WATERCOURSE CROSSINGS HYDROTECHNICAL ASSESSMENT & DESIGN RECOMMENDATIONS Liege Lateral Loop No. 2 Pelican Lake Section

Transcription

1 WATERCOURSE CROSSINGS HYDROTECHNICAL ASSESSMENT & DESIGN RECOMMENDATIONS Liege Lateral Loop No. 2 Pelican Lake Section Note: Sub Vendor supplied data January 28, 2016 Page 1 of 22

2 LIEGE LATERAL LOOP NO. 2 PELICAN LAKE SECTION WATERCOURSE CROSSINGS HYDROTECHNICAL ASSESSMENT AND DESIGN RECOMMENDATIONS Sub Supplier Data Report Prepared for: HATCH MOTT MACDONALD Prepared by: MATRIX SOLUTIONS INC. November 2015 Edmonton, Alberta 142, 6325 Gateway Boulevard NW Edmonton, Alberta, Canada T6H 5H6 Phone: Fax: PEL18181-HMM-A-DB-0002 January 28, 2016 Page 2 of 22

3 LIEGE LATERAL LOOP NO.2 PELICAN LAKE SECTION WATERCOURSE CROSSINGS HYDROTECHNICAL ASSESSMENT AND DESIGN RECOMMENDATIONS Report prepared for Hatch Mott MacDonald, November 2015 Pamela Rogers, M.Eng., P.Eng. Water Resources Engineer November 9, 2015 reviewed by Brandyn Coates, M.Eng., P.Eng. Environmental Engineer November 9, 2015 reviewed by Manas Shome, Ph.D., P.Eng. Principal, Water Resources Engineer November 9, 2015 DISCLAIMER We certify that this report is accurate and complete and accords with the information available. Information obtained during the preparation of this report or provided by third parties is believed to be accurate but is not guaranteed. We have exercised reasonable skill, care and diligence in assessing the information obtained during the preparation of this report. This report was prepared for Hatch Mott MacDonald. The report may not be relied upon by any other person or entity without our written consent and that of Hatch Mott MacDonald. Any uses of this report by a third party, or any reliance on decisions made based on it, are the responsibility of that party. We are not responsible for damages or injuries incurred by any third party, as a result of decisions made or actions taken based on this report. January 28, 2016 Page 3 of 22

4 TABLE OF CONTENTS 1 INTRODUCTION Objectives and Scope of Work DESIGN CRITERIA DESIGN METHODS Hydrologic and Hydraulic Analysis Morphologic Analysis Scour Depth Analysis CROSSING DESCRIPTION Loon Creek (WC3) Unnamed Tributary to Athabasca River (WC5) Unnamed Tributary to Livock River (WC6) Livock River (WC7) HYDROLOGY AND HYDROTECHNICAL ASSESSMENT DESIGN RECOMMENDATIONS Loon Creek (WC3) Unnamed Tributary to Athabasca River (WC5) Unnamed Tributary to Livock River (WC6) Livock River (WC7) ADDITIONAL CONSIDERATIONS REFERENCES... 9 January 28, 2016 Page 4 of 22

5 FIGURES FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 Watercourse Crossings Pipeline Route Location Plan WC3 Loon Creek NW W4M Site Photographs WC3 Loon Creek NW W4M Location Plan WC5 Unnamed Tributary to Athabasca River SE W4M Site Photographs WC5, Unnamed Tributary to Athabasca River SE W4M Location Plan WC6 Unnamed Tributary to Livock River NE W4M Site Photographs WC6 Unnamed Tributary to Livock River NE W4M Location Plan WC7 Livock River SW W4M Site Photographs WC7 Livock River SW W4M Hydrologic Analysis Results WC3 Loon Creek Hydrologic Analysis Results WC5 Unnamed Tributary to Athabasca River Hydrologic Analysis Results WC6 Unnamed Tributary to Livock River Hydrologic Analysis Results WC7 Livock River Creek Profile, Cross-Section and Pipeline Design Details WC3, Loon Creek Creek Profile, Cross-Section and Pipeline Design Details WC5, Unnamed Tributary to Athabasca River Creek Profile, Cross-Section and Pipeline Design Details WC6, Unnamed Tributary to Livock River Creek Profile, Cross-Section and Pipeline Design Details WC7, Livock River LIST OF TABLES TABLE 1 Pipeline Watercourse Crossing Summary... 1 TABLE 2 Hydrologic and Hydrotechnical Assessment Results... 6 January 28, 2016 Page 5 of 22

6 1 INTRODUCTION Hatch Mott MacDonald (HMM) contracted Matrix Solutions Inc. to provide hydrotechnical assessment and design support related to watercourse crossings as part of TransCanada PipeLines Limited s Liege Lateral Loop No. 2 Pelican Lake Section pipeline project near Fort McMurray, Alberta. The proposed pipeline will run from the existing Buffalo Creek Compressor Station located at SW W4M to the existing Pelican Lake Compressor Station located at NE W4M. The proposed 760 mm diameter (NPS 30) pipeline will transport natural gas. The proposed pipeline will cross several watercourses, as shown on Figure 1. Detailed hydrotechnical analysis and design for crossings WC1 (Boivin Creek), WC2 (Athabasca River), and WC4 (Unnamed Tributary to Loon Creek) will be addressed in a separate report. The detailed hydrotechnical analysis and design for the remaining four crossings, WC3 (Loon Creek), WC5 (Unnamed Tributary to Athabasca River), WC6 (Unnamed Tributary to Livock River), and WC7 (Livock River), are discussed herein. 1.1 Objectives and Scope of Work TransCanada is proposing an open-cut method to install the pipeline beneath the watercourses listed below in Table 1. The objectives of this assessment were to determine the burial depth below the river bed to minimize the risks of pipeline exposure due to potential scour or channel migration over the pipeline s life and to recommend preliminary design burial requirements for the pipeline crossing. TABLE 1 Pipeline Watercourse Crossing Summary Survey Crossing ID Watercourse Legal Location Latitude (m) NAD 83 ATS 4.1 Longitude (m) WC3 Loon Creek NW W4M 56 13'28.09"N '42.33"W WC5 Unnamed Tributary to Athabasca River SE W4M 56 23'43.13"N '7.84"W WC6 Unnamed Tributary to Livock River NE W4M 56 25'44.68"N '58.34"W WC7 Livock River SW W4M 56 27'4.39"N '31.21"W Matrix s scope of work for the project included the following: reviewing the proposed pipeline route and verifying the watercourse crossing locations conducting hydrologic analyses to estimate peak flows and understand the flood history at the crossings reviewing background information to assess existing channel and floodplain characteristics, identifying potential constraints, and assessing potential for erosion and channel migration comparing historical aerial photographs to evaluate channel morphology and stability completing hydraulic and scour calculations and providing design recommendations, including cover depths, sagbend setbacks, and erosion protection measures, if required, for the pipeline at the proposed watercourse crossing locations January 28, 2016 Page 6 of 22

7 preparing a report summarizing the results of the hydrotechnical assessment and design recommendations for the pipeline at the proposed watercourse crossing locations The hydrotechnical design presented in this report is based upon the following: the proposed pipeline route provided by HMM on June 9, 2015 (Peters 2015, Pers. Comm.) the Code of Practice for Pipelines and Telecommunication Lines Crossing a Water Body (COP; ESRD 2013) the Pipeline Associated Watercourse Crossings (CAPP et al. 2005) 1:50,000 scale National Topographic System (NTS) mapping streamflow data from Water Survey of Canada (WSC) monitoring stations (WSC 2014) an aquatic assessment completed by TERA Environmental Consultants (2015) survey data provided to Matrix by WSP Canada Inc. on September 18 and 22, 2015 (Peters 2015, Pers. Comm.) 2 DESIGN CRITERIA The following criteria were used for the hydrotechnical design of the pipeline at the proposed crossing locations: Design flow is the 1:100-year instantaneous peak flow as per the COP requirement for a pipeline crossing a watercourse (ESRD 2013). The potential total scour depth was estimated by combining the computed general scour and local scour, as appropriate. Maximum allowable elevation of the top of the pipe was determined from the existing minimum bed elevation and the potential scour depth. Burial depth for a pipeline crossing a watercourse is defined as the vertical distance between the existing minimum bed level (thalweg) and the elevation of the top of the pipe. The minimum cover depth will be 1.8 m or the computed total scour depth, whichever is greater. Sagbend setbacks at the pipeline watercourse crossings were calculated using the Alberta Environment and Parks equation to compute setback (Sb) distance for sand-bed streams (NOVA 1991): Sb = 0.34B 2/3 where B is the top width of the watercourse January 28, 2016 Page 7 of 22

8 A minimum sagbend setback of 1 m from the top of the banks is to be applied at the crossings. Based on the consideration of historical air photograph comparisons, channel sinuosity, the sagbend equation described above, and the field assessment, a farther setback may be required. Sagbend setback recommendations are based upon defining the potential for bank migration during the life of the pipeline. The bank stability and construction method are also considered in establishing the sagbend locations. Final setback distances are typically based on professional experience and judgment. 3 DESIGN METHODS The following methods were used to establish the design recommendations for burial depth and sagbend distances at each pipeline crossing site. 3.1 Hydrologic and Hydraulic Analysis Hydrologic analyses included estimating peak flows, monthly flows, and flow duration curves at the crossing locations. Regional hydrologic analysis or a Single Station Transfer method is typically used to estimate flows at an ungauged location. For these crossing locations, the latter method was used since a hydrometric gauging station is located on the House River in a watershed similar to that of the crossing sites. WSC Station 07CB002 is located on the House River at Highway 63 with a drainage area of 780 km 2 and data spanning 1982 to The estimated extreme peak flows for a range of return periods and flow statistics at gauging station 07CB002 were transposed to each crossing location using a ratio of the drainage area at each crossing and the WSC station. Peak flows associated with various return periods were estimated by conducting a frequency analysis of the instantaneous peak flows at WSC Station 07CB002. Missing instantaneous flow data were estimated through regression analysis of recorded maximum daily flow data and corresponding instantaneous flow data. Flood frequency analysis was conducted using HYFRAN-Plus (2007) software to determine the best fit statistical distribution (e.g., Gamma, Pearson, or Logarithmic). The design water levels corresponding to 1:100-year flood at the crossing sites were calculated using the slope-area method with the Manning equation. Channel profiles and cross-sections were developed using survey data provided by HMM. The roughness characteristics of the main channel and its floodplain areas were estimated based on the field observations and using professional judgment following the guidelines provided in Chow (1959). The potential for ice and debris jams to form at the crossing needs to be considered in the hydrotechnical design of the crossing. January 28, 2016 Page 8 of 22

9 3.2 Morphologic Analysis Potential long-term bank erosion and channel changes that could affect the crossing were estimated based on the field assessment and general experience for the watercourses in the area. The findings of this assessment were used to determine the horizontal extent of the burial depth below the watercourses, the sagbend setback, and any erosion protection requirements. Sagbend setback distances may be extended farther back from the top of the banks based upon potential for bank erosion and channel migration. 3.3 Scour Depth Analysis The potential scour depth was calculated at each crossing during the 1:100-year design flood. These estimates were used to determine the minimum burial depth of the pipeline and assist in defining setback locations. Total scour depth consists of general scour (i.e., the overall lowering of the channel bed during flooding) and local scour (i.e., scour due to secondary currents generated at channel bends, confluences, or obstructions). The general scour at the crossing location was estimated based on the bankfull or maximum confirmed flood level using the Blench (1969) regime theory and graphs developed from rivers with gravel beds in Alberta (ASME 2008). A channel shape factor (Z) was then estimated from a graph for free eroding bends (ASME 2008) and professional judgment based upon site-specific channel conditions. The maximum local scour typically occurs at the outside of the channel bend or at a channel confluence and may be much larger than general scour. Information on bed material size is required to estimate the scour depth. The median bed material size at each crossing was selected based on information provided in the aquatic assessment report (TERA 2015). 4 CROSSING DESCRIPTION Site characteristics at each crossing site were established by reviewing the findings of site assessments, photographs provided by HMM, and historical aerial photographs. 4.1 Loon Creek (WC3) Loon Creek flows east at Crossing WC3 (referred to as crossing 83-WC-02 by WSP) and joins the Athabasca River about 15 km downstream (Figure 2). Site photographs collected in October 2015 were provided to Matrix by HMM and are presented on Figure 3. Loon Creek meanders through a deep valley approximately 200 m wide and 20 m deep at the top of the crossing. The surrounding land is vegetated with shrubs, grasses, and trees. Sharp meander bends are located immediately upstream and downstream of the proposed crossing location and an active beaver dam was located 20 m downstream of the right-of-way. The drainage area of the watercourse at the proposed crossing location is 260 km 2. January 28, 2016 Page 9 of 22

10 The channel has a longitudinal slope of about 0.26%, as estimated from the surveyed profile. The channel top width at the crossing site is about 8.0 m and the bankfull depth is about 1.0 m. The channel bed is composed of fine-grained material with traces of gravel. The banks are composed of fine-grained material with erosion apparent along both banks at the crossing location (Figure 3, Photos 1 and 2). The channel banks rise gently from the banks edges and are vegetated with shrubs, grasses, and trees. 4.2 Unnamed Tributary to Athabasca River (WC5) This Unnamed Tributary flows northeast at Crossing WC5 (referred to as crossing 85-WC-01 by WSP) and joins the Athabasca River about 9 km downstream (Figure 4). Site photographs collected in October 2015 were provided to Matrix by HMM and are presented on Figure 5. The unnamed creek meanders through a deep valley approximately 180 m wide and 20 m deep at the top of the crossing. The surrounding land is vegetated with shrubs, grasses, and trees. Sharp meander bends are located immediately upstream and downstream of the proposed crossing location and an active beaver dam was located 20 m downstream of the right-of-way. At the time of assessment, the area surrounding the crossing location was flooded due to the presence of beaver dams. The drainage area of the watercourse at the proposed crossing location is 88 km 2. The channel has a longitudinal slope of about 0.57%, as estimated from the surveyed profile. The main channel splits into two channels at the proposed crossing location. The north channel top width at the crossing site is about 6.8 m wide and the bankfull depth is about 0.5 m; the south channel top width at the crossing site is about 6.0 m and the bankfull depth is about 1.0 m. The channel bed is composed of fine-grained material with trace gravel and cobble. The banks are composed of a fine-grained material with erosion apparent along the left bank at the crossing location. Large woody debris and instream vegetation were present throughout the crossing reach. The channel banks rise gently from the banks edges and are vegetated with shrubs, grasses, and trees. 4.3 Unnamed Tributary to Livock River (WC6) This Unnamed Tributary flows east at Crossing WC6 (referred to as crossing 86-WC-01 by WSP) and enters the Athabasca River, 10 km downstream (Figure 6). Site photographs collected in October 2015 were provided to Matrix by HMM and are presented on Figure 7. The unnamed creek meanders through a large floodplain area that is vegetated with grasses and trees. Beaver activity is present through the crossing reach with an old beaver dam located 50 m upstream. The drainage area of the watercourse at the proposed crossing location is 11 km 2. The channel has a longitudinal slope of about 0.66%, as estimated from the surveyed profile. The channel top width at the crossing site is about 1.3 m and the bankfull depth is about 0.5 m. The channel bed is composed of fine-grained material with trace gravel; instream vegetation was present throughout the crossing reach. The channel banks are soft and composed of fine-grained and organic material. January 28, 2016 Page 10 of 22

11 4.4 Livock River (WC7) Livock River flows northeast at Crossing WC7 (referred to as crossing 86-WC-02 by WSP) and joins the Athabasca River 11 km downstream (Figure 8). Site photographs collected in October 2015 were provided to Matrix by HMM and are presented on Figure 9. Livock River meanders through a 120 m wide valley that is 15 m deep at the top of the banks at crossing. The surrounding land is vegetated with shrubs, grasses, and trees. Sharp meander bends are located throughout the crossing reach and beaver dams are located 90 m upstream and 200 m downstream of the proposed crossing location. The drainage area of the watercourse at the proposed crossing location is 66 km 2. The channel has a longitudinal slope of about 0.5%, as estimated from the surveyed profile. The channel top width at the crossing site is about 8.0 m and the bankfull depth is about 0.5 m. The channel bed is primarily composed of fine-grained material with trace gravel and cobble. The banks are composed of fine-grained material with unstable sections and erosion apparent throughout. The channel banks rise gently from the banks edges and are vegetated with shrubs, grasses, and trees. Large woody debris was present in the channel throughout the crossing reach. 5 HYDROLOGY AND HYDROTECHNICAL ASSESSMENT The results of the flow frequency analysis and the estimated flow statistics, including minimum, maximum, and mean monthly flows, and flow duration curves at each of the crossing locations are illustrated on Figures 10 (WC3), Figure 11 (WC5), Figure 12 (WC6), and Figure 13 (WC7). The hydrologic and hydrotechnical analysis results for each crossing are summarized in Table 2 below. TABLE 2 Hydrologic and Hydrotechnical Assessment Results Crossing Drainage Area (km 2 ) 1:100 Year Flood Magnitude (m 3 /s) Manning Roughness Coefficient (n) 1:100 Year Water Level (m asl) Channel Slope (%) D 50 (mm) Channel Shape Factor (Z) Estimated Scour Depth (m below channel bed) WC WC WC WC The derived monthly flow statistics and flow duration curves provide information for selecting an appropriate water management method and developing a risk management strategy during construction. The highest monthly flows at the crossing occur between May and August, so instream construction is not recommended during this period. The monthly flow duration curves show the monthly variation of flow with a given exceedance probability. For example, a flow of 3 m 3 /s or higher can be expected 20% of the January 28, 2016 Page 11 of 22

12 time in July (Figure 10). Monthly data was not available from WSC Station 07CB002 for November through February, though seasonally low flows are to be expected during this period. There is significant potential for debris jams to form at all four crossing locations, which could cause local scour. Also, the maximum potential scour at Crossings WC3, WC5, and WC7 could potentially occur due to the development and washout of beaver dams located near the crossing location. In addition to the estimated scour depth at the four crossing sites, there is potential for long-term bed degradation due to downcutting over the lifetime of the pipeline. Therefore, an additional allowance for downcutting was considered in the hydrotechnical design. 6 DESIGN RECOMMENDATIONS The design recommendations are based solely on river engineering considerations. A deeper pipe profile may be required for non-hydrotechnical reasons considering site-specific subsurface conditions and construction installation requirements for the proposed crossing. 6.1 Loon Creek (WC3) Based on the site conditions and calculated scour depth, and due in part to the potential for channel degradation following washout of the beaver dam, a cover depth of 3.1 m below the bed of the channel is recommended at Crossing WC3. The proposed minimum cover depth corresponds to a maximum top-of-pipe elevation of m, as shown on Figure 14. Based on the morphologic assessment, signs of erosion were observed on both banks. Therefore, greater sagbend setbacks are recommended to account for potential erosion at the banks. The pipe should remain horizontal with a maximum top elevation of m between Stations 0+226S and 0+240N, as shown on Figure 14. These setback distances correspond to the anticipated extents of the 1:100-year water level. The recommended setback distances assume restoration grading and stable native vegetation on the channel banks. 6.2 Unnamed Tributary to Athabasca River (WC5) Based on the site conditions and calculated scour depth, and in accordance with the TransCanada typical design cover depth, a cover depth of 2.2 m below the bed of the channel is recommended at Crossing WC5. The proposed minimum cover depth corresponds to a maximum top-of-pipe elevation of m, as shown on Figure 15. Based on the morphologic assessment, signs of erosion were observed on the left bank. Therefore, greater sagbend setbacks are recommended to account for potential erosion at the banks. The pipe should remain horizontal with a maximum top elevation of m between Stations 0+158S and 0+179N, as shown on Figure 15. The recommended setback distances assume restoration grading and stable native vegetation on the valley walls. January 28, 2016 Page 12 of 22

13 6.3 Unnamed Tributary to Livock River (WC6) Based on the site conditions and calculated scour depth, and due in part to the potential for channel degradation following washout of the beaver dam, a cover depth of 1.8 m below the bed of the channel is recommended at Crossing WC6. The proposed minimum cover depth corresponds to a maximum top-of-pipe elevation of m, as shown on Figure 16. Based on the morphologic assessment, the banks appear to be stable at the crossing location. Therefore, the pipe should remain horizontal with a maximum top elevation of m between Stations S and N, as shown on Figure 16. The recommended setback distances assume restoration grading and stable native vegetation on the channel banks. 6.4 Livock River (WC7) Based on the site conditions and calculated scour depth, and due in part to the potential for channel degradation following washout of the beaver dam, a cover depth of 1.8 m below the bed of the channel is recommended at Crossing WC7. The proposed minimum cover depth corresponds to a maximum top-of-pipe elevation of m, as shown on Figure 17. Based on the morphological assessment, the banks through the crossing reach appear to be unstable with erosion observed throughout. Therefore, the pipe should remain horizontal with a maximum top elevation of m between Stations 0+168SE and 0+184NW, as shown on Figure 17. The recommended setback distances assume restoration grading and stable native vegetation on the channel banks. 7 ADDITIONAL CONSIDERATIONS The detailed engineering and construction phase of the crossing should consider operation and maintenance at the crossing, and include a river monitoring program to monitor potential channel changes, specifically after high flows. Should significant changes to the channel cross-section at the crossing location occur before construction, the crossing design should be reviewed by a river engineer. All regulatory requirements should be in place before construction, and an erosion and sediment control plan should be in place during construction. A suitable construction period should be verified considering all environmental requirements. Mean flows at the crossing are expected to be lowest between October and March, so construction during these months would be best. Based on the river width and expected flows, an open-cut method could be suitable during frozen conditions. Flow isolation may be required if construction occurs in non-frozen conditions. January 28, 2016 Page 13 of 22

14 Disturbance of the bed and banks should be kept to a minimum and confined as much as possible to the immediate crossing areas. Final grading should be similar to the undisturbed channel bed and banks, and all of the disturbed areas should be vegetated as soon as possible after construction. 8 REFERENCES Alberta Environment and Sustainable Resource Development (ESRD) Code of Practice for Pipelines and Telecommunication Lines Crossing a Water Body. Made under the Water Act and the Water (Ministerial) Regulation. Consolidated to include amendments in force as of June 24, Queen s Printer. Edmonton, Alberta. American Society of Mechanical Engineers (ASME) Pipeline Geo-Environmental Design and Geohazard Management. ISBN No Blench T Mobile Bed Fluviology. The University of Alberta Press. Edmonton, Alberta. Canadian Association of Petroleum Producers (CAPP), Canadian Energy Pipeline Association (CEPA), and Canadian Gas Association (CGA) Pipeline Associated Watercourse Crossings, Third Edition. Prepared by TERA Environmental Consultants and Salmo Consulting Inc. Calgary, Alberta. October Chow V.T Open-Channel Hydraulics. McGraw-Hill Inc. HYFRAN-Plus Software HYFRAN-PLUS (Version 1.2). Software for Windows. Developed by INRS-EAU with Hydro-Quebec. NOVA Corp. and NOVA Corp. International (NOVA) River Crossing Design Manual. March Peters Brianna (2015), Project Engineer, Hatch Mott MacDonald. TERA Environmental Consultants (TERA) Aquatic Technical Report for the Proposed Nova Gas Transmission Ltd NGTL System Expansion. Technical report prepared for TransCanada Pipelines Limited. Calgary, Alberta. March Water Survey of Canada (WSC) Hydrometric Data. Accessed on June 4, January 28, 2016 Page 14 of 22

15 NOVA Gas Transmission Ltd NGTL System Expansion Project January 28, 2016 Attachment NEB PEL18181-HMM-A-DB-0002 Page 15 of 22

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