xvEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/R-98/104
November 1998
Synthetic-Based
Drilling Fluids:
An Assessment of the
Spatial Distribution of
Toxicants in
Sediments from Gulf of
Mexico Drilling Platforms
A Report Prepared for the
Office of Water
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EPA/600/R-98/104
November 1998
Synthetic-Based Drilling Fluids: An Assessment
of the Spatial Distribution
of Toxicants in Sediments from Gulf of Mexico
Drilling Platforms
A Report Prepared for the Office of Water
By
Carol B. Daniels, Ph.D.
U. S. Environmental Protection Agency
National Health and Environmental Effects
Research Laboratory
Gulf Ecology Division
1 Sabine Island, Gulf Breeze, FL 32561-5299
Printed on Recycled Paper
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Abstract
Use of the amphipods, Leptocheirus plumulosus and Ampelisca
abdita, iff these bioassays presented no major difficulties in the
execution of these test protocols. Sensitivity to the toxicants was
exhibited by L. plumulosus and survival of control animals was
good suggesting the suitability of this organism for use.
Continued application of these species to evaluations of field-
collected sediments contaminated with Synthetic-based drilling
fluids (SBF) is encouraged and should enhance our
understanding of the toxicity of these products. Data from this
initial screening with Leptocheirus plumulosus indicate
sensitivity of this species to sediments collected within a 150
meter radius of platform 1 (GI95) and demonstrate the spatial
distribution of contaminants along a gradient. Sediments within
the vicinity of the other two platforms, (platform 2, SMI57C and
platform 3, ST148) proved to be less toxic than those from
platform 1 but serve to illustrate the sensitivity of the organism,
L. _ piiimulosus to a range of SBF. Data from tests with
Ampelisca abdita indicated a lower sensitivity to the field-
collected samples than was observed with L. plumulosus.
Survival values in the range of the control suggested an apparent
lack of toxicity from any of the sites to this organism above
those of background. Procedural delays were thought to have
reduced the overall responsiveness of Ampelisca abdita in these
tests. Measures of sample variability indicated variability
between replicate samples from the same grab and between
sequential grabs. Variability denoted in composite samples
suggests additional research should be conducted to improve the
protocol to achieve sample homogenization. Coarse-sieving of
field-collected sediments should also be explored to ascertain if
such procedural modifications might also reduce sample
variability.
1. INTRODUCTION
Increasing pressure from industry has prompted the U.S.
Environmental Protection Agency (EPA) to consider the
expansion of current regulatory guidelines for oil drilling to
include language to facilitate more wide-spread use of synthetic-
based drilling fluids (SBF) in the United States. Synthetic
based fluids are currently in use in US coastal waters although
no specific limitations for SBF have been set forth in current
guidelines (EPA, 1996). Historically, use of SBF has been
greatest in the North Sea (Friedheim and Conn, 1996); however,
use of these agents in the US has grown appreciably (as many as
300 wells in the Gulf of Mexico have been drilled with SBF)
since the initiation of drilling of the first well using SBF in the
Gulf of Mexico in 1992 (Candler et al., 1997).
Synthetic-based fluids have been described as being more
effective than water-base muds (WBM) and oil-based muds
(OBM) and considered more environmentally benign than their
predecessors (Veil et al., 1996; Burke and Veil, 1995; Candler
etal., 1993; Friedheim eta.l, 1991). Despite indications of some
environmental benefits use of the agents in US waters remains
tenuous until questions can be addressed about the
environmental safety of these agents and the appropriateness of
toxicity tests currently described in the coastal guideline to
adequately assess the potential impact of SBF on benthic
species.
Synthetic-based fluids are muds prepared for drilling purposes
which are manufactured from materials containing no detectable
levels of priority pollutants. All major mud suppliers are said to
offer SBF, and formulations of these materials are routinely
prepared using vegetable esters, polyalpha olefins (PAO),
internal/isomerized olefins (IO), linear alpha olefins (LAO) and
ethers (Candler et al., 1997). Traditional base-fluids such as
diesel and mineral oil, are not designated SBF since they are not
synthesized. Conversely, they are refined from crude oil and are
known to contribute to the toxicity of drilling fluids (they release
aromatics into the water fraction of the fluids). Concern
regarding the use of SBF is related largely to questions about the
biodegradability and toxicity of SBF-coated cuttings, since
cutting piles accumulate on the seafloor and synthetics, may
account for as much as 12% of the material adhering to the
surface of the cuttings (Friedheim and Conn, 1966).
Because toxicity protocols, currently incorporated in the coastal
guidelines, were designed to assess water-column effects (EPA,
1996), limited toxicological data are available on the potential
impact of Synthetic-based fluids on North American benthic
species (Candler etal., 1997; Candler, 1997; Hood, 1997a&b).
One seafloor study has been completed which directly addresses ,
the impacts of SBF discharges on benthic fauna of the Gulf of
Mexico (Candler et al., 1995) and suggests diminished biological
effects of an SBF when compared with an OBM.
Evaluation of several benthic endpoints (species richness,
diversity and number of individuals) and total petroleum
hydrocarbon (TPH) concentrations indicate a smaller area of
transition (than for OBM) surrounding the PAO discharge
platform with community level effects approaching background
for the benthic fauna.
Laboratory investigations with benthic species have focused on
use of the amphipods, • Corophium volutator, Rhepoxinius
abronius, Ampelisca abdita and Leptocheirus plumulosus, and
deal almost exclusively with the toxicity of the base fluids
(Candler etal., 1997; unpublished data by Candler, 1997; Hood,
1997a). Contaminants of interest have included enhanced
mineral oils (EMO), internal/isomerized olefins (IO), and
polyalpha olefins (PAO). Some data exist on the toxicity of a
used, whole synthetic-base mud (Hood, 1997b) and indicate
some product toxicity. The reported LC50 for the used SBF
ranged between 692 mg/kg and 3, 600 mg/kg in 10-day
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(definitive) sediment toxicity tests with R. abtonius, A. abdita
and L plumulosus. Ranking of species sensitivity to this product
indicated Leptocheirus > Rhepoxinius > Ampelisca.
Information gaps exist and suggest the need for continued
research on SBF to enhance our understanding of the toxicity
and potential hazards associated with the discharge of drilling
fluids and cuttings, contaminated with synthetic material, into
sub-tropical waters such as the Gulf of Mexico. This study
represents a singular attempt to augment the current data to
provide information on the toxicity of three product types, IO,
LAO, and a combined ester-olefin mixture, currently in use on
drilling platforms in the Gulf of Mexico.
This study was designed to provide a qualitative assessment of
a series of field sites in the Gulf of Mexico for the Office of
Water, with an indication of the potential hazards associated
with the field application/use of synthetic-based drilling fluids
(SBF). Additionally, this report supplies information on the
relative sensitivity of two infaunal amphipods, Leptocheirus
plumulosus and Ampelisca abdita, to these agents and discusses
the feasibility of adapting a standardized protocol, such as the
10-day acute sediment toxicity test (EPA, 1994), to the
evaluation of a non-homogeneous geochemical matrix of SBF
mixed with sediment.
The use of L plumulosus and A. abdita in this study, and their
consideration for use in Agency guidance for Synthetic-based
fluids, is intended to complement current regulatory trends
toward use of amphipods for the assessment of sediment-
associated contaminants and is intended to complement works
previously performed on this unique group of products. Both
Leptocheirus plumulosus and Ampelisca abdita have been used
routinely for the evaluation of the toxicity of marine and
estuarine sediments. Their sensitivity to a range of toxicants has
been documented in the scientific literature, and the method
reviewed extensively. Guidance documents (ASTM, 1993;
EPA, 1994) have been prepared for these acute bioassays and
serve to substantiate the credibility of these protocols for use in
ecological risk assessment.
Toxicity testing was conducted according to EPA Guidelines as
specified in Methods for assessing the toxicity of sediment-
associated contaminants with estuarine and marine amphipods
(EPA, 1994). Testing was conducted at Gulf Ecology Division,
NHEERL, U.S. Environmental Protection Agency, Gulf Breeze,
FL, and utilized undiluted, sediment samples collected in the
vicinity of three drilling platforms (GI95, SMI 57C and ST148)
during a reconnaissance survey conducted aboard the research
vessel S.S. Anderson (EPA) August 18-22,1997.
2. TEST SUBSTANCE
Field samples containing synthetic drilling fluids were received
from George Gibson, U.S. Environmental Protection Agency, on
August 23, 1997. Samples were contained in sample jars of a
variable nature, i.e., size (1 -1.5 liter) and construction (glass or
high-density polyethylene). Upon receipt in the laboratory, the
samples were stored in the dark in an environmental chamber at
approximately 4°C. Prior to their use in the bioassay, each
sample underwent a visual inspection to assess spoilage. An
absence of a foul odor and black spots on the surface of the
sediments were noted for each sample, indicating suitability for
testing.
3. TEST ORGANISMS
Field samples were evaluated using one marine amphipod,
Ampelisca abdita, and one estuarine amphipod, Leptocheirus
plumulosus. Leptocheirus plumulosus were purchased from
Chesapeake Cultures (P.O. Box 507, Hayes, VA 23072, 804
693-4046) and were received on August 29, 1997. Ampelisca
abdita were purchased from East Coast Amphipod (16 Ayrault
St., Suite 1, Newport, RI02840,401 849-4631). The amphipods
were collected and shipped on September 3,1997, and received
on September 5, 1997, after a 36 H delay in shipment. ,
Feeding: No food was supplied to the amphipods during holding
and testing.
Age/Length: Leptocheirus plumulosus used in this study were
mixed-age adults ranging in size from 2 to 4 mm. Ampelisca
abdita were juveniles, ranging in size from 0.71 mm to 1.18 mm.
Receipt/Handling: Water quality parameters of the overlying
water contained in each organism shipping container were
measured and recorded upon arrival at the laboratory.
Leptocheirus were shipped in water only, thus transfer of these
organisms to containers of freshly, aerated seawater was
accomplished by pouring the contents of a container through a
125 \jm\ sieve. Amphipods retained on the screen of the sieve
were flushed from the screen with a gentle stream of saline (20
ppt) water into 2L Carolina culture dishes containing 20 ppt
oxygenated seawater. Bowls were aerated and the organisms
were held at 20±1°C until the randomization process was
initiated.
As was the case with Leptocheirus, water quality parameters of
the overlying water of each shipping container of Ampelisca
were measured and recorded upon arrival at the laboratory.
Collection of Ampelisca was slightly different, however, as the
amphipods had been shipped in sediment obtained from their
collection site. Using a rubber spatula, sediment containing the
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amphipods was removed from the shipping container and placed
on the surface of a 500 ,um sieve. The sieve was placed inside
a large polyethylene tub and ambient sea water gently sprayed
over the surface to facilitate removal of the sediments. ~~
Most of the sediment passed through, leaving the amphipods
behind. A fine spray of water was again passed over the sieve
to ensure organisms had been flushed from their tubes.
Amphipods retained on the screen of the sieve were flushed
from the screen with a gentle stream of 28 ppt water into 2L
Carolina culture dishes containing 20 ppt oxygenated seawater
(28 ppt). The tubes were examined to see if any amphipods
were present. Amphipods found adhering to the water surface
were removed from the containers by placing a fine-meshed
screen just below the surface of the water and gently lifting them
out. These organisms were added to the culture dishes
containing animals previously collected. The bowls were
aerated and the organisms were held in environmental chambers
maintained at 28±1°C until the randomization process was
initiated.
4. REFERENCE & FIELD-COLLECTED SEDIMENTS
The reference sediment for these tests was sediment collected by
the supplier. In the case of Leptocheirus, no sediment was
received from the vendor; therefore a sediment obtained from a
non-polluted region of the Pensacola Bay Estuary was used as a
reference sediment. The sediments were coarse^sieved through
a 2,000 /urn stainless steel, sieve and fine-sieved through a 500
yum stainless steel, sieve to remove any large organisms that were
confused with or preyed upon the amphipods.
Field-collected sediments were not wet-sieved, in an attempt to
maintain the integrity of their geochemical properties. Stainless
steel forceps were used, however, to remove large objects (shell
and other debris) and predators from the field samples prior to
use in the bioassay. Samples collected from multiple benthic
grabs were homogenized by stirring by hand. Samples from the
same benthic grab were similarly homogenized, if the samples
were received in more than one storage container.
5. OVERLYING WATER
In the case of Leptocheirus, the overlying water added to the
exposure chambers after the addition of the sediment-test was 20
ppt natural, filtered sea water. The overlying water added to A.
abdita exposure chambers was 28 ppt natural, filtered sea water.
Synthetic sea water was prepared by adding a brine solution
(prepared from a commercial preparation of dried, balanced sea
salts [Forty Fathoms Sea Salts, Baltimore, MD]) to natural sea
water (20 ppt filtered seawater) to obtain a seawater mixture of
28 ppt salinity. The resultant solution was aerated and allowed
to age for. several days prior to use. Water for tests with
Ampelisca was maintained in a water bath at 20 °C, and seawater
for Leptocheirus maintained at 25°C.
6. EXPOSURE CHAMBERS
Exposure chambers were one-liter glass beakers. Glassware was
acid-washed prior to use, rinsed five times with deionized water
and air-dried prior to affixing sample labels to each exposure
vessel. Beakers contained approximately 2 cm of field-collected
sediment. Sediments were weighed to ensure equivalent
amounts of material were delivered to each beaker (average
weight of sediment disbursed = 253.47 g). Sea water (800 ml,
20 ppt and 28 ppt salinity, respectively, for L. plumulosus and A.
abdita) was added to each exposure chamber to bring the total
volume of sediment and overlying water to 1 liter.
7. TEST CONCENTRATION
Because a limited amount of sediment was received, the test was
conducted as a screening bioassay. As such, a geometric series
of concentrations of the sediments was not tested. Rather,
replicate samples (3) of the undiluted field-collected sediment
were evaluated against a control in the 10 day acute test.
Exposure chambers containing control and field-collected
samples were placed onto a water table maintained at 20°C.
Each exposure chamber was covered with a watch glass
containing a small hole used for insertion of an aeration
apparatus. Gentle aeration of each exposure chamber was
established using flexible air-line tubing fitted with a 1 ml
serological glass pipette. The flexible air-line tubing was
connected to a gang valve, and the tapered end of the pipette
inserted through the hole of the watch glass, suspending it to a
depth approximately 2 cm below the surface of the water in the
exposure chamber. Temperature, dissolved oxygen, pH and
salinity were measured in the overlying water in each treatment
and control.
8. PREPARATION OF TEST ORGANISM
Organisms maintained overnight in two-liter Carolina dishes
were randomly distributed using a fire-polished, wide-bore
dropping pipette to 10 ml glass beaker cups containing
approximately 10 ml of sea water. Five organisms were
randomly delivered into each cup; a total of twelve cups were
prepared for each treatment and control.
9. TEST INITIATION
The test was initiated when twenty organisms, introduced into
each exposure chamber by gently pouring the 10-ml cups over
a fine-meshed screen, were transferred from the screen into the
overlying water of the exposure chamber. This procedure was
repeated until the required number of organisms (20) was
introduced into the exposure chambers.
10. TEST MONITORING & TERMINATION
The bioassay was performed under condition of continuous light
in accordance with the recommended test conditions (Table 1).
Aeration of the exposure chambers was continuous, each
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chamber was observed daily and the airflow adjusted, as appro-
priate, to ensure maintenance of dissolved oxygen at ^90%.
Temperature, dissolved oxygen (D.O.), pH and salinity were
measured in the overlying water of each treatment and control at
the start and conclusion of the test. Water quality parameters
(D.O.. pH, salinity and temperature) were monitored daily for a
single representative of each treatment and control group.
The test was terminated 10 days after introduction of the
amphipods to the exposure chambers. Beginning with the
control treatment, the contents of each replicate were poured
onto the screen of a 500-A/m nylon, sieve held over a plastic tub.
The organisms were typically retained on the screen while most
of the sediment passed through the screen. A fine spray of water
was passed over the sieve to remove any sediments adhering to
the surface of the screen.
Animals were collected from the sieve any passing through the
screen were recovered from the surface of the water retained in
the tub (refer to the prior description of this technique) and all
were placed in a finger bowl. The finger bowls were placed on
an illuminated light table and the number of surviving
organisms determined. In cases where mortality was
questionable, determination of survival was made by examining
animals under a dissecting scope.
11. DEVIATIONS FROM PROTOCOL
Sediment toxicity tests with L. plumulosus and A. abdita
included a few departures from the standard testing protocols.
One deviation from the guidelines was the use of only three
replicate samples of each sediment evaluated, rather than the
prescribed minimum of four (EPA, 1994). This was necessitated
by the limited volume of material received and the need to
conduct testing with two test organisms. Because a reduced
number of replicates was used, test acceptability was modified
to include a minimum control survival of 80%.
Another deviation from recommended test guidelines was the
use of sediments beyond the suggested 14 day storage'limit
(ASTM, 1996). Sediments used in tests with Ampelisca were
beyond this limit at the initiation of the 10-day acute sediment
toxicity test. This was due to the initial receipt of a batch of
organisms of inferior quality and a delay in receipt (36 H) of the
replacement shipment of amphipods. Visual and olfactory
inspection of the sediments used in tests with A. abdita,
however, indicated no apparent loss of quality for these samples.
Because animals were shipped at temperatures and salinities
matching those used in the toxicity tests, animals were used
without a period of acclimation as is generally recommended.
12. STATISTICAL ANALYSIS
The determination of 10-day LC,0 values was not performed, as
a geometric series of sediment concentrations had not been
evaluated for each of the field-collected sediments. The mean
percent (%) survival was calculated for each replicate group of
samples and served as the basis for comparison. To compare
sites, split samples from composites (although not statistically
true replicates) were used to compare sample variability
(attributed to the homogenization procedure) and to test the
sensitivity of the two test organisms, L. plumulosus and A.
abdita. Replicate samples from the same benthic grab were used
to compare within-grab variability.
13. RESULTS
Leptocheirus: The bioassay Was terminated after 10 days of
exposure, and the survival for each treatment group determined.
Survival data for Leptocheirus plumulosus are tabulated in Table
2. Data from tests with Ampelisca abdita are shown in Table 3.
Data from tests with Leptocheirus indicate a high degree of
toxicity (0 - 65% survival) for sites within a 150 m (1G1, 1G3,
1G7 and 1G10) radius of drilling Platform 1 (GI95). Although
survival at the platform reference site (1 R3 A+B) was slightly
reduced compared with to that noted in the control sediment (C-
17) (83.3% compared to 95%), it was significantly different
from the four test sites (1G1, 1G3, 1G7 and 1G10) referred to
above.
Sediment samples collected at sites adjoining Platforms 2 (SMI
57C) and 3 (ST 148) were far less toxic than those collected in
the vicinity of Platform 1. The lowest recorded survival (81.7%)
for any of the sediments for stations surrounding Platform 2 was
observed with sediments from station 2G2. Although sediment
samples from stations within the survey area of Platform 3
demonstrated lower toxicity than sediments from Platform 1,
. they tended to be slightly more toxic than samples obtained from
sites near Platform 2. Sediments from the reference site for
Platform 2 (2R1) were of equivalent toxicity (95%) to the
control sediment (C17). A survival value of 86.7% was
recorded for the sediments from the Platform 3 reference site
(3R2).
Ampelisca: Tests with Ampelisca indicated lower survival
(86.67%) with the control treatments (i.e., Ampelisca control
sediment) than was observed with Leptocheirus (95%).
Contrary to indications 'of L. plumulosus adaptability to
Pensacola Bay sediments (C17), this sediment proved unsuitable
for habitation by A. abdita (0% survival). Survival of
amphipods treated with sediments from Platforms 1, 2 and 3
indicated no adverse toxicity .beyond that demonstrated for the
control treatment. The lowest survival value was 83.3% and was
recorded for organisms treated with sediments from 1 GlOB and
3G1 A+B. In one case, survival (91.7% ) for one of the field-
collected sediments (2G6) exceeded that recorded for the
Ampelisca control sediment (86.7%). Toxicity for the two
reference sites (1R3A+B and 3R2) evaluated in this series of
acute toxicity tests indicated comparability to that determined for
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the control: sediment (85.0% and 88.3 % survival, respectively,
compared with 86.7% for the control).
Reference Toxicant: Toxicity evaluations involving the
reference toxicant, copper sulfate were, performed at con-
centrations in excess of the 96-hour LC50 of copper sulfate, for
both L. plumulosus and A. abdita to ensure demonstration of a
lethal effect. In both cases, all animals had expired within 24 H
of their initial exposure.
14. CONCLUSIONS
Use of the amphipods, Leptocheirus plumidosus and Ampelisca
abdita, in these bioassays presented no major difficulties in the
execution of these test protocols. Sensitivity to the toxicants was
exhibited by both organisms, and survival of control animals was
good, indicative of the suitability of L. plumulosus and A. abdita
for use. Continued application of these species to evaluations of
field-collected sediments contaminated with synthetic-based
fluids.(SBF) is encouraged and is expected to enhance our
understanding of the toxicity of these products.
Data from this initial reconnaissance survey indicate toxicity
associated with sediments recovered from sites surrounding at
least one of the drilling platforms (Platform 1; GI95). Although
toxic responses were limited, only one (Leptocheirus
plumulosus) of the two species tested (L. plumulosus and
Ampelisca abdita) at these sites warrant closer examination,
because of the extreme degree of toxicity (0% survival) denoted
for at least one site (1G1) in close proximity (50 m) to the point
of discharge for Platform 1. Toxicity was also clearly evident at
other sites within a 150 m radius of this platform (1G3,1G7 and
1GIO), although survival was not nearly as limited for animals
exposed to these sediments as for those treated with sediments
from IGl.
These data, coupled with data from the reference site for this
platform (1R3), clearly indicate the spatial distribution of
toxicants beyond the point of discharge and illustrate the dilution
of a pollutant along a geographic gradient. Similarly, recent
work by Candler et al. (1995) demonstrated the distribution of
contaminants within a 200 m radius of a synthetic-base well
(characterized as using PAO) in the Gulf of Mexico.
Quantitative analysis and pollutant characterization have not yet
been completed for these samples, • thus the nature of the
contaminant(s) associated with these samples or the identity of
the agents eliciting this toxic response is not yet clear.
Petroleum is suspected of having contributed to the toxic
response noted with Leptocheirus, as a smell of petroleum
products was clearly evident when these samples were
distributed to the test chambers.. Furthermore introduction of
water to the beakers containing these sediments resulted in the
formation of a surface sheen. Because oil can be quite toxic to
aquatic life (Neff and Anderson, 1981), the presence of
petroleum and petroleum by-products may serve to mask or
enhance the toxicity associated with any synthetic materials
discharged from the drilling platform.
Comparison of data from 10 day, static acute sediment tests with
the two target organisms, L. plumulosus and A. abdita, indicate
comparative sensitivity of Leptocheirus > Ampelisca:
Ampelisca abdita was seen to be less susceptible to the effects
of exposure to the synthetic muds than was Leptocheirus, despite
the lower numbers of amphipods noted in sediments from both
the control treatments and the reference sites at the conclusion
of the test. The lower survival counts denoted in A. abdita
control sediments were attributed to stress experienced by the
animals prior to initiation of the test (i.e., the 36 H shipping
delay).
Comparison of survival data from treatments involving exposure
to sediments from multiple (benthic) grabs at a collection site
indicates a small degree of variability among sequential grabs.
Hand mixing of composite sample tended not to reduce the
variability associated with replicate samples, although it
appeared not to distort the toxic effect noted in the. individual
grab samples. Additional research should be conducted to see
if other methods of mixing might further reduce the variability
among sample replicates. Considerable amounts of shell and
other marine debris were associated with the samples making
recovery and counting of the amphipods rather time consuming.
The presence of this material was also thought to partially
contribute to the variability observed among sample replicates.
Additional studies should be initiated to assess the effect of
coarse-sieving of these sediments on the sample toxicity.
15. REFERENCES
American Society for Testing and Materials. Standard Guide
for Conducting 10 day Static Sediment Toxicity Tests with
Marine and Estuarine Amphipods, Designation E 1367-92.
Philadelphia, PA: American Society forTesting and Materials,
1996.
Burke, CJ. and J.A. Veil. Potential Environmental Benefits
from Regulatory Consideration of Synthetic Drilling Muds,
ANL/EAD/TM-43,Argonne, IL: Argonne National Laboratory
(1995).
Candler, J., R. Hebert and AJ J. Leuterman. "Effectiveness of
a 10-day ASTM Sediment Test to Screen Drilling Mud Base
Fluids for Benthic Toxicity." In Proceedings of SPE 37890 •
SPE/EPA Exploration and Production Environmental
Conference, Dallas, TX, March 3-5, 1997..
Candler, J. 1997. Personal Communication, June 30, 1997.
Candler, J., S. Hoskin, M. Churan, C.W. Lai and M. Freeman.
1995. "Seafloor Monitoring for Synthetic-Based Mud Dis-
charged in the Western Gulf of Mexico." In Proceedings of
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SPE 29694 SPE/EPA Exploration and Production
Environmental Conference, Houston, TX, March 27-29, 1995.
Candler, J., J.H. Rushing, and A.J.J. Leuterman. "Synthetic-
Based Mud Systems Offer Environmental Benefits Over
Traditional Mud Systems." In Proceedings of SPE 25993
SPE/EPA Exploration and Production Environmental
Conference, San Antonio, TX, March 7-10, 1993.
Daan, R., K. Booij, M. Mulder, and E. M. vanWeerlee.
Environmental effects of a discharge of drill cuttings
contaminated with esr-based drilling muds in the North Sea.
Environmental Toxicology and Chemistry I5(10):1709-1722
(1996).
Friedheim, I.E. and H.L. Conn. "Second Generation Synthetic
Fluids in the North Sea: Are they Better?" In Proceedings of
SPE 33061 presented at ADDUCE/SPE Drilling Conference,
New Orleans, LA, March 12-15, 1996.
Friedheim, J.E., G.H. Hans, A. Park and C.R. Ray. "An
Environmentally Superior Replacement for Mineral-Oil
Drilling." In Proceedings of SPE 23062 presented at
Offshore Europe Conference, Aberdeen, Scotland, September
3-6,1991.
Hood.C. 1997a^ Personal Communication, April 21, 1997.
Hood.C. 1997b. Personal Communication, July 9, 1997.
Neff, J. M. and J. W. Anderson. Response of Marine Animals
to Petroleum Hydrocarbons. Applied Science Publishers Ltd.,
London, 1981.
U.S. Environmental Protection Agency. Final Effluent
Limitation Guidelines and Standards for the, Coastal
Subcategory of the Oil and Gas Extraction Point Source
Category. Federal Register 66086 (December 16, 1966).
U.S. Environmental Protection Agency. Methods for assessing
the toxicity of sediment-associated contaminants with
estuarine and marine amphipods, EPA/600/R-94/025.
Washington, DC. U.S. Environmental Protection Agency,
1994.
Veil C. J. Burke, and D.O. Moses. Synthetic-based Muds Can
Improve Drilling Efficiency Without Polluting. Oil Gas
Journal March 4, 1996:49-54(1996).
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Table I. Test conditions for conducting a 10-d sediment toxicity test with Ampelisca abdita, Eohaustorius estuarius,
Leptochelnts plumulosus, or Rhepoxynius abronius. , "
Parameter
Conditions
1. Test type:
2. Temperature:
3. Salinity:
4. Light quality:
5. Illuminance:
6. Photoperiod:
7. Test chamber:
8. Sediment volume:
9. Overlying water volume:
10. Renewal of overlying water:
11. Size and life
stage of amphipods:
12. Number of organisms/
chamber:
13. Number of replicate
chambers/treatment:
14. Feeding:
15. Aeration:
16. Overlying water:
17. Overlying water quality:
18. Test duration:
19. Endpoints:
20. Test acceptability:
Whole sediment toxicity test, static
15°C: E. estuarius and R. abronius
20°C: A. abdita
25 °C: L. plumulosus
20ppt: E. estuarius and L. plumulosus
28 ppt: A. abdita and R. abronius
Wide-spectrum fluorescent lights
500-1000 lux
24L:OD
1-L glass beaker or jar with -10 cm I.D.
175 mL (2 cm)
800 mL
None
A. abdita: 3-5 mm (no mature males or females)
E. estuarius: 3-5 mm
L. plumulosus: 2- 4 mm (no mature males or females)
R. abronius: 3-5 mm
20 per test chamber
Depends on objectives of test. At a minimum, four
replicates must be used.
None
Water in each test chamber should be aerated overnight before start
of test, and throughout the test; aeration at rate that maintains 90%
saturation of dissolved oxygen concentration.
Clean sea water, natural or reconstituted water.
Temperature daily. pH, ammonia, salinity, and DO of overlying
water at least at test start and end. Salinity, ammonia, and pH of pore
water.
lOd
Survival (reburial optional for E. estuarius, L. plumulosus, and R.
abronius)
Minimum mean control survival of 90% and satisfaction of
performance-based criteria specifications outlined in the guidance document.
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Table 2. Survival data for Leptocheirus plumulosus exposed to field-collected sediments
containing synthetic based drilling muds.
Descriptor
Platform 1
-
Platform 2
Platform 3
Controls
Site ID
1G1
1G1 rep4
1G3A
1G3B
1G3 A+B
1G7A
1G7B
1G7 A+B
1G10A
1G10B
1G10A+B
1R3A+B
2G2
2G6
2G9
2R1
3G1 A+B
3G5 A+B
3R2
C-17
Copper sulfate
Distance from
Platform
50
50
50
50
50
150
150
150
100
100 •
100
2000
50
150
100
2000
50
150
1000
NA
NA
Survival (%)
* 0
o
51.67
56.67
55.0
61.67
63.33
65.0
51.67
56.67
58.3
83.3
81.67
90.0
91.67
95.0
86.67
90.0
86.67
95
0
Standard Error
of the Mean
0
0
3.33
8.82
8.66
8.82
9.28
, 8.66
3.33
12.02
8.33
3.33
.1.67
5.77
4.41
0
3.33
5.77
3.33
2.89
0
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Table 3. Survival data for Ampelisca abdita exposed to field-collected sediments containing synthetic based
drilling muds.
Descriptor
Controls
Site ID
Distance form
Platform (m)
Survival (%)
Ampelisca Control
Sediment
NA
86.67
Standard Error
of the Mean
Platfonn 1
„
Platfonn 2
Platform 3
1G3A
1G3B
1GIOB
1R3 A+B
2G2
2G6
2G9
3G1 A+B
3G5 A+B
3R2
50
50
100
2000
50
150
100
50
150
1000
86.67
85.0
. 83.33
85.0
85.0
91.67
83.33
83.33
85.0
88.33
8.82
7.64
6.67
2.89
0
4.41
3.33
.6.67
2.89 -
4.41
3.33
C-17
Cu
NA
NA
0
0
0
0
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