no detergents or other chemical cleaning agents are used. OHR000006 does not authorize boat wash water. Such discharges would require proper collection and disposal (i.e., sanitary sewer) or be permitted by a separate NPDES permit. MSGP Part 8, Subpart Q – Sector Q
  • Appendix B, “Standard Permit Conditions,” has been updated to reflect the “Standard Permit Conditions” language found within OEPA general permits.

For additional information regarding OHR000006, including fact sheets and a copy of the permit, visit OEPA’s Industrial Stormwater General Permit website.

If you have any questions on how the requirements of OHR000006 may affect your facility, or if you would like assistance with NOI submittal and/or updating the SWPPP for your facility, contact Amy Ritts (aritts@cecinc.com) or Andy McCorkle (amccorkle@cecinc.com).

MiProbe Environmental Sensing Technology for the Continuous Real-Time Management of Redox, Microbial Degradation Rates, and Metabolic Gases

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CEC has collaborated with Burge Environmental of Tempe, Arizona, in the development and deployment of a sensor system called MiProbe that was supported by a series of grants from the U.S. Department of Energy.

The sensor is part of a full package of environmental sensors and data management tools that incorporates telemetry, the Cloud, and computer-generated graphics to bring the dynamics of contaminated site management to life. The system is unique in many ways, but one feature that makes it truly special is its use of biofilm as the sensor itself. The sensor also has a metabolic gas capture capability that gives it a second level of application in line with the current interest in Natural Source Zone Depletion (NSZD). Taken separately, the system’s features include:

Microbial Sensing Capabilities

The microbes and the associated electrode-support structure comprise a revolutionary redox sensor that is both instantaneous in reporting to the Cloud and robust to the point where, for all practical purposes, it has an operational life of several years.

A brief explanation of how it works: a biofilm/electrode combination with associated circuitry generates a steady-state voltage that is held by the electrode, noting that every redox state has an associated voltage. For example, the voltage is highest in an anaerobic environment, but it drops upon the encroachment of aerobic conditions because electrons are drawn away; this change is then recorded and transmitted. The system can work in reverse with voltages rising as anaerobic conditions develop. The sensor data may allow for better management and cost control associated with use of reagent applications (e.g. for providing oxidizing or reducing conditions in the subsurface).

It is also possible to understand the metabolic turnover rate in the environment. Based on the voltage output for the sensor (turning it on and off via remote control and allowing the voltage to drain and recover), a rate of substrate consumption can be calculated. This then factors into natural attenuation petitions or the progress of remedial intervention with oxidative or reductive processes as noted.

Metabolic Gas Capture Capabilities

The application targets a growing interest in documenting NSZD as a means of more enlightened management of complex sites with non-aqueous phase liquids (NAPLs). At present, the focus is on Light NAPLs (LNAPLs) like petroleum hydrocarbons. Depending on the subsurface conditions, LNAPLs will naturally attenuate through aerobic and anaerobic pathways while generating carbon dioxide and methane as metabolic gas end products. Capturing representative samples of these metabolic gases can be useful in calculating the Time of Remediation (TOR) of palpable contaminant masses in the subsurface. Of course, overlaying intervention activities such as oxidants or temperature inputs on this process can accelerate the TOR, and this will be recorded.

Other Applications and Features

Because MiProbe is sensitive to microbial activity, it can detect an uptick in electron flow as a function of a change in substrate availability. This would manifest when, for example, a dissolved-phase hydrocarbon plume impacts the sensor, which has major applications in managing UST sites or accidental releases. Conversely, a lack of electron flow could indicate a lack of bioavailability of contaminants.

The bioavailability application is important in sediments work in support of Monitored Natural Recovery (MNR) strategies. In effect, if a contaminant is unavailable, a case can be made for limited environmental impacts. Additional sediment and landfill management applications include the use of the redox sensor components to allow for characterization and modeling of the water exchanges between capped sediments or landfills and surrounding sources of water. Applications for ecological monitoring are also of interest and are ripe for further exploration by interested parties.

All of these analytical results have been obtained with extremely high reproducibility. The MiProbe system can be deployed several ways, including direct insertion into the subsurface or into monitoring wells, or as part of a floating deployment configuration. Also, the system is solar powered with real-time data transmitted using either cellular or satellite communications. In locations where communications are difficult, a data logging option is available.

This information on the MiProbe System is also available as a downloadable brochure on the Environmental Site Investigation and Remediation page of CEC’s website: http://www.cecinc.com/enviro_site_redevelopment.html.

If you have questions related to MiProbe applications, please contact Chris Hortert at (800) 365-2324 or chortert@cecinc.com, or Steve Koenigsberg at (949) 262-3265 or skoenigsberg@cecinc.com.