UCRL-AR-135949 Vol. 4 Ch. 5

Volume 4: Potential Ground and Surface

Water Impacts

Chapter 5: Potential Impact of Ethanol-containing

Gasoline on Surface Water Resources

Authors

David Layton*

Jeffrey Daniels*

Editor

G. Cannon*

Contributor

B. Clark*

December 1999

*Lawrence Livermore National Laboratory, Livermore, CA 94550

University of California • Livermore, CA 94550

Lawrence Livermore National Laboratory

 Environmental Restoration Division
Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National

Laboratory under Contract W-7405-Eng-48.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

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Table of Contents

5. Potential Impact of Ethanol-containing Gasoline on Surface-water Resources .................... 5-1

5.1. Introduction................................................................................................................... 5-1

5.2. Background................................................................................................................... 5-1

5.3. Washout of Ethanol and MTBE from the Atmosphere................................................. 5-1

5.4. Releases to Rivers and Streams .................................................................................... 5-3

5.4.1. Volatilization and Biodegradation of Ethanol in Rivers and Streams .............. 5-3

5.4.2. Accidental Releases of Ethanol to Rivers and Streams .................................... 5-5

5.5. Releases to Reservoirs and Lakes................................................................................. 5-7

5.5.1. Background: Watercraft Releases of Fuel Compounds.................................... 5-8

5.5.2. Water Quality Impacts of MTBE and Ethanol Due to Recreational

Boating.............................................................................................................. 5-8

5.6. Summary..................................................................................................................... 5-10

5.7. References................................................................................................................... 5-11

List of Figures

Figure 5-1. Peak concentrations of ethanol in a channel of the Sacramento River above

Lake Shasta after a hypothetical tank-car release.................................................. 5-17

Figure 5-2. Peak concentrations of ethanol in a channel of the Sacramento River above

Lake Shasta after a hypothetical tank-car release.................................................. 5-18

Figure 5-3. Predicted peak concentrations of ethanol in epilimnion waters of Donner

Lake after a seven-day period for alternative biodegradation half-lives and

a constant discharge of 40 kg/d from watercraft.................................................... 5-19

List of Tables

Table 5-1. Physicochemical parameters for MTBE and ethanol............................................. 5-23

Table 5-2. Comparison of the predicted mass loadings, peak concentrations, and lossrate constants for an MTBE release into Donner Lake.......................................... 5-24
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Appendices

Appendix A. Estimation of Mass-transfer Parameters ............................................................. A-1

Appendix B. Transport Parameters for Riverine Releases........................................................B-1

Appendix C. Changes in MTBE and BTEX Concentrations in Lake Tahoe, CA-NV,

Following Implementation of a Ban on Selected Two-stroke Marine

Engines............................................................................................................... C-1
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5. Potential Impact of Ethanol-containing

Gasoline on Surface-water Resources

5.1. Introduction

The phaseout of methyl tertiary butyl ether (MTBE) from gasoline in California will result in

changes in the composition of gasoline in order to meet air-quality requirements. For example,

unless a Clean Air Act requirement for oxygen content is waived for California, ethanol will

have to be added to gasoline sold in areas that have not attained compliance with air-quality

standards for ozone. The importation, distribution, and use of large quantities of ethanol in the

state raises potential concerns regarding impacts to surface-water supplies from accidental

releases, discharges from recreational boats, and washout of ethanol from the atmosphere. In

this assessment, we review information on the environmental chemistry of ethanol and conduct a

series of screening-level simulations of various releases in order to understand the nature and

magnitude of potential impacts to surface waters. To put the results in perspective, we compare

the environmental behavior of ethanol with that of MTBE.

5.2. Background

Ethanol (EtOH) and MTBE are fuel compounds that have been added to gasoline for many

years. These compounds contain elevated amounts of oxygen (that is, 18 and 35 wt% for MTBE

and ethanol, respectively), and they have octane numbers over 100. In Table 5-1 we summarize

some of their key physicochemical properties affecting their behavior in the environment. Both

EtOH and MTBE are hydrophilic substances, with low octanol-water partition coefficients and

elevated solubilities in water (ethanol is miscible in water, and MTBE has a solubility of

488 mol/m3, or 43 g/L). Ethanol is subject to fairly rapid biodegradation in the hydrosphere, but

MTBE is recalcitrant biologically. Reviews of the environmental chemistry of these oxygenated

fuel compounds are contained in the Interagency Assessment of Oxygenated Fuels (National

Science and Technology Council [NSTC], 1997), and in reports by Malcolm Pirnie, Inc.

(1998a,b).

5.3. Washout of Ethanol and MTBE from the Atmosphere

Both ethanol and MTBE can enter the atmosphere directly as a consequence of volatilization

during different stages of their life cycles, such as fugitive or accidental emissions from

manufacturing, distribution, and use, and from incomplete combustion. Although these

volatilized compounds may undergo some degree of degradation in the atmosphere, that fraction

that is not degraded by chemical processes will be subject to washout by precipitation.

Accordingly, any significant rainout (i.e., wet deposition) can potentially impact surface waters.

To determine the significance of rainout, we estimated the concentrations of MTBE and ethanol

in rainwater during a precipitation event based on atmospheric concentrations of 1 part per
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billion by volume (ppb[v]) or for any other concentration of a substance (s) in units of ppb(v),

(that is, 10–9 Ls/Lair) using Equation (5-1)

 

Crain = C M cf P

H'R T

air s , (5-1)

where

Crain = concentration of substance in rain, μg/L;

Cair = concentration of substance (s) in air, ppb(v);

Ms = molar mass (molecular weight) of substance (s), g/mol;

P = pressure, 1 atm;

R = gas constant, 0.0821 atm-L/mol-K;

T = temperature, K;

cf = conversion factor, 106 μg/g; and

H ́ = dimensionless Henry’s law constant (that is, Cair/Cwater).

An important property with respect to rainout is the dimensionless Henry’s law constant,

which essentially describes the propensity for a compound to volatilize to air from water, or

conversely, to enter water and remain in the water phase. The dimensionless Henry’s law

constant (H ́) is expressed mathematically as the ratio of the air-to-water concentrations of a

compound at equilibrium (Zogorski et al., 1997). Ideally, when an ambient air concentration for

a substance is multiplied by 1/H ́, the result is the concentration in the rainwater phase. The ratio

of the dimensionless Henry’s law constants for a temperature of 298 K for MTBE and ethanol,

respectively, exceeds a factor of 80 (H ́ for MTBE = 2.16 × 10– 2 , and H ́ for

ethanol = 2.57 × 10–4). Therefore, based on H ́ alone, more ethanol than MTBE will be present

in rainwater during a precipitation event, especially if both are present at equal concentrations

(expressed as mass per unit-volume [for example, μg/Lair]).

As expected, applying Equation (5-1) reveals that the estimated concentration of ethanol in

rainwater for a 1-ppb(v) concentration of ethanol in air (that is, 1.9 × 10–3 μg/L or 41 n mol/ m3)

could be as high as 7.3 μg/L (160 n mol/L) during a precipitation event; whereas, a 1-ppb(v)

concentration of MTBE in air (that is, 3.6 × 10–3 μg/L or 41 n mol/ m3) would yield only about

0.17 μg/L (1.9 n mol/L) in rainwater during a precipitation event. This difference of more than a

factor of 40 in mass per unit-volume rainwater concentration (almost two orders of magnitude in

moles per unit volume) is due to the large difference between the dimensionless Henry’s law

constants for the two compounds because the mass per unit-volume atmospheric concentration

for MTBE is only about a factor of two greater than that for ethanol.

Equation (5-1) is particularly useful when considering the atmospheric levels of MTBE and

ethanol in a specific air basin, such as the greater Los Angeles region of California. For
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example, Allen et al. (1999a) have estimated emissions and annual-average air concentrations for

MTBE and ethanol for 1997 and 2003 in the greater Los Angeles air basin. According to that

data, the emissions of MTBE could decline by 32% between 1997 and 2003. Corresponding

maximum, annual-average atmospheric concentrations in the greater Los Angeles air basin1 are

3.9 and 2.6 ppb(v) (160 and 100 n mol/ m3, respectively). From Equation (5–1), it is estimated

these concentrations could yield maximum, average concentrations of MTBE in rainwater during

a precipitation event of 0.65 and 0.43 μg/L (7.4 and 4.9 n mol/L, respectively). Similarly, the

assessment performed by Allen et al. (1999a,b) suggests vehicular emissions of ethanol in the air

basin could increase ambient levels of ethanol by as much as 50% (from a value of 5.1 ppb[v]

[210 n mol/m3]) to a value of 7.6 ppb[v] [300 n mol/m3]) if ethanol is added to gasoline in 2003

to achieve 2 wt% oxygen; or ambient concentrations of ethanol could rise more than 72% (from

5.1 ppb[v] [210 n mol/m3] to 8.8 ppb[v] [370 n mol/m3]) if ethanol is added to gasoline in 2003

to achieve 3.5 wt% oxygen. According to Equation (5–1), the corresponding concentrations of

ethanol in rainwater for ambient levels of 5.1, 7.6, and 8.8 ppb(v) (210, 300, and 370 n mol/m3)

would be 37, 56, and 64 μg/L (about 800, 1200, and 1400 n mol/L, respectively).

5.4. Releases to Rivers and Streams

We employed a two-tiered approach for evaluating the potential water-quality impacts on

rivers and streams caused by releases of ethanol. First, we examined the relative effectiveness of

volatilization and biodegradation as removal mechanisms, using a modified version of a

methodology presented by Pankow et al. (1996). We then analyzed the consequences of a major

release to a river using a surface-water transport model. Based on the results of these analyses,

we identified uncertainties and data gaps that need to be addressed to improve our ability to

predict the behavior of ethanol in aquatic environments.

5.4.1. Volatilization and Biodegradation of Ethanol in Rivers and

Streams

Pankow et al. (1996) presented a methodology for calculating the volatilization rates of fueloxygenate compounds in rivers and streams. In their methodology, the half-life of a compound

is calculated using a rate constant for volatilization calculated from its mass-transfer velocity

(from the water column to air) and the depth of the river. Losses due to transformation processes,

such as biodegradation, were not considered. However, if such transformation processes are

rapid, they can be as effective as volatilization losses in reducing the concentrations of the fuel

compounds dissolved in water. We, therefore, calculated the half-life of a fuel oxygenate due to

the combined processes of volatilization and biotransformation as

thalf = ( ) +

0 693 .

k k v b

, (5-2)

where

 

1

 As indicated by either the “best” or “upper” baseline, population-weighted annual exposure for summer, which is

probably a lower value than that for winter, according to Allen et al. (1999b).
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thalf = half-life of oxygenate in surface water, d;

kv = rate constant for volatilization, 1/d; and

kb = rate constant for biodegradation, 1/d.

Pankow et al. (1996) also introduced another measure of the persistence of a compound,

termed the “half-life distance,” which is simply the distance traveled during the half-life of a

compound,

 

d u half w = thalf , (5-3)

where uw is the velocity of the water (m/d).

As a means of evaluating the various parameters that control the persistence of ethanol

released to a river, we examined two transport cases (after Pankow et al. [1996]), one for

conditions supporting reduced volatilization (that is, calm winds at 0.25 m/s, a river-flow

velocity of 2732 m/d, and a river depth of 3 m) and enhanced volatilization (that is, high winds at

5.5 m/s, a river-flow velocity of 27,320 m/d, and a river depth of 1 m). With a water temperature

of 25°C, the volatilization-rate constants (that is, kv) for ethanol are 0.017/d for the conditions

associated with reduced transfer to atmosphere and 0.21/d for enhanced conditions (equivalent

half-lives of 40 and 3.3 days with half-life distances over 90 km). In contrast, the rate constants

for MTBE determined using the same conditions are significantly higher—0.083/d and 1.3/d

(with correspondingly lower half-lives of 8.4 and 0.52 days and associated distances of 23 and

14 km) for reduced and enhanced volatilization, respectively. Ethanol has a much lower Henry’s

law constant than MTBE; and consequently, the relative importance of the air-side mass-transfer

velocity in controlling the overall mass transfer to air is more important (see Appendix A).

The persistence of ethanol in surface water, however, is also a function of its biodegradation

rate. As already explained (see Alvarez and Hunt, 1999, Vol. 4, Chapter 3 of this report), ethanol

represents a carbon and energy source for microorganisms2

. Howard et al. (1991) comment that,

according to best scientific judgment, the aerobic-biodegradation half-life of ethanol in surface

water is estimated to range from 6.5 h to 26 h. This judgment is consistent with results from an

experiment performed by Apoteker and Thévenot (1983) to study the biodegradation of ethanol

in samples of Seine river water that were incubated at 20°C. This experiment produced an

exponential-growth-phase rate constant of 0.22 per hour, from which the aerobic-biodegradation

half-life can be estimated to be about 3.2 h (that is, 3.2 h = 0.693/[0.22 per h]). However, this

exponential growth-phase was preceded by a 10-h lag phase, and so the effective half-life for

ethanol is closer to 13 h, rather than 3 h. This biphasic behavior was interpreted by Apoteker and

Thévenot (1983) to occur as a result of microorganism adaptation to a change in environment,

which involved the sudden introduction of the new substrate compound (that is, ethanol). Both

the lag time and subsequent degradation rate are expected to vary by receiving-water body

properties as discussed by Alvarez and Hunt (1999, Vol. 4, Chapter 3 of this report). With a

biodegradation half-life of 13 h, the rate constant for EtOH becomes 1.3/d, which is comparable

to the volatilization rate constant for MTBE under enhanced transport conditions.

 

2

 In comparison to ethanol and most other gasoline components, MTBE is considered resistant to aerobic microbial

degradation (Suflita and Mormile, 1993).
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Biodegradation is particularly sensitive to temperature, decreasing with decreasing

temperature. This low-temperature effect occurs because low temperatures reduce cellular

membrane fluidity and permeability, which thereby reduces the uptake of both nutrients and

contaminants. Thomann and Mueller (1987) suggest that the biodegradation rate for

temperatures other than 20°C can be adjusted using the following relationship:

 

k k bT b

T

() ( ) ( – ) = . 20

20 1 06 , (5-4)

where T is in degrees centigrade. Thus, if the water temperature were 5°C, the resulting

biodegradation rate would only be about 40% of the rate at 20°C. Temperatures warmer than

20°C increase the rate of biodegradation by improving enzymatic activity up to an optimum

value that is specific to the microbial species (see Alvarez and Hunt, 1999, Vol. 4, Chapter 3 of

this report). At temperatures above the species-specific optimum, proteins and nucleic acids

become denatured and inactive; and the biodegradation process will cease. Given the variable

effects of temperature and the microbial characteristics of different receiving waters, a nominal

half-life for ethanol of 24 h can be assumed.

5.4.2. Accidental Releases of Ethanol to Rivers and Streams

The transport of ethanol to various locations in California where it would be blended with

gasoline raises the possibility that transportation accidents could occur that impact rivers and

streams. There are potentially many different scenarios that could be constructed to assess the

consequences of such accidents. We note, however, that the transport of ethanol is not inherently

any different than the transport of other bulk liquids; hence, the likelihood of releases should not

differ either. For the purposes of this screening-level assessment, therefore, we simply

postulated an accidental release in which a rail tank car carrying 30,000 gal of ethanol derails

and discharges its entire inventory to a river. To estimate the concentrations of ethanol in water

resulting from such a hypothetical release, we have adopted an empirically-based methodology

developed by Jobson (1996) that is especially suited for cases where there are limited amounts of

hydrologic information on an impacted river.

The basic equation for determining the peak downstream concentration of a substance spilled

into a river is:

 

C T

k T Me

Q pc pc

pc pc s

–k T tot pc

( ) = ( )

nf (5-5)

where,

 

T x

V pc

pc

= (5-6)

and
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Cpc(Tpc) = peak concentration (pc) of spilled contaminant at a given downriver location at time

Tpc, mg/L;

kpc = dissipation-rate constant of the peak concentration (pc) due to longitudinal

dispersion, 1/s;

Tpc = arrival time of the peak concentration (pc) at a location downstream of the release

point, h;

x = distance to receptor location downstream of spill site, m;

vpc = velocity of the peak concentration (pc) of the plume, m/s;

Ms = initial mass of the substance (s) discharged, mg;

ktot = loss-rate constant for volatilization and degradation, 1/d (note: for ethanol there is

minimal degradation);

nf = normalization factor introduced by Jobson3 (1996), 1 × 106 (dimensionless); and

Q = volumetric-discharge rate for the river at time of release, L/s.

The time-concentration profile of a contaminant at a fixed location downstream from a spill

site is a complex function of channel properties, flow rate, drainage, slope, etc. As a water-borne

plume of spilled material is transported downstream, the plume will spread longitudinally in the

direction of river flow, creating a gaussian-type pattern of contaminant concentrations in the

river at any given point measured downstream (Hemond and Fechner, 1994). Longitudinal

dispersion increases with the travel time of the plume, causing the peak concentration to decrease

as the plume-width spreads. Jobson (1996) developed an empirical relationship that estimates the

value of the rate constant describing the reduction of the peak concentration (that is, kpc) in terms

of plume travel time, and the ratio of the volumetric-discharge rate at the time of the release to

the mean-annual volumetric-discharge rate of the stream (see Appendix B).

As described in Equation 5-6, the travel time of the plume’s peak concentration is equal to

the distance from the release point to the downstream receptor location divided by the velocity of

the plume’s peak concentration in the river. Jobson (1996) developed a set of empirical

relationships to determine the velocity of the peak concentration in the dispersing plume, as well

as its maximum probable velocity (see Appendix B). Input parameters include the drainage area

of the watershed, the slope of the river channel that the plume is transiting, the volumetricdischarge rate at the time of release, and the mean annual volumetric-discharge rate of the river

at a receptor location. To assess the consequences of the postulated spill, we used the

hydrological parameters of the Sacramento River (in California), south of Dunsmuir and north of

Lake Shasta. This particular section of the river has a railroad line adjacent to it and was

impacted by a tank car spill in 1991 (California Central Valley Regional Water Quality Control

Board [CalCVRWQCB], 1991). The associated watershed has a drainage area of 1100 km2

(425 mi2), a slope of 0.015, an average annual-average volumetric-discharge rate of 32.1 m3/s

 

3

 The factor 106 arises from the fact that Jobson (1996) defines a “unit concentration” (identified as kpc in

Equation [5-5]) as 106 times the concentration produced in a unit discharge due to the injection of a unit mass of

substance. Jobson (1996) relates the “unit concentration” to a mass flux of solute (mass/time) per unit of mass

injected.
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(1133 ft3/s) (see U.S. Geological Survey [USGS], 1999). The assumed volumetric-discharge rate

at the time of the hypothetical release is 5.6 m3/s (200 ft3/s).

The best estimate for the velocity of the peak concentration of the dispersing plume is

1.2 km/h, while the maximum probable velocity is 2.1 km/h, or almost double the best estimate

(see Appendix B). A biodegradation half-life of 24 h was used to simulate the total loss rate of

ethanol (volatilization loss is minimal for ethanol). Figures 5-1 and 5-2 depict the decreases in

the peak concentrations as a function of distance downriver from an assumed release point. The

predicted concentrations are highest for the maximum probable velocity of the peak

concentration for the dispersing plume, because at high velocity less longitudinal dispersion

occurs within the plume during transit over a given distance. Under the spill scenario considered

here, the concentrations in river water could affect aquatic species. In a review of the aquatic

toxicity of ethanol, for example, Malcolm Pirnie, Inc., (1998a) reported that the LC50 (lethal

concentration for 50% of a population) for different aquatic species ranged from 454 to

14,740 mg/L. The toxic levels of ethanol would, therefore, be expected to occur at variable

distances downstream from the hypothesized spill, with the extent of such toxic concentrations

depending on volumetric-discharge conditions. As shown in Figures 5–1 and 5–2, toxic effects

could occur many kilometers downstream for a catastrophic release, such as the one that was

simulated. For example, if the average volumetric-discharge rate (that is, 32.1 m3/s) were

selected at the time of release, instead of the low volumetric-discharge rate we chose to use, the

predicted concentrations would be nearly a factor of six lower—reducing the extent of any

possible toxic effects to aquatic species. In addition, if only a portion of the tank-car inventory

were released, the resulting concentrations would also be reduced proportionately. Aside from

the acute toxicity for aquatic species that might be associated with a spill and their associated

recovery, it is unlikely that there would be any long-term toxic effects, as the ethanol will not

persist in water because of its rapid biodegradation.

5.5 Releases to Reservoirs and Lakes

One of the unexpected surface-water impacts resulting from the use of MTBE in

reformulated gasoline is the occurrence of MTBE in reservoirs and lakes in California (see

McCord and Schladow, 1998; Malcolm Pirnie, Inc., 1998b). The principal source of this

contamination is recreational boating (Reuter et al., 1998), particularly carbureted two-stroke

engines (see Appendix C). Consequently, such recreational watercraft could also represent a

potential source of ethanol in surface waters used for boating. In order to assess the significance

of ethanol discharges from watercraft to surface waters, we have conducted a screening-level

analysis in which we compare the water-quality impacts of MTBE discharges into a lake with

those associated with ethanol.

5.5.1. Background: Watercraft Releases of Fuel Compounds

Concerns over the impacts of motorized watercraft on the quality of Lake Tahoe prompted

the Tahoe Regional Planning Agency to invoke a ban on two-stroke marine engines. The ban

was effective on June 1, 1999; and consequently, this provided a unique opportunity to

investigate the differences in the concentrations of MTBE and other fuel compounds in lake

water before and after the ban. Appendix C contains the results of a study recently completed by
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Allen and Reuter of the Tahoe Research Group at the University of California at Davis,

California. This study tracks the changes in fuel compounds in Lake Tahoe from 1997–1998 to

1999. They found that there were significant decreases in the concentrations of MTBE and

benzene, toluene, ethyl benzene, and xylene (BTEX) compounds after the ban. For example, for

1999 the mean concentrations of MTBE and toluene were 95.8 and 88.3% lower, respectively,

than the levels reported in 1997–1998. The only exception in 1999 was that isolated activities

associated boat launch areas, marinas, etc., produced elevated levels in certain locations or “hot

spots.”

5.5.2. Water Quality Impacts of MTBE and Ethanol Due to

Recreational Boating

The concentrations of fuel hydrocarbons in recreational lakes or reservoirs are a function of

the types of watercraft operated (that is, the mix of two-stroke versus four-stroke engines), the

temporal pattern of recreational boating (particularly during the summer months and peak

vacation periods), and the limnology of the surface water. Important limnologic parameters

determining the magnitude and persistence of fuel compounds discharged into water are the

mixing or dilution volume of surface water, wind velocity, water temperature, and rate of water

flowing through the mixing volume. The primary determinant of the mixing volume is the depth

of the epilimnion, or the relatively warm layer of water that sits atop the colder, denser waters of

the hypolimnion. Volatilization of fuel compounds increases as the wind velocity rises, thereby

decreasing the depth of the surface-boundary layer (which, in turn, increases the mass-transfer

velocity of dissolved fuel compounds). Water temperature influences the rates of volatilization

and biodegradation. The flow of water through the epilimnion is another mechanism for reducing

residual levels of dissolved fuel compounds.

During the summer boating season, the peak discharges of fuel compounds and their related

concentrations in water coincide with the holidays (namely, Memorial Day, Fourth of July, and

Labor Day), when boating activity increases (Reuter et al., 1998). Needless to say, it is not

possible to simulate the levels of fuel compounds in water at a given lake unless watercraft usage

is known along with fuel-discharge rates to water. However, as a screening-level analysis, we

have chosen to simulate a discrete period of watercraft discharges at Donner Lake in northern

California, using data presented in studies by McCord and Schladow (1998) and Reuter et al.

(1998).

The total mass and concentration of a fuel compound in the epilimnion after a continuous

watercraft discharge of a fixed duration can be estimated from

 

M T ,t E

k

1–e e s,ep d

r

tot

–k T –k t tot d tot ( ) = [ ] cf (5-7)

and

 

C

M Tt

V s ep

s ep d

ep ,

, , = ( ) , (5-8)
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where

Ms,ep(Td,t)= mass of substance (i.e., fuel compound, s) in the epilimnion (ep) at time t (days)

after a continuous discharge of duration Td (days), μg;

Cs,ep = concentration of the substance (i.e., fuel compound, s) in the epilimnion (ep),

μg/L;

Er = constant discharge rate of substance (i.e., fuel compound, s) from boating

activity, kg/d;

cf = conversion factor, 109 μg/kg;

ktot = first-order loss rate for volatilization and biodegradation, 1/d; and

Vep = volume of the epilimnion (ep), L

Reuter et al. (1998) reported that during a seven-day period lasting from July 1–7, 1997, the total

mass of MTBE in Donner Lake rose by 250 kg, resulting in an increase of 10 μg/L in the

epilimnion of the lake. The depth of the epilimnion by July was between 9 and 11 m, and the

average daily wind velocities from March to November 1997, ranged from 1.7 to 2.1 m/s. After

the last major boating activity associated with Labor Day, the mass of MTBE dropped at a rate of

8.1 kg/d, which, according to Reuter et al. (1998), reflects a half-life of 14 days (equivalent to a

first-order loss rate of 0.05/d). The MTBE loss rate was smaller after the July 7th peak (that is,

6.7 kg/day); however, inputs of MTBE from watercraft still occurred, so that this loss rate is not

an accurate indicator of volatilization losses.

We can estimate the average discharge of MTBE into the lake during this seven-day period

by solving for Er in Equation (5-7) and setting Mep(Ts,t) = 250 kg, ktot = 0.05/d, Ts = 7 days, and

t = 0 day. The resulting discharge rate is 42 kg/d. As an alternative, we also calculated the value

of kv (≅ ktot, because MTBE’s biodegradation is assumed to be negligible) for MTBE using the

mass-transfer velocities estimated from the physicochemical properties of MTBE, wind speed,

and mixing depth (as presented in the Appendix A). We used the temperature-dependent

equation for estimating HL given in Robbins et al. (1993) to estimate a value of 43 Pa-m3/mol

for MTBE at 20 ̊C. Loss-rate constants were computed for alternative values of the depth of the

epilimnion and wind velocities for the seven-day period in July and are shown in Table 5-2.

McCord and Schladow (1998) indicate that the average wind speed was approximately 3 m/s and

the surface area of the lake was 3.6 km2. While the depth of the epilimnion across the lake was

about 10 m, the effective transport depth for MTBE was probably smaller, based on the portions

of lake-surface area overlying regions with water depths under 10 m. Accordingly, we have

provided in Table 5-2 estimates of the loss-rate constants for varying depths of the epilimnion

and also two different wind speeds. We also show the corresponding mass loadings and

concentrations of MTBE in the epilimnion at the end of a seven-day period during which time

total MTBE discharged to the lake was considered to be at a constant rate of 40 kg/d from

watercraft.

The predicted concentrations decrease with increasing depth of the epilimnion because the

mixing volume increases, reducing the concentration of MTBE. The predicted mass loadings

increase due to the reduction in loss rates caused by smaller mass-transfer rates as the depth of
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-10

the epilimnion increases. The best agreement with the observed MTBE loadings and

concentrations is for an epilimnion layer of 7 m and a wind speed of 2 m/s. However, all of the

predicted values are in general agreement with the values reported by Reuter et al.

(1998)—given the uncertainties in both the measurements (for example, sampling biases) and the

mass-transfer models.

We used the MTBE-release case for Donner Lake as the basis for assessing the nature and

magnitude of surface-water quality impacts of ethanol discharged from watercraft. The reference

epilimnetic depth of the lake was set at 8 m and the wind speed is 3 m/s. We used the Henry’s

law constant given at 25 ̊C (see Table 5–1) to estimate volatilization losses (which are negligible

for ethanol). To bracket the range of potential biodegradation losses, we estimated

concentrations for biodegradation half-lives of 12, 24, and 48 h. In Figure 5-3, we show the

predicted concentrations of ethanol in the lake’s epilimnion after a continuous discharge of

40 kg/day of ethanol lasting seven days. With a nominal biodegradation half-life of 24 h, the

peak concentration is 2 μg/L, compared with 8.3 μg/L for MTBE with the same source term

(Table 5-2).

5.6. Summary

A quantitative risk assessment designed to compare the results of MTBE and ethanol releases

to surface waters was not performed and was not the objective of this chapter. Instead, we

performed a series of screening-level simulations of various releases to better understand the

nature and magnitude of the impacts of ethanol and MTBE on surface waters both temporally

and spatially. However, based on the health-protective concentrations for drinking water alone,

(which are summarized by the State of California Environmental Protection Agency, Office of

Environmental Health Hazard Assessment in Volume 5 of this report [CalEPA/OEHHA, 1999]),

it is clear that any catastrophic or even major release of MTBE to surface water is far more likely

to represent a potential public-health problem than a similar release of ethanol. This is because

the draft health-protective concentration for oral exposures to drinking water for ethanol is

1,100,000 μg/L, whereas the public-health goal for drinking water for MTBE is only 13 μg/L—a

difference of almost 5 orders of magnitude (that is, 105

 or 100,000). The problem of MTBE

release to surface water is further exacerbated because it appears to be recalcitrant to aerobic

biodegradation (Suflita and Mormile, 1993).

Our analyses indicate that ethanol is considerably less volatile than MTBE in surface waters

because of its low Henry’s law constant. Although its volatilization-loss rate from water will be

much less than that of MTBE, it will not persist in water because it undergoes fairly rapid

biodegradation.

The primary uncertainties associated with ethanol in surface water are associated with the

determination of biodegradation rates for specific surface waters, including lakes and streams, as

a function of water temperature, oxygen content, etc. Also, temperature-dependent values for the

Henry’s law constant would improve estimates of air/water partitioning for different ambient

conditions.

A key data gap involves the potential impact that rainout will have on surface waters situated

in urban areas where the ambient concentrations of ethanol are predicted to be the highest.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-11

Ethanol in urban runoff will undergo biodegradation in surface waters; however, there will be a

balance between the inputs from rainfall and losses due to degradation—with the sequencing

between storms an important variable in determining the average concentrations in surface-water

supplies.

5.7. References

Allen, P., R. Bradley, B.E. Croes, D. Luo, R. Vincent, and L. Woodhouse (1999a). Air Quality

Impacts of the Use of Ethanol in California Reformulated Gasoline (pdf online). California

Air Resources Board, Sacramento, CA. (Accessed: November 18, 1999). Available:

< http://www.arb.ca.gov/cbg/ethanol/ethfate/ethfate.htm >.

Allen, P., R. Bradley, B.E. Croes, D. Luo, R. Vincent, and L. Woodhouse (1999b). Appendix C:

Baseline and future air quality concentrations. In Air Quality Impacts of the Use of Ethanol

in California Reformulated Gasoline. California Air Resources Board, Sacramento, CA.

(Accessed: November 18, 1999). Available: <http://www.arb.ca.gov/cbg/ethanol/ethfate/

ethfate.htm >.

Alvarez, P.J.J., and C.S. Hunt (1999). The effect of ethanol on BTEX biodegradation and natural

attenuation. In: Health and Environmental Assessment of the Use of Ethanol as a Fuel

Oxygenate—Report to the California Environmental Policy Council in Response to Executive

Order D-5-99. Vol. 4, Potential Ground and Surface Water Impacts, D.W. Rice and

G. Cannon (Eds.), Lawrence Livermore National Laboratory, Livermore, CA,

UCRL-AR-135949 Vol. 4 Ch. 3.

Apoteker, A., and D.R. Thévenot (1983). Experimental simulation of biodegradation in rivers.

Water Res. 17: 1267-1274.

Boublík, T., V. Fried, and E. Hála (1984). Ethanol. In The Vapour Pressures of Pure Substances.

Selected Values of the Temperature Dependence of the Vapour Pressures of Some Pure

Substances in the Normal and Low Pressure Region. Elsevier Science Publishers, New

York, NY.

Budavari, S., M.J. O’Neil, A. Smith, and P.E. Heckelman (1989). The Merck Index: An

Encyclopedia of Chemicals, Drugs, and Biologicals. Merck and Co., Inc., Rhaway, NJ.

CalCVRWQCB (State of California Central Valley Regional Water Quality Control Board)

(1991). Final Water Sampling Report: Southern Pacific—Cantara Spill. State of California

Central Valley Regional Water Quality Control Board (Region 5), Staff Report, Sacramento,

CA.

CalEPA/OEHHA (State of California Environmental Protection Agency, Office of

Environmental Health Hazard Assessment) (1999). Volume 5. Potential Health Risks of

Ethanol in Gasoline. In: Health and Environmental Assessment of the Use of Ethanol as a

Fuel Oxygenate—Report to the California Environmental Policy Council in Response to

Executive Order D–5–99, D.W. Rice and G. Cannon (Eds.), Lawrence Livermore National

Laboratory, Livermore, CA, UCRL-AR-135949 Vol. 5.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-12

Hemond, H.F., and E. Fechner (1994). Chemical Fate and Transport in the Environment.

Academic Press, Inc., New York, NY.

Hine, J., and P.K. Mookerjee (1975). The intrinsic hydrophilic character of organic compounds,

correlations in terms of structural contributions. J. Org. Chem. 40: 292-298.

Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, and E.M. Michalendo (1991).

Handbook of Environmental Degradation Rates, H.T. Printup (Ed.) Lewis Publishers,

New York, NY.

Jobson, H.E. (1996). Prediction of Traveltime and Longitudinal Dispersion in Rivers and

Streams, United States Geological Survey, Denver, CO, Water Resources Investigation

Report No. 96-4013.

MacKay, D., W.-Y. Shiu, and K.-C. Ma (1993). Illustrated Handbook of Physical-Chemical

Properties and Environmental Fate for Organic Chemicals, Volume III. Volatile Organic

Chemicals . Lewis Publishers, Boca Raton, FL.

MacKay, D., W.-Y. Shiu, and K.-C. Ma (1995). Illustrated Handbook of Physical-Chemical

Properties and Environmental Fate for Organic Chemicals, Volume IV. Oxygen, Nitrogen,

and Sulfur Containing Compounds. Lewis Publishers, Boca Raton, FL.

Malcolm Pirnie, Inc. (1998a). Evaluation of the Fate and Transport of Ethanol in the

Environment. Report prepared for American Methanol Institute, Washington, DC. Malcolm

Pirnie, Inc., Oakland, CA, November. Report No. 3522-001.

Malcolm Pirnie, Inc. (1998b). Technical Memorandum: Modeling the Volatilization of Methyl

Tertiary-Butyl Ether (MTBE) from Surface Impoundments. Prepared for Oxygenated Fuels

Association, Inc., Arlington, VA. Malcolm Pirnie, Inc., Oakland, CA. Report No. 3195-001.

McCord, S.A., and S.G. Schladow (1998). Chapter 4. Transport and Fate Modeling of MTBE in

Lakes and Reservoirs. In Volume IV: Ground & Surface Water, prepared at Department of

Civil and Environmental Engineering, University of California, Davis, CA, and submitted as

part of the Health and Environmental Assessment of MTBE Report to the Governor and

Legislature of the State of California as Sponsored by SB 521, Delivered to the Governor’s

Office on November 12, 1998. Accessed: November 4, 1999. Available:

< http://www.tsrtp.ucdavis.edu/mtberpt/ >.

NSTC (National Science and Technology Council), Committee on Environment and Natural

Resources, Executive Office of the President of the United States (1997). Interagency

Assessment of Oxygenated Fuels. Global Change Research Information Office (GCRIO),

Palisades, NY.

Pankow, J.F., R.E. Rathbun, and J.S. Zogorski (1996). Calculated volatilization rates of fuel

oxygenate compounds and other gasoline-related compounds from rivers and streams.

Chemosphere 33: 921-937.

Reuter, J.E., B.C. Allen, R.C. Richards, J.F. Pankow, C.R. Goldman, R.L. Scholl, and

J.S. Seyfried (1998). Concentrations, sources, and fate of the gasoline oxygenate methyl tertbutyl ether (MTBE) in a multiple-use lake. Environ. Sci. Technol. 32: 3666-3672.

Riddick, J., W.B. Bunger, and T.K. Sakano (1986). Organic Solvents: Physical Properties and

Method of Purification . John Wiley & Sons, New York, NY.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-13

Robbins, G.A., S. Wang, and J.D. Stuart (1993). Using the static headspace method to determine

Henry’s law constants. Anal. Chem. 65: 3113-3118.

SRC (Syracuse Research Corporation), Environmental Science Center (1999). Interactive

LogKow (KowWin) Demo. Syracuse Research Corporation, Environmental Science Center,

Syracuse, NY. (Accessed: December 6, 1999). Available: <http://escplaza.syrres.com/interkow/kowdemo.htm > (CAS=1634044, LogKOW’s Log P Calculation

for Methyl t-butyl ether; and CAS=64175, LogKOW’s Log P Calculation for Ethanol). See

also Meylan, W.M., and P.H. Howard (1995). Atom/fragment contribution method for

estimating octonal-water partition coefficients. J. Pharm. Sci. 84: 83-92).

Stephenson, R.M. (1992). Mutual solubilities: Water–ketones, water–ethers, and

water–gasoline–alcohol. J. Chem. Eng. Data 37: 80–95.

Suflita, J.M., and M.R. Mormile (1993). Anaerobic biodegradation of known and potential

gasoline oxygenates in the terrestrial subsurface. Environ. Sci. Technol. 27: 976–978.

Thomann, R.V., and J.A. Mueller (1987). Toxic Substances. In Principles of Surface Water

Quality Modeling and Control. Harper & Row Publishers, New York, NY.

USGS (United States Geological Survey) (1999). USGS Water Resources Data—California,

Water Year 1994 for Sacramento River Basin (11342000 Sacramento River at Delta, CA).

United States Geological Survey, District Office, Sacramento, CA. (Accessed: December 13,

1999). Available: <http://ca.water.usgs.gov/data/94/sw/sw11342000.rd4.html >

(Updated: November 23, 1999).

Zogorski, J.S., A. Morduchowitz, A.L. Baehr, B.J. Bauman, D.L. Conrad, R.T. Drew,

N.E. Korte, W.W. Lapham, J.F. Pankow, and E.R. Washington (1997). Fuel oxygenates and

water quality, current understanding of sources, occurrences in natural waters, environmental

behavior, fate, and significance. In Interagency Assessment of Oxygenated Fuels. National

Science and Technology Council (NSTC) Committee on Environment and Natural

Resources, Office of Science and Technology Policy, Executive Office of the President of

the United States; Global Change Research Information Office (GCRIO), Palisades, NY.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-14
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UCRL-AR-135949 Vol. 4 Ch. 5

Figures
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11-99/Ethanol Ch. 5:rtd 5-16
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-17

Figure 5-1. Peak concentrations of ethanol in a channel of the Sacramento River above

Lake Shasta after a hypothetical tank-car release. Concentrations are based on an estimate

of the most likely river-flow velocity for peak concentration (see Appendix B) and a

biodegradation half-life of 24 h for ethanol (representing ktot in Equation [5-5]).
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-18

Figure 5-2. Peak concentrations of ethanol in a channel of the Sacramento River above

Lake Shasta after a hypothetical tank-car release. Concentrations are based on an estimate

of the maximum probable river-flow velocity for peak concentration (see Appendix B) and a

biodegradation half-life of 24 h for ethanol (representing ktot in Equation [5-5]).
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-19

0

1

2

3

4

5

12 24 48

Concentration, 

μg/L

Half-life, hours

Figure 5-3. Predicted peak concentrations of ethanol in epilimnion waters of Donner Lake

after a seven-day period based on alternative biodegradation half-lives and a constant

discharge of 40 kg/d from watercraft. Effective depth of the epilimnion for mass transport is

8 m, and the wind velocity is 3 m/s.
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UCRL-AR-135949 Vol. 4 Ch. 5

Tables
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Table 5-1. Physicochemical properties for MTBE and ethanol.

Chemical

Property MTBE Ethanol

Molecular weight (g/mol) 88.15 46.07

Density as liquid (g/mL) at 20°C 0.740a 0.789b

Kow(dimensionless) 8.71c 0.50c

Vapor pressure (Pa) at 25°C 32,664d 7869e

Solubility (mol/m3) 476 (at ≅ 20 ̊C)f Miscible in waterg

Henry’s law (Pa-m3/mol) at 25°C 53.5h 0.64i

Henry’s law (dimensionless = H/RT) 0.0216 0.00026

a Reported by MacKay et al. (1993) and based on three cited, closely agreeing recent values.

b Reported by MacKay et al. (1995) and based on four cited, closely agreeing recent values.

c Reported by Syracuse Research Corporation (SRC) (1999 WebSite) and based on one cited, recent value, for each

substance.

d Reported by Budavari et al. (1989).

e Reported by Boublík et al. (1984) and based on one cited value.

f Measured value reported by Stephenson (1992).

g Reported by Riddick et al. (1986).

h Reported by Robbins et al. (1993) as a measured value obtained using static headspace method.

i Reported by Hine and Mookerjee (1975) and based on two cited sources.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd 5-24

Table 5-2. Comparison of the predicted mass loadings, peak concentrations, and loss-rate

constants for a MTBE release into Donner Lakea.

Depth of

epilimnion

Wind

velocity

Loss-rate

constant

MTBE mass

in epilimnion

MTBE-peak

concentrationb

hep, m ua, m/s kv, 1/d Ms,ep, kg Cs,ep, μg/L

7 2 0.041 244 9.7

7 3 0.054 233 9.2

8 2 0.036 248 8.6

8 3 0.048 238 8.3

9 2 0.032 251 7.7

9 3 0.043 242 7.5

10 2 0.029 253 7.0

10 3 0.039 245 6.8

a Release rate from watercraft is 40 kg/day for seven days.

b The dilution volume is calculated as the product of the depth of the epilimnion and the estimated surface area of

the lake (that is, 3.6 × 106 m2, from McCord and Schladow [1998]). Mass loadings and peak concentrations are for

the end of the seven-day period and are calculated from Equations (5-7) and (5-8), respectively.
11-99/Ethanol Ch. 5:rtd A-i

UCRL-AR-135949 Vol. 4 Ch. 5

Appendix A

Estimation of Mass-transfer Parameters
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Appendix A

Estimation of Mass-transfer Parameters

The key parameter in determining the rate constant for volatilization is the mass-transfer

velocity, or the rate with which a compound moves from water to air as a function of its

physicochemical properties and environmental conditions, such as the water velocity of a stream,

water temperature, and wind velocity. The mass-transfer velocity is estimated using a two-layer

transfer model in which there are two thin, stagnant films at the air-water exchange

boundary—one is a water film and the other a gas film (see Liss and Slater, 1974;

Schwarzenbach et al., 1993). Contaminant movement in these layers is via diffusion, whereas

turbulent flow in air and water adjacent to these regions is the dominant method of contaminant

transport and mixing. The total transport velocity across these layers is calculated as the

reciprocal of the sum of the resistances to transport in the water and air phases, or

 

υtot w a = + [ ] r r

–1, (A–1)

where the water and air-phase resistances are computed from

 

rw

w

= 1

υ

(A–2)

 

r

H a

a L

= 1

υ

(A–3)

and the transfer velocities for water and air are estimated from

 

υ φ w O

w

riv

D u

h2 = 



 



 ( )

0 5

20 1 0241

.

– . t (for rivers, from Pankow et al., 1996), (A–4)

 

υ φ w a

2 = × +× ( ) u cf × − − 4 10 4 10 4 5 (for lakes, from Schwarzenbach et al., 1993), (A–5)

 

υ α a a = + ( ) 02 03 . . u cf × (from Schwarzenbach et al., 1993), (A–6)

given

υtot = total mass-transfer velocity through the air and water layers, m/d;

rw = resistance to mass transport in air, d/m;

ra = resistance to mass transport in water, d/m;

υa = air-side mass-transfer velocity, m/d;
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd A-2

HL = dimensionless Henry’s law constant;

υw = water-side mass-transfer velocity, m/d;

 

DO2 = diffusivity of oxygen in water, 1.8 × 10-4 in m2/d at 20 oC;

uw = water-current velocity in river or stream, m/d;

φ = compound-specific adjustment factor for the water-side transfer velocity (unitless);

ua = wind velocity at a height of 10 m, m/s;

hriv = depth of river or stream (or hep for depth of epilimnion of lake), m;

t = temperature of water, oC;

cf = conversion factor of 864 m/d per cm/s;

and

α = compound-specific adjustment factor for the air-side transfer velocity (unitless).

The rate constant for volatilization (kv) from a river or stream is equal to υtot/hriv (from

Pankow et al., 1996), while for lakes it is equal to υtot/hep, where hep is the depth of the lake’s

epilimnion (Ulrich et al., 1994). The values of φ and α for ethanol and MTBE given in Pankow

et al. (1996) are 0.738 and 0.753, and 0.586 and 0.558, respectively.

The relative importance of the air- and water-side boundary layers in controlling mass

transport can be evaluated by comparing the air and water resistances. According to

Schwarzenbach et al., (1993), values of ra/rw > 10 indicate that mass transfer is controlled by the

air film, whereas values below 0.1 indicate that mass transfer is controlled by the water film.

Values of ra/rw between 0.1 and 10 demarcate a region where both boundary layers influence

mass transport. For ethanol, both layers are important, although the air-side resistance is greater

than the water-side resistance. The mass transfer for MTBE, in contrast, is controlled primarily

by the water-side boundary layer.

References

Liss, P.S., and P.G. Slater (1974). Flux of gases across the air-sea interface. Nature 247:

181-184.

Pankow, J.F., R.E. Rathbun, and J.S. Zogorski (1996). Calculated volatilization rates of fuel

oxygenate compounds and other gasoline-related compounds from rivers and streams.

Chemosphere 33: 921-937.

Schwarzenbach, R.P., P.M. Gschwend, and D.M. Imboden (1993). The gas-liquid interface: Airwater exchange. In Environmental Organic Chemistry. John Wiley & Sons, Inc., New York,

NY, pp. 215-255.

Ulrich, M.M., S.R. Müller, H.P. Singer, D.M. Imboden, and R.P. Schwarzenbach (1994). Input

and dynamic behavior of the organic pollutants tetrachloroethene, atrazine, and NTA in a

lake: A study combining mathematical modeling and field measurements. Environ. Sci.

Technol. 28: 1674-1685.
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UCRL-AR-135949 Vol. 4 Ch. 5

Appendix B

Transport Parameters for Riverine Releases
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Appendix B

 Transport Parameters for Riverine Releases

A spill of a soluble substance into a river creates a dispersing plume that gradually spreads

out in a longitudinal direction as a function of time. Dispersion occurs as the plume moves in a

meandering stream channel, encountering various forms of current-induced turbulence. For a

conservative contaminant, the mass within the plume remains constant with time, and as the

plume spreads out along the direction of transport, the peak concentration decreases with time.

Consequently, to estimate the amount of dispersion that has occurred during transport, estimates

of the plume’s travel time are needed. Travel time is estimated by determining the distance

traveled from the release point to the measurement (or receptor) location and the velocity of the

peak concentration within the plume.

Jobson (1996) developed a series of empirical formulas for estimating the average velocity of

the plume’s peak concentration and its maximum probable velocity. Using tracer data from a

number of watersheds, the plume velocities are computed from

 

V D Q R Q

D pc area

0.919

adj

–0.469

slp

0.159

area

= + 0 094 0 014 . . (B-1)

 

V D Q R Q

D mpc area

0.919

adj

–0.469

slp

0.158

area

= + 0 25 0 02 . . (B-2)

where

 

D W

Q area area

ave

= 1 25 . g , (B-3)

 

Q Q

Q adj

ave

= , (B-4)

and

Vpc = velocity of the peak concentration in a dispersing plume, m/s;

Vmpc = maximum probable velocity of the peak concentration in a dispersing plume, m/s;

Warea = watershed-drainage area, m2;

g = acceleration due to gravity, 9.8 m/s2;
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impacts December 1999

11-99/Ethanol Ch. 5:rtd B-2

Qave = annual-average volumetric-discharge rate of the river at receptor location, m3/s;

Q = volumetric-discharge rate of the river at the time of the release, m3/s;

Rslp = slope of the river channel, m/m;

Darea = dimensionless drainage area; and

Qadj = dimensionless relative discharge.

The dissipation rate constant for the peak concentration in a plume is estimated from

 

k 857T pc pc

0.760 Q

Q

0.079

ave = − 



 





−

(B-5)

where Tpc (in hours) is the arrival time of the peak-concentration (pc) at a receptor location

downstream from the release point, which is equal to the downstream distance from the source to

receptor divided by the peak-concentration (pc) velocity or maximum probable peakconcentration (mpc) velocity (that is, Vpc or Vmpc).

References

Jobson, H.E. (1996). Prediction of Traveltime and Longitudinal Dispersion in Rivers and

Streams, US Geological Survey, Denver, CO, Water Resources Investigation Report

No. 96-4013.
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UCRL-AR-135949 Vol. 4 Ch. 5

Appendix C

Changes in MTBW and BTEX

Concentrations in Lake Tahoe, CA-NV,

Following Implementation of a Ban on

Selected Two-stroke Marine Engines
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Appendix C

Changes in MTBE and BTEX Concentrations in

Lake Tahoe, CA-NV, Following Implementation

 of a Ban on Selected Two-stroke Marine Engines

Brant C. Allen

John E. Reuter

Tahoe Research Group

University of California, Davis

Davis, CA 95616

ABSTRACT

Effective June 1, 1999, the Tahoe Regional Planning Agency imposed a ban on certain types

of two-stroke marine-engine technologies. Previous studies had shown that these types of twostroke carbureted engines accounted for only 11–12% of the total fuel used by watercraft on

Lake Tahoe, but they were responsible for approximately 90% of the methyl tertiary butyl ether

(MTBE) emissions to the lake. In 1999, Lake Tahoe was monitored in late August and over the

Labor Day weekend when peak boating activity traditionally occurs. The purpose of the

monitoring was to determine if concentrations of MTBE and gasoline constituents (benzene,

toulene, ethyl benzene, and xylene[BTEX]) were affected by implementation of the new marineengine policy. Samples were taken on three dates: (1) mid-week, (2) after a weekend, and (3)

after Labor Day. They were taken from mid-lake (open-water locations), at ten stations located

around the perimeter of the lake, and at ten “hot spots” along the south shore where boating and

boating-related activities are high. The 1999 results showed a significant decline in both MTBE

and BTEX compounds when compared to 1997–1998 levels. Many of the 1999 concentrations

of MTBE were below the 0.06-μg/L limit of analytical detection, in contrast to previous

monitoring that had many fewer samples this low. High levels of MTBE were still found at

certain “hot spots,” but these levels were attributed to isolated boating actions not related to

overall boating intensity. Combined, the data strongly suggest that the ban on certain types of

two-stroke carbureted engines at Lake Tahoe has been very successful in reducing concentrations

of both MTBE and BTEX.

INTRODUCTION

Discovery of the fuel oxygenate, methyl tertiary butyl ether (MTBE), in groundwater, lakes,

and reservoirs used for drinking water raised considerable concern among health officials and

water suppliers. The U.S. Environmental Protection Agency (US EPA) has classified MTBE as a

possible human carcinogen. Recent California legislation has established primary and secondary
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11-99/Ethanol Ch. 5 C-2

drinking-water standards at 13 μg/L and 5 μg/L, respectively. In March 1999, the Governor of

California called for a statewide phaseout of MTBE as a fuel additive to be completed by the end

of 2002.

Since 1997, the Lake Tahoe basin has received considerable state and national attention with

regards to MTBE contamination of both groundwater drinking supplies and the lake itself.

Contamination of groundwater wells serving the City of South Lake Tahoe is considered to pose

more of a potential threat to public health than MTBE concentrations that have been found in the

waters of Lake Tahoe. However, because Lake Tahoe has been designated as an Outstanding

National Water Resource (ONWR) under the federal Clean Water Act, protection of the lake

from controllable sources of pollution is paramount. Samples collected by the Tahoe Research

Group (TRG) at the University of California at Davis, the University of Nevada at Reno (UNR),

and the U.S. Geological Survey (USGS) during the summers of 1997 and 1998 showed

detectable levels of MTBE and the fuel constituents (benzene, toluene, ethyl benzene, and

xylenes [BTEX]) lake-wide (Allen et al., 1998). Concentrations were shown to vary with the

level of motorized watercraft traffic. However, at specific locations, levels exceeded not only the

California drinking-water standards but also the higher US EPA advisory value of 35 μg/L.

Samples from open water in the middle of the lake, where little summer boating occurs, revealed

the presence of fuel constituents to a depth of 10 m, but at concentrations near or below the

analytical levels of detection (mean value for MTBE and BTEX of 0.3 μg/L) (Allen et al., 1998).

Along the shoreline of the lake where motorized watercraft activity is more common, fuelconstituent concentrations were found to be about an order of magnitude higher (for example,

2.6-μg/L mean value for MTBE). However, these shoreline concentrations were still below the

established drinking-water standards. In areas where motorized watercraft traffic is considered to

be exceptionally high (such as marinas and fueling facilities), mean concentrations for both

MTBE and benzene during certain times of the summer boating season exceeded primary

drinking-water standards. Further investigation by the California Air Resources Board (CARB)

and UNR into the direct contribution of fuel constituents from various engine technologies

revealed that carbureted two-stroke engines were contributing a disproportionate share of the

fuel-component load to Lake Tahoe (Miller, no date). In fact, Allen et al. (1998) calculated that

while using only 11 to 12% of the total fuel used for Lake Tahoe boating, these engines

contributed 90% of the MTBE to the water. In contrast, four-stroke engines consumed 87% of

the fuel but were responsible for only 8% of the estimated MTBE loading to the lake from all

marine engines.

Based on the results of these cumulative studies, the Tahoe Regional Planning Agency

(TRPA) banned certain types of two-stroke marine-engine technologies (that is, carbureted twostroke engines). This ban took effect on June 1, 1999. The City of South Lake Tahoe took

additional steps to rid the Tahoe basin of MTBE by selling MBTE-free gasoline. Under pressure

from the Governor of California, several large oil companies had begun producing gasoline

without MTBE and delivering it to the south end of the lake. While this program was intended to

reduce the risk of further contamination of groundwater aquifers, it may also have had an effect

on concentration of MTBE in the lake. Because fuel costs at marine facilities are significantly

higher than at roadside gas stations, conceivably many boaters would choose to refuel while their

vessel was still on the trailer.
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With both programs to abate MTBE loading to the lake and groundwater in place by late

spring 1999, the summer boating season was expected to produce lower levels of in-lake fuel

constituents. We began sampling in August to evaluate the effectiveness of these changes; that

is, we compared lake concentrations of MTBE and BTEX in the summer of 1999 to those in the

summers of 1997 and 1998.

METHODS

We focused our sampling on locations which had had positive results (that is, those sites

where these constituents had been found during the 1997 and 1998 monitoring). We selected

sampling locations in Lake Tahoe that would best reflect any changes in MTBE and BTEX

concentrations that may have resulted from policy decisions within the basin. Therefore, we

separated site selections into three categories: 1) open-water, offshore areas above a depth of

10 m, 2) near shore, at locations around the perimeter of the lake, where the majority of boat

traffic transits the lake, and 3) locations where boat traffic is concentrated (“hot spots”), often

associated with launch ramps, refueling facilities, marinas, or a combination of the above

(Figure C-1). Within each category, we chose specific sites, whenever possible, to replicate those

sampled in previous years.

The timing of our sampling, in late August and after the Labor Day weekend in September,

coincided with the peak of the summer boating season. To avoid potential biases resulting from

increased boating on weekends and holidays, we chose three sampling dates. For mid-week

days, we chose Wednesday, August 25, and Thursday, August 26, 1999. For weekends, we

collected samples from the following Monday (August 30); and for the Labor Day weekend we

took samples on the Tuesday after the holiday (September 7).

At all locations, with the exception of mid-lake, water samples were taken by hand at a depth

of 0.5 m. (Our previous sampling at Lake Tahoe showed this to be a representative depth for the

near-shore stations.) At each location, we submerged a closed volatile organic analysis (VOA)

vial to the sampling depth and then opened it and allowed it to fill completely. We replaced the

cap while the vial was still submerged. We checked the samples to ensure no air space remained

within the VOA vials before placing them on ice in a cooler. The mid-lake samples were

collected using a 1.2-L, stainless-steel Kemmerer well sampler with Teflon end-caps. The

sampler was lowered to depth and closed with a messenger. We then transferred the water to a

VOA vial and filled it until no air spaces remained. All samples were kept on ice from collection

through transport to Lawrence Livermore National Laboratories (LLNL) in Livermore, CA. All

analytical determinations were made by LLNL staff at their facilities (Koester, 1999). Analyses

were performed using a gas chromatograph/mass spectrometer (GC/MS) operated in the

selected-ion monitoring mode and in accordance with US EPA Method 8260. An internal

standard of deuterated-MTBE was used to quantify MTBE and also to monitor instrument

performance. The limit of quantification obtained by this procedure for MTBE is 0.06 parts per

billion (ppb).

RESULTS

The raw data, as supplied by the LLNL laboratory, are presented in Table C-3. Open lake and

near-shore samples showed a significant decrease in MTBE concentration when compared to

data collected in 1997 and 1998 (Table C-1). In general, ambient concentrations decreased by an
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order of magnitude (a factor of ten). Samples around the north end of the lake (Glenbrook to

Homewood) were at or below the 0.06-μg/L level of detection. The samples we collected in the

vicinity of the south end of the lake (Zephyr Cove to Emerald Bay) showed a similar drop in

concentration from previous years but remained above the level of detection at a few tenths of a

part per billion (μg/L).

Ambient concentrations of the BTEX compounds at the near-shore locations were also found

to be lower than levels recorded during the past two years of monitoring (Table C-2). However,

we were unable to determine changes in ambient concentrations when data from all three years

(1997, 1998, and 1999) were below the analytical level of detection, as was the case for BTEX at

all samples taken from open water and at the near-shore sites of Glenbrook and Homewood.

To further characterize fuel-constituent concentrations, we collected samples from isolated

areas where motorized watercraft traffic is heavy and above the levels observed at the shoreline

locations. These “hot spots” are typically associated with marinas, launch ramps, and refueling

facilities. While all ten of the selected sites had greater mean fuel-constituent concentrations than

the open-shoreline and open-water areas, only four locations approached or exceeded drinkingwater standards. The remaining six “hot spots” had fuel-constituent concentrations similar to

near-shore areas sampled during the 1997 and 1998 monitoring. At the four “hot spots” where

fuel-constituent concentrations neared or exceeded drinking-water standards, MTBE and BTEX

concentrations were highly variable. MTBE concentrations ranged from 0.46 μg/L up to

56.5 μg/L. This highend value is over four times the primary drinking-water standard of

13 μg/L. There was no statistically significant difference in concentration for MTBE or any of

the BTEX compounds between any of the three years of data at the “hot-spot” locations

(Tables C-1, C-2a, and C-2b). The dramatic difference in results between these “hot spots” and

the remainder of the lake suggests that source contamination has not been completely eliminated

by the regulatory actions taken to date, but that contaminants entering the lake were significantly

reduced in the summer of 1999.

DISCUSSION

The sampling dates selected during this study were at the end of the summer boating season

during August and after the Labor Day weekend in September. Fuel-constituent concentrations

in surface waters can peak following the Fourth of July weekend with changes in concentration

being attributed to the dramatic increase in recreational boating (Reuter et al., 1998). However,

for a sampling program which more accurately characterizes the summer fuel-constituent load to

a waterbody, rather than a worst-case, single-day event, the month of August has proven to be

appropriate. Allen et al. (1998) showed that mean concentrations of MTBE and BTEX

compounds were the highest at Lake Tahoe during August.

With the exception of a few of the “hot spots,” the data we collected during this study

showed little variation between sampling dates. Both the open-water (mid-lake) and near-shore

samples (with the exception of the Edgewood site) remained within a few hundredths of a μg/L

at each site over the course of the three days, allowing us to pool the data for comparisons to the

monitoring data collected in previous years.

The “hot spots” around the south end of the lake showed greater variation over the three

sampling dates. However, concentrations at individual sites did not change consistently between

the three sampling dates. Half of the sites recorded their highest concentrations during the mid-
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week sampling, which was expected to represent the lowest concentrations due to suspected

lower boat traffic. The remainder of the sites recorded their highest values following the Labor

Day weekend, which is to be expected due to higher boating activity. The lowest values at each

of the “hot spots” occurred on the sampling date following the regular summer weekend. It is

assumed that this was a result of a high-wind event on both Sunday and Monday, keeping many

boaters on shore and possibly allowing increased volatilization rates of fuel constituents from the

water. We also suspect that at the “hot spots,” variation in MTBE concentration within a given

day was high. For example, if there had been a minor spillage during fueling, or if a boat’s bilge

water had drained while it was being removed from the lake, concentrations would be expected

to be temporarily higher in the vicinity of these activities. It was beyond the scope of this study

to determine if the higher concentrations persisted throughout the day or if they were simply

associated with a single action as described above.

Comparisons of data collected during this study with that of previous years shows a dramatic

decrease in MTBE concentration at both offshore and near-shore locations (86.7% and 95.8%,

respectively). This demonstrates that programs to eliminate MTBE from Lake Tahoe are having

an effect. The offshore and most of the near-shore locations around the lake had MTBE

concentrations at or near the analytical limit of detection (LOD) throughout the sampling period.

In fact, if we had used the LOD of 0.1 μg/L from the 1997 and 1998 monitoring, instead of the

very low LOD of 0.06 μg/L, samples from all but Emerald Bay, Kiva Beach, and Edgewood

would have been below detection. These remaining three locations also had dramatic decreases

in 1999, but the level of motorized watercraft traffic in these areas is greater than in other

portions of the lake (Nevada Division of Wildlife, 1988) resulting in higher fuel-constituent

concentrations. It is important to recognize that none of the recorded concentrations around the

near-shore or offshore during 1999 ever approached California or Nevada drinking-water

standards.

The sampling of “hot spots” around the south end of Lake Tahoe resulted in highly variable

results (that is, an MTBE range <0.06 to 56.5 μg/L). MTBE samples collected at Ski Run Marina

exceeded the California primary drinking-water standard of 13 μg/L by four-fold on two separate

sampling dates. Additionally, the California drinking-water standard for benzene (0.1 μg/L) was

surpassed on the post-Labor Day sampling (September 1999). These samples stand out from the

rest as being extremely high even for the “hot spot” locations. The reasons may be due to aboveaverage concentration of boats per unit-area or some problem with operations at the facilities.

The two other locations where measured concentrations of MTBE approached or exceeded

California drinking-water standards were associated with boat-launch ramps. However, because

neither boat-ramp location is in the immediate proximity of fueling facilities, the fuel

constituents may have come from the boats themselves.

While it is unclear how the fuel entered the water, any number of human errors and boat

malfunctions could have contributed. One distinct possibility associated with launch ramps is

the draining of the bilge while removing the boat from the water. Either the intentional removal

of boat plugs to allow draining while the boat was on the incline ramp or the automatic operation

of electrical bilge pumps when water rushed to the back of the boat causes fuel-laden water to

flow directly into the lake in the vicinity of the ramp.
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CONCLUSION

Overall, fuel-constituent concentrations in Lake Tahoe in 1999 were down dramatically from

previous monitoring years (1997 and 1998), possibly as a result of the TRPA regulation that

banned certain types of two-cycle marine-engine technologies, or as a byproduct of some service

stations within the Tahoe basin selling MTBE-free fuel.

We compared the decreases in ambient MTBE and toluene concentrations to determine

which of the corrective actions was having the greatest impact on Tahoe water quality. If the

MTBE-free fuel was having the greatest impact, we expected the ambient MTBE concentrations

to decrease while toluene concentrations in the lake would remain near the levels recorded in

1997 and 1998. If the new boating regulations were having the greatest impact, we expected both

MTBE and toluene concentrations to drop. Indeed, both mean MTBE and mean toluene

concentrations did drop significantly (95.8% and 88.3%, respectively), indicating that the

elimination of the highly polluting, carbureted two-stoke engines is having an impact on water

quality.

REFERENCES

Allen, B.C., J.E. Reuter, C.R. Goldman, M.F. Fiore and G.C. Miller (1998). Lake Tahoe

Motorized Watercraft: An Integration of Water Quality, Watercraft Use and Ecotoxicology

Issues. John Muir Institute for the Environment, University of California, Davis.

Contribution # 001-1998.

Koester, C. (1999). Lawrence Livermore National Laboratory, Livermore, CA. Personal

communication.

Miller, G. (no date). University of Nevada, Reno, unpublished data.

Nevada Division of Wildlife (1988).

Reuter, J.E., B.C. Allen, R.C. Richards, J.F. Pankow, C.R. Goldman, R.L. Scholl and J.S.

Seyfried. (1998). Concentrations, sources, and fate of the gasoline oxygenate methyl

tert-butyl ether (MTBE) in a multiple-use lake. Environ. Sci. Technol. 32: 3666–3672.
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impact December 1999

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Sampling sites

NORTH

Stateline

Kiva Tahoe Keys Picnic Area

Emerald 

Bay

Homewood

Tahoe City

Tahoe Vista

Sand 

Harbor

Cave Rock 

Landing

Zephyr Cove

Lake 

Forest

Mid-LakeCALIFORNIA

NEVADA

Lake Tahoe

Figure 5-1. 1999 sampling locations at Lake Tahoe.
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Table C-1. Comparative Lake Tahoe MTBE concentrations, 1997, 1998, 1999a.

MTBE Concentration (μg/L)

Site 1997b 1998c 1999d

Mid-lake 0.54 0.28 0.04

Incline Village 0.45 0.84 0.05

Kings Beach 1.7 0.08

Tahoe City 2.85 1.1 0.04

Homewood 0.45 0.78 0.06

Emerald Bay 4 0.33

Kiva Beach 1.8 0.1

Edgewood 2.4 0.2

Zephyr Cove 1 1.3 0.08

Glenbrook 0.3 0.47 0.03

Sand Harbor 0.06

Cave Rock 0.18

Zephyr Pier 0.15

Ski Run Inside 26.96

Ski Run Outside 20.8 19.77

El Dorado Ramp 2.68

Tahoe Keys Ramp 7.06

Tahoe Keys Channel 0.68 2 1.8

Camp Rich Pier 1.79 0.16

Camp Rich Pumps 0.11

Ski Boat Beach 0.1

a When more than one data point exists at a single site within a given year, a mean value is presented

(<0.1 = 0.05 for calculation of mean).

b 1997 data was collected by the University of Nevada at Reno (UNR), and the United States Geological

Survey (USGS) during July, August, and September.

c 1998 data was collected by USGS and Tahoe Research Group (TRG) in August and September.

d 1999 data was collected by TRG during August and September.
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Table C-2a. Comparative fuel-constituent data (BTEX), 1997, 1998, and 1999a.

Benzene concentration,

(μg/L)

Toluene concentration

 (μg/L)

Site 1997b 1998c 1999d 1997b 1998c 1999d

Mid-Lake 0.03 0.05 0.05 0.05 0.06 0.04

Incline Village 0.05 0.17 0.16 0.13 1 0.14

Kings Beach 0.13 0.1 0.68 0.18

Tahoe City 0.24 0.28 0.05 1.24 0.64 0.14

Homewood 0.05 0.05 0.05 0.15 0.27 0.06

Emerald Bay 0.44 0.18 1.5 0.24

Kiva Beach 0.17 0.07 0.78 0.16

Edgewood 0.21 0.07 1 0.17

Zephyr Cove 0.15 0.61 0.07 0.7 4.4 0.12

Glenbrook 0.04 0.05 0.05 0.1 0.27 0.08

Sand Harbor 0.05 0.11

Cave Rock 0.12 0.32

Zephyr Pier 0.13 0.14

Ski Run Inside 0.14 0.22

Ski Run Outside 0.88 0.43 7.3 1.75

El Dorado Ramp 0.45 0.92

Tahoe Keys Ramp 0.15 0.28

Tahoe Keys Channel 0.07 0.18 0.31 0.26 0.91 1.53

Camp Rich Pier 0.29 0.17 1.53 0.5

Camp Rich Pumps 0.14 0.38

Ski Boat Beach 0.12 0.33

a When more than one data point exists at a single site within a given year, a mean value is presented

(<0.1 = 0.05 for calculation of mean).

b 1997 data was collected by the University of Nevada at Reno (UNR), and the United States Geological

Survey (USGS) during July, August, and September.

c 1998 data was collected by USGS and Tahoe Research Group (TRG) in August and September.

d 1999 data was collected by TRG during August and September.
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Table C-2b. Comparative fuel-constituent data (BTEX), 1997, 1998, and 1999.

Ethylbenzene

(μg/L)

m,p, and o Xylene expressed as

total xylene

(μg/L)

Site 1997b 1998 c 1999d 1997b 1998 c 1999d

Mid-lake 0.02 0.04 0.04 0.04 0.05 0.09

Incline Village 0.02 0.24 0.04 0.1 1.4 0.14

Kings Beach 0.12 0.04 0.72 0.16

Tahoe City 0.24 0.11 0.04 1.39 0.58 0.12

Homewood 0.02 0.04 0.04 0.1 0.26 0.09

Emerald Bay 0.2 0.04 2.1 0.34

Kiva Beach 0.12 0.04 0.81 0.16

Edgewood 0.18 0.04 1.3 0.11

Zephyr Cove 0.12 1.1 0.04 0.75 6.7 0.14

Glenbrook 0.01 0.06 0.04 0.06 0.36 0.13

Sand Harbor 0.04 0.14

Cave Rock 0.09 0.47

Zephyr Pier 0.14 0.83

Ski Run Inside 0.04 0.55

Ski Run Outside 1.1 0.3 6.3 2.34

El Dorado Ramp 1.1 1.29

Tahoe Keys Ramp 0.08 0.47

Tahoe Keys Channel 0.04 0.17 0.12 0.3 1 0.95

Camp Rich Pier 0.4 0.12 1.45 0.84

Camp Rich Pumps 0.19 0.46

Ski Boat Beach 0.08 0.53

a When more than one data point exists at a single site within a given year, a mean value is presented

(<0.1 = 0.05 for calculation of mean).

b 1997 data was collected by the University of Nevada at Reno (UNR), and the United States Geological

Survey (USGS) during July, August, and September.

c 1998 data was collected by USGS and Tahoe Research Group (TRG) in August and September.

d 1999 data was collected by TRG during August and September.
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Table C-3. Fuel-constituent concentrations in Lake Tahoe 1999.

MTBE

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.06 <.06 <.06 Cave Rock 0.08 <.06 0.42

3m <.06 <.06 <.06 Zepher Pier 0.09 0.06 0.31

10m 0.08 <.06 <.06 Ski Run In 1.39 23 56.5

Ski Run Out 55.6 1.58 2.14

El Dorado Ramp 4.92 0.46 2.66

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp 7.28 6.93 6.98

Incline Village 0.07 <.06 Tahoe Keys Channel 2.14 0.53 2.72

Kings Beach 0.08 0.07 Camp Rich Pier 0.19 0.08 0.2

Tahoe City 0.07 <.06 <.06 Camp Rich Pumps 0.19 <.06 0.1

Homewood 0.06 0.09 <.06 Ski Boat Beach 0.11 <.06 0.16

Emerald Bay 0.35 0.36 0.29

Kiva Beach 0.14 <.06 0.13 Blanks 8/25/99 8/30/99 9/7/99

Edgewood 0.14 0.35 0.11 Field <.06 <.06

Zephyr Cove 0.09 0.06 0.08 mid-lake <.06

Glenbrook <.06 <.06

Sand Harbor 0.08 <.06

BENZENE

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <0.1 <0.1 <0.1 Cave Rock <.1 <.1 0.26

3m <0.1 <0.1 <0.1 Zepher Pier <.1 <.1 0.28

10m <0.1 <0.1 <0.1 Ski Run In <.1 <.1 0.33

Ski Run Out <.1 <.1 1.18

El Dorado Ramp 0.79 <.1 0.51

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.1 <.1 0.36

Incline Village 0.27 <.1 Tahoe Keys Channel <.1 <.1 0.84

Kings Beach 0.15 <.1 Camp Rich Pier 0.11 <.1 0.34

Tahoe City <.1 <.1 <.1 Camp Rich Pumps 0.26 <.1 0.11

Homewood <.1 <.1 Ski Boat Beach <.1 <.1 0.26

Emerald Bay 0.1 0.19 0.24

Kiva Beach <.1 <.1 0.12 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.1 <.1 0.12 Field <0.1 <0.1

Zephyr Cove 0.1 <.1 <.1 mid-lake 0.12

Glenbrook <.1 <.1

Sand Harbor <.1 <.1
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TOLUENE

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.09 <.09 <.09 Cave Rock 0.13 <.09 0.77

3m <.09 <.09 <.09 Zepher Pier <.09 <.09 0.34

10m <.09 <.09 <.09 Ski Run In <.09 <.09

Ski Run Out <.09 <.09 5.17

El Dorado Ramp 0.24 <.09 2.47

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.09 <.09 0.76

Incline Village 0.11 0.18 Tahoe Keys Channel <.09 <.09 4.5

Kings Beach <.09 0.32 Camp Rich Pier <.09 <.09 1.42

Tahoe City 0.18 <.09 0.2 Camp Rich Pumps 0.6 0.15 0.4

Homewood <.09 <.09 0.1 Ski Boat Beach <.09 <.09 0.89

Emerald Bay <.09 0.11 0.57

Kiva Beach <.09 <.09 0.4 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.09 <.09 0.43 Field 0.18 <.09

Zephyr Cove <.09 <.09 0.26 mid-lake 0.27

Glenbrook <.09 0.11

Sand Harbor <.09 0.18

ETHYLBENZENE

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.09 <.09 <.09 Cave Rock <.09 <.09 0.17

3m <.09 <.09 <.09 Zepher Pier <.09 <.09 0.34

10m <.09 <.09 <.09 Ski Run In <.09 <.09 <.09

Ski Run Out <.09 <.09 0.82

El Dorado Ramp 2.77 <.09 0.48

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.09 <.09 0.14

Incline Village <.09 <.09 Tahoe Keys Channel <.09 <.09 0.27

Kings Beach <.09 <.09 Camp Rich Pier <.09 <.09 0.27

Tahoe City <.09 <.09 <.09 Camp Rich Pumps 0.47 <.09 <.09

Homewood <.09 <.09 <.09 Ski Boat Beach <.09 <.09 0.15

Emerald Bay <.09 <.09 <.09

Kiva Beach <.09 <.09 <.09 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.09 <.09 <.09 Field <.09 <.09

Zephyr Cove <.09 <.09 <.09 mid-lake <.09

Glenbrook <.09 <.09

Sand Harbor <.09 <.09
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impact December 1999

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m,p and o Xylene, expressed as

total*

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.18 <.18 <.18 Cave Rock <.18 <.18 1.23

3m <.18 <.18 <.18 Zepher Pier <.18 <.18 2.31

10m <.18 <.18 <.18 Ski Run In <.18 <.18 1.48

Ski Run Out <.18 <.18 6.83

El Dorado Ramp <.83 <.18 3.36

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.18 <.18 1.23

Incline Village <.24 <.30 Tahoe Keys Channel <.18 <.18 2.67

Kings Beach <.19 <.46 Camp Rich Pier <.18 <.18 2.33

Tahoe City <.18 <.18 <.33 Camp Rich Pumps 0.57 <.32 0.64

Homewood <.18 <.18 <.18 Ski Boat Beach <.18 <.18 1.4

Emerald Bay <.18 <.26 0.79

Kiva Beach <.18 <.18 <.60 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.18 <.18 <.30 Field <.18 <.18

Zephyr Cove <.18 <.18 <.46 mid-lake <.18

Glenbrook <.18 <.33

Sand Harbor <.18 <.36

*m,p and o xylenes were added for total xylenes.

When either m,p or o xylenes were reported as '<' the total xylenes were also expressed as '<'

m,p-Xylene

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.1 <.1 <.1 Cave Rock <.1 <.1 1.05

3m <.1 <.1 <.1 Zepher Pier <.1 <.1 2

10m <.1 <.1 <.1 Ski Run In <.1 <.1 1.22

Ski Run Out <.1 <.1 5.89

El Dorado Ramp <.1 <.1 2.83

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.1 <.1 1.04

Incline Village <.1 0.22 Tahoe Keys Channel <.1 <.1 2.13

Kings Beach <.1 0.38 Camp Rich Pier <.1 <.1 2.03

Tahoe City <.1 <.1 0.25 Camp Rich Pumps 0.42 0.24 0.56

Homewood <.1 <.1 0.1 Ski Boat Beach <.1 <.1 1.21

Emerald Bay <.1 0.18 0.69

Kiva Beach <.1 <.1 0.52 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.1 <.1 0.22 Field <.1 <.1

Zephyr Cove <.1 <.1 0.38 mid-lake <.1

Glenbrook <.1 0.25

Sand Harbor <.1 0.28
UCRL-AR-135949 Vol. 4 Ch. 5 Potential Ground and Surface Water Impact December 1999

11-99/Ethanol Ch. 5 C-14

o-Xylene

Offshore 8/25/99 8/30/99 9/7/99 Hot Spots 8/25/99 8/30/99 9/7/99

0m <.08 <.08 <.08 Cave Rock <.08 <.08 0.18

3m <.08 <.08 <.08 Zepher Pier <.08 <.08 0.31

10m <.08 <.08 <.08 Ski Run In <.08 <.08 0.26

Ski Run Out <.08 <.08 0.94

El Dorado Ramp 0.73 <.08 0.53

Near shore 8/25/99 8/30/99 9/7/99 Tahoe Keys Ramp <.08 <.08 0.19

Incline Village 0.14 <.08 Tahoe Keys Channel <.08 <.08 0.54

Kings Beach 0.09 <.08 Camp Rich Pier <.08 <.08 0.3

Tahoe City <.08 <.08 <.08 Camp Rich Pumps 0.15 <.08 0.08

Homewood <.08 <.08 <.08 Ski Boat Beach <.08 <.08 0.19

Emerald Bay <.08 <.08 0.1

Kiva Beach <.08 <.08 <.08 Blanks 8/25/99 8/30/99 9/7/99

Edgewood <.08 <.08 <.08 Field <.08 <.08

Zephyr Cove <.08 <.08 <.08 mid-lake <.08

Glenbrook <.08 <.08

Sand Harbor <.08 <.08