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APPENDIX C - Examples of Conceptual Models

Table C-1 Example of a Conceptual Model Applicable to the Dredging Site during the Work

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	During the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Sediment dredging	Physical	Dredged sediments	Resuspension	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The sediments resuspended in the water column during dredging will reach the spawning sites of some fish species located downstream from the dredging site in sufficient quantity to significantly affect its potential.
	Physical	Noise	Diffusion	Ambient air		Fauna Human		The noise generated by dredging activities will affect the well-being of on-site workers and nearby residents.
	Chemical	Contaminants (adsorbés aux sédiments dragués)	Resuspension	Water column	Hydrodynamic and hydrosedimento-logical conditions	Human Fauna Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The contaminants resuspended in the water column during dredging (adsorbed to the particles or dissolved) will be adsorbed by the organisms in the environment in sufficient quantity to trigger acute effects.
		Contaminants (désorption du sédiment et diffusion)	Complexation Readsorption Release of potentially toxic natural substances	Water column	Hydrodynamic and hydrosedimento-logical conditions	Human Fauna Flora Particularity		The contaminants resuspended in the water column during dredging (adsorbed to the particles or dissolved) and absorbed by the organisms in the environment will be bioaccumulated by a harvested species (particularity) so as to render it unfit for human consumption.
		Contaminants (désorption du sédiment et diffusion)	Volatilization	Ambient air	Dispertion	Human Fauna Flora Particularity		The contaminants associated with the dredged sediments will be volatilized in the ambient air in sufficient concentration to affect the health of on-site workers.

Table C-2 Example of a Conceptual Model Applicable to the Dredging Site after Completion of the Work

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	After the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Dredging sediments	Physical	Suspended dredged sediments	Dispersion and sedimentation	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The sediments resuspended in the water column during dredging will reach the spawning sites of some fish species located downstream from the dredging site in sufficient quantity to affect its potential significantly.
	Physical	Undredged sediments	Sediment exposure	Sediments Interstitial water	Hydrosedimento-logical conditions	Fauna Flora Particularity		The grain-size distribution of the on-site sediments exposed after dredging precludes recolonization of the environment by a diversified benthic community.
	Chemical	Contaminants (adsorbed to the dredged sediments)	Dispersion and sedimentation	Water column	Transport by current	Human Fauna Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The contaminants resuspended in the water column during dredging (adsorbed to the particles or dissolved) will be absorbed by the organisms in the environment in sufficient quantity to trigger chronic effects.
		Contaminants (desorption from the sediment and diffusion)	Complexation Readsorption Other	Water column	Hydrodynamic and hydrosedimento-logical conditions Environmental physicochemistry
		Contaminants (desorption from the sediment and diffusion)	Volatilization	Ambiant Air	Dispersion
		Contaminants (undredged sediments)	Sediment exposure	Sediments Interstitial water	Hydrosedimento-logical conditions Environmental physicochemistry			The chemical nature of the sediments exposed after dredging will allow recolonization of the environment and result in harmful effects for the organisms that will return to it.

Table C-3 Example of a Conceptual Model Applicable to the Disposal Site during Disposal of Sediments in Open Water

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	During the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Disposal or containment of contaminated sediments in open water	Physical	Sediment disposal at sea	Dispertion	Water column	Hydrodynamic conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The sediments resuspended in the water column during disposal will reach concentrations that can clog the gills of fish located downstream from the ocean disposal site, triggering their acute mortality.
		Sediment disposal at sea	Sedimentation	SSediments receptors	Hydrosedimento-logical conditions	Fauna Human Flora Particularity		The sediments will be deposited in part on a spawning site, leading to significantly reduced productivity.
		Noise	Diffusioon	Ambient air	Topography	Fauna Human		The noise generated by the disposal activities will affect the well-being of nearby residents.
	Chemical	Contaminants (adsorbed to the dredged sediments)	Dispersion	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Flora Human Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The contaminants resuspended in the water column during disposal at sea (adsorbed to the particles or dissolved) will be absorbed by the organisms in the environment in sufficient quantity to trigger acute effects.
		Contaminants (desorption from the sediment and diffusion)	Complexation Readsorption Release of potentially toxic natural substances	Water column	Hydrodynamic and hydrosedimento-logical conditions Environmental physicochemistry	Fauna Flora Human Particularity
		Contaminants (desorption from the sediment and diffusion)	Volatilization	Ambient air	Dispersion	Fauna Flora Human Particularity		The contaminants associated with the dredged sediments will be volatilized in the ambient air in sufficient concentration to affect the health of on-site workers.

Table C-4 Example of a Conceptual Model Applicable to the Disposal Site after Sediment Disposal in Open Water

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	After the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Disposal in open water	Physical	Deposited sediments	Transport	Water column	Hydrodynamic conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The grain-size distribution of the sediments at the disposal site precludes recolonization of the environment by a diversified benthic community.
Disposal in open water	Physical and chemical	Deposited sediments	Sediment exposure	Sediments Interstitial water	Hydrosedimento-logical conditions	Fauna Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The chemical and physical nature of the dredged materials deposited will allow for the recolonization of the environment and have harmful effects on the returning organisms. The sediments transported downstream during ocean disposal will be deposited on a spawning ground, which will significantly reduce its productivity (clogging and toxicity for sensitive life stages). The sediments transported downstream during ocean disposal will be deposited on a nursery site of a valued (for whatever reason) fish species in sufficient quantity to chronically affect the population (reduced survival and breeding success).

Table C-5 Example of a Conceptual Model Applicable to On-site Sediment Capping Activities

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	During the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Capping contaminated sediments in open water	Physical	Capped sediments	Resuspension and transport during placement of materials	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The sediments resuspended in the water column during disposal will reach concentrations that can clog the gills of fish located downstream from the ocean disposal site, triggering their acute mortality. The grain-size distribution of the sediments at the disposal site precludes recolonization of the environment by a diversified benthic community.
	Physical	Capped sediments	Other mechanisms related to the technology used	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity
	Chemical	Contaminants (adsorbed to the deposited sediments)	Resuspension and transport during placement of materials	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The contaminants resuspended in the water column during the work (adsorbed to the particles or dissolved) will be absorbed by the organisms in the environment in sufficient quantity to trigger acute effects.
	Chemical	Contaminants (desorption from the sediment and diffusion)	Complexation Readsorption	Water column	Hydrodynamic and hydrosedimento-logical conditions Environmental physicochemistry	Fauna Human Flora Particularity

Table C-6 Example of a Conceptual Model Applicable to the Site after Completion of Sediment Capping Work

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	After the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Capping contaminated sediments in open water	Physical	Capped sediments	Bioturbation and erosion triggering failure of capping material and a leak	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The materials used to cap contaminated sediments do not provide protection against the hydrodynamic conditions of the watercourse, to the point of observing medium-term dispersion and downstream accumulation of contaminated sediments.
Capping contaminated sediments in open water	Chemical	Contaminants (desorption from covered sediments)	Diffusion	Water column	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The contaminants dispersed downstream (adsorbed to the particles or dissolved) due to erosion of the capping site will be absorbed by the organisms in the environment in sufficient quantity to trigger acute effects.

Table C-7 Example of Additional Conceptual Models Proposed during On-shore Disposal or Containment

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	During the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
On-shore disposal or containment	Physical	Sédiments déposés	Loss	Surface water	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The quantity of fine particles released into the watercourse by the outflow of the sediment settling tank, which serves as a containment enclosure for the contaminated sediments, exceeds the recommended level for protection of aquatic life.
On-shore disposal or containment	Chemical	Contaminants (adsorbed to the dredged sediments)	Loss	Surface water	Hydrodynamic and hydrosedimento-logical conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	Contaminants considered to be bioaccumulative and persistent percolate through the containment enclosure of the contaminated sediments, thus presenting an unacceptable risk for the aquatic environment.

Table C-8 Example of Additional Conceptual Models during Disposal in a Terrestrial Environment

Source	Stressor			Ecosystem			Apprehended response	Example of impact hypothesis
Source	During the work		Mechanism	Abiotic component	Mechanism	Receptor	Apprehended response	Example of impact hypothesis
Terrestrial disposal and containment	Physical	Deposited sediments	Air transportation	Atmosphere	Weather conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The residential population near the work site is inconvenienced by the dust generated and transported into the air by the winds from the sediment dewatering site.
	Physical	Noise	Diffusion	Ambient air	Topography	Fauna Human		The machinery and vehicles used for dredging and transport of sediments generate noise that disrupts a tourist area during the high season.
	Chemical	Contaminants (adsorbed to the deposited sediments)	Air transportation	Ambient air	Weather conditions	Fauna Human Flora Particularity	Consideration of the apprehended responses determined in the literature for each of the target receptors	The quantity of contaminants (adsorbed to the dust) breathed by the population of the nearby residential area exceeds the level considered acceptable for human health.
		Contaminants	Desorption from the sediment and diffusion or percolation/td>	Groundwater	Hydrodynamic and hydrosedimento-logical conditions Environmental physicochemistry	Human Fauna Flora Particularity		The quantity of contaminants found in the water of a sampling well installed nearby, after transport of contaminants in the soil, exceeds the acceptable criterion for human health.
				Runoff water (from the dike or spillway)	Weather conditions	Human Fauna Flora Particularity
				Adjacent soil	Geochemical conditions	Human Fauna Flora Particularity

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