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U.S. Department of the Navy-Site Characterization Analysis Penetrometer System with Laser-Induced Fluorometry (SCAPS-LIF)

Final Decision to Certify Hazardous Waste Environmental Technology

CALIFORNIA REGULATORY NOTICE REGISTER
Published Weekly by the Office of Administrative Law
Excerpted from: Register 96, No. 27-Z
July 5, 1996
pp 1282-1291

The California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) has made a final decision to certify the following company’s hazardous waste environmental technology listed below:

U.S. Department of the Navy
Naval Command, Control,
and Ocean Surveillance Center
RDT&E Division (NraD)
Code 5204
San Diego, CA 92152-5000

Site Characterization Analysis Penetrometer System
with Laser-Induced Fluorometry
(SCAPS-LIF)

Chapter 412, Statutes of 1993, Section 25200.1.5., Health and Safety Code, enacted by Assembly Bill 2060 (Weggeland) and effective January 1, 1994 authorizes DTSC to certify the performance of hazardous waste environmental technologies. Only technologies that are determined not to pose a significant potential hazard to the public health and safety or to the environment when used under specified operating conditions and which can be operated without specialized training and with minimal maintenance may be certified. Incineration technologies are explicitly excluded from the certification program.

The purpose of the certification program is to provide an in-depth, independent review of technologies at the manufacturer’s level to facilitate regulatory and end-user acceptance and to promote and foster growth of California’s environmental technology industry.

DTSC makes no express or implied warranties as to the performance of the manufacturer’s product or equipment. The end-user is solely responsible for complying with the applicable federal, state, and local regulatory requirements. Certification does not limit DTSC’s authority to require additional measures for protection of public health and the environment.

By accepting certification, the manufacturer assumes, for the duration of certification, responsibility for maintaining the quality of the manufacturered equipment and materials at a level equal or better than was provided to obtain certification and agrees to be subject to quality monitoring by DTSC as required by the statute under which certification is granted.

DTSC’s notice to certify was published in the California Regulatory Notice Register Volume 96. The DTSC’s final certification shall be effective from August 5, 1996 to August 5, 1999.

Additional information supporting DTSC’s final certification decisions is available from:

California Environmental Protection Agency
Department of Toxic Substances Control
Office of Pollution Prevention and Technology Development
P.O. Box 806
Sacramento, California 95812-0806

The final certification statement and the certification limitations for the technology follows:

U.S. Department of the Navy
Site Characterization Analysis Penetrometer System
with Laser-Induced Fluorometry
(SCAPS-LIF)

Certification Statement and Technology Specifications

Under the authority of Section 25200.1.5 of the California Health and Safety Code, DTSC hereby certifies the NRaD SCAPS-LIF technology as a Site Characterization technology when operated, monitored, and maintained according to NRaD’s protocols and specifications subject to conditions specified in this certification. The method is an in-situ field screening technique for characterizing the subsurface distribution of POL contamination prior to the installation of monitoring wells or soil borings. As a field screening method, it is not a replacement for soil sampling borings and monitoring wells; but is a means of reducing the number, and improving the placement, of borings and monitoring wells required to achieve site characterization. The method provides field screening data on the in-situ distribution of POL products indirectly from the fluorescence response induced in PNAs when the PNAs are components of the POL products; the most effective fluorescence response is obtained for POL products containing PNAs with three or more aromatic rings. The method detects PNAs in the soil matrix throughout the vadose, capillary fringe and saturated zones. The method provides a “detect/non-detect” field screening capability relative to a specified detection limit derived for a specific fuel product in a site-specific soil matrix. For each specific site, calibration procedures are required to determine a fluorescence threshold and corresponding site detection threshold, typically in terms of mg/kg Diesel Fuel Marine (DFM). The detection threshold is subsequently applied to TPH or TRPH data for parallel soil boring samples to classify each into a “detect” or “non-detect”category. Site-specific detection limits typically vary from levels equivalent to approximately 100 mg/kg Total Petroleum Hydrocarbons (TPH, Modified EPA Method 8015) or Total Recoverable Petroleum Hydrocarbons (TRPH, EPA Method 418.1) to over 1000 mg/kg TPH or TRPH. Direct comparisons of sensor data with TPH or TRPH laboratory data for field-selected, non-random samples, collected using a split spoon sampler by boring over and adjacent to the SCAPS push hole with a conventional hollow-stem auger, show approximately 85% agreement when using the “detect/non-detect” criteria determined for each site.

Although the sensor provides a nearly linear numerical response over a dynamic range of approximately three orders of magnitude starting from a minimum detection capability as low as 10’s of ppm (weight of POL product /weight soil), the certification is limited to a qualitative field screening method because sensor response has been shown to be very site specific, and vary as a function of the soil type as well as the composition of the petroleum hydrocarbon residual being investigated. In addition, varying background concentrations of naturally occurring fluorescing compounds can produce matrix interferences.

Qualitative use of spectral data provides a means of distinguishing different POL products associated with fluorescence events at different depths. Spectral differences can also be used as a means of minimizing potential false-positives arising from non-POL fluorophores. The technology is capable of making measurements from the ground surface to depths of 150 feet, when the sensor is used in conjunction with an “industry-standard” 20 ton penetrometer push vehicle. However, maximum depth of operation is governed by site-specific stratigraphy and the method is limited to sites where the cone penetrometer can be pushed to the depth of concern, through primarily unconsolidated sedimentary deposits or formations. Standard data collection rates (a composite measurement every 2 seconds) provide a vertical spatial resolution of better than 4 cm for a standard push rate of 1 m/min.

Limitations of Certification

DTSC makes no express or implied warranties as to the performance of the SCAPS-LIF site characterization technology. Nor does DTSC warrant that the SCAPS-LIF site characterization technology is free from any defects in workmanship or materials caused by negligence, misuse, accident or other causes.

DTSC believes, however, that the SCAPS-LIF site characterization technology can be used for field screening of hydrocarbon-contaminated sites when used in accordance with NRaD specifications and subject to the conditions specified in this certification. Said belief is based on DTSC’s review of data submitted by NRaD and other pertinent information, and participation in field demonstrations.

The certification is limited to use of the SCAPS-LIF technology as a qualitative to semi-quantitative field screening method for hydrocarbon-contaminated sites. Use of the technology is limited to hydrocarbon contaminated sites where sufficient levels of PNA fluorophores are present in the hydrocarbon matrix to exhibit significant fluorescent responses at the 337 nm excitation wavelength which are above and distinguishable from background fluorescence levels. The technology has been shown to be applicable to a variety of sites contaminated by POLs, including diesel fuel marine, diesel no. 2, JP-5, and unleaded gasoline. Each site and contamination problem must be assessed for applicability by both site-specific calibration procedures and confirmation boring samples. The technology has not been shown to be applicable, for instance, to JP-4 contamination.

In its present configuration, the method cannot be used for direct detection of non-PNA (e.g. aliphatic or single-ring aromatic) compounds. Importantly, the technology cannot directly detect the presence of BTEX compounds (e.g., benzene) or other compounds of concern which do not fluoresce in response to the 337 nm excitation energy. (Note: Lower emission wavelength lasers, beyond the scope of this certification, are being developed to extend the detection capability to BTEX.)

This certification makes no claims concerning the performance or effectiveness of the SCAPS-LIF site characterization technology to quantify the concentration of petroleum hydrocarbon contamination in the subsurface or to detect specific contaminants of concern, such as benzene or other BTEX compounds. DTSC does not know all of the possible combinations of hydrocarbon products and site lithologies to which the technology may be applied, nor does DTSC know all of the performance specifications required by end-users. Achieving performance specifications involves many variables including the type and amount of contamination, the subsurface hydrogeologic conditions, presence of naturally occurring fluorophores, and other potential interferences. The applicability of the technology to a specific site depends on the contaminant concentration of concern and the site-specific detection limit determined for the site. The ability to detect the presence or absence of bulk hydrocarbon contamination (TPH or TRPH) at concentrations of concern is very site specific. Detection limits will vary as a function of the petroleum hydrocarbon contaminants, site specific lithology, and other matrix effects such as the presence of interfering fluorophores. Petroleum hydrocarbons vary significantly in composition from product to product and with weathering or decomposition in the subsurface. The characteristics of the fluorescence emission can vary significantly depending on the specific product released into the environment and the degree of degradation due to physical, chemical and biological processes. The intensity of the fluorescence emission response of a given hydrocarbon contaminant has been found to correlate inversely with the surface area of the media (e.g., sands versus clays). Vertical variations in lithology at a given site can result in variations with depth in the detection capability of the technology. Naturally-occurring non-POL fluorophores in the formation under investigation can potentially cause interferences resulting in elevated detection limits. In many cases, such as for carbonates present in soils, it may be possible to distinguish the spectral response of the natural fluorophore from those of the hydrocarbon contaminants.

Site Detection Limits and Fluorescent Thresholds determined through pre-deployment calibration procedures may not be representative of all matrices and contaminants encountered at a given site. The predeployment calibration procedure usually relies on a near-surface soil sample spiked with diesel fuel marine (DFM) or other suitable calibrant throughout a range of concentrations. If major lithologic changes exist at a site, either vertically or areally, or different contaminants are present, calibration results may not be applicable for the entire site. The fluorescence spectral response and background level fluorescence of the soil used to prepare the calibration samples should be compared to the spectral response and background level fluorescence obtained throughout the SCAPS-LIF site investigation. Depending on the specific application, improved calibration accuracy may be achieved by employing a post-investigation calibration that makes use of soil samples collected from the major lithologic unit(s) encountered at the site.

The use and performance of the standard geophysical Cone and Friction-Cone Tests (ASTM method D 3441-86) or other sensors which could be deployed with the SCAPS are not a part of this certification. However, use of the LIF sensor in conjunction with these or other sensors that can be deployed with the cone penetrometer to make parallel or concurrent measurements is neither precluded nor reviewed by this certification. Note: Caution should be used when interpreting the results of standard cone penetrometer geophysical measurements in POL-contaminated areas. Based on results of the field demonstrations, it appears that geophysical results may not be accurate in POL contaminated areas, possibly due to the lubricating properties effect on sleeve friction measurements.

Specific Conditions

Certification of the SCAPS-LIF technology is subject to the following conditions:

  1. Site Applicability

    The end-user is ultimately responsible for determining the suitability of the SCAPS-LIF technology for their specific applications and for complying with the applicable Federal, State, County, and local regulatory requirements.

    For each specific application, the end-user must ensure compliance with all applicable worker health and safety standards established by OSHA, Cal/OSHA, and other state and local agencies. The end-user must understand and comply with any site-specific Health and Safety Plans.

  2. Calibration

    Calibration: The system must be calibrated in accordance with procedures described in the certification application and the certification evaluation report to determine the detection limit and fluorescence threshold. Calibrations must be carried out using spiked soil samples prepared with soil that is representative of the site, using a diesel fuel marine (DFM) standard or other POL with a fluorescence response appropriate for the site.

    It is recommended that an initial calibration be performed on a representative soil sample from the site prior to deployment to ensure that the technology is applicable to the specific site conditions. Because there may be uncertainties associated with collecting soil samples that are representative of the site conditions, improved calibration accuracy may be achieved by employing a post-investigation calibration that makes use of soil samples collected from the major lithologic unit(s) encountered at the site.

    Additionally, system checks must be carried out with a standard quinine sulfate solution for the purpose of normalizing LIF response push to push, day to day, and in conjunction with calibration procedures. A blank (clean sand) should be run to establish background response.

    System Stability: Before and after each push a standard solution of quinine sulfate should be used to assess system stability.

  3. Confirmation Borings

    Laboratory analyses of discrete depth core samples are required to confirm the in-situ qualitative results of the SCAPS- LIF sensor at a specific site. This is necessary to verify whether that the contaminants present at the site have adequate or consistent fluorescence response properties throughout the stratigraphy in which they are encountered. Also, site contaminants which are aged or of different origin than the DFM or other chosen standard may have significantly lower or different spectral response patterns than the standard which is used to prepare the calibration soil samples. Matrix effects, and even the particular contaminant or contaminants present, may vary with depth and stratigraphy. Confirmation soil boring samples will confirm the overall pattern of contamination indicated by the SCAPS-LIF system. For this purpose, conventional soil sampling borings co-located at selected penetrometer push locations may be completed. Alternatively, there are soil core sampling devices available for use with a cone-penetrometer that can collect the necessary confirmation soil samples.

    It is recommended that a minimum of three confirmation soil borings, or equivalent, be completed to confirm acceptability of the technology for use at a specific site. However, small or simple sites may require as few as one or two borings, while larger, more complex sites will require a greater number of sampling borings. The depth, size, stratigraphy, and contamination profile of a site should all be considered in determining the necessary number and locations of borings and samples. Geophysical data obtained using the cone penetrometer can be used to assess major lithologic changes and guide the placement of borings and sample locations. As a general guide, confirmation soil samples should be obtained from established clean zones in all major lithologic units and from zones which fluoresce significantly above the established fluorescence threshold for the site. Samples should be obtained from locations which exhibit high, medium, low (above fluorescence threshold) and background fluorescence levels for each major lithologic unit encountered at the site.

  4. Spectral Response Data Interpretation

    High concentrations of contaminants present in the soil can potentially saturate the photodiode array detector system. In these instances the recorded peak maxima wavelength readings as well as the emission spectra data will be incorrect, and perhaps misleading. Where detector saturation occurs, wavelength-at-peak reading must be ignored and fluorescence spectra reviewed in conjunction with other push-hole data to assess whether the fluorescence is due to the contaminants or other sources. Interpretation of spectral features, matrix interferences, detection thresholds, or interferences from naturally occurring fluorophores requires an understanding of the principles behind the technology and the practices of its use. The results should only be used in conjunction with an appropriate interpretation of the raw data by persons with applicable training and expertise.

  5. Grouting

    All cone penetrometer push holes must be grouted to eliminate the potential for the push hole to act as a conduit for the migration of hazardous contaminants. The SCAPS probe design allows for grouting of the penetrometer borings through the instrumented probe. A grouting mixture of cement/bentonite/Sikament is pumped from the surface, down through the penetrometer rods via a 3/8-inch diameter tubing included within the umbilical cable so that the push hole can be grouted from the bottom up (tremie method) as the probe is withdrawn.

    Sikament, an organic sulfonate polymer additive for concrete, is necessary to thin the grout mixture which otherwise could not be pumped down the small diameter tubing and tremied into the hole. There is insufficient space within the standard 35 mm diameter penetrometer rod to allow for a larger diameter grout tubing since the umbilical cord which passes through the rods must also contain the fiber-optic cables and electrical leads. The alternative method would be to remove the push rod string and to attempt to grout the hole afterwards. With this method, however, there is a high risk that bridging would occur, making it difficult to adequately grout the push hole.

    In general DTSC does not recommend the use of additives, such as accelerators, density additives, or thinners, to the grout mixtures because of the concern over the potential for local trace contamination of the aquifer, as well as interferences with detection of trace concentrations of contaminants of concern. Because the SCAPS-LIF technology is used as a field screening tool to delineate the extent of a petroleum contamination source area, versus detection of low concentrations of contaminants in groundwater, the use of Sikament does not appear to present a concern. However, its use in the grout mixture should be documented at each site so future investigations or monitoring programs can anticipate the potential for detecting low concentrations of the additives and any breakdown products. Additionally, water used in the grout mixture and in the grouting process should be a water of known and documented quality.

  6. Probe Cleaning

    The steam cleaning system integral to the truck should be used to automatically steam clean the penetrometer rod sections as they are being withdrawn from the push hole and prior to being handled by the field crew and placed onto the storage racks. Spent water from the cleaning process, directed to a storage drum, should be properly classified and managed.

  7. Continuous Quality Control/Quality Assurance

    By accepting this certification the applicant accepts, for the duration of this certification, responsibility for maintaining the quality of the manufactured equipment, materials, and instruction manuals and other documentation at a level equal to or better than that which was provided to obtain this certification.

  8. Modifications and Amendments at the request of the Applicant

    Modifications and amendments to this certification may be requested by the applicant. Until applicable regulations are adopted, such requests will be processed according to the provisions under which this certification was issued; following the adoption of regulations, such requests will be processed as provided for in the regulations.

  9. Requirements and Conditions of New Regulations

    This Certification is issued under the California Environmental Technology Certification Program. As a result, this Certification will be subject to the conditions set out in the regulations to be developed, such as the duration of the Certification, the continued monitoring and oversight requirements, and the procedures for certification amendments, including decertification.

  10. Maintaining Product Quality and Monitoring by DTSC

    By accepting this Certification, the NRaD assumes, for the duration of the Certification, responsibility for maintaining the quality of the manufactured materials and equipment at a level equal or better than was provided to obtain this Certification and agrees to be subject to quality monitoring by DTSC as required by the law, under which this Certification is granted.

Basis for Certification

The certification evaluation included a review of peer-reviewed publications and other literature which describe the scientific principles upon which the technology is based and the results of studies conducted by NRaD and other researchers during the technology development process; an analysis of data from previous field studies completed by the developer at a variety of sites; participation in two detailed field demonstrations of the technology; and observations of the technology in operation at other sites. Detailed results of the certification evaluation are presented in the draft DTSC Certification Evaluation Report for this technology.

Literature

The principles of UV fluorescence of PNAs are well established in the scientific literature. UV fluorescence is used in a variety of standard test methods for analysis of PNAs, such as US EPA SW-846 Method 8310. Standard UV fluorescence analytical procedures are for aqueous or liquid phase analysis. For soils, a solvent extraction step is required prior to analysis. The innovative aspect of the Laser-Induced Fluorescence sensor is the ability to make direct measurements of PNA-containing POL contaminants in soil without the need to obtain or extract a soil sample.

As part of the certification application, NRaD provided 15 papers and journal articles which presented results from a number of engineering, research, and development studies conducted by NRaD and other researchers related to the use of the SCAPS-LIF sensor for detection of petroleum hydrocarbons in soil. These studies reported on the development and optimization of the technology, and described the results of investigations into potential concerns and other issues related to the application of the technology. A number of studies focused on identifying the effect of various properties associated with different classes of soils or sediment types (e.g., pure sands versus pure clays versus mixtures) that may affect detection limits and variations in response to DFM and other fuel types. Factors investigated included available surface area, grain size distribution, mineralogy, percent soil moisture and water saturation, and degree of soil aggregation. Emission spectra/peak maxima characteristics of various fuels/POLs were investigated to identify spectral responses and key spectral features. Various fuel types were analyzed to determine the concentrations of PNA compounds present which contribute to the overall fluorescence emission spectra of these fuels. The inability of the 337 nm laser configuration of the technology to directly detect BTEX was documented. Tests were performed which suggest that only the contaminant on or in interstices between the first layer of grains against the sapphire window contributes to a measurable florescent signal. The effect of fiber optical geometry and transmission characteristics were assessed to optimize and engineer for instrument sensitivity and performance. Various calibration procedures and standards were tested and evaluated.

Previous Field Validation Studies

Data were provided from NRaD’s field validation studies, conducted at eight sites in California and one site in Arizona, with varying geologic conditions and contaminants. The lithology at these sites could be generally classified as unconsolidated sedimentary formations, primarily layers, mixtures, and combinations of sands, silts, and clays with minor occurrences of interbedded gravels. Groundwater was encountered at 6 of the sites where the depth to water table ranged from 4 to 79 feet below ground surface. Contaminants included diesel, JP-5, waste motor oil, refinery waste, oil field diluent, and unleaded gasoline. DFM was used as the daily calibration standard to determine the site detection limit and corresponding fluorescence threshold at seven of the sites. At two of the sites, Diesel No. 2 and oil field diluent were used as calibration standards. At the one site which was contaminated with unleaded gasoline, calibration was performed months after field operations were completed using a different probe. Based on these calibration data, detection limits and fluorescence thresholds for the sites ranged from 90 to 1,141 mg/kg and 106 to 199,953 fluorescence counts (arbitrary units), respectively.

Between 16 and 45 cone penetrometer pushes using the SCAPS-LIF, along with from 3 to 8 confirmation soil sampling borings, were completed at each of the study sites. Each confirmation soil sampling boring was located within a few inches of a cone penetrometer push hole such that the auger blade would overbore the push hole and that soil core samples could be obtained within several inches of the fluorescence measurements. A total of approximately 188 samples from 44 sampling borings were analyzed using EPA Method 418.1 for TRPH and modified EPA Method 8015 for TPH. These results were compared to fluorescence response results obtained from the co-located cone penetrometer push holes over the same depth intervals as the soil samples, and to the respective site-specific detection limits and fluorescence thresholds. The calibrants used to prepare the SCAPS calibration soil samples, typically DFM, were different than the calibrants used for standard TPH analyses of confirmation soil samples from these sites. Fluorescence response results were considered false positives when the fluorescence reading was greater than the established fluorescence threshold but the TPH or TRPH soil sample result was less than the site detection limit; and false negatives when the fluorescence reading was less than the established fluorescence threshold but the TPH or TRPH soil sample result was greater than the site detection limit. For the 164 TPH analyses completed there were 9 (5.5%) false positives and 12 (7.3%) false negatives. For the 164 TRPH analyses completed there were 6 (3.7%) false positives and 16 (9.8%) false negatives.

For several of the validation studies confirmation core samples were analyzed using EPA Method 8270 with tentative identification of additional peaks to determine what PNA compounds were present and to assess their relative contribution to the fluorescence emission spectra encountered at these sites. Significant concentrations of multi-ringed PNAs which are known to fluoresce were found to be present in the samples but a significant correlation between their concentrations and the fluorescence emission spectra could not be definitely established.

An unknown level of uncertainty exists in comparing fluorescence results with soil sample results due to the fundamental differences between SCAPS-LIF and the other methods. For example, the confirmation soil core samples are horizontally offset from the corresponding LIF probe push hole. There is an inherent uncertainty in determining the exact depth of a drill hole sample due to potential errors in measurement, soil sloughing, and, near the groundwater table, heaving sands. There is also an inherent difference in the soil that the LIF probe senses versus the soil core sample obtained for confirmation analysis. The LIF probe only senses fluorescence properties of the surficial layer of soil contamination adjacent to the probe’s sapphire window. The TPH and TRPH analyses use only small aliquots (e.g., 10-30 grams) of soil from soil cores. Although fluorescence response signals are integrated over the “same” depth interval as the confirmation soil sample, and the confirmation core samples are homogenized prior to analysis, the two sampling systems may not be viewing the same soil, particularly where soil and contamination heterogeneities are present or where complete homogenization is difficult. Therefore, the comparison of the fluorescence response results to soil sample results may not be amenable to detailed statistical analyses, but should be considered a good indicator of the technology’s performance.

Field Demonstrations

The certification evaluation included two detailed field evaluations/demonstrations of the SCAPS-LIF technology, the first at a fuel storage tank farm site with Diesel Fuel Marine (DFM) contamination in Port Hueneme, California, and the second at a diesel no. 2 fuel oil spill at an active tank farm (Site 190) at Sandia National Laboratories in Albuquerque, New Mexico. These field demonstrations provided an independent evaluation of the technology’s performance at site conditions representative of the performance claims for which NRaD desired certification. The field demonstrations augmented data from the field studies at other sites which NRaD had previously conducted and submitted in support of certification. The final work plans for conducting the field demonstrations are provided in the documents entitled:

  • “Laser Induced Fluorometry/Cone Penetrometer Technology Demonstration Plan at the Hydrocarbon National Test Site, NCBC Port Hueneme, California, May 1995”
  • “Addendum to the Laser Induced Fluorometry/Cone Penetrometer Technology Demonstration Plan at the Arid Demonstration Site, Sandia National Laboratories Above Ground Tank Farm, Albuquerque, New Mexico”