Upper York Sewage Solutions Environmental Assessment

Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River

Prepared for: The Regional Municipality of York

Prepared by:

Conestoga-Rovers

& Associates DECEMBER, 2013 REF. NO. 050278 (104) 1195 Stellar Drive, Unit 1 YORK REGION NO. 74270 Newmarket, Ontario L3Y 7B8

Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Executive Summary

The main objectives of the Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River are:

. To investigate the extent and magnitude of potential impacts of the proposed Water Reclamation Centre clean treated water discharge on erosion and sedimentation processes in the East Holland River and the Queensville drainage ditch1, a tributary of the East Holland River. . To identify the probable implications of the proposed Water Reclamation Centre clean treated water discharge on channel morphology and channel processes.

Study Area

The study area considered for the geomorphological assessment (referred to as the Receiving Water Assessment Area) includes the lower portion of Queensville drainage ditch, from the proposed Water Reclamation Centre Outfall location (referred to as to as the proposed Queensville Sideroad Outfall Discharge Location) to the outlet at East Holland River, the portion of the East Holland River downstream to the confluence with the West Holland River, and the main branch of the Holland River to the confluence with Cook's Bay in Lake Simcoe. This is the area considered for the proposed Water Reclamation Centre clean treated water discharge location and/or the area potentially affected by the proposed Water Reclamation Centre clean treated water discharge. For purposes of this study, the lower portion of the East Holland River within the study area limits and the main branch of the Holland River are referred to as the "East Holland River".

Ambient Condition Characterization

An analysis of existing and projected flow conditions, channel form (including historic and current (2011) channel profile surveys, and channel cross-sections), and substrate characteristics (including grain size distribution and nutrient analysis) was conducted for the Queensville drainage ditch and the East Holland River within the Receiving Water Assessment Area to determine thresholds of sediment entrainment and deposition. Modelled discharge within the Queensville drainage ditch under existing conditions ranges from 0.003 to 2.28 cubic metres per second (m3/s), with a daily mean value of 0.052 m3/s. Daily mean discharge in the East Holland River at the Holland Landing Water Survey of Canada monitoring station (02EC009) ranges from 0.062 to 53.4 m3/s over the period of record, with an average value of 1.35 m3/s. Analysis of the hydrologic regime of the East Holland River shows that peak flows typically occur in March and April during the spring freshet, while lowest flows typically occur in August. Water levels in the East Holland River within the Receiving Water Assessment Area are closely related to the lake levels in Lake Simcoe which are controlled as part of the Trent- Severn Waterway lock system.

1. Previously referred to as Queensville Drain; however, during the UYSS EA process it was determined that this roadside drainage feature is not subject to the Municipal Drainage Act.

050278 Page ii York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

The UYSS EA study area is situated in a predominantly rural setting, however the Queensville drainage ditch, East Holland River, and Cook’s Bay at the mouth of the Holland River are all influenced by anthropogenic activity. Within the Receiving Water Assessment Area, the Queensville drainage ditch is a well-defined, straightened channel extending along the south side of Queensville Sideroad. It forms part of a marsh near its confluence with the East Holland River where marsh-like conditions predominate. The East Holland River within the Receiving Water Assessment Area is best described as a low-energy estuarine system that experiences backwater effects from the anthropogenically-controlled water levels in Cook’s Bay.

The channel substrate within both the East Holland River and the Queensville drainage ditch is comprised of sediment ranging from clay to sand-sized particles with the dominant proportion being silt. Relatively high values of Total Kjeldahl Nitrogen (TKN) were measured in sediment samples from the Receiving Water Assessment Area, and particularly high values of organic carbon were measured in samples from the Queensville drainage ditch.

The channel bed profile of the East Holland River in the vicinity of the Queensville drainage ditch has a fairly consistent channel depth of approximately 1.5 to 1.6 metres (m), with no evidence of channel deepening at the outlet of the Queensville drainage ditch. Slight variation in bed elevation along the East Holland River is observed. The bed gradient is close to zero in the downstream portion of the Queensville drainage ditch. A comparison of both recent and historical channel bed profiles along the East Holland River in the vicinity of the Queensville drainage ditch indicated that while trends in sediment aggradation and degradation vary spatially within the surveyed study area, there has been an overall tendency towards aggradation. The comparison enabled the identification of four notable sedimentation zones. The average depth of accumulation in the East Holland River at the Queensville drainage ditch confluence was estimated at 1.91 m with an average accumulation rate of 0.037 metres per year (m/yr).

Approach

Any change in flow conditions in the Queensville drainage ditch and the East Holland River as a consequence of the proposed Water Reclamation Centre clean treated water discharge may have an effect on erosion, transport, and deposition of fine sediment in the Queensville drainage ditch, the East Holland River and Cook’s Bay, which may in turn affect channel form and function, water quality, and aquatic habitat. Several modelled scenarios depicting various flow events, both with and without the proposed Water Reclamation Centre clean treated water discharge, were completed for the Queensville drainage ditch and the East Holland River within the Receiving Water Assessment Area. These model scenarios are described in detail in an individual standalone report, the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a).

The model results, together with ambient condition characterization, were used in this Geomorphological Assessment to provide information on the frequency with which the thresholds for sediment entrainment and deposition are reached under existing conditions, and whether bed erosion would be exacerbated by increased discharge volume, and therefore increased flow velocity and hydraulic stress, from the proposed Water Reclamation Centre clean treated water discharge. Variations in water surface slope, water depth, flow velocity, and flow velocity vectors were all examined.

050278 Page iii York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Results

Hydrodynamic modelling results indicate that the most significant hydraulic effects would occur in the Queensville drainage ditch. Increases of 0.12 to 0.25 metres per second (m/s) in mean flow velocity and 2 to 3 Newtons per square metre (N/m2) in average bed shear stress (the fluid force per square metre on the stream bed, which is related to sediment mobilization and transport) can be expected under normal flow conditions, while increases of 0.4 to 0.7 m/s and greater than 2 N/m2 can be expected under 2-year flow scenarios. Within the East Holland River, hydrodynamic effects associated with the proposed Water Reclamation Centre clean treated water discharge are expected to be negligible, with maximum increases of up to 0.06 m/s and 0.2 N/m2 expected for mean flow velocity and bed shear stress, respectively, under all modelled scenarios.

The flow velocity changes predicted by the hydrodynamic modelling of the proposed Water Reclamation Centre clean treated water discharge were used to identify potential effects on erosion and sedimentation processes within the Queensville drainage ditch and East Holland River as follows:

. For the size of the bed material identified within the Receiving Water Assessment Area, it was determined that sediment erosion thresholds are occasionally reached under existing flow conditions. . For scenarios with the proposed Water Reclamation Centre clean treated water discharge, none of the hydrodynamic effects within the East Holland River are expected to cause major changes in erosion or sedimentation. . Within the Queensville drainage ditch, an increase in the frequency and magnitude of sediment entrainment and transport is predicted under each of the modelled scenarios with the proposed Water Reclamation Centre clean treated water discharge. . It is anticipated that the finer sediments (i.e., silt to clay-sized particles) entrained within the Queensville drainage ditch would likely be transported to the East Holland River where they would remain in suspension until they reach Cook’s Bay. Coarse sediments (i.e., sand 0.063 to 2 mm in diameter) entrained within the Queensville drainage ditch would likely settle out quickly near the confluence with the East Holland River and may result in deposition in this area. During more extreme flow events, sand particles less than 0.2 mm in diameter may also be transported downstream toward Cook’s Bay.

The probable implications of the proposed Water Reclamation Centre clean treated water discharge on channel morphology and channel processes are as follows:

. In the East Holland River, changes in hydraulic geometry (flow velocity and depth) and stream energy (power) are small or negligible under model scenarios. These changes are not sufficient to cause significant changes to channel morphology. . Increases in flows delivered through the proposed Queensville Sideroad Outfall Discharge Location would have some effects on hydraulic geometry and stream

050278 Page iv York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

energy in the Queensville drainage ditch. These increases may be sufficient to erode the channel bed and cause some channel deepening but bank erosion would likely be minimal. . It is estimated that approximately 95 cubic metres (m3) of fine sediment has the potential to be eroded from the Queensville drainage ditch as a result of both natural channel processes and the proposed Water Reclamation Centre clean treated water discharge. The existing annual sediment load within the East Holland River is approximately 6,220 m3/yr, based on Water Survey of Canada sediment and flow duration data. Any sediment derived from within the Queensville drainage ditch would be less than 1% of the annual East Holland River sediment load.

Potential mitigation measures to minimize erosion within the Queensville drainage ditch resulting from the proposed Water Reclamation Centre clean treated water discharge include installing energy dissipation measures at the proposed Queensville Sideroad Outfall Discharge Location, increasing bed roughness by covering the existing fine sediment with coarser material, and altering the channel cross-section or channel slope.

050278 Page v York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Table of Contents Page

1.0 Introduction 1

2.0 Methods 3 2.1 Study Objectives 3 2.2 Receiving Water Assessment Area 3 2.3 Bed Materials and Morphology 5 2.3.1 Sediment Samples 5 2.3.2 Channel Form Surveys 9 2.4 Hydrodynamic Model 11 2.5 Spatial Extent of Impact 12 2.6 Sediment Mobility Analyses 12

3.0 Existing Drainage Networks Properties and Watershed Characteristics 13 3.1 Physiography and Geology 13 3.2 Land Use 13 3.3 Hydrology and Lake Simcoe (Cook’s Bay) Levels 14 3.3.1 Queensville Drainage Ditch 14 3.3.2 East Holland River 14 3.3.3 Lake Simcoe (Cook’s Bay) Water Levels 16 3.3.4 Study Area Peak Flows 17 3.4 Existing Geomorphologic Conditions 18

4.0 Results of Assessment 21 4.1 Boundary (Bed) Materials 21 4.2 Long Term Aggradation/Degradation 25 4.3 Local Bathymetry 25 4.3.1 Cross-section 26 4.3.2 Profile 26 4.3.3 Bed Forms 29 4.4 Sediment Chemistry 29 4.4.1 Carbon Content 29 4.4.2 Total Phosphorus 30 4.4.3 Total Kjeldahl Nitrogen 30 4.4.4 Summary 30 4.5 Hydrodynamic Model 31 4.6 Sediment Mobilization and Transport 42 4.7 Sediment Volumes 46

5.0 Summary and Recommendations 48 5.1 Overview of Assessment 48

050278 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

5.2 Water Reclamation Centre Clean Treated Water Discharge Effects in Receivers 48 5.2.1 Queensville drainage ditch 48 5.2.2 Queensville drainage ditch Marsh Pond (Holland Marsh Wetland Complex)49 5.2.3 East Holland River 49 5.2.4 Cook’s Bay (Lake Simcoe) 50 5.2.5 Further Considerations 50 5.3 Recommendations 51

6.0 References 53

7.0 Glossary of Terms 55

List of Figures

Page

Figure 2.1 Receiver Impact Assessment Study Area ...... 4 Figure 2.2 Core Sediment Sampling Sites (February, 2012) ...... 7 Figure 2.3 Ponar Sediment Sampling Sites (April, 2012) ...... 8 Figure 2.4 Echo Sounding Profile Locations (April, 2012) ...... 10 Figure 3.1 Bathymetric Profile of East Holland River ...... 20 Figure 4.1 Bathymetric Profile of East Holland River: Sedimentation / Aggradation Zones ...... 22 Figure 4.2 Sonar Channel Profile Overlay of the East Holland River near the proposed Queensville Sideroad Outfall Discharge Location ...... 28 Figure 4.3 Hjülstrom Curve ...... 42

050278 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

List of Tables Page

Table 2.1 Hydrodynamic Model Scenarios ...... 11 Table 3.1 Flow Exceedance for the East Holland River at Holland Landing (WSC ID 02EC009) for the period 1965-2009) (reproduced from CRA et al., 2013a) ...... 16 Table 3.2 Flow Series along the East Holland River under Existing and Future Flow Scenarios1 ...... 17 Table 3.3 Overview of Receiver Area Site Characteristics from Natural Environment Baseline Conditions Report (CRA et al., 2013f) ...... 18 Table 4.1 Sediment Characteristics Based on February 16, 2013 Field Reconnaissance ...... 21 Table 4.2 Predominant Grain Size of Sediment Samples Collected in Proximity to Queensville Sideroad (Figure 2.3) ...... 23 Table 4.3 Relative Proportions of Clay, Silt, Sand and Gravel within Substrate Samples ...... 23 Table 4.4 Cumulative Grain Size Distribution ...... 24 Table 4.5 Particle Size Gradation ...... 24 Table 4.6 Overview of Sedimentation Zones Along Bathymetric Surveys ...... 25 Table 4.7 Overview of Cross-section Water Depth and Thalweg Position ...... 26 Table 4.8 Overview of Echo-sounding Channel Bed Profiles in the East Holland River ...... 27 Table 4.9 Sediment Quality Results ...... 30 Table 4.10 Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios ...... 32 Table 4.11 Hydrodynamic Data Results for the Queensville drainage ditch ...... 39 Table 4.12 Hydrodynamic Data Results for the East Holland River ...... 40 Table 4.13 Permissible Flow Velocities for Erosion of Fines in Open Channels and Hillslopes (from MNR, 2002) ...... 43 Table 4.14 Susceptibility of Erosion in Queensville drainage ditch (Assume Silty Sand, D50 0.1 mm, Erosion Velocity 0.15 to 0.3 m/s) ...... 43 Table 4.15 Susceptibility of Erosion in East Holland River Assume Silty Clay, D50 0.01 mm Erosion Velocity 0.4 to 0.9 m/s ...... 44 Table 4.16 Estimated Time of Sediment Transport to the East Holland River and West Holland River Confluence (assumes 10,585 m to Cook’s Bay, 5,891 m to confluence) ...... 46

050278 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

List of Appendices

Appendix A Photographic Log Appendix B Sediment Sample Data Appendix C Sonar Data: Cross-Sections

050278 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Section 1.0 Introduction

This report documents the Geomorphological Assessment undertaken of the proposed Water Reclamation Centre clean treated water discharge on the East Holland River carried out as part of the Upper York Sewage Solutions Environmental Assessment (UYSS EA). In March 2010, the Minister of the Environment (Minister) approved the Terms of Reference (ToR) for the UYSS EA with an amendment to consider "Innovative Wastewater Treatment Technologies" as part of the UYSS EA. In response, The Regional Municipality of York (York Region) developed the Lake Simcoe Water Reclamation Centre alternative with York Durham Sewage System (YDSS) modifications.2

In this alternative, wastewater resulting from growth in the Town of Aurora and most of the Town of Newmarket would be conveyed through the YDSS for treatment at the Duffin Creek Water Pollution Control Plant (WPCP) and discharge to Lake Ontario. To accommodate this, modifications to the existing YDSS (proposed as an additional sewage forcemain through the Town of Newmarket) would be required. To provide additional system reliability during high flow conditions, the existing YDSS would be upgraded/twinned to accommodate additional flows from the Towns of Newmarket and Aurora. Wastewater from growth in the Town of East Gwillimbury and a portion of the Town of Newmarket would be conveyed to the proposed Water Reclamation Centre for treatment, using environmentally sustainable wastewater purification and water recycling technologies, and the clean treated water would be discharged to the East Holland River within the Lake Simcoe watershed.

In particular advanced membrane technologies applied following conventional biological secondary treatment will produce high quality, phosphorus-reduced water for discharge to the East Holland River within the Lake Simcoe watershed.

The Water Reclamation Centre with YDSS modifications was selected as the Preferred Alternative to the Undertaking. In support of the wastewater purification technologies proposed for the Water Reclamation Centre, a series of studies were carried out to further assess the receiver and Water Reclamation Centre discharge requirements as part of the Alternative Methods of Carrying Out the Undertaking stage of the UYSS EA. These studies, collectively referred to as the Receiving Stream Assessment Studies, include the following:

. Study of Potential Impacts of the Water Reclamation Centre Discharge on Flooding Potential in the East Holland River (CRA, et al., 2013b) . Comprehensive Assimilative Capacity Study of the Water Reclamation Centre Discharge (CRA, et al., 2013c) . Thermal Effects of the Water Reclamation Centre Discharge on the East Holland River (CRA, et al., 2013d) . Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA, et al., 2013a)

2. The alternative described herein is considered as proposed until the Undertaking identified through the UYSS EA is approved by the Minister of the Environment.

050278 Page 1 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

. Assessment of the Water Reclamation Centre Discharge on Aquatic Habitat in the East Holland River (CRA, et al., 2013e) . Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River (CRA, et al., 2013)

The results of the preceding Receiving Stream Assessment Studies were documented in individual stand-alone reports and incorporated into the Natural Environment Impact Assessment Report. Upon completion, the Receiving Stream Assessment Studies would be made available during the UYSS EA to review agencies, First Nations and Métis organizations, and the public for their information on the project website and upon request, and would become a reference document to the submitted Environmental Assessment Report.

050278 Page 2 York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Section 2.0 Methods

2.1 Study Objectives

Whenever water is proposed to be discharged into a receiving watercourse, concerns exist regarding the potential of the additional flows to exacerbate existing erosion or sediment mobilization processes, such as potential for scour and sediment entrainment related effects from the proposed Water Reclamation Centre clean treated water discharge on the Queensville drainage ditch and East Holland River. The concern relates not only to potential bank or bed erosion, but also to the entrainment and re-suspension potential of nutrients and substances that are bound to sediment particles.

In this study, the potential impact of the proposed Water Reclamation Centre clean treated water discharge on Queensville drainage ditch and East Holland River sediment movement processes was investigated from a fluvial geomorphologic perspective and relied on results from the hydrodynamic model, as described in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a).

Specific study objectives included the following:

. Establish baseline conditions and processes to provide a context for analyses . Determine potential impact from the proposed Water Reclamation Centre clean treated water discharge at a hierarchy of spatial scales (proximal to the discharge location, East Holland River, Cook’s Bay/Lake Simcoe) . Integrate findings with other study disciplines

2.2 Receiving Water Assessment Area

The proposed Water Reclamation Centre Outfall is located on the south side of Queensville Sideroad, approximately 200 m east of the East Holland River (Figure 2.1). Rather than discharging directly into the East Holland River, the proposed Water Reclamation Centre Outfall location (referred to as to as the proposed Queensville Sideroad Outfall Discharge Location) occurs east of the East Holland River, along a tributary that is referred to as the Queensville drainage ditch3. This straightened watercourse, which is situated along the south side of Queensville Sideroad, is a 3rd order channel that flows into a pond which drains through a straightened channel to the East Holland River.

3. This tributary itself is an off-shoot of a larger Queensville drainage ditch system; however for the purposes of this report Queensville drainage ditch refers to this approximately 200 m section.

050278 Page 3 York Region No. 74270 615000 618000 621000

Cook's Bay

Sideroad 20 Line 13

Holland Marsh Wetland Complex

Town of Youngs Point Canals Georgina

Ravenshoe Road Line^_ 12 4893000 4893000

Yonge Street

Holland Marsh Leslie Street

Line 11

Holland Marsh (BW5) Outfall Location Ravenshoe/Boag Drain

Concession Road 10

Holborn Road 4890000 4890000

Town of WH1 West East Holland RiverEast Gwillimbury

Silver Lakes Golf and Country Club

Maskinonge River Significant Groundwater Recharge )" Queensville drainage ditch

Yonge Street ^_ 2nd Concession 4887000 4887000

Queensville Sideroad Holland Landings Town of Lagoons King Holland Landing Doane Road

11. 615000 / 618000 621000

Basemapping: Produced by CRA under license from Regional Municipality of York, and Ontario Ministry of Natural Resources, Land Information Ontario (LIO), 2013. © Queens Printer 2013 Legend Figure 2.1 UYSS EA Study Area Approved Infrastructure Bathurst Street Receiver Impact Conveyance Infrastructure Queensville Sideroad Outfall Graham Sideroad^_ Assessment from the Site Discharge Location Yonge Street ² 1:50,000 Study Area UTM Zone 17N, NAD 83 Conveyance Infrastructure )" Queensville West Pumping Station Metres to the Site 0 280 560 1,120 1,680 Provincially Significant December 2013 Watercourse/Drain Wetland This drawing has been prepared for the use of AECOM's client and may not be used, reproduced or relied upon by third parties, Major Road Environmentally Significant Area except as agreed by AECOM and its client, as required by law or for use by governmental reviewing agencies. AECOM accepts Municipal Division no responsibility, and denies any liability whatsoever, to any party that modifies this drawing without AECOM's express written consent.

Map Document: (E:\112138\2013\AquaticReporting\Fig_2_1_StudyArea_8_5x11.mxd) Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

The pond (originally part of Soldiers’ Bay that was separated by the Queensville Sideroad) and channel are located within a cattail marsh which forms a small portion of the greater Holland Marsh Wetland Complex, which is designated by the Ministry of Natural Resources as a Provincially Significant Wetland. The water level in the pond is affected under some flow conditions by backwater flowing up the Queensville drainage ditch from the East Holland River.

During the late summer months, the water levels in the marsh are low and the water is stagnant. Low water levels also persist into the late fall and winter as the regulated water levels in Cook’s Bay are maintained at low levels during this time. In the spring, however, the area floods and a defined channel conveys water through the marsh to the East Holland River. Backwater conditions within the East Holland River, which can extend to Holland Landing, also extend into the marsh and the Queensville drainage ditch.

The study area assessed as part of this Geomorphological Assessment includes the area in direct proximity to the proposed Queensville Sideroad Outfall Discharge Location in the Queensville drainage ditch, and the East Holland River near and extending downstream from Queensville Sideroad to where the Holland River discharges into Cooks’ Bay (Figure 2.1).

The information presented on the drainage network properties and watershed characteristics was derived from existing information sources including:

. The Natural Environment Baseline Conditions Report (CRA et al., 2013f) . Bathymetric survey data collected by CRA (2011) . Draft versions of the Receiving Stream Assessment Studies (refer to Section 6.0 for complete references)

In addition, field investigations were conducted explicitly for this study. Detailed information regarding UYSS EA study area characteristics are documented in the Natural Environment Baseline Conditions Report (CRA et al., 2013f) and are not presented here.

2.3 Bed Materials and Morphology

Assessing the potential effects of increased flows on sediment mobility requires an understanding of the hydraulic influence on channel bed morphology and of substrate material characteristics.

2.3.1 Sediment Samples

Sediment samples within the Queensville drainage ditch and the East Holland River were collected during two separate sampling visits to characterize the composition and general structure of the river bed sediments. Samples collected in proximity to Queensville Sideroad were submitted for nutrient analyses.

Reconnaissance level sediment sampling was completed on February 16, 2012 within both the Holland River and East Holland River. The sample sites were intended to represent different

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zones of perceived long-term aggradation/degradation as determined based on a review of the 1965 and 2011 bathymetric profile overlay (See Section 3.4, Figure 3.1). Samples were collected using a hand corer. The solid ice surface on the water was used as a platform from which the core sampling was completed.

Field site locations are demonstrated on Figure 2.2 and are described in brief below (photographs are in Appendix A):

. HR-1: Area of deposition between Cook’s Bay and the West Holland River confluence: Approximately 2,000 m upstream of Cook’s Bay – a Lake Simcoe embayment . HR-2: Upstream of the West Holland River confluence: 5,100 m upstream of from Cook’s Bay, in an area of apparent deposition . HR-3: Area of relative static loading between the West Holland River confluence and Queensville Sideroad: 6,000 m to 9,000 m from Cook’s Bay . HR-4: Queensville Sideroad: 11,000 m upstream of Cook’s Bay in proximity to the proposed Queensville Sideroad Outfall Discharge Location . HR-5: Area of deposition between 11,000 m and 12,000 m upstream of Cook’s Bay (upstream of the proposed Queensville Sideroad Outfall Discharge Location)

Subsequent sediment sampling on April 26, 2012 was completed using a Ponar Grab Sampler. Seven samples were collected at key locations in the vicinity of the proposed Queensville Sideroad Outfall Discharge Location (Figure 2.3). Each sampling location was selected based on the preliminary results from the hydrologic model, which identified the potential discharge plume flow path and are as follows:

. Sed 1: Identified discharge channel on south-east side of Queensville Sideroad . Sed 2: Confluence of discharge channel with main channel . Sed 3: Approximately three metres upstream of the second bridge pier (west pier) . Sed 4: Ten metres from west bank, approximately thirty metres downstream of bridge . Sed 5: Centre channel, approximately fifty metres downstream of bridge . Sed 6: Centre channel, approximately eighty metres downstream of bridge . Sed 7: Centre channel, approximately forty metres upstream of bridge

Sediment samples (April 26, 2012) were submitted to the University of Guelph, Agriculture and Food Laboratory for the following analyses:

. Particle size distribution (fraction of constituents) . Carbon content (total, organic and inorganic) . Phosphorus . Total Kjeldahl Nitrogen (TKN)

050278 Page 6 York Region No. 74270 618000 619000 620000 621000 622000 623000 624000 625000 626000

4895000 Lake Simcoe 4895000 Ravenshoe Road 4894000 4894000

HR-1 Catering Road ! Newmarket 4893000 4893000 Boag Road

Leslie Street 4892000 4892000

HR-2 ! 4891000 4891000

Woodbine Avenue 4890000 4890000

Holborn Road

HR-3

4889000 ! 4889000 4888000 4888000

HR-4 ! 4887000 4887000 Doane Road Yonge Street

2nd Concession

Bathurst Street

4886000 HR-5 4886000 !

11

4885000 ./ 4885000

618000 619000 620000 621000 622000 623000 624000 625000 626000

Basemapping: Produced by CRA under license from Regional Municipality of York, and Ontario Ministry of Natural Resources, Land Information Ontario (LIO), 2013. © Queens Printer 2013 Legend Figure 2.2 ! Sampling Sites Intermittent Stream Core Sediment Permanent Stream Sampling Sites ² Freeway (February, 2012) 1:50,000 Waterbody UTM Zone 17N, NAD 83 Expressway / Highway Metres December 2013 0 280 560 1,120 1,680 Major Road

This drawing has been prepared for the use of AECOM's client and may not be used, reproduced or relied upon by third parties, Local Road except as agreed by AECOM and its client, as required by law or for use by governmental reviewing agencies. AECOM accepts no responsibility, and denies any liability whatsoever, to any party Ramp that modifies this drawing without AECOM's express written consent.

Map Document: (E:\112138\2013\AprilReporting\Fig_2_2_EastHuronSediment_8_5x11.mxd) East Holland River Soldiers' Bay

< Sed 6 !

< Sed 5 !

< Sed 4 !

< Sed 1 !

< Sed 3 !

Queensville Sideroad West < Sed 2 !

< Sed 7 !

Basemapping: Produced by CRA under license from Regional Municipality of York, and Ontario Ministry of Natural Resources, Land Information Ontario (LIO), 2013. © Queens Printer 2013 Legend Figure 2.3 < ! Sediment Samples Ponar Sediment Sampling Sites

² 1:1,500 (April, 2012) UTM Zone 17N, NAD 83

Metres 0 10 20 40 December 2013

This drawing has been prepared for the use of AECOM's client and may not be used, reproduced or relied upon by third parties, except as agreed by AECOM and its client, as required by law or for use by governmental reviewing agencies. AECOM accepts no responsibility, and denies any liability whatsoever, to any party that modifies this drawing without AECOM's express written consent.

Map Document: (E:\112138\2013\AprilReporting\Fig_2_3_Sediment_8_5x11.mxd) Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

2.3.2 Channel Form Surveys

A preliminary assessment of changes in the bathymetric profile of the East Holland River was undertaken as part of the Natural Environment Baseline Conditions Report (CRA et al., 2013f) based on an overlay of two surveys: (1) a survey completed in 2011 for the UYSS EA and (2) a previous survey completed in 1965 by Canadian Hydrographic Survey. In order to gain insight into spatial and temporal trends in sediment accumulation and degradation within the East Holland River and near the outlet of the Queensville drainage ditch, further analyses were completed by overlaying these two surveys (the results of these analyses are described in Section 3.4, and the overlay is shown on Figure 3.1).

The comparison between these two surveys is complicated by three issues:

. The frequency (and number) of depth sampling points differs between the two surveys. Therefore, a direct spatial comparison for specific locations within the Receiving Water Assessment Area is not possible, although general comparisons are possible. . The position of the survey line differed between the 1965 and 2011 surveys by several meters in places. Therefore, cross-section variation in channel form (e.g. variation in depth across the width of the East Holland River) may account for some of the observed elevation differences between the two surveys. . Depth observations recorded in the 1965 profile appears to be limited only to 0.18, 0.47, 0.58, 0.65, 0.87 and 0.96 increments of a metre. This may be a function of the resolution of the equipment used in 1965 rather than the absolute elevation of the channel bed.

Reconnaissance level field investigations of the East Holland River and Queensville drainage ditch were completed during the course of this study to supplement information available in the Natural Environment Baseline Report (CRA et al., 2013f). Insight into channel dimensions and cross-section configuration were obtained through completing field measurements in Queensville drainage ditch and echo sounding in the East Holland River.

To supplement available bathymetric survey data, an echo-sounding (sonar) scan of the channel bed was conducted to assess the bathymetry of the East Holland River both in profile and cross- section in proximity to Queensville Sideroad and near its confluence with the Queensville drainage ditch (Figure 2.4). The echo-sounder enables a finer resolution of channel bed morphology than recorded during the 2011 bathymetric survey. However, shallow water on the channel margins (banks) of the East Holland River precluded survey across the complete bank-to-bank section.

Results of the echo-sounding provides insight into the local effects of bridge piers on bed scour and into bed forms present on the channel bed. Figure 2.4 demonstrates the location of echo sounding completed on April 26, 2012, using a Garmin GPSmap 188 Sounder.

The channel bed gradient was ascertained through review of the bathymetric survey and sonar data for the East Holland River, and through review of topographic survey data for the Queensville drainage ditch obtained in support of the hydrodynamic model.

050278 Page 9 York Region No. 74270 Transect !(1 !( Transect!( 3 !( !( !( !( !(!( !(!( !(!( !( !( !( !(!(!( !(!( Transect 4 !(!( !(!( !(!( !(!(!( !(!( !( !(!( !( !(!( !( Soldiers' Bay !(!( !( !( !( !( !( !(!( !(!(!( !(!( !( !(!(!(!( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !(!(!(!( !( !( !(!(!( !( !( !( !( !(!( !(!( !( !( !( !(!( !(!( !( !( !( !(!( !( !(!(!( !( !( !(!(!( !(!( !(!( !( !( !(!( !( !( !( !( !(!( !( !(!(!( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( Transect 2!( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !(!( !( !( !(!(!(!(!(!(!(!(!(!(!( Cross-Section 13 !(!(!(!(!(!( !( !( !( !(!(!(!(!(!( !( !( !(!(!( !(!( !(!( !( !( !( !(!( !( !( !( !(!( !(!( !(!( !( !( !( !( !(!(!( !(!(!(!(!(!(!(!(!(!(!(!(!(!(!( Cross-Section 15 !(!(!( !(!(!(!(!(!( !( !(!( !( !( !( !(!( !(!( !( !(!( !( !(!( !(!(!(!(!(!(!(!(!( !(!(!(!(!(!(!(!(!(!(!( !(!( !(!( Cross-Section 14!(!(!(!( !( !(!( !( !( !(!( !( !( !( !(!( !(!( !(!(!(!(!( !( !(!( !( !( !(!( !( !(!(!( !(!(!( !( !(!( !(!(!( Cross-Section 12 !( !( !(!( !( !(!( !( !( !( !(!( !( !( !(!(!( !(!(!( !( !(!( !(!( !(!( !(!( !(!(!(!(!( !( Cross-Section 11!(!(!(!(!( !(!(!( !( !( !(!(!( !( !( !( !( !( !(!( !( !(!( !(!( !(!(!( !(!( !(!(!(!(!(!( !(!( !(!( !( Cross-Section 10 !(!(!( !(!(!( !( !( !( !( !( !( !( !( !(!(!(!(!(!(!(!(!( !( !( !(!(!( !( !( !(!(!(!( !( !(!( !( !( !(!( !( !(!(!( !( !( !( !(!( !(!( !( !( !(!( !( !(!(!(!(!(!(!(!(!(!(!(!(!(!( !( !( !(!(!(!(!(!(!( !(!(!( !( !( !(!(!(!(!(!(!(!( !(!(!(!(!(!( Cross-Section 9 !(!(!( !(!( !( !( !( !( !( !( !(!( !(!( !(!(!( !(!(!(!(!(!(!( !(!( !( !(!(!(!(!(!(!(!(!( !(!( !(Cross-Section 8 Queensville Sideroad West !( !( !( !( !(!( !(!( !( !( !(!(!( !( !(!( !(!( !( !(!(!( !(!(!(!(!(!(!(!( !(!( !(!( !( Cross-Section 7 !(!(!(!( !( !( !( !(!(!(!( !(!(!( !( !(!( !(!(!(!( !( !( !( !(!(!(!( !( !( !( !( !(!(!(!(!(!(!(!( !(!( !(!( !( !( !( !( !(!(!(!(!(!( !( !(!( !(!(!(!(!( !( !( Cross-Section 6 !( !(!(!(!(!(!( !(!(!(!( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!(!(!( !(!( !( Cross-Section 5 !( !(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( !( !(!(!(!(!(!( !( !( !( !( !(!( !( !( !(!( !( !(!( !(!(!( !( !( !(!( !(!(!(!(!(!(!(!(!(!( !(!( !( !(!( Cross-Section 4 !( !(!(!(!( !(!( !( !( !( !(!(!(!(!(!(!(!(!( !( !( !( !(!( !( !( !( !( !(!(!( !( !( !( !( !( !(!( !(!( !( !( Cross-Section 2 !(!( !( !( !( !(!(!(!(!( !( !( !( !( !(!(!(!(!(!(!(!(!(!( !( !(!(!( !( !(!(!(!(!(!( !( !( !( !(!( !( !( !(!(!( !( !(!( !(!(!(!(!(!(!(!(!( !( !(!(!(!(!(!( Cross-Section 3 !(!(!(!( !( !(!(!( !(!(!(!(!( !(!( !(!(!(!(!(!( !(!(!(!(!(!( !( Cross-Section 1

!(!(

Basemapping: Produced by CRA under license from Regional Municipality of York, and Ontario Ministry of Natural Resources, Figure 2.4 Land Information Ontario (LIO), 2013. © Queens Printer 2013 Legend !( Bathymetric Data Points Echo Sounding Profile Locations

² 1:2,000 (April, 2012) UTM Zone 17N, NAD 83

Metres 0 10 20 40 60 December 2013

This drawing has been prepared for the use of AECOM's client and may not be used, reproduced or relied upon by third parties, except as agreed by AECOM and its client, as required by law or for use by governmental reviewing agencies. AECOM accepts no responsibility, and denies any liability whatsoever, to any party that modifies this drawing without AECOM's express written consent.

Map Document: (E:\112138\2013\AprilReporting\Fig_2_4_Bathymetry_8_5x11.mxd) Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

2.4 Hydrodynamic Model

The effect of the proposed Water Reclamation Centre clean treated water discharge on water level, water depth and flow velocity in the Queensville drainage ditch and the proximal East Holland River was modeled and documented in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2012) with a two-dimensional far-field hydrodynamic model. The model was set up as a channel, and excluded the floodplain; therefore the model is limited to simulating up to the approximately 2-year flow, or bankfull conditions, within the channel. Larger flows were modeled to enable a conservative estimate of water levels however these scenarios may overestimate actual water levels and flow velocities within the Queensville drainage ditch and East Holland River because, in reality, higher than bankfull water levels would spill onto the accessible floodplain (which is not included in the model).

Five different scenarios were assessed to examine effects of the proposed Water Reclamation Centre clean treated water discharge on average and extreme (low and high) water level and flow conditions within the receiving water bodies (Queensville drainage ditch, East Holland River, Holland River, Cook’s Bay). For each scenario, two runs were completed to enable comparison of flow conditions both with and without the proposed Water Reclamation Centre clean treated water discharge. Details of the model and analyses are provided in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2012). A summary of the modeled scenarios is provided in Table 2.1.

Table 2.1: Hydrodynamic Model Scenarios

Queensville East Holland River Cook’s Bay (CB) Water Reclamation Centre Scenario drainage ditch (EHR) Flow (m3/s) Level (mASL) Discharge (m3/s) (QD) Flow (m3/s) Typ1E1 1.35 0.016 218.88 0 Typ1F2 1.35 0.016 218.88 0.46 Ext1E3 0.082 1.5 218.44 0 Ext1F4 0.082 1.5 218.44 1.30 Ext2E5 28.7 1.5 218.88 0 Ext2F6 28.7 1.5 218.88 1.30 Ext3E7 0.082 0 218.44 0 Ext3F8 0.082 0 218.44 0.46 Ext4E9 93.9 6.70 219.49 0 Ext4F10 93.9 6.70 219.49 1.30 Notes: 1. Typical ambient conditions (average flows in EHR and QD, average water level in CB) and no Water Reclamation Centre discharge. 2. Typical ambient conditions (average flows in EHR and QD, average water level in CB) and annual average day Water Reclamation Centre discharge. Extreme ambient conditions (7Q20 flow in EHR, 2-year flow in QD, minimum water level in CB) and no Water Reclamation Centre discharge. 7Q20 refers to minimum 7 day flow with 20 year recurrence interval. 3. Extreme ambient conditions (7Q20 flow in EHR, 2-year flow in QD, minimum water level in CB) and peak hour Water Reclamation Centre discharge. 4. Extreme ambient conditions (2-year flow in EHR, 2-year flow in QD, average water level in CB) and no Water Reclamation Centre discharge. 5. Extreme ambient conditions (2-year flow in EHR, 2-year flow in QD, average water level in CB) and peak hour Water Reclamation Centre discharge. 6. Extreme ambient conditions (7Q20 flow in EHR, 7Q20 (no flow) in QD, minimum water level in CB) & no Water Reclamation Centre discharge. 7. Extreme ambient conditions (7Q20 flow in EHR, 7Q20 (no flow) in QD, minimum water level in CB) and annual average day Water Reclamation Centre discharge. 8. Extreme ambient conditions (100-year flow in EHR, 100-year flow in QD, maximum water level in CB) and no Water Reclamation Centre. discharge. 9. Extreme ambient conditions (100-year flow in EHR, 100-year flow in QD, maximum water level in CB) and peak hour Water Reclamation Centre discharge.

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2.5 Spatial Extent of Impact

In general, the zone of influence within a receiving water body due to an outfall discharge begins at the outfall and extends some distance downstream until the effects are dissipated or negligible. The area upstream of the outfall may also be affected due to backwater effects. Typically, the impact is most pronounced at the outfall location and decreases in the downstream direction as the discharge volume becomes a minor proportion of the total flow within the receiving watercourse.

In this study, the spatial extent of any potential sediment mobility effects focussed on the following distinct spatial units:

. Downstream of the proposed Queensville Sideroad Outfall Discharge Location within both the pond and the segment of the Queensville drainage ditch between the pond and the East Holland River . The East Holland River from the confluence with the Queensville drainage ditch downstream to the outlet of the Holland River to Cook’s Bay in Lake Simcoe

The analyses relied on visual examination of the model output maps in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a) and on numerical output data from the hydrodynamic model.

2.6 Sediment Mobility Analyses

Assessment of a potential change in sediment mobility due to the proposed Water Reclamation Centre clean treated water discharge into the receiver (i.e., East Holland River system) considered implications for both the entrainment/ disturbance and transport of bed sediment in the Queensville drainage ditch and East Holland River. Specifically, the analyses examined the effect of each modeled scenario on water surface slope, water depth, flow velocity, and velocity vectors for both the existing and future (with the proposed Water Reclamation Centre clean treated water discharge) conditions.

The hydrodynamic model data were used to determine the tractive force (shear stress) and stream power of flows. Data were also used to examine sediment entrainment and transport potential with reference to standard tables (e.g., MNR (2002), Fishenich (2001)), charts (e.g., Hjülstrom curve), and equations for sediment entrainment and transport (Knighton, 1998), Komar (1987).

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Section 3.0 Existing Drainage Networks Properties and Watershed Characteristics

3.1 Physiography and Geology

The geologic materials of the floodplain and watershed are important determinants of channel form (e.g., cross-section, profile) and function (e.g., sediment transport within the context of the drainage network and substrate composition). The infiltration capacity and hence characteristics of the drainage network and surface flow are also influenced by geology. The floodplain materials and bankside vegetation determine their resistance to erosion and thus their ability to absorb any change in flow regime that may occur within the channel.

The Receiving Water Assessment Area (Figure 2.1) is situated within the Simcoe Lowlands physiographic region which is characterized by low-lying, swampy sand plains, as defined by Chapman and Putnam (1984). While the topography shows an overall decrease in land surface elevation from south to north towards Cook’s Bay, the Simcoe Lowlands region exhibits very little relief and is of very low gradient. As the East Holland River approaches Cook’s Bay, recent organic deposits of peat and muck overlie the sands within the shallow river valley.

Upstream from the Receiving Water Assessment Area, the East Holland River flows through the Schomberg Clay Plains physiographic region which is characterized by a layer of stratified glaciolacustrine clay and silt that is underlain by a drumlinized till plain, causing the topography to exhibit rolling hills and more relief than is typical of most glaciolacustrine environments. Soils within the Schomberg Clay Plains region consist predominantly of well-drained silty-clay loams with localized areas of imperfect to poor drainage. The East Holland River has incised several metres through the clay sediments within the Schomberg Clay Plains.

3.2 Land Use

The East Holland River watershed is considered the most populated and environmentally degraded area of the Cook’s Bay Watershed (LSRCA, 2010). The dominant land use within the watershed includes urban development (25%), agriculture (35%) and forest (24%) (The Louis Berger Group, 2006).

Upstream of the Receiving Water Assessment Area, the East Holland River watershed is situated within the Town of Newmarket and is characterized by moderately high-density urban land development that extends to the top of the East Holland River valley in several locations. Discontinuous sections of more natural areas are present alongside the East Holland River within the UYSS EA study area, including the Bailey Ecological Reserve at the southern extent and the Fairy Lake Conservation Area, north of Mulock Drive. The developed area ends abruptly approximately 400 m south of Green Lane; north of this, agriculture is the dominant land use.

Land use within the Queensville drainage ditch watershed is predominantly rural, with some low density housing that primarily flanks the road on both sides. Land use surrounding the East Holland River in the vicinity of Queensville Sideroad consists of low-density residential dwellings

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that flank the watercourse, and a marina. There are numerous docks situated along the East Holland River banks. Farther back from the East Holland River banks, the land use in the vicinity of the Receiving Water Assessment Area is primarily rural.

3.3 Hydrology and Lake Simcoe (Cook’s Bay) Levels

3.3.1 Queensville Drainage Ditch

The Queensville drainage ditch is a third order tributary of the East Holland River and has a drainage area of 7.45 km2. Insight into the hydrology of the Queensville drainage ditch at the proposed Queensville Sideroad Outfall Discharge Location was gained through installation of a flow monitor in the watercourse. The monitor was installed in April 18, 2012 and was active until December 7, 2012 (i.e., approximately 8 months). Data from the monitoring initiative was used to extrapolate hydrologic data for input into hydrodynamic modeling, the results of which inform the analyses presented in this study.

Flow monitoring at the Queensville drainage ditch location between April 18 and December 7, 2012 yielded the following data:

. Maximum hourly flow: 0.491 m3/s . Minimum hourly flow: 0.000933 m3/s . Average hourly flow: 0.0160 m3/s

Results from hydrologic modeling for the Queensville drainage ditch (with no calibrations) yielded the following flow projections:

. Mean Daily Flow: 0.052 m3/s . Minimum Daily Flow: 0.003 m3/s . Maximum Daily Flow: 2.28 m3/s . 7Q20 (Minimum 7 consecutive day flow with 20 year recurrence interval) flow event: 0.004 m3/s . Flow from the Queensville drainage ditch represents about five percent of annual average flows in the East Holland River

Peak flow values from calibrated modelling for the Queensville drainage ditch are presented in Section 3.3.4 of this report.

3.3.2 East Holland River

The East Holland River, a 5th order channel, joins the West Holland River around 10th Line to form the Holland River which flows into Cook’s Bay. The hydrology of the East Holland River is monitored at Water Survey of Canada station 02EC009 (Holland Landing) which is located 6 km upstream of Queensville Sideroad. The drainage area of the East Holland River, at Holland

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Landing, is 181 km2. Data for this station is available from 1966 to 2011 (46 years). Analysis of the flow data was reported in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a) and is summarized as follows:

. Highest flows occur in March and April (mean monthly values of 2.87 and 2.72 m3/s, respectively) due to snowmelt-induced spring freshet. . Rainfall in late November typically causes a bi-modal seasonality in high flows, but this is typically lower than peaks observed during the spring freshet. . Lowest flows occur in the summer (mean monthly value of 0.69 m3/s). . Long-term mean daily flow: 1.35 m3/s (117 MLD). . Minimum mean daily flow calculated during the period of record (46 years): 0.062 m3/s. . Maximum mean daily flow calculated during the period of record: 53.4 m3/s. . 7Q (annual minimum consecutive 7-day flows):

 75 % of the 7Q flow events occur in the summer months (i.e., July – September); 40% of these occur in August.  The magnitude of the 7Q flow event decreases (statistically significant) over the period of record; this decrease may be a result of anthropogenic activities that affect baseflow (e.g., development decreases the pervious catchment area and thus reduces the volume of water that is infiltrated into the ground within the urbanized areas). . 7Q20 (minimum consecutive 7-day flow with return period of 20 years) is 0.082 m3/s (7.1 MLD) which equates to: 3  6 % of long term mean daily flow of 1.35 m /s 3  1.3 times larger than minimum mean daily value calculated (0.062 m /s) . Annual maximum daily flows:

 40 % occurred in March; late winter/early spring period  80 % occurred in the February to April time period

When reviewing flow data for a station, it is often helpful to place the data within the context of flow frequency or exceedance analyses. Table 3.1 (reproduced from CRA et al., 2013a) summarizes the exceedance of specific flow events along the East Holland River. Key observations include the following:

. The long-term mean daily flow has an exceedance of 25.4 % (i.e., only 25.4 % of the time was the flow larger than the mean daily flow). . The 7Q20 flow is exceeded 99.86 % of the time.

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Table 3.1: Flow Exceedance for the East Holland River at Holland Landing (WSC ID 02EC009) for the period 1965-2009) (reproduced from CRA et al., 2013a)

Exceedance Flow (%) (m3/s) 1 10.5 5 4.52 10 2.82 20 1.63 30 1.17 40 0.904 50 0.724 60 0.586 70 0.481 80 0.388 90 0.285 95 0.211 99 0.124

The comparison of flow exceedance curves for existing flow conditions with curves prepared for proposed future flows (i.e., with the proposed Water Reclamation Centre clean treated water discharge) noted that there is a small visual difference between the two curves with exceedance of up to approximately two percent, corresponding to the less frequent, high flows (CRA et al., 2013a). For flows that are exceeded more than two percent of the time, the proposed future flow regime plots above the existing flow regime. Thus, for most (98 %) of the flows, the proposed Water Reclamation Centre clean treated water discharge in the East Holland River would make a discernible difference in flow values for a given exceedance probability.

3.3.3 Lake Simcoe (Cook’s Bay) Water Levels

Information regarding Lake Simcoe water levels from 1960-2011 is available from the Jackson Point Station. Key findings from reviewing the water level data are documented in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a), which are summarized as follows:

. Water levels in Lake Simcoe are artificially induced (i.e., controlled by Trent-Severn Waterway Authority) so that lake levels are relatively high in the summer and relatively low in the winter.

 Maximum lake water levels follow spring snowmelt and occur in May and June.  Minimum lake water levels occur in late fall and early winter. . Depending on the seasonal water levels in Lake Simcoe, the lake effect can hydraulically affect the river as far upstream as Holland Landing (i.e., backwater extends to Holland Landing during the summer months).

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. Results from data analyses (1960 – 2011, Lake Simcoe at Jackson Point Station) included:

 Average water level is 218.88 metres above sea level (mASL)  Maximum recorded lake level: 219.49 mASL  Minimum recorded lake level: 218.44 mASL

3.3.4 Study Area Peak Flows

Peak flows associated with the typical flow series (2, 5, 10, 25, 50, 100 - year return storm event and regional storm event) were determined for several locations within the UYSS EA study area (Table 3.2). The analyses included determination of peak flows for existing and future flow events. Future flow events were defined based on anticipated future land use change and stormwater management strategies, as outlined in municipal planning documents including:

. York Region Official Plan – 2010 (January 14, 2013 Office Consolidation) . Town of Georgina Official Plan, Schedule A (Land Use Plan); Schedule F1 (Keswick Land Use Plan); Schedule H (Bellhaven and Ravenshoe), October, 2010 . Town of East Gwillimbury Official Plan Amendment, Queensville Community Plan Schedule A (Land Use and Transportation Plan), OPA 60 Schedule A (Land Use Plan), 2010

Table 3.2: Flow Series along the East Holland River under Existing and Future Flow Scenarios1

Peak Flow Station Existing (m3/s) Future (m3/s) 2-year 1.5 1.6 Queensville drainage ditch near Holland 5-year 2.6 3.1 Landing 10-year 3.4 5.1 2 (station 142) 25-year 4.6 7.7 3 (HTrL12) 50-year 5.6 9.9 100-year 6.7 12.1 Regional5 40.9 64.7 2-year 40.2 43.6 5-year 68.3 73.6 East Holland River at Queensville Sideroad 10-year 85.9 92.0 (station 144)2 25-year 107.3 114.6 (H12)3 50-year 123.2 131.4 100-year 140.3 152.8 Regional5 565.0 604.1

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Peak Flow Station Existing (m3/s) Future (m3/s) 2-year 95.5 101.2 5-year 161.7 169.4 Holland River at Cook’s Bay (Lake Simcoe) 10-year 205.3 214.6 (station 150)2 25-year 260.5 271.8 (H14)3 50-year 301.2 314.3 100-year 339.2 355.2 Regional5 856.2 883.9 2-year 28.7 - 5-year 44.0 - At Holland Landing4 10-year 55.6 - (WSC Station 02EC009)2 25-year 70.8 - (H7)3 50-year 82.4 - 100-year 89.1 - Regional5 93.9 - Notes: Data obtained from LSRCA, 2005. 1. Future-scenario flow volumes do not incorporate proposed discharge volumes from the Water Reclamation Centre. 2. Station numbers correspond to those in LSRCA Hydrology Report (LSRCA, 2005). Design flows were not validated by flood- frequency analysis of available flow data. 3. Station numbers correspond to those in the Natural Environment Baseline Conditions Report (CRA et al., 2013f). 4. Measured-only (no future flow volumes available) data from Water Survey of Canada Station 02EC009. 5. Regional flood condition includes no record for Hurricane Hazel.

3.4 Existing Geomorphologic Conditions

A fluvial geomorphologic characterisation of all watercourses in the UYSS EA study area was completed and presented in the Natural Environment Baseline Conditions Report (CRA et al., 2013f). A summary of key findings from that report, as it pertains to the proposed Queensville Sideroad Outfall Discharge Location within the Queensville drainage ditch (Reach HTrL12) that discharges into Reach H12 of the East Holland River are presented in Table 3.3.

Table 3.3: Overview of Receiver Area Site Characteristics from Natural Environment Baseline Conditions Report (CRA et al., 2013f)

Strahler Dominant Average Total Average Bed / Bank Reach Stream Reach Class Mapped Surficial Stream Power Grade (%)1 Materials Order Geology (W/m)2 Modern alluvial East Holland River H12 5 C backwatered 0.07 Silt 295 deposits Coarse-textured Queensville HTrL12 3 C backwatered 0.28 glaciolacustrine Sand / Silt 32 drainage ditch deposits Notes: 1. Gradients estimated from DEM 2. Based on DEM-derived slope and hydrologically modelled 2-year flows from Cumming Cockburn Limited, 2005 (transposed by drainage area)

Review of the table reveals that both the Queensville drainage ditch and East Holland River are influenced by backwater conditions from Cook’s Bay water levels. Backwatered systems are low-energy and are typically characterized by relatively slow flow velocities with deposition being the dominant process. The low average grade of the river and drainage ditch are

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consistent with the physiographic characteristics of the Receiving Water Assessment Area as outlined in Section 2.2 of this report.

Information contained within the Natural Environmental Baseline Conditions Report (CRA et al., 2013f) revealed that a cattail marsh, which is a small portion of the Holland Marsh Wetland Complex, is situated along the east bank of the East Holland River, south of Queensville Sideroad. The Holland Marsh Wetland Complex has been identified as a Provincially Significant Wetland (PSW). The proposed Queensville Sideroad Outfall Discharge Location is located along a portion of the Queensville drainage ditch east of a small pond within the PSW and that is under backwater influence of the East Holland River. The channel consists predominantly of a low-flow channel that is well connected to its floodplain during higher flows (i.e., water levels will spill onto the accessible floodplain). Bankside vegetation consists of cattails.

Review of the planform (orthographic contour of the channel banks) configuration of the East Holland River reveals that the width of the channel in the study reach (Figure 2.1), which encompasses the outlet from the Queensville drainage ditch, is typically between 60 and 65 m wide. An abrupt decrease in channel width to 20 m occurs a short distance upstream (approximately 1.5 to 2 km). This planform configuration, in light of the backwater effects towards Holland Landing, suggests that this portion of East Holland River resembles an estuary and is thus effectively an inlet from Cook’s Bay.

The Queensville drainage ditch is characterized as a channel that has a well-defined (3 m wide, 0.5 m deep) channel that is well connected to the adjacent floodplain. Floodplain vegetation consists of cattail marsh. The capacity of the channel was estimated to be less than bankfull discharge. The drainage feature is influenced by backwater conditions from within the East Holland River and is similar to an estuarine channel.

In the Natural Environment Baseline Conditions Report (CRA et al., 2013f), an overlay of 2011 (CRA) and 1965 (Canadian Hydrographic Service (CHS)) bathymetric profiles of the East Holland River was completed to gain insight into long term channel bed aggradation/ degradation processes (Figure 3.1). As both surveys were collected along the approximate centreline of the East Holland River, a precise spatial correspondence in location of the bathymetric survey route is unlikely. In addition, the CHS chart survey is generally less precise than the modern survey. Therefore any comparison between these surveys gives an imprecise indication of long-term changes in bed elevation.

Despite the imprecision in the survey comparison, there is some evidence for net aggradation – a rise in bed elevation through sedimentation – over the 46-year period of record (Figure 3.1). In the area of the confluence of East Holland River and West Holland River there has been little net change in bed elevation. In contrast, there has been an increase in bed elevation further upstream and especially upstream of Queensville Sideroad. This coincides with the morphological and process transition from fluvial to more estuarine (backwater) conditions along the East Holland River and an abrupt drop in channel gradient. Given the backwater influence and low channel grade of the river in this location, the capacity to transport sediment is reduced and thus sediment derived from upstream sources, including agricultural lands and construction areas, becomes deposited. Deposition of sediment within the East Holland River, north of Holland Landing is thus consistent with expected sedimentation processes.

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Figure 3.1: Bathymetric Profile of East Holland River

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Section 4.0 Results of Assessment

4.1 Boundary (Bed) Materials

The initial bed material sampling program was completed in the winter of 2012, enabling the ice surface to be used as a platform from which to obtain cores from the channel bed (Figure 2.2, Table 4.1). Due to thin ice, field access to two of the sample sites was considered unsafe and thus no sediment data were collected at Sites HR-4 and HR-5. At the remaining three locations (HR-1, HR-2 and HR-3), the sediment was soft and loose and provided no cohesive properties to enable retention within the core barrel. Consequently, no samples could be submitted for grain size analysis. From sediment that was partially retained on the outside of the core, a qualitative assessment of the substrate materials revealed a well hydrated slurry of soft highly organic materials that contained trace amounts of silt. A photographic log of the river at the sampling sites is provided in Appendix A.

Table 4.1: Sediment Characteristics Based on February 16, 2013 Field Reconnaissance

Ice Thickness Water Depth Site ID Location Sediment Core Description (m) (m) HR-1 South of Cook’s Bay Brown, soft sediment, highly organic 0.17 1.58 HR-2 South of the West Holland Soft, highly organic with trace 0.18 1.18 Confluence amount of brown silt HR-3 Near Marina Parallel with Soft, highly organic with trace 0.12 1.39 Holborne Road amount of brown silt HR-4 Queensville Sideroad N/A due to unsafe ice conditions <0.051 N/A HR-5 Holland Landing Lagoon N/A due to unsafe ice conditions <0.051 N/A Discharge Point Note: 1. Minimum thickness for safe walking – AECOM Standard Operating Procedure: 315 – Water, Working Around, Section: S3NA-315-WI3 Ice Safe Work Practices.

Sediment sampling completed in April 2012 was intended to obtain samples for grain size analyses in the area of the East Holland River at Queensville Sideroad. Laboratory analyses of all samples revealed fine sediment, with silt being the predominant particulate (Tables 4.2, 4.3, 4.4 and 4.5; Laboratory results provided in Appendix B). Results of the analyses are consistent with the overall characteristics of the Receiving Water Assessment Area (i.e., low-gradient, backwater setting, surficial geology). Further, the results are consistent with results obtained from the bathymetric data analyses which suggest that the East Holland River in the vicinity of the Queensville Sideroad is in a depositional area (Figure 4.1).

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Figure 4.1: Bathymetric Profile of East Holland River: Sedimentation / Aggradation Zones

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Table 4.2: Predominant Grain Size of Sediment Samples Collected in Proximity to Queensville Sideroad (Figure 2.3)

Water Sample Predominant Sediment Location Depth ID Grain Size Description (m) Sed 1 Queensville drainage ditch approximately 140 m 0.5 Sand (44%), Sandy silt upstream of East Holland River silt (39%) Sed 2 Confluence of Queensville drainage ditch with East 1.6 Silt (72%) Clayey silt Holland River Sed 3 Approximately three metres upstream of the 1.5 Silt (66%) Clayey silt second QSR bridge pier (west pier) Sed 4 Ten metres from west bank, approximately thirty 1.6 Silt (75%) Clayey silt metres downstream of QSR bridge Sed 5 Centre channel, approximately fifty metres 1.5 Silt (76%) Clayey silt downstream of bridge Sed 6 Centre channel, approximately eighty metres 1.5 Silt (78%) Clayey silt downstream of bridge Sed 7 Centre channel, approximately forty metres 1.6 Silt (66%) Clayey silt upstream of QSR bridge

Table 4.3: Relative Proportions of Clay, Silt, Sand and Gravel within Substrate Samples

Percent Distribution Very Fine Medium Coarse Very Coarse Clay Silt Fine Sand Gravel Sand Sand Sand Sand (<0.002 mm) (0.002 – 0.05 mm) (0.05 – 0.1 mm) (0.1 – 0.25 mm) (0.25 – 0.5 mm) (0.5 - 1 mm) (1 - 2 mm) (>2 mm) Sed 1 16.7 39.3 20.4 17.7 3.4 2.0 0.1 0.0 Sed 2 16.7 72.4 5.7 2.9 1.2 1.0 0.2 0.0 Sed 3 17.6 66.0 8.6 3.6 2.1 1.5 0.5 0.0 Sed 4 20.6 74.8 2.2 1.2 0.5 0.4 0.2 1.0 Sed 5 20.9 75.9 1.9 0.8 0.4 0.2 0.0 0.0 Sed 6 18.6 78.0 1.9 0.6 0.2 0.3 0.3 0.0 Sed 7 15.7 66.3 11.7 3.2 1.9 1.2 0.1 0.0

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Table 4.4: Cumulative Grain Size Distribution

Cumulative Percent Distribution Very Fine Medium Coarse Very Coarse Clay Silt Fine Sand Gravel Sand Sand Sand Sand (<0.002 mm) (0.002 – 0.05 mm) (0.05 – 0.1 mm) (0.1 – 0.25 mm) (0.25 – 0.5 mm) (0.5 - 1 mm) (1 - 2 mm) (>2 mm) Sed 1 16.7 56 76.4 94.1 97.5 99.5 99.6 99.6 Sed 2 16.7 89.1 94.8 97.7 98.9 99.9 100.1 100.1 Sed 3 17.6 83.6 92.2 95.8 97.9 99.4 99.6 99.6 Sed 4 20.6 95.4 97.6 98.8 99.3 99.7 99.9 100.9 Sed 5 20.9 96.8 98.7 99.5 99.9 100.1 100.1 100.1 Sed 6 18.6 96.6 98.5 99.1 99.3 99.6 99.9 99.9 Sed 7 15.7 82 93.7 96.9 98.8 100 100.1 100.1

Table 4.5: Particle Size Gradation

D16 D50 D84 Sample ID (mm) (mm) (mm) Sed 1 0.00200 0.0260 0.175 Sed 2 0.00200 0.0260 0.0260 Sed 3 0.00200 0.0260 0.0750 Sed 4 0.00200 0.0260 0.0260 Sed 5 0.00200 0.0260 0.0260 Sed 6 0.00200 0.0260 0.0260 Sed 7 0.0260 0.0260 0.0750 Note: 1. Particle size range limits are based on Sheldrick and Wang (1993).

The sediment sample (Sed 1) obtained from within the Queensville drainage ditch (140 m upstream from the confluence with the East Holland River, Figure 2.3) was coarser than those from the East Holland River. This finding is consistent with Receiving Water Assessment Area characteristics. Specifically, upstream of the sampling location, accumulations of sand were visible in the channel. Some of this material may have originated from upstream sediment sources and from seasonal road maintenance activities (i.e., sand and small gravel were observed on the road shoulder and on the embankment slope of the road). Further downstream from the Sed 1 sampling location, substrate materials were soft, loose, highly organic and contained a high proportion of silt.

As indicated in photos presented in Appendix A, the Queensville drainage ditch is well connected to its floodplain, allowing flood flows to spill onto the marsh. Channel banks are vegetated with cattails in a well-established cattail marsh. Roots from the vegetation enhance the structural strength of the bank materials. In the vicinity of the Sed 1 sample site, the channel is approximately 4 m wide and 0.3 m deep (water depth at time of field investigation). An approximately 0.4 m thick layer of soft sediment was on the channel bed that was easily penetrated with a ruler.

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4.2 Long Term Aggradation/Degradation

Overlay of the 1965 and 2011 bathymetric profiles along the Holland and East Holland Rivers suggests that trends in sediment aggradation/degradation vary spatially within the area surveyed. As noted in Section 3.1.2, the observed variation in channel bed elevation between the two profiles may reflect spatial variation within a cross-section, rather than actual long-term trends in sedimentation/degradation. Review of cross-sections obtained through echo-sounding (see Section 4.3 and Appendix C) suggests that the lateral variation in cross-section depth, along the approximate centreline of the East Holland River does not typically result in a bed elevation difference that is more than 0.2 m (note, a maximum difference of approximately 0.3 to 0.4 m was observed, Appendix C).

Assuming that the bathymetric profiles of the East Holland River bed were in relative close proximity such that the actual bed elevation difference between survey points is similar (i.e., within 0.2 m), four sedimentation zones were identified in Figure 4.1. Analyses were undertaken to quantify sediment volume and approximate rate of change through each zone (Table 4.6). The distances in Table 4.6 represent the distance from the outlet of the Holland River to Cook’s Bay in Lake Simcoe. The proposed Queensville Sideroad Outfall Discharge Location at Queensville drainage ditch (located 10,585 m upstream of the outlet to Cook’s Bay) occurs in Zone 4 which corresponds to a zone of aggradation for which an approximate rate of 0.037 m/yr was quantified. The zone extends from Holland Landing Lagoon downstream to the Silver Lakes Golf and Country Club (refer to Figure 2.2).

Table 4.6: Overview of Sedimentation Zones Along Bathymetric Surveys

Holland River East Holland River Zone 1 Zone 2 Zone 3 Zone 4 0 to 4,694 m 4,694 to 5,634 to 8,734 to 13,403 m (Cook’s Bay to 5,634 m 8,734 m (extends to Holland West Holland Landing Lagoon River confluence) Discharge) CHS – 1961 (area, m2)1 5558.91 1020.69 3660.18 5075.58 CRA – 2011 (area, m2) 1 8452.46 2319.67 7626.06 13440.17 Difference (m2) 2893.55 1298.98 3965.88 8364.60 Total distance (m) 4694 949 3091 4385 Average depth of accumulation (m) 0.62 1.37 1.28 1.91 Average rate of change (51 yrs) (m/yr) 0.012 0.027 0.025 0.037 Note: 1. Area between bathymetric line and elevation 214.7 m.

4.3 Local Bathymetry

The backwater influence of East Holland River due to Cook’s Bay water levels creates a low energy environment that affects development of the rivers’ cross-section and profile forms.

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4.3.1 Cross-section

Cross-sections obtained from the sonar field survey were reviewed to determine spatial diversity in thalweg position and to ascertain the influence of Queensville Sideroad on local scour processes. Review of the cross-sections (see Appendix B) revealed that the maximum water depth was nearly uniform at 1.5 or 1.6 m throughout the nearly 180 m of channel that was surveyed (See Table 4.7). A dramatic increase in water depth occurred approximately 5 m downstream of Queensville Sideroad (cross-section 10), along the west side of the channel. This apparent scour, or excavation, appears to be local and limited in extent since the deepest portion of the East Holland River appears to be only 1.8 m another 10 m downstream (cross- section 11), and is in the centre of the channel. This feature may be related to the promontory projecting from the left (west) bank immediately downstream of the bridge and constricting the flow on that side of the channel.

Table 4.7: Overview of Cross-section Water Depth and Thalweg Position

Maximum Section Location Water Depth Observation ID (See Figure 2.4) (m) 1 110 m upstream of Queensville Sideroad 1.5 Thalweg towards east side of channel 2 100 m upstream of Queensville Sideroad 1.5 Thalweg along west side of channel 3 88 m upstream of Queensville Sideroad 1.6 Thalweg in centre of channel 4 70 m upstream of Queensville Sideroad 1.5 Thalweg in centre of channel 5 56 m upstream of Queensville Sideroad 1.5 Thalweg in centre of channel 6 43 m upstream of Queensville Sideroad 1.6 Thalweg in centre of channel 7 33 m upstream of Queensville Sideroad 1.6 Thalweg in centre of channel 19 m upstream of Queensville Sideroad 8 1.6 Thalweg in centre of channel At Queensville drainage ditch confluence 9 South side (upstream) of Queensville Sideroad 1.5 Thalweg along east side of channel 10 5 m downstream of Queensville Sideroad 3.5 Thalweg along west side of channel 11 15 m downstream of Queensville Sideroad 1.8 Thalweg in centre of channel Thalweg along west side of channel 12 35 m downstream of Queensville Sideroad 1.8 but relatively uniform 13 45 m downstream of Queensville Sideroad 1.6 Thalweg in centre of channel Thalweg in centre of channel and 14 54 m downstream of Queensville Sideroad 1.5 relatively uniform along east side Thalweg in centre of channel and 15 67 m downstream of Queensville Sideroad 1.5 relatively uniform along east side Note: 1. Garmin GPSmap 188 sounder collects water depth values at a resolution of 0.1 m.

4.3.2 Profile

Due to depth restrictions, the echo sounding profiles were limited to the East Holland River. Insight into the existing channel bed morphology of the Queensville drainage ditch was gained

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by completing manual measurements made along the tributary bed and from interpolation from limited survey points collected in preparation for the hydrodynamic model set-up (CRA et al., 2013a). Results revealed an average depth of approximately 0.50 m and a channel width that was approximately 3.5 m. The channel bed morphology appeared to have minor variability (< 0.07 m) and was gently sloped (slope is 0.04%) towards the East Holland River.

Three profiles of the East Holland River bed were surveyed along the centreline, using the echo sounder, extending upstream and downstream of Queensville Sideroad (Table 4.8). A partial profile was surveyed downstream of the road, towards the west side of the river. An overlay of the channel bed profiles (Figure 4.2) demonstrates that the channel is deepest along profiles 2 and 3, in the centre of the channel. Figure 4.2 also reveals that the water depth upstream of the bridge is about 1 m, which increases to a typical value of 1.5 m downstream of the bridge. This is consistent with data for the East Holland River in support of the hydrodynamic model.

Table 4.8: Overview of Echo-sounding Channel Bed Profiles in the East Holland River

Length Location Profile (m) (See Figure 2.4) 1 104 West side of channel, from 113 m to 217 m downstream of Queensville Sideroad 2 248 Centre of channel, from 111 m upstream to 137 m downstream of Queensville Sideroad 3 330 Centre of channel, from 113 m upstream to 217 m downstream of Queensville Sideroad 4 325 East side of channel, from 130 m upstream to 194 m downstream of Queensville Sideroad

Surveys of the East Holland River bed do not show any obvious deepening of the channel at the mouth of the Queensville drainage ditch. Although the cross-section closest to the Queensville drainage ditch (cross-section 8, Appendix C) does not extend all the way across the channel, the general trend of the cross-section profile suggests a gradual increase in bed elevation towards the east bank. In contrast, the bed elevation of cross-section 9 appears to progressively deepen towards the east bank (Appendix C). This local deepening is likely due to the trajectory of flow from the Queensville drainage ditch, which is oriented in the downstream direction.

In general, the presence of bridge piers within a watercourse often leads to local changes in flow hydraulics that contribute to river bed scour in proximity to the piers (adjacent, upstream and downstream). Review of the echo sounding profiles and sections revealed a small scour channel on the downstream side of the most western pier of the Queensville Sideroad bridge over the East Holland River. The channel bed elevation dropped 1.5 m below average bed depth in that area (recorded approximate depth of 3 m) and extended approximately 2 m downstream (Section 10, Appendix C). Scour along this side of the channel would be influenced by the western most pier, and may also be affected by the contraction of flow caused by local west bank channel hardening downstream of the bridge.

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Figure 4.2: Sonar Channel Profile Overlay of the East Holland River near the proposed Queensville Sideroad Outfall Discharge Location

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4.3.3 Bed Forms

In addition to the primary trend in longitudinal channel bed configuration along the profiles, a secondary trend of minor undulations superimposed on the general profile is visible. Although the uniformity of the bed form heights may also reflect limitations in depth readings of the sonar, there appears to be some correspondence in the location of the bed forms between profiles 2 and 3. It is possible that these undulations correspond to dunes (i.e., indicative of sufficiently strong hydraulic forces on the channel bed) with a lee height of 0.10 to 0.20 m.

Review of sediment data collected in this area (Figure 2.3) indicates that the bed materials are silt dominated (Tables 4.2 to 4.5) which are too fine to enable dune formation (i.e., dunes don’t tend to occur when bed materials are less than 0.1 mm). Instead, if silt materials are entrained, then these will be transported. Formation of dunes also typically requires an average flow velocity of 0.5 m/s. Review of data from the hydrodynamic models indicates that flow velocities exceed 0.5 m/s only for the modelled 100 year flow events. The likelihood of hydraulically formed bed forms in the East Holland River does not appear to be valid, based on the silt materials and infrequency of sufficient hydraulic conditions within the river.

4.4 Sediment Chemistry

Four of the sediment samples were selected to be analyzed for the additional parameters beyond grain size distributions as defined in Section 3.1.1 (Table 4.9). The samples selected include:

. Sed 1: Queensville drainage ditch . Sed 3: East Holland River, approximately 3 m upstream of the second pier (west pier) of the Queensville Sideroad bridge . Sed 4: East Holland River, 10 m from west bank, approximately 30 m downstream of the Queensville Sideroad bridge . Sed 7: East Holland River, centre channel, approximately 40 m upstream of the Queensville Sideroad bridge

Results from laboratory analyses were reviewed and compared to the Ministry of Environment (MOE) Sediment Quality Guidelines for lowest effect level (LEL) and severe effect levels (SEL).

4.4.1 Carbon Content

As noted in Table 4.9, total carbon content ranged from 80,500 milligrams per kilogram (mg/kg) (Sed 4) to 145,000 mg/kg (Sed 1), with organic carbon predominating. Organic carbon concentrations ranged from 29,930 mg/kg to 111,000 mg/kg for Sed 7 and Sed 1, respectively. The large quantity of organic carbon is related to the grain size distribution of these sediments with Sed 1, which is associated with a wetland in the Queensville drainage ditch, having both the finest matrix and the highest organic carbon concentration. Concentrations at Sed 1 exceed the SEL while samples from the other sites indicate a moderate level of impacts.

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4.4.2 Total Phosphorus

Total phosphorus content for the samples (Table 4.9) was generally low and ranged from 153 mg/kg (Sed 1) to 416 mg/kg (Sed 4). The lower phosphorus concentration in the sediment from the tributary is likely the result of a slightly larger grain size (44% sand) which is less able to adsorb phosphorus to the particles due to the reduced surface areas. The clayey silt from the other sites have greater adsorption surface areas to accumulate the phosphorus. None of the samples exceed the MOE LEL concentration of 600 mg/kg.

Table 4.9: Sediment Quality Results

Carbon Content (mg/kg) Total Total Kjeldahl Sample ID Phosphorus Total Organic Inorganic Nitrogen (mg/kg) Carbon Carbon Carbon (mg/kg) MOE Sediment Quality 10,000 600 550 Guideline – Lowest Effect Level1 MOE Sediment Quality 100,000 2000 4800 Guideline – Severe Effect Level2 Sed 1 145,000 111,000 33,700 153 1,390 Sed 3 108,000 74,900 33,100 287 1,550 Sed 4 80,500 39,600 40,900 416 1,190 Sed 7 132,000 29,930 102,000 274 1,690 Notes: 1. Lowest Effect Level (LEL) indicates a level of contamination that can be tolerated by the majority of sediment- dwelling organisms. Sediments meeting this level are considered clean to marginally polluted (MOE, 2008) 2. Severe Effect Level (SEL) indicates a level of contamination that is expected to be detrimental to the majority of sediment-dwelling organisms. Sediments exceeding the SEL are considered heavily contaminated (MOE, 2008) 3. Red cells indicate that concentrations in the sediment exceed the LEL whereas orange coloured cells exceed the SEL but not the LEL.

4.4.3 Total Kjeldahl Nitrogen

Total Kjeldahl Nitrogen (TKN) content in the samples ranged from 1,190 mg/kg (Sed 4) to 1,690 mg/kg (Sed 7). All samples exceeded the LEL but did not exceed the severe effect level (SEL). Concentrations of TKN are essentially similar among the sites.

4.4.4 Summary

The high organic carbon concentrations found in the sediments and the relatively high nitrogen concentrations in the Queensville drainage ditch and the East Holland River indicate that the sediments are generally of poor quality. Sed 1 exceeds the SEL for organic carbon indicating that aquatic biota in this area are likely affected. Scouring of these sediments or further flooding of the adjacent wetland may deteriorate sediment quality further. In particular, anoxia at the sediment/water interface and within the sediments may result in the release of phosphorus to

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the surface water. The most common periods for anoxia (low oxygen) would be under low flow conditions during the summer and under ice conditions when there is no air/water exchange.

Alternatively, the increased flow of oxygenated treated water from the proposed Water Reclamation Centre may increase oxygen levels in the water column reducing the frequency and duration of anoxic levels in the water, at the sediment/water interface and perhaps even in the sediment. The flow of relatively warm, oxygenated water to the Queensville drainage ditch during the winter season may also improve conditions during the winter. In general, the largest effects of the clean treated water discharge could be from erosion of the sediments in the Queensville drainage ditch and the mobilization of these into the East Holland River where they will be transported downstream during high flow events. The extent of anticipated erosion is discussed further in Section 4.6.

4.5 Hydrodynamic Model

Five scenarios were modeled (see Table 4.10) to assess both existing conditions and the implications of the proposed Water Reclamation Centre clean treated water discharge on flows and hydraulic conditions within the Queensville drainage ditch and the East Holland River as they pertain to the entrainment and transport of sediment. Results from the hydrodynamic model are presented within the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a), and a summary of overall conditions within each of the receiving waterbodies during existing and proposed future (i.e., with Water Reclamation Centre flow) scenarios is provided in Table 4.10. Data for primary flow variables extracted from the centreline of each of the Queensville drainage ditch and East Holland River directly from model output data are summarized in Tables 4.11 and 4.12.

Tables 4.11 and 4.12 show flow depth, flow velocity and water surface slopes extracted along profiles down the centre line of the Queensville drainage ditch and East Holland River from the hydrodynamic model, as described in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA, et al., 2013a). Slopes are generalized by best-fit linear fits to profiles of water surface elevations and do not reflect local variations in gradient along each profile. Values vary along the length of these profiles and the extracted values give a general indication of typical average and extreme conditions under each modeled flow scenario based on existing channel dimensions for Queensville drainage ditch and East Holland River. These provide an indication of flow conditions for sediment entrainment and transport in the two channels under the modeled flow scenarios.

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Queensville drainage ditch Flow Velocity  Flow velocity typically >  Flow velocity < 0.5 m/s  Flow velocity is negligible  Flow velocity (1 m/s) is  Queensville drainage ditch is 0.5 m/s  Deceleration of flow in highest at marsh pond outlet subject to backwater  Highest flow velocity in area downstream direction  Deceleration of flows through influence and flow velocity is extending from marsh pond  Minimal/no flow velocity at Queensville drainage ditch to near 0 m/s outlet to approximately 90 m downstream end < 0.1 m/s downstream, maximum value of 0.65 m/s  Deceleration of flow towards downstream end of Queensville drainage ditch

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Increase in flow velocity  Dissipation of flow velocity in  Flow velocity up to 0.5 m/s  Slight increase in flow velocity  Deceleration of flow in marsh through entire Queensville pond along length of Queensville at marsh pond outlet to pond drainage ditch downstream of  Approximately 1.0 m/s, drainage ditch between 1.75 to 2 m/s  Flow velocity increases to marsh pond: average value of maximum at outlet of marsh  Flow velocity reduction in 0.5 m/s downstream of pond 0.9 m/s is higher than pond marsh pond maximum velocity without  Typical velocity is 0.5 to proposed Water Reclamation 0.75 m/s Centre discharge  Deceleration of flow along  1.3 m/s, maximum Queensville drainage ditch, approximately 70 m from decreases to < 0.25 m/s near outlet of marsh pond the mouth  Deceleration of flow towards downstream end of Queensville drainage ditch

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Velocity  Straight through Queensville  Straight through Queensville  Straight through Queensville  Straight through Queensville  Straight through Queensville Vectors drainage ditch, velocity drainage ditch, flow drainage ditch, velocity is 0.0 drainage ditch, velocity is 0.4 drainage ditch, velocity is 0.0 ranges from 0.5 to < 1.0 m/s, dissipation downstream, to 0.1 m/s to 0.8 m/s to 0.1 m/s decreases to between 0.0 velocity ranges from 0.0 to < and < 0.5 m/s near 0.4 m/s downstream end of Queensville drainage ditch

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Straight through Queensville  Straight through Queensville  Straight through Queensville  Straight through Queensville  Straight through Queensville drainage ditch, velocity ranges drainage ditch, flow dissipation drainage ditch, velocity drainage ditch, velocity drainage ditch, velocity is 0.1 from 0.5 to < 1.0 m/s, increased downstream, velocity ranges predominantly 0.1 to < between 0.4 and 0.8 m/s, to 0.2 m/s values through thalweg from 0.2 to < 0.6 m/s, local 0.3 m/s with local increase to local increase to 0.8 to 1.2 between 1.0 to < 1.5 m/s increase to > 0.6 m/s 0.3 to 0.4 m/s m/s at upstream end  Less evident decrease in velocity at downstream end of Queensville drainage ditch Depth  Fairly uniform depth along  Uniform depth along  Uniform depth with slight  >2 m along thalweg of  Low, nearly-uniform depth Queensville drainage ditch Queensville drainage ditch increase downstream Queensville drainage ditch, along Queensville drainage  Slight thalweg extending with slight increase near uniform depth along the ditch approximately 27 m down- mouth Queensville drainage ditch stream of marsh pond outlet  Deepest point immediately upstream of marsh pond

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Increase in length of thalweg  No change  Almost uniform depth along  No change  No change downstream of marsh pond; Queensville drainage ditch, extends 57 m downstream of increased slightly upstream outlet  Increase in depth through Queensville drainage ditch upstream of marsh pond; uniform depth of 0.7 m

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Water  Small gradient  Small gradient  Same as East Holland River,  High elevation upstream  Small gradient Surface no gradient (220 m+) and some Elevation downstream gradient

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Water surface gradient and  Water surface gradient and  Increase in gradient  No change  Water surface elevation and elevation increase, greatest at elevation increase, greatest at  Backwater in downstream gradient increase upstream end upstream end 20 m Marsh Pond Flow Velocity  Flow velocity is negligible  Flow velocity is < 0.3 m/s at  Flow velocity is negligible  Flow velocity is < 0.3 m/s at  Flow velocity is negligible mouth mouth

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Minimal increase in flow  No change  Minimal increase in flow  No change  Minimal increase in flow velocity through northern velocity velocity portion of pond  Flow velocity movement through pond as indicated by flow vectors Velocity  Flows extend into upper tier  Flows extend into upper tier  Flows extend slightly into  Flows extend into upper tier  Flows extend into upper tier Vectors of pond of pond upper tier of pond of pond of pond  some water circulation through pond

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Straighter / more direct flow  No change  Flows extend farther into  Reduction in water circulation  Flows extend farther into through northern portion of pond, minimal through upper tier of pond pond, minimal pond in line with Queensville  Reduction in water circulation drainage ditch through upper tier of pond

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Depth  Deepest point in north-centre  < 2.0 m depth is deepest cell  < 2.0 m depth is deepest cell  < 2.5 m depth is deepest cell  < 1.5 m depth is deepest cell of pond in pond in pond in pond in pond

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Change in depth is negligible  No change  Change in depth is negligible  No change  Change in depth is negligible Water  Small gradient  Small gradient  Small gradient  Small gradient  Small gradient Surface Elevation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Elevation increase negligible  Water surface gradient and  Minimal water surface  Water surface gradient and  Minimal water surface  Decreased gradient elevation increase negligible gradient and elevation elevation increase negligible gradient and elevation increase increase Confluence Location Flow Velocity  Confluence appears  Confluence appears  Flow velocity is negligible  Flow velocity is < 0.1 m/s at  Backwater zone at backwatered, negligible flow backwatered, negligible flow mouth confluence, no projection of  Poorly defined plume  Poorly defined plume  Plume oriented somewhat plume into East Holland River upstream

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Very small flow velocity plume  Very small flow velocity plume  Flow velocity decelerates  No change  Flow decelerates at mouth of close to Queensville drainage close to Queensville drainage rapidly to < 0.25 m/s within Queensville drainage ditch ditch mouth ditch mouth 15 m into East Holland River projects into East Holland  Possible recirculation eddy on  Plume enters East Holland River with a downstream arc right bank downstream of River in perpendicular angle  A reduction occurs within the confluence centre of the East Holland River, in vicinity of Queensville drainage ditch confluence

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Velocity  Minor trajectory into East  Minor trajectory into East  Minor trajectory into East  Minor trajectory into East  Minor trajectory into East Vectors Holland River, 0.0 to 0.5 m/s Holland River at 0.0 to Holland River at 0.0 to Holland River (0.4 to 0.8 m/s), Holland River, 0.0 to 0.1 m/s 0.4 m/s 0.1 m/s back-eddy along west side of bridge

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Slight increase in trajectory  No change  Trajectory of flow towards  No change  No change in velocity, velocity, 0.0 to 1.0 m/s west side of river at velocity of Queensville drainage ditch 0.0 to 0.1 m/s trajectory extends approximately 5 to 7 m further into East Holland River Depth  Slightly shallower at  Slightly shallower at  Same as East Holland River  Depth similar to channel  Depth at outlet of Queensville Queensville drainage ditch Queensville drainage ditch margin margins, approximately 1.5 m drainage ditch very similar to mouth than East Holland mouth than East Holland that at margins of East River margin River margin Holland River

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  No change  No change  No change  No change  No change Water  Backwater  Elevation of river extends  Backwater Surface small distance up the Elevation Queensville drainage ditch

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  No change  No change  No change  No change  Small increase in water elevation

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 East Holland River Flow Velocity  Negligible flow  Ambient flow velocity in centre  Negligible flow  Reduction of flow velocity in  Flow velocity in centre of of channel is 0.50 to 0.75 m/s centre of channel, in vicinity channel is 0.25 m/s  Minimal or no flow along edge of Queensville drainage ditch  No flow along edge of bank of bank confluence  Reduction in flow velocity in  Reduction of flow velocity in  Flow velocity in centre of vicinity of Queensville centre of channel, in vicinity of channel is up to drainage ditch confluence Queensville drainage ditch approximately 1.75 m/s confluence

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  No change  Ambient flow velocity 0.5 to  Flow velocity increases  No change  Flow velocity remains relatively 0.75 m/s throughout the downstream of drainage ditch constant in centre of channel channel to 0.10 m/s and a maximum  No flow along edge of bank  Flow velocity reduction in of 0.25 m/s downstream of  Velocity 0.05 to 0.1 m/s at centre of channel, in vicinity of bridge centre of channel Queensville drainage ditch  Very local flow velocity ‘plume’ confluence (similar to existing) from Queensville drainage ditch Velocity  Thalweg flow is 0.0 to 0.5 m/s  Thalweg flow is 0.4 to 0.6 m/s  Thalweg flow is 0.0 to 0.1 m/s  Thalweg flow is 0.8 to 1.2 m/s,  Eastward diversion around Vectors local increase between 1.2 and bridge abutment in open area 1.6 m/s downstream of bridge

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  Further definition of back-  No change in thalweg flow;  No change in velocity;  No change  Additional eastward diversion eddy immediately local increase in thalweg flow trajectory of confluence flows around bridge abutment in downstream of confluence, on to between 0.6 and 0.8 m/s towards west bank open area east side of channel approximately 60 m upstream  No change in velocity (presumably unrelated to the Water Reclamation Centre discharge)

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Table 4.10: Hydrodynamic Conditions Within the Receiver Study Area for Existing and Future (with Proposed Water Reclamation Centre Clean Treated Water Discharge) Scenarios

Location of Scenario Change Ext1 Ext2 Ext3 Ext4 Typ1 Depth  Thalweg depth up to 1.2 m  Thalweg depth up to 2.5 m  Maximum thalweg depth  Maximum thalweg depth >3 m  Maximum thalweg depth 1.6 approximately 1.5 m to 2 m

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  No change  No change  No change  No change  No change Water  Uniform elevation, minimal  Small downstream water  Uniform elevation, minimal  Downstream gradient,  Small increase in water at Surface gradient surface gradient gradient steepest downstream of same level as the Queensville Elevation Queensville drainage ditch drainage ditch with small downstream gradient

With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation With Water Reclamation Centre discharge: Centre discharge: Centre discharge: Centre discharge: Centre discharge:  No change  No change in elevation and  No change  No change  No change gradient

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Table 4.11: Hydrodynamic Data Results for the Queensville drainage ditch

Discharge Mean Max Maximum Discharge (Water Total QD Mean Max Stream Flow Flow Slope Shear QD Reclamation Discharge Depth Depth Power 3 3 Velocity Velocity (m/m) Stress 1 (m /s) Centre) (m /s) (m) (m) 2 (W/m) 3 (m/s) (m/s) (N/m ) (m /s) Typ1 0.016 0 0.016 0.003 0.008 0.727 0.764 0.0000 0 0 Typ1 with Water Reclamation Centre discharge 0.016 0.46 0.476 0.142 0.256 0.746 0.789 0.0004 3.09 1.87 Change 0.46 0.46 0.139 0.248 0.019 0.025 0.0004 3.09 1.87

Ext1 1.5 0 1.5 0.456 0.645 0.37 0.486 0.0018 8.58 26.49 Ext1 with Water Reclamation Centre discharge 1.5 1.3 2.8 0.872 1.30 0.457 0.70 0.0033 22.6 90.6 Change 1.3 0.416 0.655 0.087 0.214 0.0015 14.02 64.1

0.00006 1.5 0 1.5 0.206 0.335 1.057 1.097 0.72 0.98 Ext2 7 Ext2 with Water Reclamation Centre discharge 1.5 1.3 2.8 0.407 0.666 1.067 1.11 0.0002 2.18 5.49 0.00013 1.3 1.3 0.201 0.331 0.01 0.013 1.46 4.51 Change 3

Ext3 0 0 0 0 0.001 0.281 0.318 0 0 0 Ext3 with Water Reclamation Centre discharge 0 0.46 0.46 0.216 0.39 0.316 0.366 0.0006 2.15 2.71 Change 0.46 0.46 0.216 0.389 0.035 0.048 0.0006 2.15 2.71

Ext4 6.70 0 6.7 0.551 0.918 1.875 1.919 0.0002 3.76 13.14 Ext4 with Water Reclamation Centre discharge 6.70 1.3 8.0 0.656 1.101 1.877 1.921 0.0002 3.77 15.69 Change 1.3 1.3 0.105 0.183 0.002 0.002 0 0.01 2.55 Note: 1. Rate of energy expenditure EHR: East Holland River QD: Queensville drainage ditch

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Table 4.12: Hydrodynamic Data Results for the East Holland River

Discharge Total Discharge Total Mean Max Max Bed EHR EHR Mean Max Stream Discharge Flow Flow Slope Shear Upstream Downstream Depth Depth Power from QD Velocity Velocity (m/m) Stress 1 of QD 3 of QD (m) (m) 2 (W/m) 3 (m /s) 3 (m/s) (m/s) N/m (m /s) (m /s) Typ1 1.35 0.016 1.366 0.037 0.059 1.232 1.691 0.000004 0.066 0.053 Typ1 with Water Reclamation Centre discharge 1.35 0.476 1.826 0.045 0.059 1.233 1.692 0.000005 0.083 0.089 Change 0.46 0.46 0.008 0 0.001 0.001 0.000001 0.017 0.036

Ext1 0.082 1.5 1.582 0.025 0.048 0.788 1.248 0.000003 0.054 0.047 Ext1 with Water Reclamation Centre discharge 0.082 2.8 2.882 0.051 0.099 0.79 1.25 0.000007 0.085 0.19 Change 1.3 0.026 0.051 0.002 0.002 0.000004 0.031 0.151

Ext2 28.7 1.5 30.2 0.54 0.725 1.544 2.01 0.00009 1.77 25.33 Ext2 with Water Reclamation Centre discharge 28.7 2.8 31.5 0.561 0.751 1.548 2.016 0.0001 1.98 29.42 Change 1.3 1.3 0.021 0.026 0.004 0.006 0.00001 0.21 4.09

Ext3 0.082 0 0.082 0.003 0.005 0.787 1.246 0 0 0 Ext3 with Water Reclamation Centre discharge 0.082 0.46 0.542 0.012 0.022 0.788 1.247 0.000002 0.024 0.011 Change 0.46 0.46 0.009 0.017 0.001 0.001 0.000002 0.024 0.011

Ext4 93.9 6.70 100.6 1.085 1.345 2.322 2.815 0.0002 5.52 184.1 Ext4 with Water Reclamation Centre discharge 93.9 8.00 101.9 1.093 1.342 2.324 2.819 0.0002 5.53 186.7 Change 1.3 1.3 0.008 -0.003 0.002 0.004 0 0.01 2.56 Note: 1. Rate of energy expenditure EHR: East Holland River QD: Queensville drainage ditch

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Proportionally, the largest hydraulic effects of the proposed Water Reclamation Centre clean treated water discharge are anticipated in the Queensville drainage ditch. Under normal low flows (Typ1 and Ext3 scenarios), flow velocity in the Queensville drainage ditch is minimal (a few mm/second) and bed shear stress is effectively zero. The addition of typical proposed Water Reclamation Centre clean treated water discharge flows would increase velocities to between 0.15 and 0.25 m/s and shear stress to between 2 and 3 N/m2.

Large relative changes would also occur in the Ext2 scenario with 2-year flow in the Queensville drainage ditch and peak proposed Water Reclamation Centre clean treated water discharge. Mean flow velocity approximately doubles to between 0.4 and 0.6 m/s and typical bed shear stress increases from less than 1 to over 2 N/m2. Highest flow velocity and shear stress occur under the extreme flows of Ext4 but the relative effect of the proposed Water Reclamation Centre clean treated water discharge is small in this case. Increases in flow depth are very small, with none exceeding a maximum of 0.05 m (Ext3) and increases of only 0.01 to 0.02 m in Typ1 and Ext2 scenarios.

Stream power (rate of energy expenditure per unit channel length) increases in all scenarios, with increases of between 2 and 5 watts per metre (W/m). In scenarios Typ1 and Ext3 these increases reflect that in both cases the initial flows (without the proposed Water Reclamation Centre clean treated water discharge) are either very small or zero. In Ext2, stream power increases by a factor of about five reflecting the increase in shear stress and flow velocity.

The most extreme conditions and largest changes occur in Ext1. This is an extreme scenario in which large flows occur in Queensville drainage ditch while water levels are very low in the East Holland River and Cook’s Bay. The consequence is that water surface slopes are much higher in this scenario, producing flow velocity, shear stress and stream power that are much higher than even Ext4 and which increase significantly with the addition of proposed Water Reclamation Centre clean treated water discharge because of further increases in water surface gradient. These conditions and changes are sufficient to cause substantial erosion and possibly channel enlargement if they occur. In all other scenarios, no changes in the Queensville drainage ditch channel dimensions are expected.

Hydrodynamic effects of the proposed Water Reclamation Centre clean treated water discharge in the East Holland River are relatively small. Flow velocity increases in the modeled scenarios are a maximum of 0.05 m/s (Ext1) and shear stresses and changes in shear stress are similarly small (maximum increase of 0.2 N/m2) in all modeled scenarios. Except for the extreme peak flow scenario of Ext4, the highest velocities and shear stresses in the East Holland River occur under Ext2 when peak shear stress is approximately 2 N/m2.

Depth increases in the East Holland River are negligible (less than 0.005 m) in all cases. Increases in stream power are negligible in scenarios Typ1 and Ext3. Ext1 increases are proportionally large but stream power values remain very small. In Ext2 the stream power increase is less than 20 % with the addition of the proposed Water Reclamation Centre clean treated water discharge and proportional to the proposed increase in discharge along with a possible very small increase in water surface gradient, and proportionally similar to the increase in bed shear stress. No changes in the East Holland River channel dimensions are expected as a consequence of these hydraulic changes.

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4.6 Sediment Mobilization and Transport

Any changes in flow conditions in the Queensville drainage ditch and East Holland River due to the proposed Water Reclamation Centre clean treated water discharge may have an effect on erosion, transport and deposition of fine sediments in the East Holland River and Cook’s Bay. Mean flow velocity and shear stress in these channels, even under peak flows, is sufficient to erode and transport grain sizes no larger than fine to medium sand, except under extreme flow conditions when entrainment of coarse sand and granules may occur. In general, fine sand and coarse silt are the most erodible grain size with erosional resistance increasing with both larger particles (larger mass) and smaller particles (because of cohesion and other effects). Once entrained, these particles tend to go into suspension and then remain in suspension until flow velocity reduces sufficiently to allow settling. This is demonstrated in the classic “Hjülstrom curve” for critical flow velocity of erosion as a function of sediment particle size (Figure 4.3).

Figure 4.3: Hjülstrom Curve

In addition, agencies including the Ministry of Natural Resources (MNR) have established estimates of ‘permissible’ flow velocity to minimize erosion, and select lining for engineered channels, for particular grain sizes (Table 4.13). As a result, the potential increased susceptibility to erosion of existing channel bed materials resulting from increased flows due to

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the proposed Water Reclamation Centre clean treated water discharge can be estimated using this approach. Knowledge of channel material is currently limited to a few samples, the details of which are given in Section 4.1 and Tables 4.2 to 4.5. In the East Holland River, the samples are classified as clayey-silt (typically 60-70 % silt) and in Queensville drainage ditch the only sample obtained is classified as silty sand (40 % silt, 40 % sand). Erosion and transport flow velocity for these sediment types is approximately 0.6 to 0.9 m/s and 0.5 to 0.75 m/s, respectively. Permissible shear stresses as defined by MNR (2002) are 2.3 to 5.3 N/m2 and 1.8 to 3.63 N/m2, respectively (Table 4.13).

Alternatively, using the Hjülstrom curve (Figure 4.3) for erosion velocity, fine sand (particle diameter 0.1 mm) and fine silt (diameter 0.01 mm) have critical erosion velocities of 0.15 to 0.30 m/s and 0.4 to 0.9 m/s, respectively.

A general analysis of the susceptibility to erosion of the existing bed sediments in the Queensville drainage ditch and East Holland River is shown in Tables 4.14 and 4.15. The analysis is based on the critical erosion velocities from the Hjülstrom curve because these are more conservative than the permissible velocities presented in Table 4.13.

Table 4.13: Permissible Flow Velocities for Erosion of Fines in Open Channels and Hillslopes (from MNR, 2002)

Permissible Flow Velocity (m/s) Permissible Shear (N/m2) Minimum Maximum Minimum Maximum Fine Sand 0.46 0.76 1.29 3.59 Sandy Silt 0.53 0.76 1.77 3.59 Silty Clay 0.61 0.92 2.30 5.27 Silt 0.61 1.07 2.30 7.18

Table 4.14: Susceptibility of Erosion in Queensville drainage ditch (Assume Silty Sand, D50 0.1 mm, Erosion Velocity 0.15 to 0.3 m/s)

Exceeds Exceeds Mean Exceeds Exceeds Max Exceeds Exceeds Maximum Min. Max. Flow Min. Max. Flow Min. Max. Shear Erosion Erosion Velocity Erosion Erosion Velocity Erosion Erosion Stress Shear Shear (m/s) Velocity Velocity (m/s) Velocity Velocity (N/m2) Stress Stress Typ1 0.003 No No 0.008 No No 0 No No Typ1 with Water Reclamation 0.142 No No 0.256 Yes No 3.09 Yes No Centre discharge

Ext1 0.456 Yes Yes 0.645 Yes Yes 8.58 Yes Yes Ext1 with Water Reclamation 0.872 Yes Yes 1.30 Yes Yes 22.6 Yes Yes Centre discharge

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Exceeds Exceeds Mean Exceeds Exceeds Max Exceeds Exceeds Maximum Min. Max. Flow Min. Max. Flow Min. Max. Shear Erosion Erosion Velocity Erosion Erosion Velocity Erosion Erosion Stress Shear Shear (m/s) Velocity Velocity (m/s) Velocity Velocity (N/m2) Stress Stress Ext2 0.206 Yes No 0.335 Yes Yes 0.72 No No Ext2 with Water Reclamation 0.407 Yes Yes 0.666 Yes Yes 2.18 Yes No Centre discharge

Ext3 0 No No 0.001 No No 0 No No Ext3 with Water Reclamation 0.216 Yes No 0.39 Yes Yes 2.15 Yes No Centre discharge

Ext4 0.551 Yes Yes 0.918 Yes Yes 3.76 Yes Yes Ext4 with Water Reclamation 0.656 Yes Yes 1.101 Yes Yes 3.77 Yes Yes Centre discharge

Table 4.15: Susceptibility of Erosion in East Holland River Assume Silty Clay, D50 0.01 mm Erosion Velocity 0.4 to 0.9 m/s

Mean Exceeds Exceeds Max. Exceeds Exceeds Maximum Exceeds Exceeds Flow Min. Max. Flow Min. Max. Shear Min. Max

Velocity Erosion Erosion Velocity Erosion Erosion Stress Erosion Erosion (m/s) Velocity Velocity (m/s) Velocity Velocity (N/m2) Stress Stress Typ1 0.037 No No 0.059 No No 0.066 No No Typ1 with Water Reclamation 0.045 No No 0.059 No No 0.083 No No Centre discharge

Ext1 0.025 No No 0.048 No No 0.054 No No Ext1 with Water Reclamation 0.051 No No 0.099 No No 0.085 No No Centre discharge

Ext2 0.54 Yes No 0.725 Yes No 1.77 No No Ext2 with Water Reclamation 0.561 Yes No 0.751 Yes No 1.98 No No Centre discharge

Ext3 0.003 No No 0.005 No No 0 No No Ext3 with Water Reclamation 0.012 No No 0.022 No No 0.024 No No Centre discharge

Ext4 1.085 Yes Yes 1.345 Yes Yes 5.52 Yes Yes Ext4 with Water Reclamation 1.093 Yes Yes 1.342 Yes Yes 5.53 Yes Yes Centre discharge

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Flow velocity in the Queensville drainage ditch tends to be below the estimated erosion thresholds for most existing conditions, except the extreme flows of Ext4, the maximum velocities in Ext2, and the extreme conditions of Ext1. Thus, bed erosion of the typical bed material is expected to be minimal except at very high flows or when significant flows occur in the Queensville drainage ditch when water levels are very low in the East Holland River (Ext1).

The increased flows from the proposed Water Reclamation Centre clean treated water discharge make the bed sediment susceptible to erosion under some conditions at which they were not previously erodible, especially in scenarios Ext2 and Ext3. In these cases, the proposed Water Reclamation Centre clean treated water discharge may induce erosion and transport of fine sediments from the bed of the Queensville drainage ditch where previously such erosion was limited. In other cases, the proposed Water Reclamation Centre clean treated water discharge may increase erosion rates under conditions in which erosion already occurs such as in Ext1. Once eroded, these fine particles would stay in suspension and be transported down to the East Holland River. Note that the proposed Water Reclamation Centre clean treated water discharge would be clear (i.e., the proposed Water Reclamation Centre clean treated water discharge will not contribute any additional suspended solids to the watercourse).

In the East Holland River, entrainment and transport of silty-clay bed material occurs under current conditions at flows at and above the 2-year flow (Ext2 and Ext4) based on the flow velocity criterion. The addition of the proposed Water Reclamation Centre clean treated water discharge to the Queensville drainage ditch is not sufficient under any scenario to substantially change the susceptibility of the bed of the East Holland River to erosion and remobilization of silty-clay deposits.

Fine sediment entering the East Holland River may either be deposited in the East Holland River or remain in suspension and be transported to Cook’s Bay. The Hjülstrom curve (Figure 4.3) indicates that, once in suspension, fine silt and clay particles would remain in suspension except at very low flow velocity. Settling velocity for these particles depends quite strongly on water temperature (i.e., the settling rate of particles becomes much slower as the temperature drops), but even in water at 20 degrees Celsius, fine silt in stagnant water settles at a rate of only about 0.01 cm/sec. Silt and fine sand would stay in suspension at mean flow velocity down to 0.05 m/s.

The flow velocity in the East Holland River is sufficient to keep these fines in suspension under most modeled flows except the low flows of Ext3, both without and with the proposed Water Reclamation Centre clean treated water discharge. In this case, the increased flow due to the proposed Water Reclamation Centre clean treated water discharge may reduce settling of these particles and increase transport to Cook’s Bay.

In general, any silt or fine sand eroded from Queensville drainage ditch is likely to encounter flow conditions in the East Holland River sufficient to keep it in suspension and transport it to Cook’s Bay, even under low flow conditions in the East Holland River. The increased flows resulting from the proposed Water Reclamation Centre clean treated water discharge would, if anything, increase this tendency to keep material in suspension as far as Cook’s Bay.

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For sediment that is carried in suspension, the delivery time to Cook’s Bay would depend on the rate of flow within the East Holland River. The hydrodynamic model was not intended to examine flow conditions to Cook’s Bay but, instead, modeled flows along approximately 880 m of the East Holland River. Assuming that velocities remain relatively consistent all the way to the confluence of the East Holland River and West Holland River, then Table 4.16 provides an estimate of times associated with the mean and maximum velocities predicted by the hydrodynamic model for each of the modeled scenarios that includes the proposed Water Reclamation Centre clean treated water discharge.

Flow data downstream of the confluence of the East Holland River and West Holland River is not available; however, the flow is presumably slower than within the East Holland River. Nevertheless, using the assumption that flow velocities in the Holland River are similar to those in the East Holland River, Table 4.16 provides a reasonable approximation of time to Cook’s Bay.

Table 4.16: Estimated Time of Sediment Transport to the East Holland River and West Holland River Confluence (assumes 10,585 m to Cook’s Bay, 5,891 m to confluence)

Mean Flow Time to West Max Flow Time to West Time to Time to Lake Velocity Holland River Velocity Holland River Cook’s Bay Simcoe (hr) (m/s) Confluence (hr) (m/s) Confluence (hr) (hr) Typ1 0.05 36 65 0.06 28 50 Ext1

Ext2 0.56 3 5 0.75 2 4 Ext3 0.01 136 245 0.02 74 134 Ext4 1.09 1 3 1.34 1 2

4.7 Sediment Volumes

The channel bed in the Queensville drainage ditch consisted of a thick slurry of sediment (approximately 0.40 m deep at the sampling location) before a harder, underlying material was encountered. In the worst case scenario, over time, all of this sediment would be removed by the range of flows that are conveyed through the Queensville drainage ditch.

In general, the highest volume of sediment that is transported during the annual hydrograph occurs during the 2-year flow event, which is reflected in Ext2. Flow velocities in Ext2 exceed the thresholds of erosion for all particles up to and including the coarse sands within the Queensville drainage ditch. In this scenario, the sediment would also be transported in the East Holland River. A portion of sediment from the Queensville drainage ditch would be removed during periods of lower flow, when sand sized particles would become deposited in the East Holland River, and only the silt and clay would be transported (in suspension) downstream.

In the worst-case scenario, all sediment that is in the Queensville drainage ditch would be transported downstream to Cook’s Bay. Assuming a Queensville drainage ditch length of 142 m downstream of the proposed Queensville Sideroad Outfall Discharge Location, a channel width

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of 3 m and a constant slurry thickness of 0.4 m, this would produce approximately 170 m3 of sediment. However, this is conservative and it is unlikely that all of the sediment in the Queensville drainage ditch would be transported in suspension to Cook’s Bay due to the role of the annual hydrograph.

If it is assumed that the silt and clay materials will always be transported to Cook’s Bay, and that the proportion of this grain size is similar to that obtained for SED-1 (Tables 4.2 to 4.5), then a minimum of 56 % (95 m3) of the total volume (170 m3) would be conveyed to Cook’s Bay. Again, this is a conservative estimate which may over-predict the actual volume of sediment that may be delivered to Cook’s Bay given local variations in carrying capacity that are affected by backwater effects and a changing baseline as sediment is gradually eroded.

Once removed, the cohesive materials underneath the slurry would be more resistant to erosion and gradually weather (e.g., hydration). A reduced volume of sediment would then be available for erosion. It is important to recognize that the additional volume of sediment loading to Cook’s Bay that is due only to the proposed Water Reclamation Centre clean treated water discharge would be less than 95 m3.

To provide context for the potential sediment loading of 95 m3 from the Queensville drainage ditch, the volume of sediment that is currently conveyed through the East Holland River over an average year was quantified. Suspended sediment concentration data for various flow events were collected at the Water Survey of Canada (WSC) Holland Landing monitoring station (02EC009) between 1989 and 1994 (excluding 1993). A relationship derived from these data allows the determination of suspended sediment concentration, in mg/L, as a function of discharge in the East Holland River. The relative proportions of sand, silt, and clay comprising the bed material at Holland Landing were found to be the same as those sampled in the vicinity of Queensville Sideroad (Table 4.3). Since both sites are affected by backwater influence from Cook’s Bay, the sediment-discharge relationship established for the WSC station was assumed to be representative of the East Holland River at Queensville Sideroad.

The estimated average annual sediment load of the East Holland River at Holland Landing was calculated using the sediment-discharge relationship described above and daily mean discharge values measured at the WSC monitoring station 02EC009 between 1990 and 2011. The average annual sediment load for the period between 1990 and 2011 is approximately 6,220 m3/yr, which representative of existing conditions. The estimated 95 m3 of sediment that may be entrained because of the proposed Water Reclamation Centre clean treated water discharge would result in only a 1.5 % increase in transported suspended sediment in the East Holland River. This is a conservative estimate because the 95 m3 of sediment that may be eroded from the Queensville drainage ditch is not anticipated to occur over one year but over a more extended period of time. Thus, the volume of sediment added to the East Holland River due to the proposed Water Reclamation Centre clean treated water discharge in a given year is expected to be less than 1 % of the existing average annual sediment load.

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Section 5.0 Summary and Recommendations

5.1 Overview of Assessment

Due to the extensive backwater conditions that occur in the East Holland River and its tributaries, the setting is more representative of a lake inlet or estuary than of an alluvial river system. This affects sediment entrainment, transport and depositional processes. Review of historical and recent bathymetric data provides an indication that a net gain of sediment within the Receiving Water Assessment Area has occurred, extending between the Holland Landing Lagoon and the Silver Lakes Golf and Country Club. The outlet of the Queensville drainage ditch into the East Holland River occurs within this depositional area. Although the confluence of two tributaries typically creates a downstream pool or scour area, this is not observed in this setting, in part due to the estuarine-like setting that occurs here.

Bed material samples along the East Holland River bed were classified as clayey silt. Sediments on the Queensville drainage ditch bed were defined as sandy silt. These materials are too fine to be sculpted into dune bed forms by flow within the East Holland River since, once entrained, the sediment goes directly into suspension rather than becoming bedload. Entrainment and transport of the clayey silt sediment in the East Holland River occurs under existing conditions for flows at, and above, the 2-year flow. Fine sediments entering into the East Holland River would either be deposited or remain in suspension. These findings, in addition to the low gradient/energy and backwater conditions all contribute to the site conditions that create an aggradational zone as determined from the bathymetric overlay.

Sediments within both the Queensville drainage ditch and East Holland River were characterized as a thick slurry of sediment, indicative of an overall depositional and low energy environment.

5.2 Water Reclamation Centre Clean Treated Water Discharge Effects in Receivers

The proposed Water Reclamation Centre clean treated water discharge would enter the Queensville drainage ditch, upstream of a small pond situated within a cattail marsh that is part of the greater Holland Marsh Wetland Complex. Upon exiting the pond, the Queensville drainage ditch continues approximately 160 m downstream to the East Holland River.

Five different hydrodynamic model scenarios were undertaken by the study team in the Hydrodynamic Analysis of the Water Reclamation Centre Outfall (CRA et al., 2013a) to examine the flow velocity, water depth, velocity vector, and water surface elevation data under existing and proposed Water Reclamation Centre discharge conditions.

5.2.1 Queensville drainage ditch

Increases in flows delivered by the proposed Queensville Sideroad Outfall Discharge Location would have some effects on hydraulic geometry (flow velocity and depth) and stream energy

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(power). The effects on depth are relatively small (less than 0.05 m) but some significant increases in flow velocity may occur, typically by 0.2 to 0.3 m/s. Bed shear stress and stream power would also increase with the addition of the proposed Water Reclamation Centre clean treated water discharge although values are small. These increases may be sufficient to erode the channel bed and cause some channel deepening but bank erosion is likely to be minimal.

Under the existing conditions for the Ext2 (i.e., 2-year flow) and Ext4 (i.e., 100-year flow) scenarios, velocities within the Queensville drainage ditch exceed the minimum required for erosion (based on the Hjülstrom curve) of silty sand (D50 of 0.1 mm). During average flow conditions within the Queensville drainage ditch (Typ1 and Ext3), thresholds of erosion are not exceeded. Under the proposed Water Reclamation Centre clean treated water discharge scenarios, erosion of sediment in the Queensville drainage ditch would also occur during the Ext3 scenario (extreme ambient condition, average day proposed Water Reclamation Centre clean treated water discharge), and a potential increase in erosion would occur in Ext2. Increased flows within the Queensville drainage ditch are thus expected to contribute to sediment entrainment and transport to the East Holland River.

From an impact perspective, hydrodynamic changes that would occur once the proposed Water Reclamation Centre clean treated water discharge is added result in exceedances of erosion velocity thresholds which are not presently exceeded. This applies to scenarios Typ1, Ext2 and Ext3. This suggests that the potential effects of the proposed Water Reclamation Centre clean treated water discharge are most pronounced during the 2-year and smaller flow events, and especially during periods of extreme low flows in the drainage ditch (e.g., 7Q20, which refers to the minimum 7 day flow with a 20 year recurrence interval).

Nutrient analyses of the sediment sampled in the Queensville drainage ditch revealed that the organic carbon content was higher than observed within the East Holland River. Sediment loading into the East Holland River will thus include delivery of this carbon, in addition to some phosphorus (below LEL), and TKN (between LEL and SEL). Since the total annual volume of sediment loading from Queensville drainage ditch is expected to be less than 1% of the annual load in the East Holland River, this effect is considered small in magnitude.

5.2.2 Queensville drainage ditch Marsh Pond (Holland Marsh Wetland Complex)

Flows from the proposed Queensville Sideroad Outfall Discharge Location and the upstream Queensville drainage ditch both discharge into a small pond feature within a cattail marsh. Review of the hydrodynamic model data indicates that, for all scenarios, minimal or no changes in flow velocity and velocity vector configuration is expected. No/minimal change to the erosion potential of sediment in the marsh pond is expected.

5.2.3 East Holland River

Under modeled scenarios, changes in hydraulic geometry (depth and flow velocity) and stream energy (power) are small or negligible. Depth increases are less than 0.005 m, and mean flow velocity increases are less than 0.01 m/s in most cases. Increases in bed shear stress and stream power (energy expenditure) are similarly small, with the largest changes occurring in Ext2 when increases are less than 20 % in a case where both values are already relatively high

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under 2-year recurrence flows. These changes are not sufficient to cause significant changes to channel morphology.

Modeled hydrodynamic data from within the East Holland River suggested that under existing conditions, entrainment of sediment may occur under the 2-year and 100-year flood conditions. No change in the erosion potential of flows is expected with the proposed Water Reclamation Centre clean treated water discharge. The dissipation effect that occurs as the volume of water in the receiving waterbody increases with upstream drainage area (e.g., additional contributions from tributaries, overland drainage and groundwater) would further reduce any erosion potential due to flows from the Queensville drainage ditch and the proposed Water Reclamation Centre clean treated water discharge. At Cook’s Bay (2-year flow: 95.5 m3/s, Table 2.2), flows are at least twice the magnitude of those at the Queensville Sideroad (2-year flow: 40.2 m3/s, Table 2.2). Thus, effects of the proposed Water Reclamation Centre clean treated water discharge (maximum flow: 1.5 m3/s) would be dissipated before it enters Cook’s Bay and no effect from the proposed Water Reclamation Centre clean treated water discharge is expected in Cook’s Bay.

Clay, silt, or very fine sand sized sediment received from the Queensville drainage ditch in the Ext2, Ext3 and Ext4 scenarios with the proposed Water Reclamation Centre clean treated water discharge are expected to remain in suspension. The amount of added suspended sediment is expected to be less than 1 % of the existing sediment load carried by the East Holland River. Sediment larger than very fine sand (i.e., 22 % of sample, Table 4.3) would be deposited in the East Holland River for the Ext3 scenario (extreme ambient conditions in the East Holland River, no flow in Queensville drainage ditch, and average day proposed Water Reclamation Centre clean treated water discharge of 0.46 m3/s). The time for delivery to Cook’s Bay is dependent on flow velocity, and under the Ext4 scenario would be expected to arrive within 2 to 3 hours. Under the Ext3 scenario, this may take 10 or more days.

5.2.4 Cook’s Bay (Lake Simcoe)

Cook’s Bay in Lake Simcoe is the ultimate receiver of flows and sediment that enter the East Holland River. Results of analyses indicate that while most of the sand fraction of sediment that enters the East Holland River will be deposited, clay, silt, and very fine sand may be transported to Cook’s Bay. During high flow events, larger sand sized particles may similarly move to Cook’s Bay. A volume of 95 m3 could be delivered to Cook’s Bay, assuming that all silt and clay that is contained within a 0.4 m thick slurry on the Queensville drainage ditch bed would be entrained. More precise determination of minimum sediment volumes would require further analyses.

5.2.5 Further Considerations

There are several items that should be considered when reviewing the results of this assessment including:

. Given site conditions, entrainment of sediment from the Queensville drainage ditch is expected to be a gradual process rather than an event based scour process.

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. The hydrodynamic model included only the channel, and did not include the floodplain onto which higher flows would spill. Flow velocities of the 2-year and higher flows may therefore be lower than those presented in the model output data (CRA et al., 2013a) leading to an over-estimate of the grain sizes entrained in the Queensville drainage ditch. . Effects of existing turbidity in the East Holland River will reduce the carrying capacity of flows. This will reduce the carrying capacity of the water, which, in a low energy environment, may cause suspended particle sizes that are above the erosion threshold to become deposited. . Sediment erosion and transport would not be caused solely by the proposed Water Reclamation Centre clean treated water discharge. Sediment entrainment and transport represent natural channel processes that occur regularly due to scour resulting from increased flows due to storm events.

5.3 Recommendations

Results from the analyses presented in this assessment reveal that minimum erosion velocity thresholds for silt sized sediment (i.e., dominant in the bed materials) would be surpassed once the proposed Water Reclamation Centre clean treated water discharge flows into the Queensville drainage ditch (i.e., for all modeled scenarios). As a result, an increase in the total volume of sediment that is carried in suspension to Cook’s Bay may occur. Only a small increase (less than 1 % of the existing sediment load in the East Holland River) is anticipated to occur as a result of erosion of sediment from the Queensville drainage ditch.

Mitigation of the hydraulic effects, due to the proposed Water Reclamation Centre clean treated water discharge flows, to reduce the potential for sediment loading to both the East Holland River and Cook’s Bay may include the following which will be included as part of the Impact Assessment stage of the UYSS EA in concert with preliminary design:

. Dissipate flow energy at the proposed Queensville Sideroad Outfall Discharge Location by installing an in-water energy dissipating structure in the channel to minimize local scour potential. . Modify existing drainage ditch configuration (e.g., alter bank slopes to increase top width) to minimize the change to flow velocity and water depth due to the proposed Water Reclamation Centre clean treated water discharge. . Protect existing soft sediment accumulation on the drainage ditch bed from future erosion, if possible (note: given the depth of soft material, this may not be possible). . Remove soft slurry of sediment from channel bed to expose underlying cohesive sedimentary unit and protect to reduce hydration potential. . Implement roughness elements (e.g., large woody debris, large boulders) to reduce in-stream flow velocity.

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In addition to the mitigation measures described above, the following monitoring program will be included as part of the Impact Assessment stage of the UYSS EA in concert with preliminary design:

. Establish baseline suspended sediment conditions prior to construction through suspended sediment sampling in the East Holland River and Queensville drainage ditch. . Monitor suspended sediment in the East Holland River and Queensville drainage ditch during operation of the proposed Water Reclamation Centre to confirm the anticipated negligible change in sediment loading.

The recommended mitigation measures and monitoring program for addressing the potential for sediment loading to both the East Holland River and Cook’s Bay will be documented in the Natural Environment Impact Assessment of the Preferred Alternative Water Reclamation Centre Site WH1 West and the Preferred Alternative YDSS Modifications Route A (CRA et al. 2013g) report4.

4. ‘WH1 West’ is the Preferred Site for the proposed Water Reclamation Centre. The Site is located on the east side of 2nd Concession in the Town of East Gwillimbury, approximately one kilometre north of Queensville Sideroad, and is approximately 45 ha in size.

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Section 6.0 References

Chapman, L.J. and D.F. Putnam, 1984: The Physiography of Southern Ontario, Third Edition. Ontario Geological Survey, Special Volume 2, 270 pp.

Conestoga-Rovers & Associates (CRA), 2011: East Holland River Bathymetric Survey, data provided to AECOM.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013a: Upper York Sewage Solutions Environmental Assessment, Hydrodynamic Analysis of the Water Reclamation Centre Outfall. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, (DRAFT) 2013b: Upper York Sewage Solutions Environmental Assessment, Study of Potential Impacts of the Water Reclamation Centre Discharge on Flooding Potential in the East Holland River. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013c: Upper York Sewage Solutions Environmental Assessment, Comprehensive Assimilative Capacity Study of the Water Reclamation Centre Discharge. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013d: Upper York Sewage Solutions Environmental Assessment, Thermal Effects of the Water Reclamation Centre Discharge on the East Holland River. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013e: Upper York Sewage Solutions Environmental Assessment, Assessment of the Water Reclamation Centre Discharge on Aquatic Habitat in the East Holland River. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013f: Upper York Sewage Solutions Environmental Assessment, Natural Environment Baseline Conditions Report. Prepared for the Regional Municipality of York.

Conestoga-Rovers & Associates (CRA), AECOM, and Black & Veatch, 2013g: Upper York Sewage Solutions Environmental Assessment, Natural Environment Impact Assessment of the Preferred Alternative Water Reclamation Centre Site WH1 West and the Preferred Alternative YDSS Modifications Route A. Prepared for the Regional Municipality of York.

Knighton, D., 1998: Fluvial Forms and Processes: a new perspective. London: Edward Arnold. 383 pp.

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Komar, P.D., 1987: Selective gravel entrainment and the empirical evaluation of flow competence. Sedimentology (34): 1165-1176.

Lake Simcoe Region Conservation Authority (LSRCA), 2005: Hydrology Report (Final): Hydrologic and Hydraulic Modeling for the West Holland River, East Holland river and Maskinonge River Watersheds. Prepared for Lake Simcoe Bay Region Conservation Authority by Cumming Cockburn Limited (CCL), Reference No. 7591, 77 pp.

Lake Simcoe Region Conservation Authority (LSRCA), 2010: 2010 Annual Report. Lake Simcoe Region Conservation Authority.

Louis Berger Group, 2006: Pollutant Target Loads: Lake Simcoe and Nottawasaga River Basins. The Louis Berger Group Inc., Prepared for the Lake Simcoe Region Conservation Authority, June 2006.

Ontario Ministry of Natural Resources (MNR), 2002: Technical Guide – River & Stream Systems: Erosion Hazard Limit. Ontario Ministry of Natural Resources, Water Resources Section, 133 pp.

Sheldrick B.H. and C. Wang, 1993: Particle Size Distribution. Pages 499-507. In: Carter, M.R. (ed), Soil Sampling and Methods of Analysis, Canadian Society of Soil Science, Lewis Publishers, Ann Arbor, MI.

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Section 7.0 Glossary of Terms

Glossary of Terms

Alternative Methods of Different ways of doing the same activity. Alternative methods Carrying out the could include consideration of one or more of the following Undertaking alternative technologies; alternative methods of applying specific (Interchangeable with technologies; alternative sites for a proposed undertaking; Alternative Methods) alternative design methods; and alternative methods of operating any facilities associated with a proposed undertaking.

Aquatic Refers to an environment that consists of, relates to, or is in water; or to animals and plants living or growing in, on, or near the water.

Baseline Conditions The existing conditions that are the physical, chemical, biological, social, economic, and cultural setting in which the proposed project is to be located and where local impacts (both positive and negative) might be expected to occur.

Channel Order The designation by a dimensionless integer series (1, 2, 3, …) of the relative position of stream segments in the network of a drainage basin.

Drain Drains remove excess water from agricultural lands and can be either natural watercourses or manmade ditches. Municipal Drains are described as drainage systems located primarily in agricultural areas of Ontario that may consist of either ditches or closed systems such as pipes or tiles, grasses waterways, storm water detention ponds, culvert and bridges. Some creeks and small rivers may also be considered municipal drains.

Environment The Environmental Assessment Act defines “environment” broadly to include: i) air, land or water ii) plant or animal life, including human life iii) social, economic, and cultural conditions influencing the life of humans or a community iv) any building, structure, machine or other device or thing made by humans v) any solid, liquid, gas, odour, heat, sound, vibration, or radiation resulting directly or indirectly from the human activities vi) any part or combination of the foregoing and the inter- relationships between any two or more of them, in or of Ontario

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Glossary of Terms

Environmental A generic term for a study that assesses the potential Assessment (EA) environmental effects (positive or negative) of a proposal. Key components of an environmental assessment include consultation with government agencies and the public; consideration and evaluation of alternatives; and the management of potential environmental effects. Conducting an environmental assessment promotes good environmental planning before decisions are made about proceeding with a proposal. For the purposes of the Terms of Reference, an Environmental Assessment refers to the process and related documentation, including the submission of a Terms of Reference and final Environmental Assessment Report for approval by the Minister of the Environment, in accordance with the requirements of Part II of the EA Act.

Habitat The physical location or type of environment in which an organism or biological population occurs or lives, grows, and carries out life processes.

Holland Marsh Consists of 2900 ha of organic (muck) soil draining to the Holland River used for farming.

Impact Assessment The process of studying and identifying the future consequences of a current or proposed action.

Lake Simcoe Region Established under the Conservation Authorities Act (1946), the Conservation Authority LSRCA prepares and delivers programs for the management of (LSRCA) the renewable natural resources within watersheds in its jurisdiction.

Ministry of the The Ministry of the Environment is responsible for protecting air, Environment (MOE) land and water to ensure healthy communities, ecological protection, and sustainable development for present and future generations of Ontarians.

Ministry of Natural The Ministry of Natural Resources manages and protects Resources (MNR) Ontario’s natural resources for wise use across the province.

Mitigation Measure Action(s) that remove or alleviate to some degree the negative effects associated with the implementation of an alternative.

Potential Effect An effect that is deemed possible to result from an activity or implementation of a particular alternative.

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Glossary of Terms

Provincially Significant Wetlands identified as provincially significant by the Ministry of Wetland (PSW) Natural Resources using evaluation procedures established by the province, as amended from time to time.

Terms of Reference (ToR) The first step in an application for approval to proceed with a project or undertaking under the Environmental Assessment Act is the submission of a Terms of Reference (ToR) for the Environmental Assessment (EA). Public and agency consultation is required on the preparation and submission of the ToR to the Ministry of the Environment. Approval is required by the Minister of the Environment. If approved, the ToR provides a framework / work plan for the EA.

Undertaking An enterprise, activity, proposal, plan or program in respect of a commercial or business enterprise or activity of a person or persons that has potential environmental effects and is assessed in accordance with the requirements of the Environmental Assessment Act.

Watercourse A body of water having defined bed and banks with permanent or intermittent flow that may include rivers, creeks, streams and springs.

Watershed An area that is drained by a river and its tributaries.

Wetland Lands that are seasonally or permanently covered by shallow water, as well as lands where the water table is close to or at the surface. In either case the presence of abundant water has caused the formation of soils saturated with water and has favoured the dominance of either hydrophytic plants or water tolerant plants. The four major types of wetlands are swamps, marshes, bogs, and fens.

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APPENDICES

Appendix A Photograph Logs

Appendix B Sediment Sample Analysis Results

Appendix C Cross-Section Profiles from Sonar Survey

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Appendix A

Photograph Logs

050278 (112) York Region No. 74270 Geomorphological Assessment of the Water Reclamation Centre Discharge on the East Holland River Upper York Sewage Solutions EA

Photographic Log

Sediment Sampling Photos illustrated below were taken during field visits February 16, 2012

HR-1 – Holland River North of Confluence of East Holland River and West Holland River

Photograph 1. Holland River – Downstream View  Photograph 2. Holland River – Upstream View 

Photograph 3. Holland River – Augured Hole  Photograph 4. Holland River – Augured Hole 

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Sediment Sampling

Photos illustrated below were taken during field visits February 16, 2012

HR-2 – East Holland River South of Confluence with West Holland River

Photograph 1. East Holland River – Downstream View Photograph 2. East Holland River – Upstream View  

Photograph 3. East Holland River – Looking East  Photograph 4. East Holland River – Looking West 

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Sediment Sampling

Photos illustrated below were taken during field visits February 16, 2012

HR-3 – East Holland River North of Queensville Sideroad

Photograph 1. East Holland River – Downstream View Photograph 2. East Holland River – Upstream View  

Photograph 3. East Holland River – Looking East  Photograph 4. East Holland River – Looking West 

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Sediment Sampling

Photos illustrated below were taken during field visits February 16, 2012

HR-4 – East Holland River at Queensville Sideroad

Photograph 1. East Holland River – Photograph 2. East Holland River – Downstream View  Upstream View 

Photograph 3. East Holland River – Looking West  Photograph 4. East Holland River – Looking West 

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Sediment Sampling

Photos illustrated below were taken during field visits February 16, 2012

HR-5 – East Holland River South of Queensville Sideroad

Photograph 1. East Holland River – Photograph 2. East Holland River – Downstream View  Upstream View 

Photograph 3. East Holland River – Looking East 

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Queensville drainage ditch and East Holland River at Queensville Sideroad

Photos illustrated below were taken during field visits April 26, 2012

Photograph 1. Queensville drainage ditch Upstream Photograph 2. East Holland River at Queensville of East Holland River Outlet – Remnants of Beaver Dam drainage ditch Outlet – Upstream View, East Side  in Channel 

Photograph 7. East Holland River at Queensville drainage ditch Outlet – Upstream View, West Side 

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Queensville drainage ditch and East Holland River at Queensville Sideroad

Photos illustrated below were taken during field visits March 26, 2013

Photograph 1. Queensville drainage ditch – Photograph 2. Queensville drainage Upstream of Pond  ditch – Online Pond 

Photograph 3. Queensville drainage ditch – View Photograph 4. Queensville drainage ditch – View Upstream Towards Pond  Downstream from Pond Towards East Holland River 

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Queensville drainage ditch and East Holland River at Queensville Sideroad

Photos illustrated below were taken during field visits March 26, 2013

Photograph 5. Queensville drainage ditch – View of Photograph 6. View of Queensville drainage ditch and Channel Bed, Downstream of Pond  East Holland River Confluence 

Photograph 7. East Holland River at Queensville Photograph 8. East Holland River at Queensville Sideroad – Upstream View, West Side  Sideroad – Upstream View, East Side 

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Queensville drainage ditch and East Holland River at Queensville Sideroad

Photos illustrated below were taken during field visits March 26, 2013

Photograph 9. East Holland River at Queensville Sideroad – View of West Bank Upstream of Bridge 

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Appendix B

Sediment Sample Analysis Results

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Particle Size

Submitter 1000 500 250 100 Sampling disp gravel 2 mm Clay clay+ Inst inst+ 50 to sand sand+ total clay inorganic sand Silt Sample ID Sample to to to to Date /Time factor mass mass dish dish dish dish 100 dish dish mass mass mass mass mass ID 2000 1000 500 250 g g g g g g g g g g g g g g g g g g g 4/26/12 12-038837-0001 SED 1 0.011 0.000 100.000 1.020 1.068 0.996 1.131 0.010 0.180 0.300 1.570 1.810 1.017 4.920 100.000 1.48 8.86 3.90 3.48 12:00 AM 4/26/12 12-038837-0002 SED 2 0.011 0.000 100.000 0.994 1.044 1.013 1.232 0.020 0.090 0.110 0.270 0.530 1.049 2.067 100.000 1.56 9.34 1.02 6.76 12:00 AM 4/26/12 12-038837-0003 SED 3 0.011 0.000 100.000 1.014 1.066 0.997 1.203 0.020 0.140 0.200 0.340 0.800 1.026 2.563 100.000 1.64 9.34 1.54 6.16 12:00 AM 4/26/12 12-038837-0004 SED 4 0.011 1.300 128.400 1.036 1.096 1.027 1.265 0.020 0.040 0.050 0.110 0.210 1.005 1.443 129.700 1.96 9.52 0.44 7.12 12:00 AM 4/26/12 12-038837-0005 SED 5 0.011 0.000 100.000 1.044 1.105 1.022 1.265 0.000 0.020 0.040 0.080 0.180 1.007 1.316 100.000 2.00 9.59 0.31 7.28 12:00 AM 4/26/12 12-038837-0006 SED 6 0.011 0.000 100.000 0.989 1.044 1.011 1.251 0.030 0.030 0.020 0.060 0.180 1.031 1.354 100.000 1.76 9.48 0.32 7.40 12:00 AM 4/26/12 12-038837-0007 SED 7 0.011 0.000 100.000 0.994 1.041 1.012 1.211 0.010 0.110 0.170 0.290 1.070 1.035 2.686 100.000 1.44 9.17 1.65 6.08 12:00 AM

Parameter Very Fine Fine Medium Coarse Very Coarse Submitter Sample Sampling Gravel Sand Silt Clay Sample ID Sand Sand Sand Sand Sand Sample ID Type Date / Time 0.063-2 mm 0.063-0.125 mm 0.125-0.25 mm 0.25 - 0.5 mm 0.5-1 mm 1 - 2 mm 0.002-0.063 mm <0.002 mm % % % % % % % % % 12-038837-0001 SED 1 Soil 4/26/12 12:00 AM 0.0 44.0 20.4 17.7 3.4 2.0 0.1 39.3 16.7 12-038837-0002 SED 2 Soil 4/26/12 12:00 AM 0.0 10.9 5.7 2.9 1.2 1.0 0.2 72.4 16.7 12-038837-0003 SED 3 Soil 4/26/12 12:00 AM 0.0 16.5 8.6 3.6 2.1 1.5 0.2 66.0 17.6 12-038837-0004 SED 4 Soil 4/26/12 12:00 AM 1.0 4.6 2.2 1.2 0.5 0.4 0.2 74.8 20.6 12-038837-0005 SED 5 Soil 4/26/12 12:00 AM 0.0 3.2 1.9 0.8 0.4 0.2 0.0 75.9 20.9 12-038837-0006 SED 6 Soil 4/26/12 12:00 AM 0.0 3.4 1.9 0.6 0.2 0.3 0.3 78.0 18.6 12-038837-0007 SED 7 Soil 4/26/12 12:00 AM 0.0 18.0 11.7 3.2 1.9 1.2 0.1 66.3 15.7

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Appendix C

Cross-Section Profiles from Sonar Survey

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