grad=entmde.state.md.us/programs/land/mining/marcellus/...3 note, nysdec’s assumption of 25%...

Review of Surface Impoundment EmissionsModeling Performed by

New York State Department of Environmental Conservation

Draft Supplemental Generic EnvironmentalImpact Statement

On The Oil, Gas and Solution Mining Regulatory Program

Prepared for

Halliburton Energy Services, Inc.P.O. Box 42806

Houston, TX 77242-2806

December 31,2009

Grad=ent

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Table of Contents

1

2

3

Introduction ..............................................................................................................1

4

NYSDEC Air Modeling Scenario ............................................................................2

Flaws in NYSDEC Air Modeling ............................................................................43.1 Air Modeling Mass Balance Flaws .....................................................................................43.2 Inappropriate Air Guideline Concentrations For Several Chemicals .................................6

Conclusion ................................................................................................................9

References .........................................................................................................................11

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List of Tables

Table 1Table 2

Surface Impoundment Air Emissions Mass BalanceSummary of Corrected Comparisons to NYSDEC Air Guideline Values

List of Abbreviations

AGCCAdSGEISECHESIHFIURNYSDECREDRfCRSLSGCSRBCUS EPAVOC

Air Guideline ConcentrationContaminant Concentration in AirDraft Supplemental Genetic Environmental Impact StatementExposure ConcentrationHalliburton Energy Services, Inc.Hydraulic FracturingInhalation Unit RiskNew York State Department of Environmental ConservationReregistration Eligibility DecisionReference ConcentrationResidential Screening LevelShort-term Guideline ConcentrationSusquehanna River Basin CommissionUnited States Environmental Protection AgencyVolatile Organic Compound

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1 Introduction

The New York State Department of Environmental Conservation (NYSDEC) published a Draft

Supplemental Generic Environmental Impact Statement (dSGEIS), dated September 2009, which contains

generic permit requirements for the development of natural gas production wells in the Marcellus Shale

formation using horizontal drilling and high volume hydraulic fracturing techniques. One component of

the NYSDEC evaluation included an assessment of potential volatile organic compound (VOC) emissions

from surface impoundments storing the hydraulic fracturing (HF) flowback fluids. This report contains

Gradient’s review of the NYSDEC air modeling analysis. Gradient has prepared this report on behalf of

Halliburton Energy Services, Inc. (HESI).

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2 NYSDEC Air Modeling Scenario

The NYSDEC air emissions modeling procedures are described in Section 6.5 of the dSGEIS. As

noted in the dSGEIS, "the Department has relied upon a United States Environmental Protection Agency

(US EPA) document 44 on emissions from water treatment facilities which provide [sic] such methods for

surface impoundments" (dSGEIS, p. 6-77).1 The NYSDEC identified chemicals to model based on

chemical additives used in the HF fluids, selecting those that had the more stringent air quality guidelines

among the additive ingredients used in the HF fluids (see dSGEIS, p. 6-76). NYSDEC made a number of

conservative assumptions when modeling chemical emissions that result in overstating air concentrations

and human health risks:

Estimated the constituent concentration in the flowback fluids in the impoundments to beequal to the maximum constituent content in the HF additives, as mixed for use duringinjection and fracturing (i.e., 100% flowback of the constituents, assuming no attenuationof concentrations due to mixing with liquids in the Marcellus Shale or due to removal ofadditives during the fracturing process);

Did not consider the potential dilution effects of precipitation on the impoundments, orother weather conditions such as freezing conditions during the winter months, both ofwhich would tend to reduce chemical emissions; and

Did not consider attenuation mechanisms, such as photolysis, which could reduceconcentrations for certain compounds.

Thus, the conservative assumptions adopted by NYSDEC yield high end estimates of chemical emissions.

NYSDEC evaluated emissions for two impoundment scenarios. One scenario is a centralized

impoundment designed to serve multiple well pads. The centralized impoundment was assumed to have a

surface area of 150m × 150m. The second scenario modeled was a smaller, on-site, impoundment meant

to serve a single well pad with a surface area of 15m × 45m (dSGEIS, p. 6-62). Although recognizing

that current NYSDEC regulations call for flowback water to be removed within 45 days of well

completion, if flowback from multiple wells is managed in centralized impoundments, such

impoundments could manage flowback water over the course of a full year. Thus, for the NYSDEC air

emissions modeling, the HF constituent emissions were calculated for a full year, with the assumption

that the impoundments would contain flowback water continuously for at least a year (dSGEIS, p. 6-63).

For the centralized impoundment scenario, NYSDEC assumed that each centralized impoundment

1 The US EPA document is not cited in the dSGEIS, however it appears to be US EPA (1994).

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handled the flowback water from 10 wells constructed and developed during a year (dSGEIS, p. 6-62).

Each well was assumed to employ 5,000,000 gallons of HF fluid of which 25% was assumed to be

recovered as flowback fluid (dSGEIS, p. 6-57). Based on these parameters, each well would yield

1,250,000 gallons of flowback fluid, or 12,500,000 gallons per year for a centralized impoundment

serving the needs of 10 wells per year (according to the NYSDEC analysis).


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3 Flaws in NYSDEC Air Modeling

Although the chemical emission and air dispersion models used by NYSDEC are generally

accepted models, there are at least two significant technical flaws with the implementation of the models

rendering the results and conclusions unreliable:

Based on a chemical mass balance analysis, the NYSDEC emissions are implausible formany of the chemicals modeled, and demonstrate a flawed modeling scenario.

The annual air guideline concentrations (AGCs) for several chemicals used by NYSDECin the analysis are based on a lifetime of exposure, yet the modeling scenario is a one (1)year exposure duration. The modeled one-year concentrations should not be compared toAGCs derived on the basis of a long term (e.g., 70-year) exposure without adjusting forthe different exposure durations.

These flaws are described in more detail in the following two sections.

3.1 Air Modeling Mass Balance Flaws

We conducted a mass balance to assess the appropriateness of the NYSDEC air emissions

modeling results. Using the NYSDEC stated emission rates for the impoundments, and their modeled

duration (one year), we calculated the total mass of the HF constituents that were modeled to be emitted

from the surface impoundments. The mass emitted over the course of a year is simply the emission rate

reported by NYSDEC (in grams/second) multiplied by the modeled duration (one year). In Table 1, we

summarize the modeled total mass emitted (in kg/yr) for the HF constituents, several of which NYSDEC

indicates exceed their respective guideline concentrations or AGCs. Based on the total mass emitted, we

then calculated the volume of flowback fluid needed to release the chemical mass in one year as shown in

the equation below and summarized in Table 1.2

Volume (9al/yr) = ).sec.

Emissions ~ x 3.15 x 107 (-~--)

Concentration x 9a~ x 10.3 ~

2 The calculated volumes assume 100% loss of chemical from the impoundment. If less than 100% of the chemical is emitted,

then an even greater volume of fluid would be required to generate the calculated emissions.


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The results of this mass balance calculation are striking. For the majority of the chemicals

evaluated, the volume of fluid necessary to yield the NYSDEC modeled emissions is significantly inflated

compared to anticipated HF operational conditions. For example, it would take 454 million gallons of

flowback fluid in a centralized impoundment to yield the stated emissions for "heavy naphtha" claimed by

NYSDEC. Similarly implausible fluid volumes would be necessary to yield the stated emissions for

benzene, xylene, and methanol: 508 million, 538 million, and 202 million gallons, respectively.

A centralized impoundment, serving 10 wells per year (dSGEIS p. 6-63), could not possibly

generate these enormous flowback fluid volumes. As stated in the dSGEIS, the upper bound HF injection

volume is expected to be approximately 5 million gallons per well, of which flowback volume was

estimated to be approximately 25% of this amount, giving 1.25 million gallons of flowback per well.3

For 10 wells managed through a centralized impoundment this yields an upper bound estimate of 12.5

million gallons of flowback fluid per year. A single impoundment serving one well would generate 1.25

million gallons of flowback water.

For both xylene and benzene, the annual emission rates calculated by NSYDEC would require

the flowback fluid from over 400 wells per year at the stated respective xylene and benzene

concentrations in flowback fluid to yield the reported annual emission rates. Similarly, the NYSDEC

calculated emission rates for heavy naphtha and methanol would require flowback fluid from over 350

and over 150 wells per year, respectively. As shown in Table 1, the mass balance error ratios (the ratio of

the implied fluid volume divided by the annual maximum flowback volume) for two constituents exceed

40-fold, and several others have mass balance error ratios greater than an order of magnitude.

Based on these unrealistic results, the NYSDEC air emissions modeling results are technically

unreliable.

Correction Of Mass Balance Errors

Because the air dispersion modeling performed by NYSDEC was based on "unit" emission rates

which were scaled to the calculated emission rates for each constituent,4 it is a straightforward matter to

adjust the calculated chemical concentrations in air to correct for the mass balance errors in the emission

3 Note, NYSDEC’s assumption of 25% flowback is conservative since the Susquehanna River Basin Commission (SRBC) has

concluded that the average flowback rate in New-York is expected to be 18% (SRBC, 2009).4 This is a commonly adopted approach when modeling air dispersion of multiple chemicals from the same source.


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rates. In Table 2, we summarize the NYSDEC modeled maximum annual and maximum 1-hour airborne

chemical concentrations, as well the NYSDEC comparisons to the Short-term Guideline Concentrations

(SGCs) and AGCs. For methanol and heavy naphtha, the NYSDEC air emissions estimates predict both

of these constituents to exceed annual AGCs and short term SGCs, with ratios ranging from 25.6-fold to

1.7-fold (see Table 2). However, as shown in Table 1, the emissions for heavy naphtha exceed mass

balance by factors of 36-fold and 11-fold for the centralized and onsite impoundments, respectively.

When the respective NYSDEC modeled heavy naphtha concentrations are adjusted by these factors, the

predicted airborne concentrations are less than the AGC and SGC values for the maximum annual and

maximum 1 hour scenarios. Similarly, when the NYSDEC modeled methanol concentrations are adjusted

downward by 16-fold (centralized) and fivefold, the calculated concentrations in air fall below the AGC

and SGC values. As a further note, although benzene, xylene and several other constituents had mass

balance errors, the NYSDEC modeled concentrations in air did not exceed AGCs or SGCs.

While we have corrected these mass balance errors in the NYSDEC analysis, we have not made

any changes to the remaining conservative assumptions in the NYSDEC emissions analysis, identified in

Section 2.

3.2 Inappropriate Air Guideline Concentrations For Several Chemicals

Not only are the air modeling results themselves flawed, for several chemicals the approach used

by NYSDEC to assess potential risks to human health is also inappropriate and results in a significant

overestimation of risks. NYSDEC compared modeled chemical concentrations in air due to emissions

from impoundments in operation for one year against air guideline concentrations derived on the basis of

a lifetime exposure. In addition, the AGCs used by NYSDEC differ from their respective human health

based values reported by US EPA.

Acrylamide and formaldehyde are two HF additives that are regulated as potential human

carcinogens. In the dSGEIS, the maximum annual concentrations of acrylamide and formaldehyde

modeled by NYSDEC are reported to be 5.7-fold (acrylamide) and 6.2-fold (formaldehyde) greater than

their respective AGC values.

As we discuss below, the comparison of a one-year exposure (e.g., emissions calculated to occur

over one year) to air guidelines that presume a lifetime of exposure, inappropriately inflates the

implication of risk associated with such exposures. In addition, the NYSDEC AGC values for these


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compounds differ systematically from published US EPA risk-based guidelines, yet NYSDEC guidance

documents containing the AGC values purport to adopt US EPA toxicity values.

US EPA has derived risk-based concentrations ("Residential Screening Levels" or RSLs) for

these chemicals based on a one in a million cancer risk assuming daily inhalation for 30 years and

averaged over a 70-year lifetime. As summarized below, the US EPA RSLs are 2.5 to 3.2 times higher

than their respective NYSDEC AGCs. Note that we include benzene in the comparison because the US

EPA RSL again is 2.4-fold higher than the NYSDEC AGC, indicating a systematic difference between

the USEPA and NYSDEC values for chemicals regulated as carcinogens.5 The NYSDEC modeled

benzene concentrations do not exceed its AGC.

It appears that the main reason for this systematic difference between the RSL and AGC values is

that NYSDEC assumes a 70-year exposure duration in its guidelines.6 Thus, the AGC values against

which NYSDEC compared its one year emissions modeling results are guidelines that presume a lifetime

(70 years) of exposure, not one year.

Chemical NYSDEC AGCIal U.S. EPA RSL[b] Ratio(~tg/m3) (~tg/m3) RSL/AGC

Acrylamide 0.00077 0.0019 2.5

Benzene 0.13 0.31 2.4

Formaldehyde 0.06 0.19 3.2

Notes:[4 NYSDEC "DAR-1 AGC/SGC Tables," dated September 10, 2007 (http://www.dec.ny. gov/docs/air~df/agcsgcOZpdJ).[b] http://www.epa.gov/reg3hwmcYrisk/human/rb-concentration table/Generic Tables/pdf/resair sl table run APRIL2OO9.pdf

Comparing modeled maximum annual (e.g., one year) concentrations against these benchmarks is

misleading and inappropriate. The US EPA RSL values are derived based on the presumption of

continual long-term exposure over a lifetime (e.g., daily exposure over 30 years averaged over a 70-year

lifetime), whereas the NYSDEC AGCs are derived based on 70-year exposure averaged over a 70-year

lifetime. Thus, the implication in the dSGEIS that acrylamide and formaldehyde emissions would exceed

5 In addition, the NYSDEC Division of Air Resources "DAR-1 AGC/SGC Tables," dated September 10, 2007, state: "When a

contaminant has both an RfC and Unit Risk Estimate value published on the IRIS website, NYSDEC will choose the moreconservative of both limits as the AGC." In all cases the Unit Risk Estimates are lower than the RfC (non-cancer ReferenceConcentrations), thus the stated NYSDEC policy effectively indicates the selection of the Unit Risk Estimate for the AGC.6 NYSDEC, 1997, Appendix C, p. C-5

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health based concentrations at the edge of the surface impoundments is based on a flawed scenario. That

conclusion would only hold if an individual were to stand at the edge of an impoundment 24 hours per

day, daily for 70 years. Clearly, that is an unreasonable presumption and contradicts the very scenario

modeled by NYSDEC which was one year of emissions from surface impoundments.

As described in US EPA’s, "Risk Assessment Guidance for Superfund, Part F: Supplemental

Guidance for Inhalation Risk Assessment" (US EPA, 2009), when evaluating health risks over a

particular exposure duration, the chemical concentrations used in the exposure calculation should be

calculated as time-weighted concentrations:

The estimation of an EC [exposure concentration] when assessing cancer riskscharacterized by an IUR [inhalation unit risk] involves the CA [contaminantconcentration in air] measured at an exposure point at a site as well as scenario-specificparameters, such as the exposure duration and frequency. The EC typically takes theform of a CA that is time-weighted over the duration of exposure [added emphasis]and incorporates information on activity patterns for the specific site or the use ofprofessional judgment.

If the modeled acrylamide and formaldehyde concentrations are correctly applied as their time-weighted

"effective concentrations" of exposure for one year, that is averaged over a lifetime (70 years), this

reduces the modeled concentrations by 1/70. When this adjustment is made, neither of these constituents

would exceed their respective AGC values which are derived on the basis of a lifetime averaging period.

This result is shown in Table 2, where the corrected maximum annual AGC ratios (the modeled

concentration in air divided by the AGC) are in both instances < 1, indicating that neither compound

would exceed its respective risk-based concentration guideline.7 It should be noted further, that this same

conclusion holds if the emissions from the impoundments are assumed to last three years (i.e., in this case

the modeled concentrations would be adjusted by 3/70).8 For an assumed exposure duration of three

years, the ratio of the maximum annual chemical concentration (adjusted for three years exposure) to the

AGC is 0.25 and 0.27 for acrylamide and formaldehyde, respectively (e.g., three times the values shown

in Table 2).

7 Note that the adjustment for the "effective" concentration does not affect the short-term scenario; however, neither compound

exceeds its respective SGC value.8 If the emissions are assumed to occur over three years, the annual emissions (e.g., grams/year) are the same, and the modeled

concentrations in air would also be unchanged (the air model results are based on a unit emission rate). The only thing a three-year scenario changes is the exposure duration.


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4 Conclusion

As described in this report, the NYSDEC emissions modeling of HF additives from flowback

water managed in surface impoundments is technically flawed and is not reliable. The calculated

emission rates for many compounds represent releases that demonstrate severe mass balance errors, and

cannot be relied upon. Furthermore, the health-based benchmarks for several chemicals, which are based

on a lifetime of daily exposure, are inappropriately compared to a one-year exposure scenario.

When the mass balance errors are corrected, and the "effective concentration" correctly calculated

for acrylamide and formaldehyde, the HF additive emissions from the impoundments based on the

NYSDEC model all fall below their respective NYSDEC risk-based short-term (SGC) and annual (AGC)

benchmarks, with the exception of glutaraldehyde. If glutaraldehyde were excluded from this analysis,

then the corrected NYSDEC air modeling results presented here indicate that none of the modeled HF

chemical emissions from the impoundments would exceed health-based air guidelines even in the absence

of setback requirements (e.g., these guidelines are met at the maximum point of modeled impact which

was set to 10 meters from the edge of an impoundment by NYSDEC).9 Consequently, based on the

corrected emissions analysis, no additional setback requirements are needed on the basis of air emissions

to comply with NYSDEC air guidelines - air guidelines are met at the edge of the impoundments with the

possible exception of glutaraldehyde (for which, as discussed below, emissions have not yet been

adequately assessed). The NYSDEC analysis was based on its assessment of the list of HF additives

disclosed by the industry for use in New York State (discussed in Section 5 of the dSGEIS) and

NYSDEC’s assessment of those additives deemed to present the greatest potential concern for air

emissions. It also bears noting that NYSDEC’s consultant (ICF), who evaluated air emissions from

equipment and operations during the HF well development process, indicated that the chemical emissions

from the impoundments handling flowback water would be negligible (dSGEIS, p. 6-62).

Although the modeled glutaraldehyde concentration exceeds its air guideline value, based on

these modeling results it cannot be concluded that emissions of glutaraldehyde from open surface

impoundments would present a significant risk to human health. As noted above, NYSDEC adopted

several conservative assumptions in its analysis, which are expected to overestimate chemical emissions

from surface impoundments. Furthermore, a detailed analysis of several key factors that affect the fate of

glutaraldehyde in HF fluid would need to be undertaken before any conclusion could be reached that

9 NYSDEC indicated that the only requirement for the impoundment was that it be fenced, and that the closest practical distance

that a fence could be placed was approximately 10 meters from an impoundment (dSGEIS, p. 6-67).


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emissions of glutaraldehyde from open surface impoundments would pose any threat to human health.

These factors include: the degree to which glutaraldehyde could be retained (adsorbed) in the Marcellus

formation, its relative concentration in flowback fluid, its actual emission rate, and its fate in air (e.g.,

half-life). All of these considerations would need to be evaluated to determine whether the emissions of

glutaraldehyde calculated by NYSDEC are actually achieved or whether the actual emissions of

glutaraldehyde are actually much lower, as is likely to be the case in light of the numerous conservative

assumptions. For example, the US EPA Office of Pesticides Reregistration Eligibility Decision (RED)

for glutaraldehyde indicates a half-life of three hours in the atmosphere.l° Such a short half-life would

lead to far lower glutaraldehyde concentrations in air than those modeled by NYSDEC. Thus, the fate of

glutaraldehyde, and attenuation by mechanisms as noted above, would need to be evaluated, in order to

adequately address potential health effects of glutaraldehyde used in HF additives.

10 US EPA, 2007

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References

New York State, Dept. of Environmental Conservation (NYSDEC). 2009. "Well Permit Issuance forHorizontal Drilling and High-Volume Hydraulic Fracturing to Develop the Marcellus Shale and otherLow-Permeability Gas Reservoirs (Draft)." Division of Mineral Resources, Bureau of Oil & GasRegulation / Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution MiningRegulatory Program. September.

NYSDEC. 1997. "The DEC Policy System: Guidelines for the Control of Toxic Ambient AirContaminants" Accessed at http://www.dec.ny.gov/docs/air~df/darl .pdf. DAR- 1. November 12.

Susquehanna River Basin Commission (SRBC). 2009. "Susquehanna River Basin Commission - NaturalGas Development." Presented to the Independent Oil and Gas Association of New York, November 4.Accessed on December 28, 2009 at http://www.srbc.net/programs/docs/69796_l.pdf.

United States Environmental Protection Agency (US EPA). 1994. "Air Emissions Models for Waste andWastewater." Office of Air Quality Planning and Standards. EPA-453/R-94-08A.

US EPA. 2007. "Reregistration Eligibility Decision for Glutaraldehyde." EPA 739-R-07-006.

US EPA. 2009. "Risk Assessment Guidance for Superfund, Part F: Supplemental Guidance for InhalationRisk Assessment."

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o oo

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