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Overview of the remediation process at sites with creosote related contamination in soil, groundwater and river sediment Reidar Zapf-Gilje, Guy C. Patrick, and Robert McLenehan
Abstract: Industrial production and use of creosote dates back to the middle of the 1800s, with the largest production occurring in the first part of the 20th century. In British Columbia, the historical use of creosote for wood treatment and other industrial applications has been large. The characteristics of creosote have led to widespread contamination from spills and leaks at sites where creosote was used. Three such sites are located along the Fraser River within the Fraser River delta. Two of these sites have been subject to provincial remediation orders, as the potential risk to aquatic life in the Fraser River was considered to be high. Several phases of investigation and remediation have taken place over the past three years, with varying rates of progress, influenced by the complexity of the individual groups of responsible persons and by site conditions. The remediation is, to a large extent, completed at two of the sites, and is well underway at the third site. The remediation involved a combination of reduction of contaminant mass through removal of the near surface contaminated soils, in-place management of polycyclic aromatic hydrocarbon contamination at depth and in the river sediments, and hydraulic control of dissolved and free-phase contamination through pumping from on-site wells. The completed remediation works will allow for continued industrial and (or) commercial use of the site, and provide long-term protection of the Fraser River and its aquatic habitat. The measures implemented are expected to satisfy the provincial Waste Management Act and the Contaminated Sites Regulation for protection of human health and the environment, as well as the federal provisions under the Canadian Fisheries Act for controlling release of deleterious substances and for providing adequate foreshore fish habitat. Key words: coaltar, containment, contaminated site, creosote, hydraulic control, interception, regulatory process, risk-based remediation, river sediments. Résumé : La production industrielle et l’utilisation de la créosote date du milieu des années 1800, avec la plus grande production ayant eu lieu dans la première partie du 20e siècle. En Colombie-Britanique, l’usage historique de la créosote pour le traitement du bois et d’autres usages industriels fut grand. Les caractéristiques de la créosote ont mené à d’importantes contaminations provenant de renversements et de fuites aux endroits où la créosote était utilisée. Trois de ces sites sont situés le long de la rivière Fraser, à l’intérieur du delta de la rivière. Ces sites ont été sujets à des ordres de réhabilitation provinciale, vu que le risque potentiel sur la vie marine dans la rivière Fraser était considéré élevé. Plusieurs phases d’investigation et de réhabilitation ont eu lieux depuis les trois dernières années, avec différents niveaux de progrès influencés par la complexité des groupes de personnes responsables et par les conditions sur le terrain. La réhabilitation est, en grande partie, complétée à deux des sites, et sera déjà bien entamée au troisième site au printemps 2001. Lorsque complétée, chaque site aura été réhabilité avec succès pour un usage industriel/commercial continu par le biais d’un contrôle de la source sur place, d’une réduction de la masse de contaminants par la disposition partielle du sol contaminé et de la récupération de créosote en phase libre. La réhabilitation fournira une protection à long terme à la rivière Fraser et à son habitat aquatique par une combinaison d’atténuations naturelles, de quota et de suppressions partielles des sources de contaminants. Les mesures misent en oeuvre satisferont le Waste Management Act provincial et le Contaminated Sites Regulation pour la protection de la santé humaine et environnementale, ainsi que les clauses fédérales du traité canadien des pêches afin de contrôler l’émission de substances nuisibles et de fournir un habitat marin adéquat. Mots clés : goudron, confinement, site contaminé, créosote, contrôle hydraulique, interception, procédé réglementaire, réhabilitation basée sur le risque, sédiments fluviaux. [Traduit par la Rédaction]
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Received February 18, 2000. Revised manuscript accepted October 11, 2000. Published on the NRC Research Press Web site on February 28, 2001. R. Zapf-Gilje,1 G.C. Patrick, and R. McLenehan. Golder Associates Ltd., #500 – 4260 Still Creek Drive, Burnaby, BC V5C 6C6, Canada. Written discussion of this article is welcomed and will be received by the Editor until July 31, 2001. 1
Corresponding author (e-mail:
[email protected]).
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DOI: 10.1139/cjce-28-S1-141
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Introduction Zapf-Gilje et al. Industrial use of coaltar and associated creosote production dates back to the middle of the 1800s, with the largest production occurring in the first part of the 20th century (Austin 1984). Coaltar was produced by coal gasification facilities that produced gas for city lighting and power usage, and the production of coke for the steel industry. The ready availability of coaltar provided ample supply for distillation into creosote for the wood preserving industry. Most major cities in North America and Europe had coal gasification and coking plants. In the United States, 1150 city gasworks were registered (Lotimer et al. 1992). The number of gasworks in Canada was approximately 150 (Environment Canada, unpublished report), and in Denmark 125 gasworks were registered (Johansen et al. 1997). The coaltar production in the mid 1950s was in the order of 20 × 109 L in the United States (Austin 1984). In Canada, the peak period of the coal gas operations was around 1925. Most of these sites were located near navigational waters, for transportation of raw material (coal) and products (coke and coaltar). The reported annual production of coke and by-products in 1931 was about 2.25 million tons (1 ton = 0.984 tonne) (Environment Canada, unpublished report). Assuming that the tonnage of coal used in the process was at least as high as the coke and by-products generated, and a typical yield of coaltar of 40 L per ton of coal, indicate a coaltar production in the order of 100 000 000 L@a–1. Typically the coaltar distillation processes would yield about 3% of creosote oils, the remainder being a range of products from crude light oils, benzene, toluene, xylene, naphthalene, tar, and pitch. By the mid-1900s, coal gasification for production of domestic gas was phased out; however, the coking plants continued to supply coaltar for the production of creosote. In British Columbia, the quantity of creosote used for wood treatment has been large. Even today approximately 6 000 000 kg of creosote is used annually by wood treatment plants, and creosote alone accounts for nearly 70% of the total quantity of pesticide used in the province (British Columbia Ministry of Environment, Lands and Parks (BCMELP) 1995). Creosote oils were also used by various other industries for thinning of tars and pitches, to achieve the optimum consistency for products such as roof shingles and road tars. There were several coal gasification plants in British Columbia; the largest was located at the east end of False Creek (Fig. 1). Coaltar from this plant was used by several local industries situated on the Fraser River. This paper provides an overview of the contamination found at three sites, which used or produced creosote oils, and of the regulatory process involved for the selection and implementation of site remediation.
Creosote production and characteristics Creosote was historically derived from coaltar. Today, it is also derived from petroleum. Coaltar is produced by hightemperature carbonization of bituminous coals (Austin 1984; Stranks 1976; American Wood Preservation Association 1977). Creosote oils are one of several classes of complex hydrocarbon mixtures obtained by distilling coaltar.
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Creosote is a mixture containing more than 160 hydrocarbon compounds including polycyclic aromatic hydrocarbons (PAH) (85% of mass), phenolic compunds (10% of mass), heterocyclic aromatic compounds (HAC) (5% of mass), and a small fraction (less than 1% of mass) of benzene, ethylbenzene, toluene, and xylene. The dominant PAH compounds in creosote are naphthalene, 2-methylnaphthalene, phenanthrene, anthracene, 1-methylnaphthalene, biphenyl, and fluorene. These seven compounds comprise approximately 75% of the total mass of PAH (Mueller et al. 1989). Phenolic compunds may include phenol, cresols, pentachlorophenol, xylenols, and 2,3,5-trimethylphenol. Heterocyclic aromatic compounds may include quinoline, isoquinoline, carbazole, 2,4-diethylpyridien, acridine, 2-methyquinoline, 4methylquinoline, pyrrole, pyrrolidine, benzo(b)thiophene, dibenzothiophene, and dibenzofuran. For coaltar-based creosote, the exact composition will vary depending on the origin of the coaltar and the distillation temperature. The physical properties of creosote that largely determine its behaviour in the subsurface include its specific gravity (which is near that of water), its high viscosity, and low interfacial tension. The specific gravity of creosote is typically around 1.05 or less at ambient soil temperatures. Consequently, it is a dense nonaqueous phase liquid (DNAPL) that will slowly sink when placed in water, although separation into both floating and sinking phases has been reported. Viscosity will vary widely depending on creosote composition and temperature, but typically is much higher than water; it ranges from that of a crude oil (about 0.020 Pa@s) to that of thick molasses (perhaps 0.050–0.080 Pa@s). Such viscosities reduce the velocity at which the creosote can migrate through soil, although they will have little effect on the ability of the creosote to flow. Creosote migration through a porous medium is determined to a much greater extent by the interfacial tension between the creosote and soil porewater or groundwater. Where creosote has been recovered from soil, interfacial tensions are typically low, of the order of 0.005–0.01 N@m–1. This suggests that the creosote may travel further and leave behind much lower residual concentrations in soil, than would be expected for a comparable petroleumbased, heavy oil.
Main environmental issues Polycyclic aromatic hydrocarbons (PAH) are a diverse group of organic compounds composed of hydrogen and carbon atoms arranged in two or more fused aromatic (benzene) rings. Polycyclic aromatic hydrocarbons are grouped into two categories based on their molecular structure: (1) low molecular weight (LMW) compounds with fewer than four rings; and 2) high molecular weight (HMW) compounds with four or more rings. Low molecular weight-polycyclic aromatic hydrocarbons are generally more soluble in water than HMW-PAH. About 75% of the PAH fall into the LMW category. Polycyclic aromatic hydrocarbons are also formed by a variety of other natural and anthropogenic processes including biosynthesis and incomplete combustion of organic materials (Environment Canada 1999). Several studies have demonstrated that PAH associated with creosote can pose risks to aquatic organisms. At sufficiently high concentrations, PAH can cause reduced survival, © 2001 NRC Canada
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Fig 1. Creosote and coaltar dense nonaqueous phase liquid sites. Lower Fraser River, Vancouver, British Columbia.
reduced growth, tumours, developmental effects, enzyme induction, behavioural abnormalities, habitat degradation, fish tainting, and ultraviolet-induced skin lesions (Sved et al. 1997; Environmental Applications Group 1988; Eisler 1987; Neff 1979). Terrestrial activities are much less affected by PAH contamination found at these sites, as it is generally located at depth, and the hydrocarbons present in creosote are not sufficiently volatile to create soil vapour concentrations that would pose a potential threat to people, plants, or animals.
Regulatory framework Provincial In British Columbia, creosote is considered a pesticide, and its handling, transportation, sales, and use are regulated by the Pesticide Control Act, R.S.B.C. 1996, c.360 and the Pesticide Control Act Regulation (to British Columbia Regulation 131/97 and S.B.C. 1997-18). The Waste Management Act, R.S.B.C 1996, c.482, and its regulations, governs the identification and remediation of contaminated sites in British Columbia. The primary regulations include the Contaminated Sites Regulation (BCMELP 1997), and the Special Waste Regulation 1988 (including amendments to British Columbia Regulation 52/95). The Contaminated Sites Regulation provides standards for a variety of compounds that may be present in water and
soil, and establishes processes for the identification and remediation of contaminated sites. Standards have been developed for PAH, phenols, as well as benzene, ethylbenzene, toluene, and xylene. No Contaminated Sites Regulation standards are available for HAC. The Contaminated Sites Regulation provides no specific guidance on the management of contaminated sediments, and as a result a draft document titled Criteria for Managing Contaminated Sediment in British Columbia was released in 1999 (BCMELP 1999). The document includes Level I and Level II criteria reflecting the different sensitivity of contamination at a pristine versus an urban site, as well as with depth (Level II applies at depths below 100 cm at pristine sites). The sediment criteria include a number of chemicals such as PAH. One HAC is included for sediment porewater (acridine). Amendments to the Waste Management Act, which introduced the Contaminated Sites Regulation, came into effect on April 1, 1997. The purpose of these changes was to establish processes for identifying and remediating contaminated sites; provide authority to government authorities to order site investigations and remediation where environmental risk warrants such action; and clarify responsibility and liability for contaminated sites. Legally defining a contaminated site, according to prescribed standards and clarifying responsibility and liability for a contaminated site, are two of the most significant © 2001 NRC Canada
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Table 1. Regulatory remediation Process in British Columbia. A. Ministry review and certification
This is the most common process. Milestone site usage events such as change of use, sale, and re-development may force screening or site investigations to occur. Screening is triggered by zoning applications, zoning applications, development permit applications, soil removal, or demolition permit applications. Screening, investigation, and site cleanup may be initiated voluntarily to access and reduce liability, or to enhance property value. Ministry reviews may be voluntary or mandatory. Certification of remediation is not mandatory. The Ministry, at specified review and decision points, require or order the next component of the remediation process.
B. Independent remediation (with/without rostered certification)
Screening, investigation and comparing to standards can proceed without Ministry involvement. When remediation is initiated, the Ministry must be notified, and the Ministry may require or order Ministry review and the next component of the process. If the contaminated site represents low to moderate risk to human health or the environment, a rostered professional can recommend that the Ministry issue certification of remediation upon its completion without Ministry review. For intermediate and high risk sites, certification can only be obtained with full Ministry review.
C. Ordered by Ministry 1. Remediation order 2. Pollution abatement order 3. Pollution prevention order
Site profiles used in the screening process, investigations, remediation, and public consultation can be ordered by the Ministry. The remediation order requires responsible persons to remediate a contaminated site, either to numeric or risk-based standards. These orders are appealable.
D. Minister’s order
The Minister of B.C.’s Environment, Lands and Parks has authority to require or undertake investigation and remediation of a contaminated site if it is necessary for the protection of human health or the environment, or if the site is not otherwise being adequately remediated, or if the site is a high-risk orphan site. If the Ministry directly undertakes remediation, authority to seek cost recovery from responsible persons is provided. This order is not appealable, but a submission for judicial review is available.
E. Emergency declaration
This authority is provided under the Environmental Management Act (EMA) and provides the Ministry with authority to take any steps necessary to protect human health and the environment. An environmental emergency must be declared to invoke this authority. This authority is not appealable, but is subject to judicial review upon application.
Note: Each of the above remediation processes share five basic components, these being (1) screening (site profiles), (2)investigating (preliminary and detailed site investigations), (3) comparing with standards (numeric standards), (4) remediating (numeric or risk-based standards), and (5) confirming remediation (confirmation of remediation report). The Waste Management Act defines remediation as being “action to eliminate, limit, correct, counteract, mitigate or remove any contaminant or the negative effects on the environment or human health of any contaminant, and includes, but is not limited to (A) preliminary site investigations, detailed site investigation, analysis and interpretation, including tests, sampling, surveys, data evaluation, risk assessment and environmental impact assessment; (B) evaluation of alternative methods of remediation; (C) preparation of a remediation plan, satisfactory to the manager, including a plan for any consequential or associated removal of soil or soil relocation from the site; (D) implementation of a remediation plan; (E) monitoring, verification and confirmation of whether the remediation complies with the remediation plan, applicable standards and requirements imposed by the manager; and (F) other action that the Lieutenant Governor in Council may prescribe”. An additional remediation process, called a voluntary remediation agreement, is available; however, this process is perhaps best described as a contractual agreement that can be super-imposed upon the processes described above. It can be used to define responsibility and liability, and it is a vehicle through which the ordered remediation process may be avoided. It should not be confused with the independent remediation process.
changes in British Columbia’s regulation of contaminated sites. Exceeding standards means that the usefulness of the site has been impaired, and potentially, the environment or human health is at risk. Additionally, a site is defined not by legal boundaries, but by the area affected by the contamination. This definition of impairment, damage, or harm was then coupled with clarification of responsibility and liability for contaminated sites. In its simplest terms, this legislation and regulation is based on polluter pay principles, with joint and several, absolute, and retroactive liability. These liability principles are far reaching in that the definition of persons responsible for remediation at contaminated sites includes: current and previous owners, current or previous operators, chemical transporters, and others who caused a site to become a contaminated site. It is therefore very possible
that a number of persons or companies will share responsibility for a contaminated site and its remediation. The amended Waste Management Act and the Contaminated Sites Regulation also increased BCMELP’s authority (Table 1) to “order” potentially responsible persons to investigate or remediate sites considered to be of higher risk to human health or the environment. With these changes, the Ministry was given the authority to make owners and operators investigate and determine the presence or absence of contamination, and if present, the risk to human health or the environment posed by the contamination. Regulatory authority shifted from reactive to proactive. Then, for the higher risk contaminated sites, the ministry was given the authority to require remediation. The remediation processes defined by the Waste Management Act and the Contaminated © 2001 NRC Canada
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Sites Regulation, with brief descriptions, are presented in Table 1 for clarification. The sites discussed in this paper were among the first to be exposed to the new processes and powers under the amended Waste Management Act and the Contaminated Sites Regulation, and as such, many ordered process details were developed or defined as remediation progressed on these sites. Also, many legal precedents regarding investigation and remediation orders, and the definitions of responsible persons and environmental risk are being set through ongoing legal actions at these sites.
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of the Department of Fisheries and Oceans’ Fish Habitat Management Policy is to maintain the productive capacity of fish habitats by preventing further erosion of the productive capacity of existing habitat (i.e., no net loss principle). The first step in the process is to design projects such that current productive capacity is maintained. If the harmful alteration, disruption, or destruction of habitat cannot be avoided, then losses to habitat must be mitigated, or compensated by habitat replacement or enhancement initiatives on a case-by-case basis.
Site characteristics Federal Creosote and associated carcinogenic PAH compounds are included in the Priority Substance List 1 (PSL1) published by Health Canada (Canadian Environmental Protection Act 1993). These substances were assessed pursuant to Section 11 of the Canadian Environmental Protection Act and were identified as “toxic” under the Act. A substance is considered toxic if (1) it may have an immediate or long-term harmful effect on the environment; (2) it may constitute a danger to the environment on which human life depends; or (3) it may constitute a danger to human life or health. The Canadian Council of Ministers of the Environment has published sediment quality guidelines for a variety of compounds including those present in creosote (Canadian Council of Ministers of the Environment 1998). The guidelines for contamination in sediment exist for phenols, chlorinated phenols, benzene, ethylbenzene, toluene, and xylene, but not for HAC. Water quality guidelines for protection of aquatic life are available for two HAC compounds, acridine and quinoline (Canadian Council of Ministers of the Environment 1999) Although contamination on provincial land is under provincial jurisdiction (Contaminated Sites Regulation), a site which has the potential to impact areas recognized as fish habitat and (or) areas frequented by fish must also meet the provisions under the federal Fisheries Act (Fisheries Act 1973). The Fisheries Act, introduced in 1973, addresses the deposition of deleterious substances (Section 36), and habitat protection (Section 35). The deposition of deleterious substances is a broad-reaching provision, which applies to releases from a variety of sources such as outfalls, spills, and contaminated sites. Section 36(3) of the Fisheries Act prohibits deposition of a deleterious substance, but does not provide a clear definition of “deleterious”. This can cause considerable controversy when identifying or remediating contaminated sites. The Contaminated Sites Regulation allows certain concentrations of contaminants in soil, groundwater and sediments, and the regulation allows for the use of ecological risk assessment to determine site-specific “safe” concentrations of contaminants. The allowable concentrations under the provincial regulatory system may be deleterious under the federal system. This uncertainty has profound affects on the development of remediation plans and on associated costs. The Department of Fisheries and Oceans Fish Habitat Management Policy (Department of Fisheries and Oceans 1986) guides the administrative process of the habitat protection provision under the Fisheries Act. One of the goals
History and use The sites discussed in this paper have several similar characteristics in terms of the historical use of creosote and the resulting site contamination. The sites are all located within deltaic deposits along the Fraser River, and have similar site geology. The following is a summary of the history at the various sites: • Creosote was used for wood treatment (two sites) and as part of the production of roofing and building materials (one site). • All three sites were in operation over an approximate 50 year period, beginning in the 1920s and 1930s. • Soil and groundwater became contaminated through creosote use, and as a consequence of actions such as spills, leaks, and drips during unloading, transfer, handling, and storage of raw materials and distilled products; placement of materials containing creosote waste along the foreshore of the river during foreshore filling; random on-site filling using materials containing creosote waste; and releases of chemicals during the demolition and decommissioning of storage tanks and other structures on each site. Regional geological setting Regionally, the sites all lie within a geological bedrock basin that has been infilled with glacio-marine, alluvial (deltaic), swamp, and flood plain deposits (Figs. 1 and 2). The infilled deposits are a few hundred metres thick near the Fraser River, and decrease in thickness to the north. Following the last glacial episode, sediment deposition at the mouth of the Fraser River accumulated in Georgia Straight, gradually building up a thick sequence of fine-grained deltaic sand deposits that now comprise the Fraser River Delta. The deltaic sands, which are laterally extensive, are typically between 20 and 35 m in thickness and are referred to regionally as the Fraser River Sand. On the delta, natural sand levees that formed adjacent to the river channels deposited finer-grained silty sands and silts (overbank silts) in the quieter areas north of the levees. Consequently, the present topography at each of the sites is characterized as relatively flat, with native silt and (or) peat overlying a thick, interbedded sequences of sands which, in turn, overlie thick Pleistocene deposits. Fraser River Sand Aquifer The deltaic sands comprise a regional aquifer commonly referred to as the Fraser River Sand Aquifer. The aquifer is hydraulically connected to the Fraser River, and responds to © 2001 NRC Canada
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Fig 2. Conceptual hydrogeologic diagram.
diurnal fluctuations in water levels caused by tides. Average groundwater flow is typically horizontal toward the river, and then upward into the river where it discharges. However, during periods in late spring when river flows are high and the water table is low, hydraulic gradients may reverse inland for periods of up to one or two months. River sediment mobility Sediments along the riverbed are eroded during large flow events and are replaced with sediment eroded from upstream areas as the flow event wanes. Contaminated sediments may be transported away from a site during the large flow events leaving behind freshly exposed contaminated sediments that will be subsequently reburied by newly arriving uncontaminated material from upstream. Fine sediments such as silt may accumulate over a site during the low-flow periods. These fine sediments form a surficial layer (veneer) that is remobilized during the next large flow event.
Site investigations Scope and methods Detailed investigations have been conducted at each of the sites to characterize the physical, chemical, and biological subsurface conditions, including an assessment of potential exposure pathways. This information has been used to facilitate the subsequent evaluation of a range of remedial alternatives including in-place management of the contamination.
Approaches that have been used in characterizing each of the sites are described elsewhere (Patrick and Anthony 1998), and include conventional shallow excavations (test pits), hollow stem drilling and sampling, the use of push technologies (cone penetrometer testing), and continuous soil coring to define stratigraphy, soil chemistry, and the presence and extent of DNAPL. Groundwater assessments have included conventional nested well installations as well as vertical chemistry profiling using, for example, the Waterloo Profiler™. Continuous water-level monitoring of tidal-response and damping in the aquifer, as well as conventional pumping tests have been conducted to evaluate aquifer properties, hydraulic gradients, and groundwater flow velocities and flux. Continuous coring, using the rotary sonic drilling method, as well Macro-Core™ methods (Geoprobe Systems), has been used extensively at each site to allow detailed stratigraphic description and direct observation of DNAPL, where present. Typical coring depths have ranged from 5 to 30 m, providing information through the full thickness of the Fraser River Sand Aquifer at each site. Characterizing river sediment has been largely conducted from a barge using a conventional hollow-stem drill rig, shallow coring, and dredging devices. Where obvious DNAPL is observed in soil or sediment cores, it is found almost exclusively in medium to coarse sand, and appears as viscous dark-brown to black globules or oily coatings. However, extensive areas of much lower DNAPL concentrations are often revealed in fine sands by © 2001 NRC Canada
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weak sheens, soil staining, and strong odours. Occasionally, root holes stained by DNAPL may be observed in cores of overbank silts located within source zones. Comparison of source zones The inferred extent of the zones of DNAPL at each site is illustrated in a schematic cross section in Fig. 3. Each DNAPL zone contains a heterogeneous distribution of creosote, where concentrations may range from absent to several percent. Lateral spreading at all sites has occurred through relatively coarse-grained strata bounded on the bottom by apparent capillary barriers of fine-grained material. The deepest zones of vertical penetration appear to have been limited to the areas where chemicals were released (i.e., within those areas where chemical use and handling were greatest). Dense nonaqueous phase liquid has reached depths of about 22 m below ground surface at one site, whereas it is estimated to to reach about 12–15 m depth at the other two sites. Dissolved polycyclic aromatic hydrocarbons Dissolved PAH emanating from the DNAPL source zones are found in both shallow fill onshore, and within the Fraser River Sand Aquifer both onshore and beneath the bed of the Fraser River. Concentrations of dissolved PAH within the source areas approach the expected solubility limits (e.g., 36 mg@L–1 for napthalene) and, in some cases, appear to have exceeded solubility limits where conventional sampling methods (e.g., purging using foot-valve samplers or bailers) may have entrained DNAPL micelles and (or) PAH sorbed to sediment in the water samples. Groundwater PAH concentrations in sediment a few metres beneath the discharge zones at the river (e.g., 0.01–0.5 mg@L–1 for naphthalene) are commonly one to two orders of magnitude lower than concentrations measured at the source zones (approximate1y 10 mg@L–1). For reference, the numerical standard for naphthalene in groundwater discharging to aquatic habitat is 0.01 mg@L–1). Further reductions in dissolved PAH concentrations are observed within the riverbed, as a consequence of tidally induced dilution and natural attenuation, as described in the section on natural attenuation. Dense nonaqueous phase liquid mobility The DNAPL plumes were delineated at each of the sites. The vertical extent of each plume was largely controlled by underlying fine sands or silts that were too fine to allow entry of the DNAPL. Extensive lateral spreading was common within more permeable strata, and at two of the sites DNAPL reached the river. Of concern at each of the sites has been the possibility that DNAPL was continuing to migrate from source zones toward and into the river. For the most part, the soil chemistry data and stratigraphy suggested that the potential for DNAPL migration under natural hydraulic gradients was low, and that the majority of DNAPL represents residual, immobile product. However, DNAPL has been recovered from wells at each of the sites. Demonstrating whether DNAPL could still potentially migrate under natural hydraulic gradients is complicated be-
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cause of the unpredictable nature of DNAPL flow, and because of its very low migration velocities. (e.g., perhaps on the order of 1 m@a–1) Such low velocities are to be expected because of the high DNAPL viscosity, weak stratigraphic slopes along which the DNAPL moves, and that the DNAPL density is near that of water. Natural attenuation Natural attenuation processes are likely occurring within dissolved plumes at each site. The plumes extend from the DNAPL sources onshore to zones of groundwater discharge within the river, within 20–90 m of the shoreline (Fig. 2). With the exception of a thin mixing zone in the bed of the river, each of the plumes is anaerobic (as indicated by low O2 and redox potential), and composed mainly of naphthalene (Fig. 4). At the river, a groundwater–river water mixing zone is created in the sediment by tidal fluctuations, which at high tide force oxygenated river water into the sediments due to the corresponding reversal of the hydraulic gradient. This diurnal reversal of flow effectively dilutes the plume and introduces dissolved oxygen for enhanced biodegradation. The thickness of this zone is variable, depending on the permeability of the river bed, and has been measured to be about 0.5 m thick in sand at one site. As a consequence of mixing, PAH degradation is promoted and the sediment porewater often has low to nondetectable PAH. (Anthony 1997; Zawadski et al., in press). Sediment At two of the sites, DNAPL occurs randomly in river sediment over comparably sized areas, each measuring about 20–50 m in width, and extending about 130–160 m in length. Within these DNAPL areas, the surficial sediments (to 0.6 m depth) have mean total PAH concentrations ranging between 100 mg@kg–1 and 200 mg@kg–1, although much higher concentrations are occasionally reported. These concentrations are about an order of magnitude greater than the draft provincial guidelines of 9.2 mg@kg–1 (Level I) for pristine sites and 17 mg@kg–1 (Level II) for urban sites (BCMELP) Total PAH concentrations in deeper sediments can be much higher, probably reflecting less weathering and higher DNAPL mass. At one site, the higher concentration at depth was related to preferred DNAPL migration through coarser lenses in the interbedded sand and gravel aquifer. Outside of the primary PAH zone, a “halo” of surficial PAH-contaminated sediments (secondary zone) can be defined at each of the two sites. This secondary surficial contamination is the result of ongoing natural river processes of erosion, deposition, and tidal influences, which have mobilized and redistributed PAH-contaminated sediment from the primary zone. The mean total PAH concentrations within these secondary zones are typically around 10 mg@kg–1, which is roughly equal to the Level I criterion of 9.2 mg@kg–1. Typical background PAH concentration in the Lower Fraser River due to anthropogenic sources are about 1 mg@kg–1 total PAH. The riverbed along the foreshore of these sites is generally dominated by silt and sand, with little overhanging or instream cover (e.g., riparian vegetation, boulders). Fish spawning and © 2001 NRC Canada
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Fig 3. Schematic cross section of typical site conditions.
Fig 4. Relative portion of individual polycyclic aromatic hydrocarbons as compared to total polycyclic aromatic hydrocarbons.
rearing habitat is, therefore, limited. Although the river adjacent to each site is used as a migration corridor for salmonids, it provides only a very small percentage of the route within the Fraser River. Apart from salmonids, species such as starry flounder and peamouth chub may use the area for rearing and migration. Common benthic invertebrates found in these sediments include oligochaetes, chironomids, nematodes, and copepods.
Polycyclic aromatic hydrocarbons composition in soil and sediment The mean composition of PAH in creosote-contaminated soil, groundwater, and sediment from one of the sites is shown in Figs. 4 and 5. The PAH composition in soil represents the mean concentrations of soil samples with visible creosote contamination. The composition of PAH in sediment represents the mean concentrations in the top 0.5 m of © 2001 NRC Canada
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the sediment within a zone of visual or olfactory evidence creosote contamination. The “background sediment” refers to samples collected upstream and downstream of the site. As shown, almost half of the total PAH concentration in soil consisted of napthalene (Fig. 4), and the low molecular weight (LMW) PAH made up more than 80% of the total (Fig. 5). This is consistent with the make-up of creosote and indicates that little degradation or dissolution has taken place at the main source of the contamination. The surficial site sediments have been contaminated as a result of past migration of DNAPL. The reason for the lower percentage of naphthalene and other LMW-PAH in these samples are believed to be due to biological degradation and dissolution through tidal flushing (for the reasons discussed earlier). The PAH composition of background sediment is distinctly different from the composition of the creosote contaminated soil and sediment, and is similar to combustion related PAH, with about 10% benzo (a)pyrene and more than 60% being HMW.
Site remediation Considerations for remediation Once a site has been determined to be a “contaminated site”, as defined in the Contaminated Sites Regulation, then remediation planning and implementation is expected. Several factors may influence or control the remediation process, and each must be taken in consideration. These are discussed below in detail. Regulatory issues The need and responsibility to remediate The remediation of contaminated sites can be a very expensive and complex business, and before any commitment to remediation can be made, there must be an identifiable need to take action. There must also be recognition of responsibility by the persons undertaking the remediation. In some cases, need is based on the desire of owners and responsible persons to realize the full value and use of their property. Remediation may also be undertaken to reduce or eliminate future liability. In some cases, however, where the risk to human health and environment is considered unacceptable, the need can be shifted towards compliance with regulatory authority. Time lines and costs are greatly influenced by why remediation is being undertaken. Flexibility is significantly reduced if remediation is ordered. In British Columbia, responsibility for the remediation of contaminated sites is defined by statute, namely the Waste Management Act. This liability is not dependent on, or subject to, actions by BCMELP. It is not created when a BCMELP manager issues a remediation order, although remediation orders can only be issued to responsible persons. Responsibility simply exists by statute if a person falls within the definition and does not qualify for one of the exemptions which are provided to ensure fairness. Responsibility is, however, subject to interpretation by the courts. Where a site history extends over many years, with changing site activities, owners, and operators, then determining responsibility for remediation can become a major
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and critical issue. Responsible persons ultimately finance remediation, and to varying degrees, control remediation activities. Legal arguments about responsibility and shares of responsibility can impede timely decisions, or can block remedial actions needed to maintain compliance with regulatory requirements. Conflicting remediation objectives, or the absence of clear remedial objectives, can result when multiple persons are responsible for the remediation of a contaminated site. Available Options Remediation processes and alternatives are provided in British Columbia’s Waste Management Act and Contaminated Sites Regulation. Direction is also provided as to what constitutes acceptable remediation. A contaminated site, as explained earlier, is determined solely on whether or not numerical standards are exceeded. Acceptable remediation, however, can be based on satisfying either numerical standards or risk-based standards. Where risk-based standards are used, additional factors must be considered. The legislation has a preference towards permanent remedial solutions to the maximum extent possible, taking into consideration risk to human health and the environment, the technical feasibility of alternate remediation options, remediation costs associated with alternative remediation options, and the potential economic benefits, costs and effects of the remediation options. Essentially, all risk-based remediation plans must evaluate risks, consider how to reduce contaminant mass and how to financially secure any risk management works. Determining a balance between these sometimes conflicting considerations is often the most challenging task in developing a remediation plan. If remediation of a contaminated site is required under the terms and conditions of a remediation order, some flexibility in developing this balance can be lost. Remediation orders As most creosote contaminated sites are very likely to be candidates for receiving remediation orders, the reasons why and the implications of receiving a remediation order are presented in greater detail below. Prior to 1997, the British Columbia Ministry of Environment, Lands and Parks had authority to issue an environmental emergency order (under the Environmental Management Act, or pollution abatement and pollution prevention orders under the Waste Management Act. These order powers are predominantly reactive, in that a serious problem had already occurred or was likely to occur in the very near future. The authority of each is also based on the definition of pollution, which legally can be difficult to define and consequently, often difficult to defend. In 1997, a fundamental change was made to Ministry regulatory order powers. The existing order powers were retained, but new order powers were provided. First, a Waste Management Act manager was given the authority to order investigations if the manager reasonably suspected that a “site may be a contaminated site”, or if a “site contains substances that may cause or threaten to cause adverse effects on human health or the environment”. As discussed earlier, a contaminated site was then defined solely on the basis of exceedances of numerical standards. From a scientific and legal perspective, this is a very simple, but powerful test to determine if the Contaminated Sites Regulation applies. © 2001 NRC Canada
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Fig 5. Concentration of low molecular weight-polycyclic aromatic hydrocarbons and high molecular weight-polycyclic aromatic hydrocarbons in sediment.
Once a site is determined to be a contaminated site, the manager can then set the boundaries of the contaminated site, and order remediation of the site. However, all of these powers come with obligations. Predominantly, the manager’s powers depend on the risk posed by the contaminated site to human health or the environment. The manager must evaluate this risk and determine whether or not remediation is required immediately and under order, or if it can be undertaken in progressive steps, with or without Ministry involvement. The National Classification System for Contaminated Sites, developed by the Canadian Council of Ministers of the Environment is used to determine intermediate and high risk contaminated sites (Canadian Council of Ministers of the Environment 1992). Sites representing intermediate to high risk to human health and (or) the environment are the most likely recipients of remediation orders, especially if these sites are in close proximity to a river, lake, or other aquatic life water body. Site operations at creosote-contaminated sites often depended on water access for barging of supplies and products; therefore, these sites almost without exception are located adjacent to a water body. Additionally, the industrial operation, and constituents and properties of creosote combine to make these sites intermediate to high risk sites. Many substances within creosote, such as some PAH, are extremely toxic. Generally, the creosote-contaminated source area is large, meaning that the contaminant mass is large. Contaminants are generally very mobile and potentially can be transported in multiple phase states, these being vapour, dissolved liquid in groundwater, and DNAPL. The site operations generating the contamination have been around for many years, providing time for transport of the contaminants from the source site to neighbouring properties and receiving water environments. There have usually been many owners and operators, with no one responsible person taking charge of
the contamination problem, and preventing harm or risk to human health or the environment. There is frequently disagreement among persons potentially responsible for the contamination, making it unlikely that any remedial action will occur without regulatory intervention. In summary, most creosote contaminated sites represent high risk to human health and the environment; all remediation options are very expensive; there are multiple potentially responsible and responsible persons; and, it is unlikely that any remedial action will occur without regulatory intervention. Any sites with such characteristics become BCMELP priority sites, and as staff and resources become available, remediation orders will probably be issued. The remedial process therefore must consider increased regulatory involvement, assigned time lines, and a decreased set of remedial options. Effects of remediation orders The most immediate and obvious effect of a remediation order is the increase in legal activity and cost to potentially responsible persons. Appeals can be made within 30 days of receipt of a remediation order to British Columbia’s Environmental Appeal Board. Ordered persons can appeal their presence on the order by claiming they are not a responsible person. They can appeal on grounds of unfairness that some persons were not included on the order that in their opinion should have been. They can appeal on grounds that the order was not required or is unreasonable in its requirements. There are many reasons that an ordered person can use to file an appeal; however, it is important that everyone doing so recognize that an appeal in itself does not operate as a stay of the requirements of the order, and that during the period required for the appeal to be decided, all ordered requirements must be satisfied. The failure to comply with a remediation order, even if it is under appeal, is a serious offence with potentially severe penal© 2001 NRC Canada
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ties attached. A monetary penalty of up to $200 000 per day as well as imprisonment for up to six months may be applied. Additionally, if a responsible person benefits monetarily by not complying with an order, the court can impose a fine equal to the court’s estimation of the monetary benefit. Also, if another party, including the crown, remediates the site upon which remediation has been ordered, the responsible person is liable for the remediation costs incurred. It is also possible that the failure to comply with an order will result in intentional damage or loss of the use of the environment. Under these circumstances, failure to comply may result in a maximum daily fine of up to $3 000 000, or imprisonment for not more than three years, or both. Where contaminated sites have multiple potentially responsible or responsible persons, as is common with creosote contaminated sites, the filing of an appeal by one or more of the ordered parties usually ends or severely restricts communication and cooperation between potentially responsible persons. In turn, remediation planning and decisions on objectives can be significantly delayed. For high risk sites under remediation order, the process of appeals can be further complicated if a stay is requested. A successful stay request means that the requirements of the order are set aside or modified until a decision on the appeal is made. At this juncture, communications with regulators deteriorate significantly; in addition, if the regulators consider the contaminants from the contaminated site are presently discharging offsite and will continue to discharge into a receiving environment, and the environment is being affected, or if human health is being affected, a Minister’s order could be issued. This type of order supercedes a remediation order and is not appealable. They are only subject to judicial review. As Minister’s orders are very high profile, remedial planning must also contend with media involvement and public consultation. Federal Fisheries Act Most high risk contaminated sites are presently discharging contaminants into a receiving water body, or have deposited contaminants into the water body at some time in the past. In the former case, unless immediate efforts are made to contain and control contaminant migration, charges under section 36(3) of the Federal Fisheries Act for deposition of a deleterious substance could be laid against site owners and operators. In the latter case, even if responsible parties successfully remediate under provincial regulations, it is possible that existing deposits left in place under a risk assessment and risk management remedial approach, could be considered deleterious. This conflict arises from the fact that deleterious is not defined, leaving open the interpretation of whether assessment should be based on non-lethal effects at the population level or acute lethal effects at the organism level. Charges appear to become more probable the longer remediation is delayed, and if remediation orders have been issued. More importantly, the Federal Fisheries Act can profoundly influence what the final remediation objectives will be. The federal regulators appear to have an almost absolute preference for permanent remediation, and in-place management of contaminants in river sediments is viewed as a very unfavourable remedial alternative.
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Site constraints In developing remedial options, consideration must be given to site constraints. Remedial activities must minimize the disturbance to on-going site operations. Additionally, the effects of remediation on the stability of site structures must be considered carefully. In one of the three sites under discussion, a barge docking facility limits the locations for installing a DNAPL cut-off wall. This increases installation costs associated with this option substantially. A warehouse also covers a sizeable portion of one site, limiting access and placement of groundwater interceptor wells. An adjacent shipping channel, with heavy commercial (tugboats with barges and log booms) and recreational traffic, also poses some restrictions on potential sediment remedial options. In addition, to constraints caused by these facilities or activities, a number of natural conditions have to be considered when evaluating remedial options, including: riverbank geotechnical stability; concerns for the implementation of dredging or cut-off wall construction; presence of cobble layers at depth which could impede the installation of sheet pile cut-off walls; and the erosion and mobility of the river sediments caused by annual freshet flooding. Affected neighbouring properties Under the provincial Waste Management Act, persons responsible for a contaminated site are also responsible for contamination that has migrated from that site and affected neighbouring properties. Remedial planning must carefully consider the implications of having to work on a neighbouring property, whose owner is not responsible for the contamination. Often there are site access conditions and these can be very restrictive. Delays are very possible. Multiple responsible persons and interdisciplinary teams For each of the three sites under discussion, there are several responsible and potentially responsible persons with respect to site contamination. Remediation planning takes on an added level of complexity when more than one party is trying to direct a process. This complexity is magnified when shares of responsibility vary, and where one party is the current land owner. The objectives of each party will not necessarily be the same. For example, the person with the greatest share of responsibility may be focussed on the least expensive remedial option, which also has the greatest on-going monitoring and maintenance requirements, and the most land-use restrictions attached. The current land owner, who may also have the lowest share of responsibility, may be focussed on the most permanent, and possibly the most expensive remediation option which has the lowest on-going maintenance requirements, and the least restrictions on land use. The model that appears to work well involves establishing one remedial consulting company to plan and implement remediation, and establishing a joint management team of the responsible persons. Clear rules need to be established from the outset regarding the decision process and how disputes are resolved. Generally, each responsible person will have their legal council and technical consultant to provide them with advice. Where multiple responsible persons are involved with the remediation, considerable time must be allotted to communi© 2001 NRC Canada
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cations and to establishing a working authority structure within which everyone is comfortable. Failure to do so may result in a modified remediation order. If responsible persons cannot resolve their differences and successfully remediate the contaminated site, the British Columbia Ministry of Environment can order one of the responsible persons to complete the remediation and seek financial redress from the other responsible persons through the courts. The regulators to date have never taken this approach.
of low-permeability caps, and restrictions on land use, as well as control of local groundwater using shallow interceptor trenches. To date, BCMELP has ordered the removal of shallow PAH contamination at one site where concentrations exceed the Special Waste Regulation. These standards are typically ten times higher than the Contaminated Sites Regulation standards for industrial landuse (e.g., naphthalene: Contaminated Sites Regulation standard = 50 mg@kg–1; Special Waste Regulation = 500 mg@kg–1).
Remedial strategy and implementation The unique aspects of the environmental contamination from facilities using creosote has led to a remedial strategy of partial source removal, containment and interception. These strategies reflect the knowledge of where the leaks and spills occurred, such as tanks and pipes, and the science of creosote (DNAPL) migration. These locations are easily identified based on historical information and targeted for investigation, remediation and (or) containment. The remaining contamination is significantly more diffuse as a result of physical displacement (dumping) or natural migration. Based on the considerations discussed above, the remedial strategy at each of the three sites involved a series of steps to achieve source control and risk reduction. Source control involved groundwater pumping and treatment systems to hydraulically control dissolved chemicals (two sites) and further DNAPL migration (one site) from the upland source zones. With these controls in place, the approach to final remediation is based on defining actual risk to human health and the environment posed by the contamination, and on developing and implementing remedial works that (1) reduce the risks to acceptable levels and (2) meet the provincial regulators requirement for contaminant mass reduction. Therefore, a large part of the remedial effort currently on-going, is focussing on identifying areas of potential mobility of DNAPL at these sites, defining DNAPL control measures to address potential DNAPL migration, and defining ecological risks posed by DNAPL and dissolved components to benthic communities in the river bed.
Long term hydraulic control Hydraulic control of dissolved PAH contamination in the local sand and gravel aquifer has been implemented at two sites, and is being considered at the third. Each hydraulic control system includes pumping of groundwater from wells, and treating the pumped water on-site, using either activated carbon with pre-treatment to remove naturally occurring iron and manganese, or chemical oxidation of PAH based on Fenton’s chemistry. Treated water is currently discharged to the sanitary sewer, although alternatives are being explored because the sanitary sewer system is nearing capacity at some locations. Several in situ remedial technologies were considered for both soil and groundwater contamination (e.g., chemical oxidation, steam injection, chemical and (or) physical stabilization). However, these methods were considered to be impractical and prohibitively costly, and had a low probability of being successful in meeting numerical standards or controlling and (or) containing the contamination. At one of the sites, hydraulic control was upgraded with more wells and higher pumping rates to control both the dissolved PAH plume as well as to arrest potential DNAPL migration. In addition, DNAPL recovery from the deep aquifer underlying the upland area was enhanced through cyclic stressing of the aquifer by pumping. Groundwater modelling and on-going monitoring indicate that the hydraulic containment and control system in place is effective, with a reversal of the groundwater gradient away from the river ranging from 1% at low tide to 2% at mean tide. This reverse gradient is sufficient to arrest or reverse the flow of DNAPL as well as capture the entire dissolved phase plume.
Temporary abatement works At one site, the remediation order specified the implementation of several temporary abatement works to be installed during the site investigation stage, to affect controls on potential environmental impacts, particularly discharges of dissolved contaminants to the Fraser River. The temporary abatement remediation works included Level 1installation of a DNAPL collection well and groundwater pump-and-treat system to control the offsite discharge of dissolved constituents in groundwater entering the river and to collect free-phase creosote; and Level 1excavation and restoration of the exposed foreshore and beach area, to remove contaminated fill material. Uplands source reduction In the uplands at each of the sites, an approximately 1 m thick layer of fill was placed over native soil during development. Polycyclic aromatic hydrocarbons contamination occurs in this near-surface fill layer at each site, and is being safely managed in-place by preventing surface exposures through construction of concrete building slabs, placement
Sediment removal or control At one of the sites, DNAPL within the river sediments was found to extend to a depth of over 8 m below the bed of the river, adjacent to a structurally sensitive wharf and building. Ecological health risk assessment was conducted to evaluate various removal and containment options. Given regulatory considerations, options under consideration included partial sediment removal through dredging, and inplace management using either a reactive containment layer in the sediments, or encapsulating the sediments within a sheet-piled wharf structure to create a contained disposal facility. The concept of the biological reactive containment layer is to provide a means to collect and remove DNAPL from the sediments, while providing an overlying biologically active layer to degrade dissolved PAH prior to groundwater discharge into the river. The concept is being pursued as it may provide, a cost-effective means to prevent DNAPL migration and exposure in the biologically active shallow © 2001 NRC Canada
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sediment; it may also fully treat the dissolved PAH, thereby rendering hydraulic controls redundant and unnecessary. At another site it was concluded that capping and (or) containment will provide the best level of protection. The selection of this option was based on regulatory considerations, the results of the aquatic risk assessment, the already existing source control measures (mass reduction and hydraulic control of DNAPL and dissolved PAH), and specific site constraints. These constraints included: mobility of river sediments, river slope stability concerns if disturbed, and increasing PAH contamination with sediment depth to depths below the surface sediments of 4–5 m. The sediment cap considered consists of engineered rock armour. The cap will prevent erosion and downstream transport of contaminated sediments, provide a barrier between the contaminated sediments and the aquatic community, and provide a dispersion and attenuation zone for any groundwater that may contact sediments if groundwater pumping containment was terminated. At the third site, the sediment is not appreciably affected (above urban background) as only dissolved PAH in groundwater are reaching the river.
Conclusions Two of the creosote-contaminated sites discussed in this paper were subjected to BCMELP remediation orders, since the potential risk to aquatic life in the Fraser River was considered to be high. Several phases of investigation and remediation have taken place over the past three years, with variable rates of progress, influenced by the complexity of the responsible persons group and by site conditions. The remediation is, to a large extent, completed at two of the sites, and is well underway at the third site. The remediation involved a combination of contaminant mass reduction through removal of near surface contaminated soils, in-place management of PAH contamination at depth and in the river sediments, and hydraulic control of dissolved and free-phase contamination through pumping from on-site wells. The completed remediation and management works will allow for continued industrial and (or) commercial use of the sites and will provide long term protection of the Fraser River and its aquatic habitat. The remediation at these sites is expected to be completed in a timely manner satisfying both the provincial Contaminated Sites Regulation, which is intended to protect human health and the environment, and providing for an overall site improvement. In addition, the conditions of the remediated sites should meet the provisions under the Federal Fisheries Act, by controlling releases of deleterious substances to the aquatic environment, and by providing a foreshore fish habitat of equal or better value. Complete removal or reduction of PAH contamination to applicable standards was not possible at any of the three sites with today’s technologies, and even if the removal or reduction of all accessible contamination had been pursued, this would have resulted in a lengthy and very costly process. The partial removal of the source of the contamination, but containment of the majority and less accessible contamination in the ground and sediment; have provided for an effective remediation, at reasonable cost. The remediated sites
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will require long-term operation and maintenance of hydraulic control sediment cap systems, under an environmental management plan and a provincially required financial security, to ensure adequate funding for its continued implementation.
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