draft environmental assessment west carleton …draft environmental assessment west carleton...

Draft Environmental Assessment West Carleton Environmental Centre

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chapter 6. detailed impact assessment of the undertaking

Figure 6-12 Final Operation Year – Preferred Leachate Management System Isopleths of the Maximum Predicted Odour Concentration – 10-Minute Average Period


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Figure 6-13 Final Operation Year – Contingency Leachate Management System Isopleths of the Maximum Predicted Odour Concentration – 10-Minute Average Period


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Although the maximum predicted odour concentrations at the property line are predicted to

exceed the 3 OU/m³ annoyance threshold from time to time, the MOE guidance document

indicates that odour concentrations need only be assessed at odour-sensitive receptor

locations, such as residences, commercial buildings, and outdoor parks and recreation areas.

Discrete Receptors

In the intermediate operation year, the maximum odour concentration resulting from the WCEC

operations was predicted to occur at Receptor R1, with a value of 4.2 OU/m³. The odour

concentration at Receptor R1 was predicted to exceed the detection threshold of 1 OU/m³

1.15% of the time and to exceed the annoyance threshold of 3 OU/m³ 0.15% of the time.

Predicted odours at the remaining sensitive receptors were less than the annoyance threshold.

Although predicted odours at some of the remaining sensitive receptors were predicted to

exceed the detection threshold, the frequency of exceedance of 1 OU/m³ at each of these

receptors was less that 0.5% of the time.

In the final operating year, the maximum odour concentration resulting from the WCEC

operations was predicted to occur at Receptor R3, with a value of 2.7 OU/m³. The odour

concentration at Receptor R3 was predicted to exceed the 1 OU/m³ detection threshold less

than 0.5% of the time and was not predicted to exceed the 3 OU/m³ annoyance threshold. The

predicted concentrations for all other sensitive receptors were predicted to exceed the 1 OU/m³

detection threshold less than 0.5% of the time.

Therefore, for the Preferred Leachate Management System, all sensitive receptor locations are

predicted to comply with the MOE’s current guidelines for odour, with the exception of R1 during

the intermediate operation year.

Contingency Leachate Management System results are similar to the results for the Preferred

Leachate Management System. This is consistent with the finding that the leachate evaporator

is not a main contributor to off-site odour impacts. Overall, the maximum predicted odour

concentrations for the Contingency Leachate Management System are the same as those

predicted for the Preferred Leachate Management System, while the predicted frequencies of

exceedance of the 1 OU/m³ detection threshold increased slightly at some sensitive receptor

locations.

Therefore, for the Contingency Leachate Management System, all sensitive receptor locations

are predicted to comply with the MOE’s current guidelines for odour, with the exception of R1

during the intermediate operation year.


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Potential Odour Effects

The impact of the expansion is evaluated based on the maximum predicted concentration and

frequency of time that the predicted concentration exceeds the odour detection threshold of

1 OU/m³ and the odour annoyance threshold of 3 OU/m³. The predicted odours at all of the

discrete receptors are in compliance with the MOE’s current guidelines in terms of both

predicted concentrations and frequency of predicted impacts, with the exception of Receptor 1,

with the implementation of the mitigation measures described in the following sub-section.

Predicted impacts at Receptor 1 exceed the 1 OU/m³ detection threshold 1.15% of the time and

exceed the 3 OU/m³ annoyance threshold 0.15% of the time. These predicted impacts are

slightly above the MOE guideline, which allows for predicted exceedances of the 1 OU/m³

detection threshold 0.5% percent of the time. Consequently, the impact of the expansion is

considered low at all discrete receptors for all future build scenarios, with the exception of

Receptor 1, where it is considered medium.

These results assume that the worst-case operations are occurring in the same locations for a

five-year period. In reality, the working face, which has been shown to be a dominant contributor

to off-site impacts, particularly at R1, will move to various locations within each landfill Stage

over the modelled period. The impact from the working face at a particular receptor will be

lessened as the distance between this source and the receptor increases. Therefore, the

frequencies of exceedance of the 1 OU/m³ and 3 OU/m³ thresholds at Receptor 1 may be

reduced relative to what was predicted by the dispersion modelling.

Mitigation and/or Compensation Measures for Odour

The odour assessment considered the following mitigation measures:

Development of an Odour Best Management Practices (BMP) Plan, which

will include all mitigation measures proposed, along with additional measures

determined during Detailed Design;

Progressive installation of the LFG collection system for the Preferred

Alternative Landfill Footprint;

Flaring or otherwise combusting all collected LFG;

Increase in stack height of the leachate evaporator to a minimum of 22 m

above grade;

Maintaining the leachate collection system under negative pressure and

sending the collected gas to the LFG collection system;

Minimizing the size of the working face; and,

Daily covering of the working face.

In addition to these mitigation measures, additional mitigation measures may be undertaken to

further reduce odour impacts and will be specified in the Odour BMP Plan.


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Odour Net Effects

The impact of the expansion is evaluated based on both the maximum predicted concentration

as well as the frequency of exceedance of the detection and annoyance thresholds for odour.

The maximum predicted impacts show increased odour levels relative to the baseline condition.

However, the only odour source included in the baseline scenario was the existing landfill under

final cover with full gas collection at an efficiency of 85%. The comparison indicates that the

proposed landfill expansion will result in increased detection of odours at the discrete receptors,

relative to baseline conditions; however, the detection frequencies are relatively low and are

within MOE guidelines for all receptors with the exception of Receptor R1.

6.7.1.4 Landfill Gas

The Landfill Gas Detailed Impact Assessment included the generic On-Site, Site-Vicinity, and

Regional study areas, as shown in Figure 6-3 and described below:

On-Site ............. the lands required for the Preferred Alternative Landfill Footprint;

Site-Vicinity ...... the lands in the vicinity of the Preferred Alternative Landfill

Footprint, extending about 500 m in all directions; and,

Regional ........... the lands within approximately 3 to 5 km of the Site and the

Preferred Alternative Landfill Footprint.

Landfill gas (LFG), although consisting mainly of methane and carbon dioxide, contains trace

amounts of volatile organic compounds (VOCs) and reduced sulphur compounds. Although

these contaminants account for less than 1% by volume of LFG escaping from the landfill, their

concentrations must be assessed because they can potentially result in health impacts at

residences or businesses that surround the landfill site. The type and concentration of

compounds within the LFG can vary greatly, depending on the composition of the decomposing

waste from which the LFG is created. Based on the Ministry of the Environment’s (MOE) Interim

Guideline to Assess Air Impacts from Landfills and the approved ToR, 24 contaminants of

interest in the LFG were reviewed. These compounds, which include 20 VOCs and 4 reduced

sulphur species, were assessed in the LFG study.

Contaminants emitted from the leachate management system were not previously assessed in

the LFG Baseline Conditions report. Contaminants emitted in common from the landfill and the

leachate management system were assessed (i.e., benzene and dichloromethane), as well as

ammonia, which is solely emitted from the leachate management system. Ammonia was

included in the LFG assessment because it is the typical contaminant of concern emitted from

leachate management systems.


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Vinyl chloride, benzene and hydrogen sulphide were selected as contaminants of particular

interest based on historical issues at the existing WCEC.

Predicted concentrations of VOCs, reduced sulphur compounds, and ammonia were compared

against Ontario Regulation 419/05 Air Pollution, Local Air Quality (O.Reg. 419) Point of

Impingement (POI) Standards.

The on-site sources of VOCs and reduced sulphur compounds include the existing landfill

mound under final cover, the Preferred Alternative Landfill Footprint and associated sources

(i.e., working face and contaminated soil stockpiles), the landfill gas-fired engines, the LFG

flares, and the leachate management system (preferred and contingency methods).

The evaluation considered the potential impacts from the Site sources including the Preferred

Alternative Landfill Footprint at 24 discrete receptor locations (refer to Figure 6-14),

representing receptors of interest in the Site-Vicinity and the Regional study areas. The discrete

receptor locations, considered in the dispersion model, include nearby residences, schools,

businesses, and other sensitive receptor locations. For all cases, humans were assumed to be

present at these receptors for 24 hours per day. Further details on LFG sources, receptors, and

dispersion modelling are found in the Atmospheric (Landfill Gas) Detailed Impact Assessment

Report in Supporting Document #5 – Detailed Impact Assessment.

The potential air quality impacts that would result from the construction and operation of the

proposed Preferred Alternative Landfill Footprint were assessed at the worst case future build

stages and phases of development. The future build scenarios were assessed by determining

odour associated with the significant emission sources in each scenario and determining the

potential off-site impacts through dispersion modelling. The scenarios assessed include the

intermediate operation scenario (Year 2018) and final operation scenario (Year 2023). In

addition to the two operation scenarios, two proposed leachate management methods used to

treat the leachate were assessed: the preferred method (pre-treatment with discharge to City of

Ottawa sanitary sewer) and the contingency method (pre-treatment with leachate evaporator).

Landfill Gas Methodology/Additional Investigations

The LFG impacts from the existing landfill and the Preferred Alternative Landfill Footprint

conditions were determined using a dispersion model and reasonable worst-case emission

rates. Dispersion modelling was performed using the U.S. EPA’s AERMOD dispersion model

(AERMOD) to predict concentrations of LFG emitted from the WCEC preferred alternative

existing landfill at various receptors in the Study Area.


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Figure 6-14 Landfill Gas Detailed Impact Study Area and Receptor Locations


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Detailed Description of the Environment Potentially Affected by Landfill Gas

On-Site and Site-Vicinity

Maximum predicted concentrations did not exceed the applicable standards for any of the 24

contaminants of interest.

The maximum predicted off-site concentrations associated with the construction and operation

of the Preferred Alternative Landfill Footprint including the preferred leachate management

system is predicted to occur in 2018 scenario near the northeast corner of the facility. The vinyl

chloride concentrations are predicted to be the highest concentrations relative to the

corresponding limit. The maximum predicted 24-hour vinyl chloride concentration was

0.73 µg/m3, which represents 73% of the Schedule 3 Standard of 1 µg/m3. The predicted vinyl

chloride concentration was influenced by both emissions from the landfill mound as well as

emissions from the leachate treatment system (SBR).

Hydrogen sulphide was the only contaminant which had the calibration factor applied. The

maximum predicted calibrated hydrogen sulphide 24-hour concentration at any off-site location

in 2018 was 1.68 µg/m3, which represents 24% of the Schedule 3 Standard of 7 µg/m3.

The maximum predicted concentration of hydrogen sulphide in 2018 is influenced by the close

proximity of the most recently developed stage (Stage 1), to the property line. For conservative

purposes, it was assumed that the installation of the LFG collection system in Stage 1 in 2018 is

not complete and the gas collection efficiency is approximately 50% for this Stage. Landfill

sources with such reduced gas collection efficiency are generally the most dominant in causing

off-site impacts. Although the Preferred Alternative Landfill Footprint in the 2023 scenario

generates more LFG and also has an active stage (Stage 8) with a reduced gas collection, the

location Stage 8 is not as close in proximity to the property and therefore the 2023 scenario

concentration is not as influenced by this source as it is in the 2018 scenario. Consequently, the

maximum concentrations predicted throughout the future operating scenarios occurred in 2018.

Discrete Receptors

Predicted 24-hour vinyl chloride, benzene and hydrogen sulphide concentrations did not exceed

the POI limit or criteria at any of the receptors. The predicted 10-minute hydrogen sulphide

concentrations at the discrete receptors did not exceed the POI limit or criteria at any of the

receptors. The hydrogen sulphide concentrations were evaluated against the 10-minute

averaging standards only at the discrete receptors, in accordance with the MOE’s “Methodology

for Modelling Assessments of Contaminants with 10-Minute Average Standards and Guidelines

under O.Reg 419/05” Technical Bulletin.


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Maximum concentrations are predicted to occur at Receptor 2 (southeast corner of the WCEC

facility) for most of the time, with exception of the 10-minute hydrogen sulphide maximum

concentration which occurs at Receptor 3 (west of the WCEC facility) for all future build years.

Potential Landfill Gas Effects

For both the preferred leachate management system and the contingency leachate

management system, the maximum predicted concentrations are less than the applicable

standards or criteria at all receptors in the area, including both the discrete receptors and the

receptor grid. Consequently, the impact of the expansion is considered low at all discrete

receptors for all future build scenarios.

Mitigation and/or Compensation Measures for Landfill Gas

The LFG assessment considered several mitigation measures that are part of the design of the

preferred landfill alternative and include the following:

Development of an LFG BMP Plan which will include all mitigation measures

proposed, along with additional measures determined during Detailed Design;

Progressive installation of the LFG collection system for the Preferred

Alternative Landfill Footprint;

Flaring or otherwise combusting all collected LFG;

Increase in stack height of the leachate evaporator to a minimum of 22 m

above grade;

Maintaining the leachate collection system under negative pressure and

sending the collected gas to the LFG collection system;

Minimizing the size of the working face; and,

Daily covering of the working face.

In addition to these mitigation measures additional mitigation measures may be undertaken to

further reduce LFG impacts. These additional mitigation measures will be specified in the LFG

BMP Plan.

Landfill Gas Net Effects

The proposed landfill expansion will result in increased concentrations of the LFG compounds at

the discrete receptors, relative to baseline conditions; however, the maximum predicted

concentrations are within MOE guidelines for all receptors and all off-site locations. The

predicted concentrations at the discrete receptors and all other off-site locations do not exceed

the applicable standards or criteria under the preferred leachate management system or the

contingency leachate management system. Consequently, the impact of the expansion is

considered low at all discrete receptors for all future build scenarios.


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6.7.1.5 Noise

For the purposes of the Noise Detailed Impact Assessment, the On-Site Study Area includes

the lands owned or optioned by WM within the area enclosed by Highway 417, Richardson Side

Road, and Carp Road. The Site-Vicinity Study Area includes the area within 500 m of the On-

Site Study Area and the Regional Study Area stretches approximately 5 km from these lands

(refer to Figure 6-15).

Receptors of interest under MOE’s Noise Guidelines for Landfill Sites include noise-sensitive

land uses to be permanent or seasonal residence, hotels/motels, nursing/retirement homes,

rental residences, hospitals, camp grounds, as well as noise sensitive buildings such as schools

and places of worship.

As part of the undertaking WM will exercise property options within the On-Site Study Area. This

will result in current noise-sensitive receptors leaving the On-Site Study Area during the life of

the proposed undertaking. As a result, On-Site noise impacts have not been considered, as

there will be no noise-sensitive receptors within the Study Area.

The receptors considered within the Site-Vicinity include the following:

2-storey home on Richardson Side Road NNW (PR4);

2-storey home David Manchester Road (PR9);

1-storey home at 2485 Carp Road North (NR1);

2-storey home at 2166 Carp Road East (NR2);

2-storey home at 292 Moonstone Road South (NR4);

2-storey Terrace Youth Residential Services (NR8);

2-storey Sensitive Business Operation (NR9);

2-storey David Manchester Road Central (RR12);

2-storey at 607 William Mooney Road (RR14); and

2-storey Wilbert Cox Drive (RR15).


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Figure 6-15 Noise Detailed Impact Study Area and Receptor Locations


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Receptor NR1 is a single dwelling that is located on a single large parcel of land bounded by

Richardson Road to the north, Carp Road to the east, William Mooney Road to the west and the

proposed WCEC Landfill site boundary to the south. This parcel of land is designated Carp

Road Corridor Rural Employment Area in the City of Ottawa’s Official Plan and Light Industrial

within the Carp Road Corridor Community Design Plan. The zoning for this property is Rural

General Industrial. This parcel of land is currently non-conforming with future planned uses and

any future residential development in this parcel of land is not permitted. The noise assessment

therefore assumes any future use of this land would be commercial/industrial. Only the existing

single dwelling, located to the northeast of this parcel, has been used in the assessment and

identified as NR1.

Two site-vicinity residential receptors (PR4 and PR9) and one regional receptor (PR7) were

selected to account for the worst-case noise impacts from WCEC sources.

The receptors considered within the Regional Study Area include the following:

2-storey home at 2096 Carp Road South (PR7);

St. Stephen Catholic Elementary School (NR5);

Huntleigh United Cemetery (NR6);

Lloydalex Park (NR7);

2-storey Spruce Ridge Road Central (RR10);

2-storey David Manchester Road North (RR11);

2-storey David Manchester Road South (RR13);

2-storey Carp Road North (RR16);

2-storey Oak Creek Road (RR17);

2-storey West Carleton Industrial Park (RR18);

2-storey Timbermere (RR19);

2-storey Stittsville (RR20);

2-storey Jackson Trails (RR21);

2-storey Fairwinds (RR22);

2-storey Arcadia (RR23); and,

2-storey Kanata West (RR24).

Further details on noise sources, receptors, and dispersion modelling are found in the

Atmospheric (Noise) Detailed Impact Assessment Report in Supporting Document #5 –

Detailed Impact Assessment.


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Noise Methodology/Additional Investigations

The detailed assessment of environmental noise from the Preferred Alternative Landfill Footprint

focussed on landfill and construction operations as the major activities. The noise assessment

was completed by:

Reviewing available land use, traffic, and design data;

Determining the noise sources associated with the Preferred Alternative

Landfill Footprint landfill and construction operations;

Estimating sound emissions from sources using measured or theoretical

methods;

Establishing a three dimensional acoustic model of the project to predict

WCEC expansion noise levels;

Comparing predicted noise levels to the criteria contained in the MOE’s Noise

Guidelines for Landfill Sites; and

Assessing landfill noise levels cumulatively with background sound levels.

Noise impact modelling was completed using Cadna/A, a commercially available software

package implementing the ISO 9613 environmental noise propagation algorithms, and took into

account the following factors:

Source sound power level and directivity;

Distance attenuation;

Source-receptor geometry including heights and elevations;

Barrier effects of the facility, the surrounding buildings and surrounding

topography;

Duration of events;

Ground and air (atmospheric) attenuation;

Temperature and humidity effects on propagation; and,

Moderate downwind or inversion conditions (per the ISO 9613 standard,

where sound contributions at a receptor from multiple sources are calculated

under a downwind condition, regardless of spatial orientation).

The determination of change in environmental noise is rated based on both compliance with

applicable regulation, as well as the degree of change expected in the cumulative noise

environment. The criteria relevant to the WCEC EA are the MOE “Stationary Source” guidelines

for Class 2 (suburban) and Class 3 (rural) areas as set out in MOE Publication NPC-205 and

NPC-232, and the MOE Noise Guidelines for Landfill Sites.


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The criteria define the amount of noise that may be generated by activities on the Preferred

Alternative Landfill Footprint for the WCEC. Where the existing background noise levels exceed

these criteria, facility generated noise must not exceed the existing background level.

The MOE criteria establish the allowable noise contributions from the WCEC landfilling and

stationary source activities separately. To evaluate the amount of change in noise levels at

receptors, a cumulative approach is required. The changes in noise levels were determined by

comparing the existing environmental noise levels (including the Ottawa WMF, its gas collection

system and traffic) with the expected future noise levels due to the landfill expansion, gas

collection system, leachate treatment system and traffic. The definition of an effect will be based

on the “Just Noticeable Difference (JND)” of about 3 dBA. The JND is a defined value regarding

human response to sound. In cases where the change in sound level due to the WCEC is

greater than 3 dBA, mitigation/compensation is recommended to reduce the net effects.

Sound Level Increase[1]

(dB)

Qualitative Assessment of Change

1 to 3 Just Noticeable

3 to 6 Clearly Noticeable

6 to 9 Substantial Change

9 and over Very Substantial Change

Notes: [1 The increase in sound level at the receptor from the existing

condition to the proposed condition.

Detailed Description of the Noise Environment Potentially Affected

Existing noise levels within the environmental noise study area are influenced by traffic on

Richardson Side Road, Carp Road, Highway 417 and Highway 7. Natural sound also influences

the cumulative noise environment.

On-Site

The existing On-Site environment will include the LFG to energy facility and associated traffic.

Site-Vicinity

The sound levels surrounding the WCEC will be influenced primarily by road traffic noise from

along Richardson Side Road, Carp Road, Highway 7, and Highway 417. No existing noise

regulated industry surrounding the WCEC was identified or considered in this assessment as

discussed in consultation with the MOE. As such, only traffic noise impacts have been

considered for the assessment of the baseline noise conditions at Site-Vicinity receptors.


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Regional

The baseline noise levels in the Regional Study area are influenced by the existing sources on

the WCEC, surrounding light and heavy industrial activity, and traffic. However, only traffic noise

was considered in establishing baseline conditions on a regional scale.

Potential Noise Effects

The applicable guideline limit for steady-state sources may be exceeded by approximately

6 dBA at NR1. Similarly, predicted impulsive sound levels at receptors NR1, NR2, NR4, and

NR8 indicate the applicable guideline limit may be exceeded by 1 to 5 dBA. The potential

changes to noise levels are approximately 0.1 dBA with the addition of landfill traffic on public

roadways. Due to the large existing volumes of traffic, and the fact that most of the landfill traffic

will use Highway 417, the effects are considered negligible and are not carried into the net

effects assessment.

The potential effects of noise are the combined sound level contributions from the baseline

noise condition and all proposed WCEC landfill activities. The potential effects and sound level

increase from existing conditions are presented in Table 6-3. The results show that receptors in

the Site-Vicinity may experience changes in sound levels of up to 6 dBA in the daytime due to

landfilling. Regional receptors may experience potential change of up to 1 dBA, assuming

minimal influence from other local noise sources. This amount of change is not expected to be

noticeable, as background at these locations may have other local sources influencing noise

levels and the amount of change predicted is below 3 dBA.

Mitigation and/or Compensation Measures for Noise

Basic noise controls that were assumed to exist or be maintained at the WCEC were

incorporated into the noise modelling. These controls were either integral to the facility design or

assumed to be implemented. The specific controls considered include the following:

All WM trucks should use standard (factory) silencers and be kept in good

working order;

Stationary sources are enclosed in buildings where practical;

The existing landfill height of approximately 172 m will act as a berm for

receptors to the south;

The finished height of the preferred landfill footprint of approximately 156 m

will act as a berm for receptors to the north for sources travelling on the main

access road; and

Conduct construction and landfill operations between the hours of 7:00 am

and 7:00 pm to reduce the potential impacts.


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Table 6-3 Potential Increase in Sound Levels over Existing Conditions – Landfill Operations

Point of Reception

ID Point of Reception (PoR) Description

Resulting Landfill Guideline Limit

[1]

(dBA)

Cumulative Sound Level

[2]

(dBA)

Overall Increase in Sound Level

[3]

(dBA)

Sit

e V

icin

ity

Re

ce

pto

rs

PR4 2-storey home on Richardson Side Road NNW 56 58 2

PR9 2-storey home David Manchester Road 59 60 --

NR1 1-storey home at 2485 Carp Road North 55 61 6

NR2 2-storey home at 2166 Carp Road East 60 61 --

NR4 2-storey home at 292 Moonstone Road South 64 65 1

NR8 2-storey Terrace Youth Residential Services 57 59 1

NR9 2-storey Sensitive Business Operation 64 65 1

RR12 2-storey David Manchester Road Central 63 63 --

RR14 2-storey at 607 William Mooney Road 61 62 1

RR15 2-storey Wilbert Cox Drive 55 57 2

Reg

ion

al

Re

ce

pto

rs

PR7 2-storey home at 2096 Carp Road South 60 61 --

NR5 St. Stephen Catholic Elementary School 55 55 --

NR6 Huntleigh United Cemetery 55 56 1

NR7 Lloydalex Park 55 55 --

RR10 2-storey Spruce Ridge Road Central 55 55 --

RR11 2-storey David Manchester Road North 60 60 --

RR13 2-storey David Manchester Road South 55 55 --

RR16 2-storey Carp Road North 55 56 1

RR17 2-storey Oak Creek Road 61 62 --

RR18 2-storey West Carleton Industrial Park 55 56 1

RR19 2-storey Timbermere 55 55 --

RR20 2-storey Stittsville 55 55 --

RR21 2-storey Jackson Trails 55 55 --

RR22 2-storey Fairwinds 55 55 --

RR23 2-storey Arcadia 55 55 --

RR24 2-storey Kanata West 55 55 --

Notes: - All values shown are rounded to the nearest digit. Any apparent discrepancies are due to rounding.

[1] The higher of MOE Landfill guideline limit or background sound level (see Table C3.1). This is also referred to as the “baseline

noise condition”.

[2] Cumulative sound levels include contributions from the baseline noise conditions, total landfill activities and total ancillary

facilities.

[3] Change from baseline noise condition.


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Investigation of potential mitigation measures indicates that placement of temporary berms at

the active working faces could sufficiently control noise levels at NR1. In the worst-case

scenario, 7 m berms (i.e., blocking line of sight and 4 m above the equipment) placed at both

the construction and landfilling working faces for operations occurring at grade in cells 1 and 3

(north-eastern cells) would result in a daytime noise level of approximately 55 dBA at NR1,

which complies with the MOE landfill criteria. The berm heights at the working faces can

gradually decline with increase in separation distance from the receptor as the activities migrate

west and south. At a minimum, the berms should block line of sight and be 1 m above the

equipment in north-western cells (cells 5 and 7). The progression of landfilling from north to

south allows the use of the landfill itself as a berm to further reduce noise impacts. Therefore,

berms are not required for landfilling or construction activities in the southern cells. In addition,

aligning the initial site preparation activities with quarry operations east of Carp (i.e., during

summer months) would account for elevated background sound levels.

Mitigation for the potential exceedance of applicable criteria for impulsive sources may be

problematic. Impulsive sources that show potential to exceed the criteria are propane cannons.

Propane cannons are a directional noise source. The current predictions assume no advantage

due to directionality. The degree of potential exceedance for these sources is 5 dBA or less, so

careful placement of the cannons in a manner that they are pointed away from the residences is

expected to mitigate any effects. This should be verified through measurement during

operations.

The use of trained raptors, such as falcons, and other visual deterrent techniques should be

considered as a bird control alternative.

Noise mitigation needs will vary over the life of activity in the Preferred Alternative Landfill

Footprint depending on the spatial arrangement of equipment in the landfill, including the landfill

height.

Noise Net Effects

The modelling results indicate that landfill activity located on the Preferred Alternative Landfill

Footprint will generate noise at some of the receptors in the Site Vicinity but is expected to

comply with MOE requirements once mitigation is applied. Noise levels at some of the

representative receptors may be affected by landfill activity, but the amount of change is not

expected to be noticeable.


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6.7.2 Geology and Hydrogeology

The specific On-Site, Site-Vicinity, and Regional study areas for the Geology and Hydrogeology

Detailed Impact Assessment are shown in Figure 6-16 and described as follows:

On-Site .............. the lands required for the Preferred Alternative Landfill

Footprint and includes the area immediately north of the

existing landfill footprint and extends west to William Mooney

Road, east to Carp Road and north to the northern boundary of

lands under option to Waste Management;

Site-Vicinity ....... the lands in the vicinity of the Preferred Alternative Landfill

Footprint, extending about 500 m in all directions, including the

licensed area of the existing WM Ottawa WMF landfill and the

Contaminant Attenuation Zones (CAZs); and,

Regional ............ the lands within natural hydrogeologic boundaries, including

Huntley Creek to the north, Feedmill Creek to the south, and

extending to Carp River in the east. The upgradient boundary

of the Regional Study Area coincides with the boundary of the

Site-Vicinity Study Area.

6.7.2.1 Geology and Hydrogeology Methodology/Additional Investigations

The environmental characteristics of the Study Area were reviewed based on the FCR to verify

the accuracy of the assessment of net effects from the Preferred Alternative Landfill Footprint.

From this review, it was determined that the SWM ponds identified in the preliminary landfill

design could have potential effects on groundwater flow and contaminant transport within the

On-Site and Site-Vicinity Study Areas. Consequently, a detailed groundwater modelling

investigation was conducted in order to assess the potential effects on the Geology and

Hydrogeology discipline from the preliminary landfill design.

The results from the initial modelling exercise to identify potential effects led to the development

of additional mitigative measures that are predicted to achieve acceptable net effects from the

Preferred Alternative Landfill Footprint.

The predicted potential effects, mitigation measures and net effects are described in the

following subsections.


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Figure 6-16 Geology and Hydrogeology Detailed Impact Assessment Study Area


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6.7.2.2 Detailed Description of the Geology and Hydrogeology Environment Potentially

Affected

On-Site Study Area

Topography and Drainage

The On-Site Study Area consists of well-drained sandy areas, representing the upland side of a

post-glacial beach ridge. The topography is flat-lying on the western half of the property with an

elevation of approximately 125 mASL, and slopes downward toward the eastern edge of the

ridge, reaching approximately 120 mASL. The land surface has been modified by former

aggregate extraction activities and landfill operations on the south half of the On-Site Study Area.

Surface drainage on the southern half of the On-Site Study Area is controlled by ditches and a

SWM pond. Surface flow is from the southwest to northeast across the south half of the

property, and the majority of surface water flow in this area collects in shallow ponded areas. On

the north half of the On-Site Study Area, surface water flow follows the land contours and

agricultural ditches in a northerly orientation. Surface drainage collects in Huntley Creek, which

ultimately flows into the Carp River.

Geology

Overburden deposits were found to be relatively homogeneous, grading from sand-gravel in the

eastern portion along the post-glacial beach ridge, to fine sand further west, away from the edge

of the ridge. The overburden thickness ranges from approximately 4 to 16 m. The bedrock

surface slopes toward the north and northeast.

The bedrock consists of light to medium grey, fine to medium-grained fossiliferous limestone

with some shaly and sandy interbeds. The bedrock is classified as the Bobcaygeon Formation,

which is described regionally as a limestone with shaly partings and intermittent sandstone. The

bedrock is generally most fractured in the upper few metres, although at the western end of the

On-Site Study Area, relatively high fracture frequencies are observed for 5 to 10 m below the

bedrock surface.

Hydrogeology

Shallow groundwater flow generally follows the trend in bedrock surface topography.

Groundwater flows in a northerly orientation on the western half of the On-Site Study Area, and

gradually becomes northeasterly across the eastern portion. In the northwest corner of the

existing landfill, there is localized groundwater mounding which results in a small component of


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flow to the northwest in the immediate vicinity of the landfill mound; however, the natural

hydraulic gradient, which is oriented north-northeast, controls the direction of flow further away

from the landfill mound.

The groundwater elevations in the deep bedrock are similar to the trend in overburden-shallow

bedrock, with the regional groundwater flow in the deep bedrock being toward the northeast.

With few exceptions, the water quality parameters from monitoring wells screened in the

overburden-shallow bedrock on the western side of the On-Site Study Area are within the

expected range of background concentrations.

The southern boundary of the On-Site Study Area lies along the northern edge of the existing

landfill. Groundwater monitoring completed as part of the regular environmental monitoring

program for the operating landfill site has shown that leachate-impacted groundwater is moving

northward away from the landfill, in a direction consistent with the local groundwater flow.

Elevated concentrations of dissolved parameters are also seen downgradient of the SWM pond,

in a former area of biosolids storage.

Site-Vicinity Study Area


Within the Site-Vicinity Study Area, the natural topography, which has been modified by

extraction and waste disposal activities, ranges from an elevation of approximately 131 mASL

southwest of the landfill site to less than 110 mASL on the Huntley Quarry property, located east

of Carp Road.

North and west of the existing landfill site, surface drainage flows within the Huntley Creek

subwatershed. Tributaries of Huntley Creek generally flow northward to Richardson Side Road,

and then eastward past Carp Road. Huntley Creek discharges to Carp River east of Huntmar

Road.

From within the boundaries of the existing landfill property, there is minimal direct off-site

discharge of surface water. Surface water drainage is primarily contained within the landfill

property and is directed to on-site ponds. The exceptions to this are the external slopes of the

vegetated site perimeter berms along the east and south boundaries of the landfill property;

however, this amount of surface runoff is very minor and is not in contact with operational

activities at the landfill. Runoff from the vegetated berms flows into the Carp Road and Highway

417 drainage systems. There is also a small area of drainage from the extreme western end of


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the site, north of the service entrance, which flows into the ditch along William Mooney Road,

and then northward into a tributary of Huntley Creek.

The Highway 417 drainage system controls surface water flow immediately south of the existing

landfill property. Surface water drainage south of the landfill property is controlled by ditches,

catch basins and culverts along Highway 417 and generally flows from west to east, eventually

reaching Feedmill Creek and ultimately Carp River.

Surface water drainage on the quarry property on the east side of Carp Road is influenced by a

series of excavated ponds that are used as a recirculation system for on-site aggregate washing

and dust control.

Geology

The surficial geology across the Site-Vicinity Study Area reflects the glacial history of the Ottawa

region. The unconsolidated deposits observed during subsurface investigations consist

principally of sand, silt, gravel and glacial till, and range in thickness from approximately 3 to

17 m. The surficial deposits are interpreted to be ice-contact stratified drift sediments, consisting

of a mixture of poorly to well-sorted, stratified gravels and sands, interbedded with a silty sand-

gravel till. The deposits are interpreted to have been submerged during the Champlain Sea

encroachment, and therefore show indications of re-working in a subaqueous environment.

The bedrock surface generally slopes toward the northeast across the Site-Vicinity Study Area,

ranging between elevations of 125 mASL and 108 mASL. The bedrock surface features two

apparent topographic highs: one located near the southwest extremity of the study area, and the

other in the western portion of the existing landfill site.

Bedrock consists of light to medium grey, fine to medium-grained fossiliferous limestone with

some shaly and sandy interbeds. The bedrock is classified as the Bobcaygeon Formation which

is described regionally as a limestone with shaly partings and intermittent sandstone. The

bedrock is generally most fractured in its upper few metres, while the frequency of fractures in

the bedrock decreases starting at depths of approximately 6 to 8 m below the bedrock surface.

Hydrogeology

In the higher topographic elevations along Carp Road, the water table in the unconsolidated

deposits (i.e., sand, silty sand and silty sand-gravel till) is generally found at over 10 m depth,

indicating that the majority of the unconsolidated deposits are unsaturated. The saturated

thickness of these deposits, which represents the water table aquifer, is generally limited to 5 m

or less. In areas where the bedrock is closer to the surface or where the topographic elevations


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decline, the depth to the water table decreases, however, the saturated thickness remains

limited. Groundwater is also found in the weathered bedrock at the overburden-bedrock

interface. This part of the unit extends to a depth of approximately 6 to 8 m below the bedrock

surface.

Shallow groundwater flow within the Site-Vicinity Study Area generally follows the bedrock

topography, with a water table elevation varying from 128 to 129 mASL in the southwest portion

of the landfill property to less than 112 mASL east of Carp Road. The direction of groundwater

flow within the overburden-shallow bedrock in the southwest portion of the study area is towards

the north-northeast. In the northwest corner of the existing landfill site, the topographic high

present in the bedrock appears to influence shallow groundwater flow and induces an area of

localized northwesterly flow toward the northwest corner of the site. Across the majority of the

study area, the direction of groundwater flow in the overburden-shallow bedrock is towards the

northeast.

The regional direction of groundwater flow in the deep bedrock is interpreted to be toward the

northeast. Groundwater flow in the deep bedrock is interpreted to be influenced by isolated

fracture zones, which do not appear to be well-connected across most of the Site-Vicinity Study

Area. However, across the western portion of the Site-Vicinity Study Area, where the bedrock is

found at shallower depths, the hydraulic heads in the deep bedrock zone are generally more

consistent with those in the overburden-shallow bedrock zone than they are on the eastern

portion of the study area. This indicates that there may be more hydraulic connectivity between

the shallow and deep hydrostratigraphic units in this area.

The groundwater quality within the Site-Vicinity Study Area is highly variable due to influences

on natural groundwater quality from the existing landfill, major transportation corridors,

aggregate processing, and local agricultural/commercial/industrial practices.

Regional Study Area


The Regional Study Area consists of sandy upland areas in the northwest and west to poorly

drained swampy areas, clay plains and the Carp River floodplain toward the northeast. The

primary natural topographic feature in the area is a northwest-southeast trending sand and

gravel ridge, which has historically been exploited for aggregate extraction.

Within the area, the natural topography, which has been modified by extraction and waste

disposal activities, ranges from an elevation of approximately 131 mASL southwest of the

existing landfill site to less than 100 mASL along Carp River. The dominant man-made


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topographic features in the study area are the WM Ottawa Landfill, which extends to an

elevation of approximately 172 mASL, and the Huntley Quarry, which has been mined to a floor

elevation of less than 75 mASL.

The Regional Study Area is situated within the Carp River watershed. The watershed drains

approximately 306 km2 of land in the northwestern portion of the City of Ottawa. Carp River is

located approximately 4 km northeast of the existing landfill and discharges to the Ottawa River

at Fitzroy Harbour, approximately 20 km northwest of the landfill property. Surface drainage

within the Regional Study Area is controlled by the ground surface topography and small

tributaries of Carp River, as modified by the surrounding quarry and landfill operations and the

Highway 417 drainage system.

Geology

The surficial deposits in the Regional Study Area consist of glacial and related materials from

the late Wisconsian glaciation. During this glacial period, thick sequences of sand and gravel

were deposited along the Ottawa River valley, followed by deposits of silt and clay during

encroachment of the Champlain Sea.

The materials observed in the vicinity of the WM Ottawa Landfill are interpreted to be ice-

contact stratified drift sediments, consisting of a mixture of poorly to well-sorted, stratified

gravels and sands, interbedded with lenses of silty sand-gravel till. The deposits are interpreted

to have been submerged during the Champlain Sea encroachment, and therefore show

indications of re-working in a nearshore, subaqueous environment. Closer to Carp River, thick

deposits of silt, clay and organic materials (peat and muck) have been deposited in a lower

energy, offshore marine environment consistent with the deeper waters of the Champlain Sea.

Organic deposits are found on the southeastern portion of the quarry property, east of Carp

Road.

The Regional Study Area is underlain by several carbonate rock-types. Throughout the majority of

the portion of the Regional Study Area that also encompasses the Site-Vicinity and On-Site,

bedrock consists of grey, fine to medium-grained fossiliferous limestone with some shaly or sandy

interbeds of the Bobcaygeon Formation, a member of the Middle Ordovician-aged Ottawa Group.

Within the Regional Study Area, the Bobcaygeon Formation is in contact with interbedded silty

dolostone, limestone, shale and sandstone of the underlying (older) Gull River Formation and

overlying (younger) Verulam Formation, which are classified as limestone with shale interbeds.

Both formations are also members of the Middle Ordovician-aged Ottawa Group.

The bedrock surface generally slopes at less than 1 degree in a northeasterly direction under

the Regional Study Area.


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The Paleozoic formations in the Ottawa area are transected by steeply dipping normal faults,

three of which are found within the Regional Study Area oriented from northwest to southeast.

Carp River follows the orientation of the Hazeldean Fault, which separates the Paleozoic

bedrock found within the Regional Study Area from the much older Precambrian rocks that

compose the Carp Ridge northeast of the study area. A second line of faults separates the

Bobcaygeon and Verulam Formations east of the Huntley Quarry. A third fault has been

mapped west of the existing landfill, separating the Gull River and the Bobcaygeon Formations.

Hydrogeology

Groundwater occurs within the unconsolidated overburden units and the Paleozoic bedrock

fracture systems found within the Regional Study Area. The general direction of regional

groundwater flow is northeast toward Carp River. Water table elevations range from

approximately 135 m southwest of the existing landfill to between 92 and 105 m along Carp

River.

Locally, groundwater recharge occurs along the sand and gravel ridge and upland areas

extending north and south of the existing landfill. Overall, the western portion of the Regional

Study Area is interpreted as having strong to weak downward gradients, indicating that these

areas are considered recharge zones. Closer to Carp River, groundwater discharge zones

occur, with upward hydraulic gradients becoming more pronounced in proximity to the river.

Groundwater quality within the Carp River watershed is generally acceptable for potable usage,

and is free from recognizable regional-scale groundwater impacts. Non-health related water

quality parameters, such as total dissolved solids, hardness, iron, sulphate and chloride

commonly exceeded the Ontario Drinking Water Standards, although the concentrations in the

groundwater tend to vary considerably with the type of bedrock formation. In general, the

regional groundwater quality reflects the characteristics of the limestone bedrock, being

dominated by calcium carbonate (hardness) and also containing iron and sulphur compounds

(sulphate, hydrogen sulphide) from the shaley interbeds.

6.7.2.3 Future Baseline Geology and Hydrogeology Conditions

Computer modelling simulations were used to predict future conditions for groundwater flow and

quality in the On-Site and Site Vicinity areas. The simulations were run using chloride as an

indicator of contaminant movement, because of its conservative nature in dissolved phase

transport. Whether chloride is appropriate to be used as a monitoring indicator and compliance

trigger for the site will be determined during the detailed design phase of the landfill and the

development of an Environmental Monitoring Plan.


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Groundwater Flow

The future baseline conditions for groundwater flow are predicted to be consistent with the

observed conditions seen at the landfill. The full extent of the landfill footprint and site

infrastructure have been established, and the site conditions at the time of the groundwater flow

model development and calibration are not expected to change significantly in the future. The

future baseline groundwater head contours for the Regional Study Area and the Site-Vicinity

Study Area are shown on Figures 6-17 and Figures 6-18, respectively.

Groundwater Quality

The western two-thirds of the existing landfill footprint is unlined, and leachate generated from

the waste can come into contact with the underlying groundwater. The direction of groundwater

flow from this area is toward the northeast. The concentrations of leachate indicator parameters

immediately adjacent to the unlined landfill are elevated above background and indicate

migration of leachate away from the toe of the landfill. It is expected that this movement of

elevated concentrations of dissolved parameters will continue in future, following the direction of

groundwater flow.

The existing purge well system installed along Carp Road to the east of the existing landfill

footprint and the closed south cell will continue to be operated in the future. The system

provides containment of leachate-impacted groundwater east of the site. As long as the purge

wells are operating, groundwater impacts on the Contaminant Attenuation Zone (CAZ)

properties are expected to gradually decrease over time.

In order to predict the future orientation and extent of leachate-impacted groundwater from the

unlined landfill footprint, computer-based numerical modelling of groundwater flow and

dissolved phase transport was completed. The groundwater flow model was calibrated to the

observed water levels on the landfill site and to water levels reported in the MOE’s Water Well

Information System (WWIS). The groundwater flow model simulates the flow system in the

study area and is used as the basis for establishing the direction that leachate impacts are

expected to migrate away from the landfill. To simulate movement of the leachate-impacted

groundwater, source concentration profiles were estimated for the landfill footprint based on

observed leachate concentrations, and by fitting an exponential decay curve post-closure. The

source concentrations were input to the groundwater flow system model, and allowed to migrate

with the groundwater flow according to the principles of advective-diffusive contaminant

transport. As noted previously, chloride was used as a modelling parameter to examine plume

orientations and trends. This is because of its conservative nature and elevated source

concentrations.


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Figure 6-17 Modelled Groundwater Heads in the Regional Area, Future Baseline Conditions


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Figure 6-18 Modelled Groundwater Head Contours in the Site-Vicinity, Future Baseline Conditions


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The results from the future baseline transport modelling indicate that leachate-impacted

groundwater is expected to continue to migrate away from the unlined landfill footprint. Figure

6-19 illustrates the simulated progression of impacted groundwater. The figure shows the

approximate orientation and extent of chloride concentrations that are predicted to exceed

130 mg/L (the Reasonable Use Limit for an aquifer with a background chloride concentration of

10 mg/L). It is seen that the impacted groundwater is predicted to eventually extend beyond the

current boundaries of the CAZ properties. This is because the orientation of groundwater flow

takes the dissolved constituents north of the existing purge well system, beyond its zone of

influence. Measures to control and abate the predicted extent of leachate impacts from the

existing unlined landfill are expected to be required.

It should be noted that the computer modelling simulations are not considered sufficiently

accurate to predict actual groundwater concentrations at specific locations and/or times.

Instead, the simulations are used to provide a reasonable projection of future contaminant

orientations and trends. Field observations (groundwater elevations and concentration trends)

will be necessary to measure actual leachate impacts at specific monitoring well locations.

6.7.2.4 Potential Geology and Hydrogeology Effects

Groundwater Flow

The potential effects on Groundwater Flow from the Preferred Alternative Landfill Footprint

(including the SWM ponds) are as follows:

1. Recharge to the groundwater is expected to be reduced within the area of

the new landfill footprint. This will have the effect of lowering the

groundwater elevations immediately below the landfill, but is predicted to

have minimal effects away from the footprint. The local and regional

groundwater flow directions are not expected to be impacted.

2. Infiltration from the SWM ponds is predicted to cause the groundwater

levels to rise under the unlined pond stages. The effects of this

groundwater mounding diminish with increased distance from the ponds.

The groundwater flow will be radially away from the ponds, which is

predicted to affect the orientation of the local flow regime and influence

groundwater quality in the vicinity.

The predicted groundwater head contours in the Site-Vicinity Study Area from the development

of the new landfill and the SWM ponds are shown on Figure 6-20.


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Figure 6-19 Predicted Chloride Concentrations under Future Baseline Conditions


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Figure 6-20 Modelled Groundwater Head Contours in the Site-Vicinity, Assuming Operation of the New Landfill Footprint and Stormwater Management Ponds


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Groundwater Quality

The proposed development of the new landfill footprint and the SWM ponds is expected to have

the following potential effects on the future baseline conditions for Groundwater Quality:

1. Surface water that infiltrates to the groundwater table from the SWM ponds

may contain elevated concentrations of contaminants from surface runoff,

traffic and landfill operations. These contaminants may migrate with the

groundwater flow toward the downgradient property boundary, which is

situated approximately 200 m to the east of the ponds.

2. Radial groundwater flow predicted to occur around the SWM ponds is

expected to intercept the movement of leachate-impacted groundwater

from the existing unlined landfill. This is expected to have the effect of re-

orienting leachate-impacted groundwater further northward across the On-

Site Study Area and extending beyond the northern property boundary. A

southern arm of leachate-impacted groundwater is expected to migrate

eastward onto the existing CAZ; however, because of the reduced mass of

contaminants being transported in this direction, the impacts may not

extend as far east as the future baseline scenarios, and may potentially

remain within the CAZ boundaries.

The potential effects from the SWM ponds and from the migration of leachate-impacted

groundwater from the existing unlined landfill are shown on Figure 6-21. Figure 6-21(a) shows

the maximum predicted extent of chloride concentrations greater than 130 mg/L from the SWM

ponds. Note that the maximum source concentration of chloride infiltrating from the ponds that

was used in the modelling simulations was set at 165 mg/L during landfill operations. This

effluent concentration limit restricts the mass of contaminant that is available for transport, as

will be discussed in the Geology and Hydrogeology Mitigation and/or Compensation Measures

subsection. Once the landfill site is closed, final cover will be applied and operations traffic

reduced. In the simulations, the projected source concentration was linearly reduced to 0 mg/L

over five years of post-closure.

Figure 6-21(b) shows the predicted maximum extent of leachate-impacted groundwater from

the existing unlined landfill, as influenced by the new landfill footprint and SWM ponds. From the

results of the simulations, it is apparent that the leachate-impacted groundwater would be

transported further northward than the future baseline scenarios. With no mitigation measures in

place, it is predicted that the potential effects to groundwater quality would extend off-site to the

north.


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Figure 6-21 Predicted Chloride Concentrations, Assuming Operation of the New Landfill Footprint and Stormwater Management Ponds


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The predicted contaminant flux through the double-composite liner of the new landfill footprint is

described in Supporting Document #4 – Facility Characteristics Report. The chloride

concentrations predicted to discharge through the base of the attenuation layer of the new

landfill were used as source concentration inputs to the groundwater model. Since the mass flux

of contaminant through the double-composite liner is very small (transport through the low

permeability liner components is dominated by diffusion rather than by advection), the changes

in chloride concentrations in the groundwater at the base of the attenuation layer are negligible.

This is consistent with the regulatory definition of the GII liner system, which is designed to

provide protection to groundwater quality without reliance on attenuation in the landfill buffer

area.

6.7.2.5 Geology and Hydrogeology Mitigation and/or Compensation Measures

Mitigation measures will be required to reduce the potential effects of the Preferred Alternative

Landfill Footprint on Groundwater Quality to acceptable levels. The proposed mitigation

measures are design-based and operational in nature, related to the movement of leachate-

impacted groundwater from the existing landfill and effluent from the SWM ponds, respectively.

Within the context of the EA, the proposed mitigation measures have been developed to a

conceptual design level, using computer-based numerical modelling simulations. This is

considered reasonable and sufficient in order to evaluate general trends in flow orientation and

contaminant concentrations, and to assess the conceptual feasibility of the proposed measures.

A detailed design of the mitigation measures, including additional modelling simulations and

field testing, would need to be completed at such time as actual contaminant transport dictates.

Purge Wells

The potential effects of the Preferred Alternative Landfill Footprint and associated operations

relative to the future baseline conditions are that contaminant concentrations from leachate-

impacted groundwater exceeding acceptable levels (as defined by the Reasonable Use Limits1

and as modelled using chloride as an indicator parameter) are predicted to extend beyond the

northern boundary of the site. The source of the leachate-impacted groundwater is the existing

unlined (closed) landfill footprint.

Purge wells are an effective method for controlling leachate migration from landfills in

permeable geologic environments. The existing purge wells on the site control the eastward

movement of impacted groundwater. A proposed mitigation measure to reduce the potential

1. The Reasonable Use Policy is aimed at ensuring that a proponent’s undertaking does not impair the ‘reasonable

use’ of ground water on neighbouring properties. It sets limits to the level of ground water impact that can occur at the proponent’s site property boundaries.


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effects of the Preferred Alternative Landfill Footprint is to install a series of purge wells along the

northern toe of the existing landfill, between the landfill and the new footprint. The existing

geologic conditions in the area consist of sand to sand-gravel overburden, underlain by

fractured limestone bedrock of the Bobcaygeon Formation. The average hydraulic conductivity

in the overburden-shallow bedrock zone is on the order of 1.5x10-4 m/s, which is considered a

permeable formation with favourable conditions for hydraulic capture via purge wells. The purge

wells would target the saturated overburden and the upper 6 to 8 m of fractured limestone as

the primary pathway for leachate migration.

The concept of purge wells installed as a mitigation measure was simulated using the numerical

model of groundwater flow and contaminant transport. The results of the modelling simulations

indicate that sufficient capture could be achieved by installing nine purge wells spaced evenly

along the toe of the existing landfill, completed in the overburden-shallow bedrock zone. The

predicted maximum extent of leachate-impacted groundwater with chloride concentrations

greater than 130 mg/L with the operation of the new purge wells is shown in Figure 6-22. Each

purge well was simulated to pump 45 m3/day (31.3 L/min), which is considered to be a

reasonable pumping rate for this type of aquifer, and is less than the average pumping rate for

the existing purge wells.

Under this modelling scenario, the predicted distribution of leachate-impacted groundwater

exceeding Reasonable Use Limits would not extend beyond the property boundaries of the

Preferred Alternative Landfill Footprint. In addition, although there would be drawdown of

groundwater levels in the vicinity of the purge wells and changes to the localized groundwater

flow directions, it is not expected that there would be any impacts to groundwater levels or flow

directions beyond the property boundaries.

The actual number and spacing of purge wells required and the design pumping rates will be

determined during the detailed design of the mitigation measures, when required. However, for

conceptual design purposes, the proposed mitigation measure is considered to provide a

reasonable method of reducing the potential effects on groundwater quality to acceptable levels.

Operational Controls on Stormwater Management Pond Effluent

The SWM ponds have the potential effect of allowing elevated concentrations of contaminants

to infiltrate to the groundwater table. The ponds are designed with two stages: surface runoff

first flows into a lined stage and then overflows to an unlined stage. Effluent in the lined stage

can be contained in case of a spill or other emergency.

The SWM ponds are located relatively close to the downgradient property boundary and beyond

the zones of influence of the existing purge well system and the proposed northern purge wells


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Figure 6-22 Predicted Chloride Concentrations, Assuming Operation of the New Landfill Footprint and Stormwater Management Ponds, and with Mitigation Measures In-Place


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described in the previous section. Because of the pond locations and the types of underlying

geologic formations, once in the groundwater there is limited attenuation capacity available to

further reduce the effluent concentrations. Therefore, the potential effects on groundwater

quality from the operation of the SWM ponds should be controlled by establishing limits on the

concentration of effluent in the unlined pond stages. These operational effluent limits would

restrict the concentrations of dissolved constituents entering the groundwater system such that

groundwater quality at the property boundaries would continue to meet acceptable levels.

Several predictive analyses of groundwater quality were completed using maximum effluent

concentrations from the ponds ranging from 50 to 300 mg/L. The results of the simulations

indicate that a chloride concentration of approximately 165 mg/L would reduce the potential

effects from the ponds to acceptable levels. Figure 6-22 shows the predicted maximum extent

of impacted groundwater with chloride concentrations greater than 130 mg/L, using a maximum

effluent concentration of 165 mg/L from the SWM ponds. The impacted groundwater in this

scenario (i.e., groundwater with chloride concentrations greater than 130 mg/L) does not extend

beyond the property boundaries.

Based on this conceptual assessment, the proposed mitigation measure for the potential effects

from the SWM ponds is to establish concentration limits on the effluent infiltrating to the

groundwater from the unlined pond stages. Further evaluation to confirm the final recommended

chloride effluent concentration and to determine whether other parameter limits should be

established will be completed during the detailed design phase for the landfill.

6.7.2.6 Geology and Hydrogeology Net Effects

The mitigation measures proposed for Groundwater Flow are sufficient to reduce the potential

effects from the Preferred Alternative Landfill Footprint to acceptable levels.

Implementation of the mitigation measures proposed for Groundwater Quality also result in net

effects that are considered acceptable.

6.7.3 Surface Water

The study area for the Surface Water environmental component is shown in Figure 6-23 and

described as follows:

On-Site .............. the lands owned or optioned by WM bounded by Highway 417,

Richardson Side Road, and Carp Road;

Site-Vicinity ....... the lands within 500 m of the On-Site Study Area; and

Regional ............ Huntley Creek subwatershed


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Figure 6-23 Surface Water Detailed Impact Assessment Study Area


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6.7.3.1 Detailed Description of the Surface Water Environment Potentially Affected

The existing landfill site and proposed landfill expansion area are situated adjacent to the south

tributary of the Huntley Creek subwatershed of Carp River. The subwatershed area is relatively

flat with a significant amount of wetland and scattered agricultural use as well as ongoing

estate-lot residential development.

The south tributary has a limited drainage area with a headwater area generally defined to the

west and south by Highway 417, to the north by Cavanmore Road, and to the east by Carp

Road. Local drainage patterns are somewhat undefined and are characterized by large wetland

areas that have significant storage potential, especially in the vicinity of the landfill site.

Depending on the magnitude of rainfall and the storage-discharge characteristics of the various

wetland areas, flow from these locations may or may not be realized on adjacent lands and at

the new landfill site. However, flow estimates were developed that reflected minimal storage to

provide a conservative estimate of peak flows.

A portion of the existing landfill site was a former gravel pit and has relatively permeable, silty-

sandy soils. Municipal water supply in adjacent built-up areas to the south (Ottawa – Stittsville)

and east (Ottawa - Kanata) is from the Ottawa River at the Britannia intake, while water supply

for the built up area to the north (Ottawa-Carp) is from local municipal wells. Water supply for

the rural areas is from private wells.

6.7.3.2 Potential Effects on Surface Water

Without mitigation, flow would outlet to South Huntley Creek upstream of Carp Road either by

flow north to South Huntley Creek in an existing swale across private lands or west to the Carp

Road westside ditch.

Construction

With no permanent mitigation during construction, surface water runoff from the landfill would

have to be contained by in-line or offline temporary SWM ponds to ensure that water quality

impacts from construction-related equipment and vehicles would be minimised and any

sediments from erosion would be contained.

Operation

From a water quality perspective, operation of the new landfill has the potential to impact water

quality due to accidental leachate seeps to the surface and/or increases in Total Suspended

Solids (TSS) concentration due to runoff from the landfill side slopes and the internal gravelled

access roadways.


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From a water quantity perspective, two main potential impacts are possible. The first is the

effect on local drainage patterns as surface water runoff from the landfill would likely have to be

diverted away from private lands to the north, and the swale that runs through it conveying

surface water north to South Huntley Creek. This diversion would:

Reduce flows to the swale, which would then be maintained only by adjacent

surface and groundwater flow. This impact would not be mitigated.

Reduce flows (by less than 5%) to South Huntley Creek tributary along

Richardson Side Road. This impact would not be mitigated.

Increase flows along the west ditch of Carp Road. This could be mitigated.

Require the re-location of existing SWM Facility (SWMF) #1 as a new two

stage SWMF to the east.

The second potential impact is a change in local topography provided by the relatively steep-

sloped (from a hydrologic perspective) landfill configuration and a resulting reduction in travel

time (as a result of increased flow velocities) that would create increased peak flows with

potential to increase downstream water levels and flood damage.

6.7.3.3 Surface Water Mitigation and/or Compensation Measures

Construction

SWM ponds managing all of the surface water runoff from the expanded site would be

constructed first and, as such, would provide the necessary quantity and quality control during

the remaining construction period and the operational lifetime of the site.

Other items for consideration during construction should include:

Implement appropriate BMPs (to be drafted at the Detail Design stage) for

protecting aquatic habitat and for limiting soil mobilization and trapping

sediment as close to the source as possible. The sedimentation and erosion

protection measures are to reflect these principles: minimize the duration of soil

exposure, retain existing vegetation where feasible, encourage re-vegetation,

divert runoff away from exposed soil, and keep runoff velocities low.

Maintain the integrity of all sediment trapping devices through regular

monitoring. In the event that it is determined that that controls are

unacceptable, WM shall cease those operations. Such structures should be

removed only after the soils from the construction areas have been stabilized

and then only after the trapped sediments have been removed.


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Direct runoff and overland flow away from working areas and areas of

exposed soils and maximize length of overland flow through to points where

stormwater is collected.

Swales and culverts will be installed, as required, to allow for surface flow to

pass under the on-site roads.

Any accidents or malfunctions (i.e., spills to surface water) will be limited in

their spatial and temporal extent, such that they will not result in the loss of

any component of the aquatic system.

A sediment control plan has been developed to mitigate effects associated with construction of

the project to prevent suspended sediment, mud, debris, fill, rock dust, etc., from entering

adjacent lands and the stormwater system. The following activities will be incorporated as part

of the sediment and erosion control plan:

Limit the zone of construction impacts to minimize disturbance of existing

vegetated areas where grading is required;

Minimize exposure time for un-vegetated soils;

Store and stabilize any stockpiled materials away from open water through

the installation of sediment and erosion control fencing such as silt

fences/curtains, sediment traps and check dams as appropriate;

Install silt fences, blankets, and/or berms around construction areas,

including the laydown area, and across sloping terrain/areas to prevent

surface runoff from carrying sediment off-site;

Properly site and contain all materials and equipment used for site

preparation and completion of work to prevent any deleterious substance

from entering the water;

Conduct refuelling and handling of potential hazardous substances away

from the SWM system;

Leave sediment and erosion control measures in place until all disturbed

areas have been stabilized;

Implement vehicle and timely equipment cleaning procedures of tracked mud,

dirt and debris along the access routes and areas outside of the immediate

work area where sediment and control measures are not in place;

Suspend work if excessive flows of sediment discharge occur and capture

and adequately filter drainage from any unstabilized surface to reduce

sediment loading;


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Install temporary security fence to surround and secure the site prior to

commencement of any site excavation, filling or grading works and maintain

on regular basis prior to and after runoff events. Clean out any accumulated

materials during maintenance and prior to removal;

Restoration of all disturbed areas on land to natural conditions and re-

vegetation as soon as conditions allow to prevent erosion and restore habitat

functions; and

Land based measures will not be removed until vegetation has been re-

established to a sufficient degree (or surface soils stabilized using other

measures) so as to provide adequate erosion protection to disturbed work

areas.

Operation

Water quality impacts would be mitigated by a two-staged SWMF to remove larger particle size

TSS loading and provide for emergency leachate/spill containment in a Stage 1 sediment

forebay with a Stage 2 providing extended control for additional TSS removal. SWMF outflow

would be as groundwater discharge (infiltration), with the SWMF incorporating existing local

excavation as previously practised at the existing site.

The water quantity impacts would be mitigated by Stage 1 and Stage 2 of the SWMF providing

attenuation of post-development flows to pre-development levels. SWMF outflow would be as

groundwater discharge (infiltration), with the SWMF incorporating existing local excavation that

would contain the 1:100 year runoff.

In more detail, SWM for the expanded site will be achieved through integration of the existing

and proposed system of ditches, culverts, stormsewers and SWM ponds that have been

designed to mitigate the impacts of stormwater runoff on water quantity and water quality before

discharge to South Huntley Creek. The SWM criteria, as identified by the MOE in Ontario

Regulation 232/98 and related Landfill Standards Guidelines (1998), include:

ditching designed to accommodate runoff from a 1:25 year rainfall event;

detention of runoff from a 4-hour 25 mm rainfall event; and

attenuation of peak flows to pre-development levels for all rainfall events up

to and including the 1:100 year Return Period event.

The existing site and proposed new landfill footprint area is founded on relatively permeable

soils and there is currently no direct discharge to South Huntley Creek from the landfill proper or

its servicing roads and operational areas. Rather, discharge is to three defined recharge areas,


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two of which have sedimentation forebays, the recharge areas eventually discharging through

groundwater, to South Huntley Creek. The proposed SWM system for the expansion is planned

in a similar manner and will account for the relocation of one of the existing recharge areas that

will be removed to accommodate the new landfill footprint.

The three proposed SWM ponds, including the relocated facility, are located in Figure 6-24 with

one pond to the southwest accommodating flow from the access road; one to the Southeast,

replacing existing SWMF #1 and Depression #3; and one to the north accommodating flow from

the proposed landfill and perimeter access road.

The three new SWM ponds are designed as two-stage facilities with an emergency flow control

system in-between the two stages. A typical two-stage facility is illustrated in cross-section in

Figure 6-25.

The first stage will function not only as a sedimentation cell but also as an emergency response

cell where runoff can be stored in case of surface water contamination by leachate or on-site

spills. Discharge can be shut-off in case of an emergency in which leachate has been found to

be contaminating the surface water runoff. There will be regular inflow monitoring of indicator

parameters (possibly including Oil and Grease, Conductivity, pH and TDS) to trigger a shutdown

response using either a control valve or gate. This pond will be lined and designed to retain

runoff from the 1:100 year rainfall until appropriate treatment can be applied and the runoff

either treated and discharged to the second stage or pumped and hauled for treatment

elsewhere.

The second stage will be an unlined pond for recharge purposes and is sized to accommodate

the volume from the 1:100 year runoff from respective catchment areas. Other design features

will include:

First stage invert higher than the invert of the second stage and likely higher

than the design water level to ensure positive drainage.

Design water level for the volume of runoff from the 1:100 year rainfall event

since the SWMF would likely have no natural positive outlet given the

adjacent topography.

Design water levels not higher than adjacent service roads.

Emergency overflow routes to be defined once the facility characteristics are

more clearly understood. With no positive outflow, the recharge rate governs

the rate of water level reduction and available capacity for the next rainfall

event.


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Figure 6-24 Proposed Stormwater Management Ponds

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