metro vancouver Inflow and Infiltration Management Plan Template Working Draft January 2011
metro vancouver Inflow and Infiltration Management Plan Template Working Draft January 2011 KWL File No. -300
METRO VANCOUVER WORKING DRAFT STATEMENT OF LIMITATIONS This document has been prepared by Kerr Wood Leidal Associates Ltd. (KWL) for the exclusive use and benefit of Metro Vancouver and the member municipalities. No other party is entitled to rely on any of the conclusions, data, opinions, or any other information contained in this document. This document represents KWL's best professional judgement based on the information available at the time of its completion and as appropriate for the project scope of work. Services performed in developing the content of this document have been conducted in a manner consistent with that level and skill ordinarily exercised by members of the engineering profession currently practising under similar conditions. No warranty, expressed or implied, is made. KERR WOOD LEIDAL ASSOCIATES LTD. 251-242
METRO VANCOUVER WORKING DRAFT CONTENTS 1. EXECUTIVE SUMMARY...1-1 1.1 BACKGROUND...1-1 1.2 OVERVIEW OF I&IMP TEMPLATE...1-1 CONTEXT FOR I&I MANAGEMENT...1-2 I&I QUANTIFICATION...1-2 I&I SOURCES...1-3 ACTION AND IMPLEMENTATION...1-3 BENCHMARKING AND VALIDATION...1-4 2. CONTEXT FOR I&I MANAGEMENT...2-1 2.1 OVERVIEW...2-1 2.2 BACKGROUND STUDIES AND REPORTS...2-1 SEWER CONDITION REPORTING TEMPLATE STANDARD...2-1 I&I ENVELOPE METHODOLOGY...2-2 STUDY OF EFFECTIVENESS OF I&I REDUCTION MEASURES...2-2 PRIVATE SEWER LATERAL REHABILITATION...2-2 I&I RELATIVE TO CATCHMENT AGE...2-3 3. I&I QUANTIFICATION...3-1 3.1 INTRODUCTION...3-1 3.2 ROLES...3-1 FLOW MONITORING/ANALYSIS ROLES FOR METRO VANCOUVER...3-1 FLOW MONITORING/ANALYSIS ROLES FOR MUNICIPALITIES...3-2 3.3 KEY ISSUES...3-2 3.4 GUIDING PRINCIPLES...3-3 3.5 METHODS...3-3 DOCUMENTING FLOW MONITORING IN THE I&IMP...3-3 FLOW MONITORING CATCHMENT SELECTION...3-4 FLOW MONITORING SITE SELECTION...3-4 FLOW MONITORING TECHNOLOGY SELECTION...3-4 FIELD WORK: MUNICIPAL/REGIONAL CREWS AND CONTRACTORS...3-5 QA/QC PROCEDURES...3-5 ANALYZING THE DATA: I&I ENVELOPE METHODOLOGY...3-6 I&I CATCHMENT AGE RELATIONSHIPS...3-7 4. SOURCES OF I&I...4-1 4.1 ROLES...4-1 4.2 KEY ISSUES...4-1 4.3 GUIDING PRINCIPLES...4-2 4.4 METHODS...4-3 I&I AGE CURVE...4-4 RDII HYDROGRAPH ANALYSIS...4-5 I&I FIELD INVESTIGATION TECHNIQUES...4-6 HYDROLOGIC MODELLING...4-8 5. ACTION AND IMPLEMENTATION...5-1 5.1 INTRODUCTION...5-1 GOAL-BASED VS. PRESCRIPTIVE PLANS...5-1 5.2 ROLES...5-1 5.3 KEY ISSUES...5-3 KERR WOOD LEIDAL ASSOCIATES LTD.
WORKING DRAFT METRO VANCOUVER 5.4 GUIDING PRINCIPLES...5-4 5.5 METHODS...5-4 IDENTIFY GOAL-BASED VS. PRESCRIPTIVE PROGRAM...5-4 GOAL-BASED ACTION AND IMPLEMENTATION...5-5 PRESCRIPTIVE ACTION AND IMPLEMENTATION...5-6 ACTION AND IMPLEMENTATION PROGRAM COMPONENTS...5-6 6. MONITORING AND VERIFICATION...6-1 6.1 ROLES...6-1 6.2 METHODS...6-1 7. REPORT SUBMISSION...7-1 7.1 REPORT SUBMISSION...7-1 FIGURES Figure 3-1: Typical Sewer Flow Monitoring Data Plot...3-1 Figure 3-2: Flow Hydrograph Showing DWF, RDII and Total Flow...3-6 Figure 3-3: Typical Relationship Between 24-Hr RDII and 24-Hr Rainfall...3-7 Figure 3-4: Example of an I&I Rate Catchment Age Relationship...3-8 Figure 4-1: Example of an I&I-Age Curve as Tool for Identifying Abnormal I&I...4-4 Figure 4-2: Example of an RDII Envelope...4-6 Figure 4-3: Example of Smoke Test Data Geocoded and Overlaid with Sewer System...4-7 Figure 5-1: Example of Selection of a Sanitary Catchment for I&I Rehabilitation...5-7 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT TABLES Table 4-1: I&I Components and Points-of-Entry...4-3 Table 4-2: Summary of I&I Source Identification Methods...4-3 Table 5-1: Rehabilitation Work Targeting I&I Sources...5-6 APPENDICES Appendix A: Flow Monitoring Program Development and Data Analysis Appendix B: Flow Monitoring Contract Guidelines Appendix C: QA/QC for Flow Monitoring Data Appendix D: I&I Envelope Methodology Appendix E: I&I Age Relationship WEF paper Appendix F: Description of Rehabilitation Technologies KERR WOOD LEIDAL ASSOCIATES LTD.
Section 1 Executive Summary
METRO VANCOUVER WORKING DRAFT 1. EXECUTIVE SUMMARY 1.1 BACKGROUND The Greater Vancouver Sewerage & Drainage District (GVS&DD) of Metro Vancouver serves a population of approximately 2.2 million and is responsible for the conveyance of municipally collected sewage and for the treatment of the collected liquid wastes at its five wastewater treatment plants. The GVS&DD and its members are regulated by the BC Ministry of Environment under the Environmental Management Act through an approved Liquid Waste Management Plan. The new Liquid Waste Management Plan, titled Integrated Liquid Waste and Resource Management (ILWRM), was adopted by the GVS&DD Board on May 21, 2010 and has been submitted to the Minister of Environment for approval. This plan applies to the GVS&DD and its member municipalities. A key strategy in the plan is the reduction of wet weather sewer overflows through regional and municipal asset management, coordinated planning, combined sewer separation and wet weather treatment and storage. To implement this plan, several actions have been required to reduce and control inflow and infiltration (I&I) into the sanitary sewer system through ongoing management of whole sewer system: regional, municipal and private, using formalized Inflow and Infiltration Management Plans (I&IMPs). This I&IMP template has developed with the intent to guide GVS&DD and its member municipalities in the preparation of I&IMPs as identified by ILWRM Actions 1.1.8 and 1.1.18. ILWRM Action 1.1.8 ILWRM Action 1.1.18 Metro Vancouver will develop and implement inflow and infiltration management plans that identify reduction strategies and timelines to ensure wet weather inflow and infiltration are within targeted levels (2012). Municipalities will develop and implement inflow and infiltration management plans, using the Metro Vancouver template as a guide, to ensure wet weather inflow and infiltration volumes are within Metro Vancouver s allowances as measured at Metro Vancouver s flow metering stations ( by 2012). 1.2 OVERVIEW OF I&IMP TEMPLATE The contents of the template are organized in an order that addresses the following questions: Why are we doing this? (Context for I&I Management) How much I&I do we have? (I&I Quantification) KERR WOOD LEIDAL ASSOCIATES LTD. 1-1
WORKING DRAFT METRO VANCOUVER Where is our I&I coming from? (Sources of I&I) What will we do to reduce I&I? (Action and Implementation Plan) How did we do? (Follow-up Monitoring and Verification) An I&IMP template document is included as Schedule A. It is intended that Municipalities use the form of Schedule A to develop their own I&IMPs, referring to this report as a guide. The plan and this report are organized in sections as identified by the following subheadings. CONTEXT FOR I&I MANAGEMENT The Context for I&I Management section summarizes findings from previous studies and presents a rationale for whole system management: private lateral, municipal collector, and regional trunk sewers. The ILWRM identifies I&IMPs as part of broader asset management plans that will support sanitary sewer overflow reduction strategies. I&I QUANTIFICATION I&I quantification begins with accurate, reliable, and repeatable sewer flow data. Measurement of the success of repair and rehabilitation programs and initiation of capital projects is often tied to this data, so Metro Vancouver and Member Municipalities should place a high value on this resource. There are opportunities to share responsibility for collection and analysis of sanitary sewer flow data between Metro Vancouver and the member Municipalities. It is envisioned that the main role of Metro Vancouver is to build, operate, and maintain a network of wet-weather meter stations. In most cases this network already exists, although some upgrades and/or new stations are required. This network (in the context of I&I) could provide each municipality with the data and a transparent analysis of their overall I&I rates. The goal of flow monitoring conducted by and within the Member Municipalities is thus to focus on discretization of that global (I&I rate) into smaller, discrete catchments. This information is crucial in assisting with prioritizing repair and rehabilitation efforts within the municipality, and quantifying the success of such efforts. Analysis of the data must use consistent, repeatable methods that are accurately applied. Two methods for this analysis are summarized in the text of this template and described in detail in appendix material. The I&I Envelope Method is relatively easy to apply to collected data and provides a means for normalizing I&I results measured both within a Municipality and across the wider Metro Vancouver area. This method was introduced to Metro Vancouver in the 1-2 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Sewer Condition Reporting Template Standard, (DRAFT Sept. 2002). It is adopted in various regions throughout North America and is still recommended, with some modifications, for use by Metro Vancouver. The Catchment Age Relationship is a newer concept which relates I&I rates to the average age of the pipes within a catchment. This method can assist in highlighting areas that are not behaving normally for their age. The goal of this template section is to provide the reader with the knowledge needed to plan and execute a flow monitoring program with subsequent analysis for I&I values, regardless of whether the work is conducted in-house or by qualified contractors and consultants. I&I SOURCES I&I sources change both spatially and temporally, depending upon a range of local conditions including soils, pipe condition, materials and construction practices, storm drainage and presence of cross-connections, age of systems and climatic conditions. Isolation of individual flow components and points of origin is an ideal goal (to guide rehabilitation programs). Techniques to characterize the components of I&I include deriving an I&I-Age relationship, RDII Hydrograph Analysis, Field Investigations, and Hydrologic Modelling. Direction for application of each of these techniques is provided. A linkage between specific field investigation techniques and observed flow data is made to assist with characterizing I&I components. The intent is to provide direction for specific rehabilitation techniques. ACTION AND IMPLEMENTATION This section of the I&I Management Plan Template provides a summary of actions a municipality may proceed with in order to achieve I&I reduction based on the completion of I&I quantification and characterization. The objective of the action plan is to identify repair or replacement works, help establish priorities for rehabilitation, and meet I&I reduction targets. There are two approaches for Metro Vancouver and its member municipalities to choose from in preparation of their respective I&IMPs: (A) Prescriptive or (B) Goal-based. (A) A Goal-based approach seeks to achieve a specified I&I target (e.g. 11,200 L/ha/d city-wide, or 20,000 L/ha/d in a particular catchment). Flow monitoring is used to measure the effectiveness of the work performed, and incremental (e.g. Tier 1, Tier 2, Tier 3) work programs may be applied successively until the target is achieved. Where KERR WOOD LEIDAL ASSOCIATES LTD. 1-3
WORKING DRAFT METRO VANCOUVER targets are below 20,000 L/ha/d, it is likely that the plan will require a private lateral rehabilitation component (B) A Prescriptive approach applies best practices based on available assessment data to reduce or maintain I&I rates, but differs from the Goal-Based approach in that the work plan is not iterative, and no specific I&I rate is targeted at the outcome of the work. Measurement of the success of the work (through post-rehabilitation flow monitoring) is still recommended to determine program effectiveness and refine cost-benefit analyses. The Prescriptive approach allows municipalities to remediate sewer systems by following a prescribed rehabilitation program and allows annual expenditure certainty. It is recommended that Prescriptive plans be adopted where I&I targets are currently being met. It is recommended that Goal-Based plans be adopted where I&I targets are being exceeded, or where capacity concerns warrant aggressive I&I reduction (e.g. overflows or capacity is limiting development). Program Components described in the template include Infrastructure Rehabilitation, Prioritization of Rehabilitation Works, Private Lateral Programs, Public Education, Municipal Bylaws, Preventative Measures (such as specifications and design standards), and a Funding Plan. BENCHMARKING AND VALIDATION The ILWRM requires that Metro Vancouver review progress in reducing I&I every four years. Municipalities should update their I&IMPs on the same timeline. Furthermore, every two years municipalities will summarize and forward to the Metro Vancouver a biennial LWMP progress report that includes, but is not limited to: The extent of new sewer construction and sewer repair and replacement work over the past two years; and A summary of the results of all flow monitoring work undertaken as part of the sewer system evaluation program. It is anticipated that the I&I Age relationship established for each individual municipality will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards / technologies improve, or as climate change alters rainfall patterns. Nevertheless, the relationship remains a useful benchmarking tool both within a municipality and regionally. A need exists for a central or regional repository for the I&I-Age curves so that they may be shared for mutual benefit. 1-4 KERR WOOD LEIDAL ASSOCIATES LTD.
Section 2 Context for I&I Management
METRO VANCOUVER WORKING DRAFT 2. CONTEXT FOR I&I MANAGEMENT 2.1 OVERVIEW Uncontrolled I&I in sanitary sewer systems can have detrimental effects on social, economic, and environmental aspects of urban areas. Excessive flows as a result of I&I can result in health risks associated with sanitary overflows, increase operation and maintenance costs, and may limit capacity otherwise reserved in the existing sanitary sewer system to serve future populations. As I&I becomes a significant component of sanitary flow, it may be cost-effective to reduce I&I rather than upgrade infrastructure to convey additional flows. The literature shows that success reducing I&I has been mixed, and that a well-planned I&I management plan is required to achieve satisfactory I&I control with the limited infrastructure funds available. Traditionally, most I&I reduction efforts have been targeted at rehabilitating publicowned sewer infrastructure. Dealing with private service laterals for I&I reduction now occupies a sizable space at most international sewer collection system conferences. To achieve an effective I&I reduction, it is becoming recognized that a complete and holistic approach to managing the entire sanitary sewer system (regional trunk sewers, municipal collectors, and private laterals) is necessary. Expanding programs to include service laterals is now gaining momentum throughout North America as many cities are arriving at the same conclusion. 2.2 BACKGROUND STUDIES AND REPORTS SEWER CONDITION REPORTING TEMPLATE STANDARD In response to 2002 Liquid Waste Management Plan commitments C19 and C23, a common reporting standard 1 for Metro Vancouver member municipalities was developed. The reporting standard ensures that biennial LWMP progress reports submitted by the member municipalities are consistent. The 2010 ILWRM extends the biennial reporting requirement, and the Sewer Condition Reporting Template Standard continues to be a tool used by municipalities to report their infrastructure management progress. 1 Sewer Condition Reporting Template Standard, Working Draft Reporting, Nov 2002. KWL and Earth Tech KERR WOOD LEIDAL ASSOCIATES LTD. 2-1
WORKING DRAFT METRO VANCOUVER I&I ENVELOPE METHODOLOGY The I&I Envelope method was identified in the Sewer Condition Reporting Template Standard (2002) as an economical and practical method of standardizing I&I analysis in Metro Vancouver. It is a graphical method based on a summary of rainfall and sewer flow data from flow monitoring. By plotting these results, a relationship between rainfall and rainfall-dependent I&I (RDI&I) can be developed. It is then possible to develop return-period design values for RDI&I, based on the rainfall analysis. The I&I Envelope method is relatively easy to apply to collected data and provides a means for normalizing I&I results measured both within a municipality and across the wider Metro Vancouver area. STUDY OF EFFECTIVENESS OF I&I REDUCTION MEASURES A 2008 study 2 for Metro Vancouver looked at two subjects: the work conducted to reduce I&I upstream of two historic SSO locations, and the effectiveness of various I&I reduction measures employed across North America. The study found the highest reductions have been achieved where the entire system was rehabilitated. The next highest I&I reductions were noted where the private laterals were rehabilitated. PRIVATE SEWER LATERAL REHABILITATION A 2007 study by Metro Vancouver 3 explores governance issues and strategies used by communities across North America to tackle I&I problems associated with private sewer laterals. The 2008 Sheltair report 4 provides a synopsis of the range of private lateral I&I reduction programs that have been carried out in other jurisdictions, analyzes these options within the context of the Metro Vancouver regulatory environment, and provides recommendations / pathways for moving forward. 2 Study of Effectiveness of I&I Reduction Measures, Final Report, July 2008, KWL 3 Private Sewer Laterals: A Summary of Governance Issues and Strategies to Address Infiltration and Inflow, GVRD, August 2007 4 Private Sewer Lateral Programs: A Study of Approaches and Legal Authority for Metro Vancouver Municipalities. Final Report, December 2008, The Sheltair Group 2-2 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT I&I RELATIVE TO CATCHMENT AGE Studies have shown that I&I tends to increase as a sewer system ages. A relationship between sewer catchment ages and I&I rates can be developed to demonstrate, on average, how I&I rates in a typical catchment will change over time. This relationship is a useful tool to identify practical I&I reduction targets as part of broader I&I management practices. KERR WOOD LEIDAL ASSOCIATES LTD. 2-3
Section 3 I&I Quantification
METRO VANCOUVER WORKING DRAFT 3. I&I QUANTIFICATION 3.1 INTRODUCTION I&I quantification begins with accurate, reliable, and repeatable sewer flow data. Flow data is defined as continuously recorded, electronic, time-series sewer flow. Depending on the metering technology, other parameters including level and velocity may also be recorded at the same time. Figure 3-1 shows a sample of typical sewer flow monitoring data plotted along with rainfall data. Figure 3-1: Typical Sewer Flow Monitoring Data Plot 3.2 ROLES There are opportunities to share responsibility for collection and analysis of sanitary sewer flow data between Metro Vancouver and the member Municipalities. FLOW MONITORING/ANALYSIS ROLES FOR METRO VANCOUVER A need exists to build, operate, and maintain a network of wet-weather meter stations. In most cases this network already exists, although some upgrades and/or new stations are required. The goal of this network (in the context of I&I) is to provide each municipality with the data and a transparent analysis of their overall I&I rates. Metro Vancouver is well suited to take on the role of capturing and analyzing the monitoring data. KERR WOOD LEIDAL ASSOCIATES LTD. 3-1
WORKING DRAFT METRO VANCOUVER One of the benefits of the proposed I&I analysis method (I&I Envelope Method) is that it can be updated as new flow data is acquired with relatively little effort. It is therefore technically feasible to provide yearly updates on global I&I values to each municipality. FLOW MONITORING/ANALYSIS ROLES FOR MUNICIPALITIES The goal of flow monitoring conducted by and within the member municipalities is to focus on discretization of the cumulative, system I&I into smaller, discrete catchments. This information is crucial in: Prioritizing repair and rehabilitation efforts within the municipality; Quantifying the success of such efforts. The Metro Vancouver monitoring points will generally not be able to resolve the results of specific individual programs within a municipality, thus it is essential that each municipality conduct their own flow monitoring efforts tied to repair and rehabilitation programs. 3.3 KEY ISSUES Flow data is of little value if it does not meet the following criteria: Reliable much of the analysis technique for I&I relies on successful capture of significant storm events. A flow meter that works correctly 360 days in a year may not be of use for I&I analysis if the meter fails to work correctly during the other 5 days when crucial storm events occur. Accurate the very nature of open channel sewage monitoring makes good accuracy a challenging goal to achieve. Realistic accuracies in the field can range from 5-10% for a well-calibrated, carefully maintained primary device (such as a flume or weir), to 30% or worse for a temporary area-velocity meter installed in difficult conditions. Accuracy is a function of equipment type and condition, site conditions, and field staff techniques. Repeatable flow measurement must be repeatable from year to year, otherwise the net benefits obtained by repair and rehabilitation programs could easily be lost in the inaccuracies caused by using and installing different equipment from season to season. Expense The equipment, training, and maintenance required to produce good data require an investment commensurate with the value of the exercise. 3-2 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Without data collected following these criteria, expensive decisions relying on the data may be at risk. 3.4 GUIDING PRINCIPLES The following principles are suggested when developing flow monitoring and I&I analysis procedures. Quantifying the success of repair/rehabilitation programs and initiation of capital projects are based on the quality and reliability of sewer flow data. Good quality data can be achieved by: Building, repairing or upgrading the Metro Vancouver metering network where needed, in order to provide each member municipality with a fair and accurate assessment of their total I&I contributions. Conducting field studies and analysis using flow monitoring specialists. And; Analysis of the data must use consistent, repeatable methods that are accurately applied, by: Committing to a consistent quality control program for source data. Adopting a standard method for calculation of I&I values. 3.5 METHODS DOCUMENTING FLOW MONITORING IN THE I&IMP The I&IMP records a municipality s intended monitoring program and progress to date, and as such identifies: All discrete flow monitoring catchments in the municipality/region; History and results of previous monitoring; and Time frame for monitoring all catchments, with known monitoring priorities stated. The I&IMP should also contain an I&I vs. catchment age graph, as outlined in detail later in this section, to present the current conditions of the catchments and show potential candidates for rehabilitation or repair. KERR WOOD LEIDAL ASSOCIATES LTD. 3-3
WORKING DRAFT METRO VANCOUVER Methods for designing and conducting a flow monitoring program, and subsequent analysis of the data, are described in detail in Appendix A. The following material is a summary of the key points from that material. FLOW MONITORING CATCHMENT SELECTION Selecting which catchments to monitor is a balancing act between the need for data and budget restrictions. Numerous factors are considered when designing a flow monitoring program, including: Characterizing catchments by factors such as pipe age, material, soil conditions, and land use; Selecting suitably sized areas for measurement; Prioritizing monitoring programs based on expected areas of development and existing planned programs; and Looking for opportunities to share the data with other users that could benefit. FLOW MONITORING SITE SELECTION Sometimes what seems like a simple exercise on paper turns into something quite different once manhole locations are inspected for potential monitoring sites. Select sites that have: Easy access or reasonable traffic control requirements; and Good hydraulic conditions allowing accurate measurement. Be aware of possible pitfalls such as: Undocumented sewer laterals; and Manholes that simply do not exist or were paved over. FLOW MONITORING TECHNOLOGY SELECTION Technology to monitor sewer flows varies widely in cost, accuracy, and suitability for a given condition. Some of the more common types used include: Area-velocity (AV) meters relatively inexpensive to deploy but intrusive and with less accuracy than other systems; 3-4 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Flumes and Weirs better accuracy but intrusive and can cause deposition or grease issues in some locations; Radar velocity meters non-intrusive with good accuracy but expensive; and Acoustic Doppler Profilers very good accuracy but intrusive and expensive. FIELD WORK: MUNICIPAL/REGIONAL CREWS AND CONTRACTORS Many factors weigh into the decision to use municipal/regional staff, contractors, or a blend of both to implement the field portion of the flow monitoring program: Best results will come from continuously dedicated staff (a minimum of two are required to satisfy confined space entry requirements), who will benefit from and maintain their skills through ongoing practise and training; Significant investment is needed in flow monitoring and support equipment, including vehicles, confined space entry equipment, field computers and a variety of flow monitoring gear to meet onsite requirements; Costs of ongoing repair and replacement of equipment; Maintenance of safety programs and permits to satisfy WorkSafeBC requirements; Costs for training programs for confined space entry and flow monitoring concepts; and Occupational health and safety workplace requirements (e.g. medical vaccinations for those who work in and around the sewer sites). The alternate to in-house staff is to hire a dedicated flow monitoring services contractor. Guidelines on hiring and using their services are provided in detail in Appendix B. QA/QC PROCEDURES Quality control and assurance of the sewage flow data is essential, but may be overlooked. Assumptions may be made by contractors that the engineers will check it, and engineers may assume the same of the contractors. Responsibility for this important task must be clearly defined during the planning and hiring stages. A set of QA/QC guidelines is provided in Appendix C for reviewing flow monitoring data. These guidelines are meant to help prevent of some of the most common problems that occur before they can have serious impact on the I&I analysis. KERR WOOD LEIDAL ASSOCIATES LTD. 3-5
WORKING DRAFT METRO VANCOUVER ANALYZING THE DATA: I&I ENVELOPE METHODOLOGY The I&I Envelope Method was first introduced to Metro Vancouver in the Sewer Condition Reporting Template Standard, (DRAFT Sept. 2002). With various modifications it is used by many agencies and consultants throughout Canada and the United States to assess the magnitude of I&I using data from a flow monitoring program. While not as detailed as other methods that use computer modelling, it benefits from being relatively simple (i.e. inexpensive), and transparent to use. With a few modifications from the 2002 version, the Envelope Method is applicable for use by Metro Vancouver and member municipalities. A detailed discussion on how to perform this analysis is provided in Appendix D. The purpose of the I&I Envelope Method is to use a collection of recorded storm events to create a correlation between the amount of rain that falls in a catchment and the amount of I&I that shows up at the flow monitoring site. Knowing the return period of the rainfall, combined with the assumption that rainfall return period correlates to I&I return, allows the correlation to be used to produce estimates for return period based I&I. This allows catchments that were monitored in different seasons with different storm events to be compared on an apples to apples basis. Figure 3-2 shows the breakdown of a storm into the dry weather flow (DWF), rainfall dependent I&I (RDI&I) and total flow components. Figure 3-2: Flow Hydrograph Showing DWF, RDII and Total Flow 3-6 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT With enough storms analyzed and plotted, Figure 3-3 shows the correlation developed for a typical site, correlating rainfall (and return period) with 24-Hour RDI&I. Figure 3-3: Typical Relationship Between 24-Hr RDII and 24-Hr Rainfall In the above figure, the value for the 5-Year, 24-Hour RDI&I can be read directly off the graph as 45 L/s. The flow rate can then be normalized using catchment area, converting L/s into L/ha/day. Area-weighted I&I rates can be directly compared against other catchments, and also against targets and guidelines as set out by Metro Vancouver. I&I CATCHMENT AGE RELATIONSHIPS I&I Catchment Age Relationships can be derived from multiple I&I analyses. The calculated I&I total for each catchment can be plotted on the Y-axis of a graph. On the X-axis, the average age of the catchment (determined by a pipe length-weighted average using a GIS calculation) is plotted. With enough catchments plotted, a curve fit through the data can represent the average I&I response for all of the catchments considered within the dataset. The catchments could include just those from a specific municipality, or, where rainfall and soil conditions are similar there could be benefit in combining and comparing data from multiple municipalities as well. The intent of this graph is to show catchments that have excessive I&I response for their age, relative to other catchments in the data set. There are several opportunities to use this type of analysis when planning and assessing the success of infrastructure rehabilitation efforts, as well as identifying potential candidates for such programs. KERR WOOD LEIDAL ASSOCIATES LTD. 3-7
WORKING DRAFT METRO VANCOUVER Another potential use for this method is as a predictor for how infrastructure will decay (and hence how I&I will increase) as the catchments grow older. The following figure is excerpted from a paper that was submitted to Water Environment Federation in 2005 on the topic. A copy of this paper is provided in Appendix E. Important note: the procedure described in the WEF paper analyzes 100-year return peak one-hour RDI&I and uses I&I envelope methodology that differs to the recommended procedure for Metro Vancouver municipalities. The paper is included in the appendix for context only. Analysis of Metro Vancouver data should be based on 5-year return, peak 24-hour RDI&I for regional reporting, using the I&I envelope methodology described in Section 3.2 and Appendix D. SANITARY SEWER AGE VERSUS RAINFALL-DEPENDENT I&I RATE 5 to 40 Year Age-of-Sewer 200,000 Peak 1-hour, 100-year RDI&I (L/H 180,000 160,000 140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 Relationship Using All Data y = 12355e 0.0325x Relationship Using Only Data up to 40 Years y = 542x + 12,418 R 2 = 0.4177 0 10 20 30 40 50 60 70 80 90 100 Areas Less than 40-Years Age (years) Areas Greater Than 40-Years Figure 4 Figure 3-4: Example of an I&I Rate Catchment Age Relationship 3-8 KERR WOOD LEIDAL ASSOCIATES LTD.
Section 4 Sources of I&I
METRO VANCOUVER WORKING DRAFT 4. SOURCES OF I&I 4.1 ROLES It is estimated by Metro Vancouver that the length of installed linear sanitary infrastructure is +/- 15,350km. This infrastructure is distributed as follows: Metro Vancouver 2.9% Municipalities: 41.7% Connections to Private Homes: 55.4% Key roles in determining the sources of I&I include: Metro Vancouver: Facilitates regional benchmarking of I&I sources, and sets regional targets to protect trunk sewers, WWTPs, and to minimize SSOs. Member Municipalities: Has the largest role to play, in that I&I source identification is generally carried out through asset management and detailed I&I investigations leading into I&I reduction work; and Private Property: where Municipalities are conducting I&I investigations, most sewer bylaws require residents and business owners to allow access to private property for inspections. Generally, roles in determining sources of I&I are dependent upon the nature of the I&I investigation being conducted. Currently, regular inspection and maintenance is performed only on collector and trunk sewers that account for only 45% of the sewer system. The remaining 55% of the system the small diameter sewer connections have not been assessed, reconditioned or replaced except in small number of pilot projects or after failure. 4.2 KEY ISSUES I&I sources change both spatially and temporally, depending upon a range of local conditions including soils, pipe condition, materials and construction practices, storm drainage and presence of cross-connections, age of systems and climatic conditions. On a region-wide basis, sources of I&I are not easy to identify. Key Issues identified for determining sources of I&I include: Relative contributions from Metro Vancouver, member municipalities and private sewers vary and may not be easily generalized; KERR WOOD LEIDAL ASSOCIATES LTD. 4-1
WORKING DRAFT METRO VANCOUVER Identification of the hydrologic components of I&I requires extensive data collection and modelling; Access to private property may be required to confirm the presence of stormwater inflow; and Identified sources of I&I can often dictate the best approach to I&I reduction. 4.3 GUIDING PRINCIPLES Isolation of individual flow components and points of origin is an ideal goal (to guide rehabilitation programs); I&I contribution from all system levels (regional, municipal, private) should be understood; Reliable and high-quality data is required for determining I&I sources; and, Determinations of I&I sources should be verified with independent data, if possible. HYDROLOGIC COMPONENTS Total I&I is comprised of several flow components, which were introduced in the 2001 Draft Sewer Condition Reporting Template. These are described in the following table. Component Acronym Calculated As Definition / Explanation Groundwater Infiltration Rainfall-Induced Infiltration Snowmelt-Induced Infiltration Stormwater Inflow Snowmelt Inflow Rainfall-Dependant Inflow & Infiltration GWI RII RP RII RP-slow RII RP-fast SII SWI RP SMI RDI&I RP SWI RP + RII RP Extraneous flow from the ambient longterm water table, not influenced by individual rainfall events Rainfall that follows a path to the sewer through the soil and/or from short-term, rainfall-based increases in water table elevation. Often occurs in two discernible components, slow and fast. Snowmelt that follows a path to the sewer through the soil. Rainwater that enters the sewer through direct (non-soil) connections to the runoff surface. Snowmelt that runs overland and enters the sewer through direct (non-soil) connections to the surface. Total peak rainfall-sourced extraneous flow, averaged over short-terms ranging from 5 minutes to 24 hours depending on catchment characteristics. 4-2 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Component Acronym Calculated As Definition / Explanation Total peak snowmelt-sourced extraneous Snowmeltflow, averaged over short-terms ranging Dependant Inflow & SDI&I SMI + SII from 5 minutes to 24 hours depending on Infiltration catchment characteristics. RP=Return Period. All of the rainfall-related parameters must be expressed with a return period if they have been derived from flow data or have been estimated with a hydrologic model. It may be appropriate to express the return period as major event in some cases. I&I sources should be understood in terms of these definitions, as they relate to the different parts of the system in which extraneous water can enter the sanitary sewer system. Table 4-2 cross-references the I&I components with the different parts of the sanitary sewer system. Table 4-1: I&I Components and Points-of-Entry Main Manhole Public Lateral Private Lateral GWI X X High GW only High GW only RII slow (+ SII) X X X X RII fast (+ SII) X X X SWI + SMI X X X The above cross-reference introduces the possibility of linking specific field investigation techniques with observed flow data to characterize the I&I behaviour of a basin. This can also lead to selection of specific rehabilitation methods to target problematic sources of I&I. 4.4 METHODS Several methods are available for determining sources of I&I, all of which have different requirements for data and expertise in I&I assessment. The following table provides a brief guideline for determining which methods are appropriate based on availability of data and I&I planning requirements. Table 4-2: Summary of I&I Source Identification Methods I&I Source Expertise Data / Systems Results Identification Required I&I Rates Indicative, not I&I-Age Curve Moderate RDII Hydrograph Analysis Field Investigations Hydrologic Model Catchment Age RDII Hydrograph I&I Envelope Smoke Testing Dye Testing Air Testing CCTV Collection System Model Hydrologic Model Moderate Low High conclusive Indicative, not conclusive Potential points of origin, not conclusive for flows Determines points of origin and flow composition Relative Costs Low if data already available Low if data already available Moderate to High High KERR WOOD LEIDAL ASSOCIATES LTD. 4-3
WORKING DRAFT METRO VANCOUVER These methods are discussed below. It is envisioned these methods would be implemented sequentially from least-expensive to most-expensive. I&I AGE CURVE The I&I Age Curve can be used to identify catchments with abnormal I&I rates given their age, or as compared with other catchments of a similar nature. In some cases, as shown in the following figure, the outlier catchments become obvious. Monitored Results I&I-Age Curve 250,000 200,000 Total I&I (L/ha/day) 150,000 100,000 Typical I&I (CRD + Surrey) 50,000 0 0 10 20 30 40 50 60 70 80 90 100 Average Catchment Age (Years) Figure 4-1: Example of an I&I-Age Curve as Tool for Identifying Abnormal I&I The outlier catchments likely have a different I&I profile than the catchments landing nearer or on the line. A catchment significantly above the line at an early age would tend to indicate excessive SWI. In older catchments, it may indicate SWI as well as deteriorating laterals and mainlines. Such catchments can be targeted for smoke testing or lateral inspections to further diagnose I&I sources. If a municipality has several catchments with flow monitoring data, the I&I Age Curve is an inexpensive way to initially determine whether additional investigation to identify I&I sources is required. Catchments behaving their age would generally not be targeted for additional investigations outside planned asset management activities. Over time the I&I-Age relationship will change because of changing construction standards, materials, and climate variations. A new relationship could be established at a 4-4 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT frequency coinciding with infrastructure renewal cycles, climate change intervals or a period of industry adoption of new pipe materials that might be on the order of 10-30 years. More study is proposed to clarify this timeframe. RDII HYDROGRAPH ANALYSIS Hydrologic analysis involves examining responses to various rainfall events, and in doing so, paying particular attention to the shape and magnitude of an RDII hydrograph, or the slope of an I&I envelope. I&I components are generally indicated on a hydrograph as follows: RII slow deep groundwater, delayed response to rainfall, attenuated peak occurs up to several hours after peak rainfall, observed as decay toward the end of an RDII event; RII fast shallow groundwater, fast response to rainfall, generally only fully developed during saturated conditions; and SWI surface runoff, immediate response to rainfall, presence during dry antecedent conditions can be indicated using I&I envelope. Hydrologic analysis alone is generally not sufficient to draw conclusions regarding specific sources of I&I, but is most useful for identifying SWI (inflow). SWI sources may be identified by examining RDII responses to storms after long periods of dry weather, in particular, summertime convective storms greater than 10-15 mm in 24 hours. When plotted as an envelope, this will form a lower bound line and indicate the amount of SWI present. If compared with total rainfall during the event a rough approximation of cross-connected area can be estimated. KERR WOOD LEIDAL ASSOCIATES LTD. 4-5
WORKING DRAFT METRO VANCOUVER Figure 4-2: Example of an RDII Envelope If I&I envelopes have been developed, the necessary data to conduct hydrologic analysis is already present. Reviewing storm drainage practices, soils mapping and any knowledge of ambient groundwater conditions is also helpful. Hydrologic analysis requires the time of someone with sufficient experience to review the RDII responses to rainfall events. Modelling and/or field investigations would generally be required to verify any assumptions derived from the hydrologic analysis. I&I FIELD INVESTIGATION TECHNIQUES There are several methods to detect I&I in the field using physical investigation techniques: Smoke Testing forcing smoke compound under pressure into sanitary or storm drain system to identify leaks and cross-connections; Dye Testing used to trace the pathway of water from a known entry point to an exit point; Visual typically with CCTV robotic or push camera; 4-6 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Air Testing pressurizing isolated sections of sewer to determine whether system is airtight to specified test pressure; and Exfiltration Test filling an isolated section of sewer with a known volume of water, and measuring the drawdown rate. Smoke and dye testing are most often used to indicate SWI (inflow), while the latter three are indicative of infiltration. Smoke testing is often carried out across basins or entire municipalities, and is relatively inexpensive to complete. Leaks noted during smoke tests should be referenced to addresses, and use a standard description. Once completed, it is most effective to georeference the smoke test results by using the address information. This can be crossreferenced against flow monitoring catchments to correlate I&I results with field data, as shown in the following figure. Areas with higher frequencies of leak reports may have higher SWI rates. Highlighted Catchments have high indication of stormwater cross-connections. Potential Cross-Connection Sanitary Sewer Flow Monitoring Catchment Figure 4-3: Example of Smoke Test Data Geocoded and Overlaid with Sewer System Dye testing is generally used to follow smoke testing, in order to confirm the presence of cross-connections. Dye testing programs can be difficult to conduct on private property, and require the consent of property owners before proceeding. Communications to residents are important prior to initiating smoke and dye testing programs, as these will affect private property. In particular, smoke testing may affect people with respiratory problems if smoke enters buildings, and local fire departments should be notified of smoke testing programs. KERR WOOD LEIDAL ASSOCIATES LTD. 4-7
WORKING DRAFT METRO VANCOUVER Air and exfiltration testing are more time-consuming and costly than smoke and dye testing. In particular, exfiltration testing is generally only used when commissioning new sewers as it requires the sewer not be in service during the test. Air testing costs may vary between different types of sewer pipe, for instance, clay pipe will cost up to four times as much as PVC simply because there are more joints to test. CCTV inspections can provide vital clues to the presence of infiltration. Areas with high ratios of connections versus buildings are likely to have abandoned service laterals, which can contribute significant amounts of I&I. Visual assessments are sometimes combined with dye testing to identify abandoned laterals. In order to get reliable information from field investigations, it is important to select a contractor with I&I experience, and have a comprehensive set of specifications when tendering investigation works. In particular, the reporting requirements should include electronic submissions in an electronic database or spreadsheet format to assist in archiving. HYDROLOGIC MODELLING A hydrologic computer model can be used to simulate the response of sewer catchments to rainfall. Once calibrated using flow monitoring data, the models can simulate historical antecedent moisture and rainfall patterns and run design wet-weather events. A design rainfall event is usually selected to simulate the typical response of each of the basins. Typically, hydrologic models are complex and require specialist knowledge and significant time to calibrate. Recently, the USEPA developed the public-domain Sanitary Sewer Overflow Analysis and Planning (SSOAP) Toolbox. The SSOAP toolbox uses the synthetic unit hydrograph (SUH) approach for predicting RDII. Specifically, this approach employs the RTK method to characterize the RDII response to a rainfall event. This methodology is currently the only means of characterizing I&I approved by the USEPA. The free SSOAP software is a powerful means to determine the amount of inflow, fast infiltration, slow infiltration and groundwater measured in a sanitary sewer as a percentage of rainfall. 4-8 KERR WOOD LEIDAL ASSOCIATES LTD.
Section 5 Action and Implementation
METRO VANCOUVER WORKING DRAFT 5. ACTION AND IMPLEMENTATION 5.1 INTRODUCTION This section of the I&I management plan provides a summary of actions a municipality intends to proceed with in order to achieve I&I reduction based on the completion of I&I quantification and characterization. The objective of the action plan is to identify repair or replacement works, help establish priorities for rehabilitation, and meet I&I reduction targets. There are two approaches for Metro Vancouver and its member municipalities to choose from in preparation of their respective I&IMPs: Prescriptive or Goal-based. GOAL-BASED VS. PRESCRIPTIVE PLANS A Goal-based approach seeks to achieve a specified I&I target (e.g. 11,200 L/ha/d citywide, or 20,000 L/ha/d in a particular catchment). Flow monitoring is used to measure the effectiveness of the work performed, and incremental (e.g. Tier 1, Tier 2, Tier 3) work programs may be applied successively until the target is achieved. Where targets are below 20,000 L/ha/d, it is likely that the plan will require a private lateral rehabilitation component. A Prescriptive approach applies best practices based on available assessment data to reduce or maintain I&I rates, but differs from the Goal-Based approach in that the work plan is not iterative, and no specific I&I rate is targeted at the outcome of the work. Measurement of the success of the work (through post-rehabilitation flow monitoring) is still recommended to determine program effectiveness and refine cost-benefit analyses. The Prescriptive approach allows municipalities to remediate sewer systems by following a prescribed rehabilitation program and allows annual expenditure certainty. It is recommended that Prescriptive plans be adopted where I&I targets are currently being met. It is recommended that Goal-Based plans be adopted where I&I targets are being exceeded, or where capacity concerns warrant aggressive I&I reduction (e.g. overflows or capacity is limiting development). 5.2 ROLES The role of Metro Vancouver is to: Maintain regional conveyance infrastructure. KERR WOOD LEIDAL ASSOCIATES LTD. 5-1
WORKING DRAFT METRO VANCOUVER In addition, selected Metro Vancouver roles from the ILWRM that apply to this IIMPT include: Work with the real estate industry and their regulators, and the municipalities to develop and implement a process for the inspection and certification of private sewer laterals being in good condition as a required component of real estate transactions within Metro Vancouver (ILWRM 1.1.7-2011action) Develop and implement inflow and infiltration management plans that identify reduction strategies and timelines to ensure wet weather inflow and infiltration are within targeted levels. (ILWRM 1.1.8-2012 action) Work with municipalities to review historical data and adjust as necessary the average inflow and infiltration allowance for regional trunk sewers and wastewater treatment plants, and develop associated target allowances for municipal sewer catchments associated with a 1:5 year return frequency storm event for sanitary sewers to a level that ensures environmental and economic sustainability. (ILWRM 1.1.9-2013 action) Review progress in reducing inflow and infiltration every four years. (ILWRM 1.1.10 - action every 4 years) Enhance enforcement of sewer use bylaw prohibition against the unauthorized discharge of rainwater and groundwater to sanitary sewers. (ILWRM 1.1.11-2010 action) The role of the Municipalities is to: Maintain municipal infrastructure (sanitary & drainage); Manage infrastructure renewal funding; Select appropriate remediation practices; and Enact appropriate bylaws for control of private lateral I&I. In addition, the ILWRM requires municipalities to: Develop and implement inflow and infiltration management plans, using the Metro Vancouver template as a guide, to ensure wet weather inflow and infiltration volumes are within Metro Vancouver s allowances as measured at Metro Vancouver s flow metering stations (ILWRM 1.1.18 - develop by 2012); Enhance enforcement of sewer use bylaw prohibition against the unauthorized discharge of rainwater and groundwater to sanitary sewers. (ILWRM 1.1.19-2010 action); 5-2 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Update municipal bylaws to require on-site rainwater management sufficient to meet criteria established in municipal integrated stormwater plans or baseline region-wide criteria. (ILWRM 1.1.20-2014 action); Biennially produce a progress report on plan implementation for distribution to the Ministry of the Environment that: (a) summarizes progress from the previous two years on plan implementation for all municipal actions, including the status of performance measures. (ILWRM 3.5.8 biennial action). Private property owners play a role by complying with enacted bylaws, being responsible for maintaining private sewer laterals and disconnecting stormwater crossconnections from the sanitary system. 5.3 KEY ISSUES Based on the LWMP Biennial Report (2010), there were 28 and 41 sanitary sewer overflows (SSOs) recorded at Metro Vancouver s trunk sewer system in 2008 and 2009, respectively. Metro Vancouver is striving to maintain conveyance capacity in the regional sewer system to reduce incidence of overflows during wet weather. The member municipalities are also faced with SSOs issues. The 2010 LWMP Biennial Report records a total of 87 SSOs within the municipalities sewer collection systems during the 2008-2009 reporting period. Other issues faced by the municipalities include: Legality framework regarding access and liability exposure for damages due to work on private property; Quality control of new sewer installation and repair; Funding; and Prioritizing remediation. For private homeowners, financial burden incurred as a result of repair or inspection of private laterals is a primary concern. Quality of service for lateral repairs and access to qualified contractors is also a key issue. KERR WOOD LEIDAL ASSOCIATES LTD. 5-3
WORKING DRAFT METRO VANCOUVER 5.4 GUIDING PRINCIPLES When developing the Action and Implementation section of the I&IMP, the following Guiding Principles can be considered: Metro Vancouver Minimize the occurrence of SSOs. Delay or eliminate the need for capacity upgrade of conveyance and treatment facilities due to I&I. Reduce or eliminate the need for on-site storage/treatment of SSOs through I&I reduction. Municipalities Minimize the occurrence of SSOs. Reduce or eliminate the need for on-site storage/treatment of SSOs through I&I reduction. Design a program to meet ILWRM/Metro Vancouver targets. Clearly define responsibility for removing I&I from municipal sewers and private sewer laterals. Develop a cost effective program. Ensure there are enforceable legal means for actions/methods. Employ actions/methods that are measurable. Promote public acceptance of the I&I Management Plan. 5.5 METHODS IDENTIFY GOAL-BASED VS. PRESCRIPTIVE PROGRAM The initial step required to determine the proper course of action is differentiating between the need for a Goal-Based or Prescriptive Program. This decision can be made at two levels City-wide, and at the catchment level. If a municipality is not achieving the Metro Vancouver target for I&I city-wide, a Goal- Based approach is recommended. If the city-wide target is being met, a Prescriptive 5-4 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT approach is appropriate, however, special conditions may dictate a Goal-Based program at the catchment level. These conditions could include: Sanitary sewer overflows in a catchment; Reduced conveyance capacity limiting development; Excessive pumping/energy costs; or, An I&I response that greatly exceeds the measured rates in other catchments with similar characteristics (i.e. above the municipality s Age-I&I rate relationship). GOAL-BASED ACTION AND IMPLEMENTATION Recommended components of a Goal-Based plan include: Flow monitoring to identify I&I rates in all catchments greater than 20 ha within 20 years (at a minimum, a 10-year cycle is recommended where targets are greatly exceeded). CCTV inspection of all linear sewer assets on a maximum 20-year cycle (more frequent for assets in poor condition). Tracking of I&I rates using the I&I-Age relationship. In catchments not achieving the target I&I rate, characterization of I&I components through hydrologic modeling or field programs. Incremental, targeted I&I reduction including one or more of the following: - Tier 1 rehabilitation (mainline and lateral interface repairs); - Tier 2 rehabilitation (public lateral repair/replacement); - Tier 3 rehabilitation (private lateral repair/replacement); - Private lateral evaluation or certification and repair/replacement; - Inflow reduction (manhole repair, cross-connection elimination); and - Targeted infiltration reduction (service lateral repair, manhole repair, abandoned lateral elimination, mainline repair/replacement). Iterative follow-up flow monitoring (to determine program effectiveness and to evaluate next rehabilitation steps) and successive rehabilitation works until target is achieved. A Goal-Based program seeks to reduce I&I to a target level, and the success of the program can be quantified by the L/s reduction in I&I. For city-wide programs, a flowbalance can be calculated to determine the required reduction overall, and progress can be tracked catchment by catchment. KERR WOOD LEIDAL ASSOCIATES LTD. 5-5
WORKING DRAFT METRO VANCOUVER PRESCRIPTIVE ACTION AND IMPLEMENTATION Recommended components of a Prescriptive Plan include: Flow monitoring to identify I&I rates in all catchments greater than 20ha within 20- years; CCTV inspection of all linear sewer assets on a maximum 20-year cycle (more frequent for assets in poor condition); Tracking of I&I rates using the I&I-Age relationship; and Where warranted (as per Section 5.5.1), targeted I&I reduction. A Prescriptive program employs responsible management practices to monitor rates and rehabilitate catchments as a preventative measure to maintain compliance with ILWRM/Metro Vancouver targets. ACTION AND IMPLEMENTATION PROGRAM COMPONENTS Infrastructure Rehabilitation The Action and Implementation Program documents intended rehabilitation works as they become evident. I&I reduction achieves the greatest result when rehabilitation works are based on the results of I&I quantification and characterization (and preferably in concert with asset condition assessment). Selection of appropriate sewerage remediation measures will depend on local conditions (soil, groundwater, rainfall) and pipe condition. A brief description of rehabilitation technologies is included in Appendix G. Table 5-1 shows rehabilitation work targeted at removing specific sources of I&I. Table 5-1: Rehabilitation Work Targeting I&I Sources I&I Source Common Causes Repair Work SWI RII (fast) GWI + RII (slow) - Defective manhole cover - Storm-sanitary cross-connection - Defects at upper portion of manhole - Defective service connections - Defects in sewer mainline (cracks, defective joints, etc) - Defects at lower portion of manhole - Defects at service lateral-mainline interface - Repair defective manhole - Correct storm-sanitary cross connection - Plug abandoned service connections - Repair service lateral - Repair manhole - Repair sewer mainline - Repair manhole 5-6 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT A secondary consideration when prioritizing repair work is the cost per work type. Based on average cost per meter of mainline in a rehabilitation basin, cost increases (from $5/m to $1,000 +/m) in the following order: Storm-sanitary cross-connection and abandoned service lateral removal; Pipe lining, grouting, etc, mainline rehabilitation; Pipe and manhole replacement; and Service lateral rehab / replacement. It is not recommended that rehabilitation works be selected by cost alone, as this will result in random I&I reduction effectiveness. Prioritization of Rehabilitation Program In areas tributary to combined sewer treatment plants, combined sewer overflow plans will take precedence over I&I management because of the potential for vastly greater flow reduction and CSO control relative to the investment required. In separated sewer systems, rather than referring only to the absolute I&I rate, it is suggested that the I&I-Age relationship be used to prioritize rehabilitation works, as demonstrated in Figure 5-1 below. Figure 5-1: Example of Selection of a Sanitary Catchment for I&I Rehabilitation The advantage to this is that catchments with I&I rates well above the I&I-Age relationship are likely to yield the greatest reductions. Catchments near the line may still KERR WOOD LEIDAL ASSOCIATES LTD. 5-7
WORKING DRAFT METRO VANCOUVER exceed the I&I target, but significant I&I reduction is likely to require multiple work types and larger expenditures relative to the amount of I&I reduced. It is recommended that municipalities develop their own I&I-Age relationships to account for local variations (rainfall intensities, soil conditions, construction practices). It is anticipated that the relationship will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards improve, or as climate change alters rainfall patterns. I&I rehabilitation programs can be integrated with structural repair programs for increased cost-effectiveness. However, local work has shown that a structural program alone commonly results in no I&I reduction. Private Lateral Rehabilitation Programs In the two Metro Vancouver municipalities that have experimented with private lateral rehabilitation, a 69% reduction in 5-year, 24-hour I&I was achieved. A public side I&I reduction program in these catchments would never have reduced I&I to a target level associated with a Goal-based program. Where I&I management opportunities on municipal collector sewers have been exhausted or would deliver limited benefit, a private lateral program may be necessary in some jurisdictions. A private lateral program may also be required for catchments with very high groundwater infiltration or with a history of poor lateral sewer construction. The December 2008 Sheltair Private Sewer Lateral Programs study identifies multiple approaches and legal authority for municipalities to implement private lateral rehabilitation programs. The study notes that Implementing a private sewer lateral program is the responsibility of the individual municipalities; however, a coordinated effort made by all levels of government (federal, provincial, and municipal) will ensure municipalities have the required resources to effectively address the issue of I&I from the private system. Further work by Metro Vancouver and the member municipalities to establish components of a common private lateral program is recommended in the report. A summary of possible private lateral rehabilitation approaches identified in the Sheltair report include: Incentive-based - Incentive-based programs encourage a targeted activity by offering a reward (e.g. a refund for some or all of the costs involved, reduction in taxes, or reduced sewer rate). Regulatory - Enforcement-based programs impose requirements on private property owners to maintain their private sewer laterals in good condition. (e.g. a bylaw requiring replacement of a private lateral when an owner applies for a development permit for work exceeding a value threshold). 5-8 KERR WOOD LEIDAL ASSOCIATES LTD.
METRO VANCOUVER WORKING DRAFT Municipally-driven - A municipally-driven approach is one in which the municipality conducts the work on private property, as selected by evaluation of need. Where private lateral programs are considered, the Action and Implementation section of the I&IMP should identify any requirements of the program, and outline the proposed approach. Public Education for Dealing with I&I Issues A public education program is recommended both to inform citizens about the consequences of I&I, and to encourage cooperation with I&I reduction programs. Targets of the program are to raise awareness of the causes and consequences of I&I, identify regulatory provisions, convince citizens that the benefits of the program outweigh the costs, and prepare residents for a private lateral program. Alternately, the benefits could be explained in terms of risk management i.e. the benefits of preventing sewer back-up and the potential for costs and damages to home owners if I&I is not managed adequately. Typical methods could include: Public media announcement; Rates notice insert; Local advertising; Brochures, displays; Signage at work sites; Mailout bulletins; and Website features. A sample Private Sewer Lateral Program brochure is included in the 2008 Sheltair report. The brochure is centered around adoption of a private lateral certification program, but could easily be modified to communicate broader private lateral I&I issues. When developing the action and implementation section of the I&IMP, an organization could include the following: extent of education program (timeframe, region); target audience of public education program; messages to be conveyed; and media to be used to convey message. Development of Municipal Bylaws In British Columbia, the Community Charter (SBC 2003) Chapter 26 provides the basis and the powers for municipalities to develop bylaws to address I&I on private property. KERR WOOD LEIDAL ASSOCIATES LTD. 5-9
WORKING DRAFT METRO VANCOUVER The 2008 Sheltair Report presents an exhaustive study of bylaw options available to Metro Vancouver municipalities for inspection and repair/replacement of private sewer laterals. A draft bylaw is included that is drawn around inspection and certification of private laterals as a condition of sale, construction, or renovation. Municipalities are encouraged to modify this draft bylaw to suit, or at a minimum to adopt bylaws that grant access and the means to execute repairs such as those enacted by the City of Surrey or the City of Vancouver. Key wording from the City of Surrey Sanitary Sewer Regulation and Charges Bylaw, 2008, No. 16611 includes: Every owner of real property and every occupier of premises to which a service connection has been installed must allow, suffer and permit the General Manager, Engineering and all associated inspection equipment, to enter into or upon the real property and premises for the purpose of inspecting the premises including building sanitary sewer, drains, fixtures and any other apparatus used with the service connection or plumbing system, as well as to observe, measure, sample and test the quantity and nature of sewage being discharged into the sanitary sewerage system, to ascertain whether the terms of this Bylaw are being complied with. No person may discharge or continue to allow to be discharged into a building sanitary sewer or the sanitary sewerage system any storm water or permit any groundwater infiltration. I&IMP actions relevant to bylaws include: review of existing bylaw to determine property access rights for inspection and/or repair of sanitary sewer laterals; and intent to draft (and adopt) a bylaw restricting owners from permitting stormwater or groundwater from entering sanitary sewer laterals. Preventative Measures Efforts to prevent I&I occurring in new construction should be ongoing as the I&I reduction program addresses existing I&I sources. Preventative measures may include: the use of sound engineering specifications in the design and inspection; enforcement of specifications and design standards during construction; and plumbing inspections and certifications can also help prevent I&I. Funding Plan for I&I Rehabilitation Work It is recommended that funding for the I&IMP be identified in the Action and Implementation section of the plan. Approaches for determining the level of funding may differ depending on whether the work is Goal-Based or Prescriptive. At a minimum, a funding level could be derived based on the ILWRM commitment to target a 100-year cycle of replacement or rehabilitation of sewerage infrastructure. 5-10 KERR WOOD LEIDAL ASSOCIATES LTD.
Section 6 Monitoring and Verification
METRO VANCOUVER WORKING DRAFT 6. MONITORING AND VERIFICATION 6.1 ROLES Key roles in I&I reduction progress monitoring and verification include: Metro Vancouver: review progress in reducing inflow and infiltration every four years (ILWRM 1.1.10 - every 4 years) Member Municipalities: Maintain and, if necessary, expand the existing municipal sewer flow and sewer level monitoring network. (ILWRM 3.3.8 - Ongoing) Benchmark I&I rates through development of I&I-Age relationship Update I&I Management Plan 6.2 METHODS REVIEW I&I REDUCTION PROGRESS The ILWRM requires that Metro Vancouver review progress in reducing I&I every four years. Typical activities may include: Flow monitoring; I&I quantification using I&I Envelope method, taking into account possible expanded development area; Comparison of I&I rates with previous historic values (i.e., quantified 4 years ago, or initial baseline I&I rates); Determine whether I&I targets are being met; and Summarize findings and discuss results with municipalities to help update I&IMPs as necessary. Every two years, municipalities will summarize and forward to the Metro Vancouver a biennial LWMP progress report that includes, but is not limited to: KERR WOOD LEIDAL ASSOCIATES LTD. 6-1
WORKING DRAFT METRO VANCOUVER The extent of new sewer construction and sewer repair and replacement work over the past two years; and A summary of the results of all flow monitoring work undertaken as part of the sewer system evaluation program. Where a goal-based approach is adopted for targeted I&I reduction, effectiveness of each phase of the I&I rehabilitation efforts should be quantified using catchment flow monitoring and I&I analysis. BENCHMARK I&I RATES It is anticipated that the I&I Age relationship established for each individual municipality will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards / technologies improve, or as climate change alters rainfall patterns. Nevertheless, the relationship remains a useful benchmarking tool both within a municipality and regionally. A need exists for a central or regional repository for the I&I-Age curves so that they may be shared for mutual benefit. UPDATE I&I MANAGEMENT PLANS As the ILWRM requires that Metro Vancouver review progress in reducing I&I every four years, it is recommended that I&IMPs be updated every four years at a minimum. 6-2 KERR WOOD LEIDAL ASSOCIATES LTD.
Section 7 Report Submission
METRO VANCOUVER WORKING DRAFT 7. REPORT SUBMISSION 7.1 REPORT SUBMISSION Prepared by: KERR WOOD LEIDAL ASSOCIATES LTD. Andrew Boyland, P.Eng. Municipal Sewer Sector Leader Reviewed by: Chris Johnston, P.Eng. Vice President KERR WOOD LEIDAL ASSOCIATES LTD. 7-1
Appendix A Flow Monitoring Program Development and Data Analysis
APPENDIX A I&IMP TEMPLATE DRAFT REPORT 1. APPENDIX A FLOW MONITORING PROGRAM DEVELOPMENT 1.1 INTRODUCTION The task of laying out a successful flow monitoring program and analyzing the results is complex. The following sections provide guidance on the process, regardless of whether the planning and execution of a flow monitoring program is done entirely in-house, entirely by qualified contractors and consultants, or by a mixture of both. 1.2 CATCHMENT SELECTION Assume that the goal is to determine discrete I&I values for catchments within your municipal boundaries. 1. Establish a rough budget for the flow monitoring program. As an approximation, use $2,000/site/month for a full-service flow monitoring contractor to supply data for a site. Consider a 6 month period, from October to March, as the time period for a winter flow monitoring season. 2. Based on your budget, determine the approximate number of sites that can be implemented over the winter season. Your budget may be insufficient for monitoring all of your desired catchments in a given season, but it is useful to have an idea of the number of sites that your organization can afford per year. 3. As a way of addressing budget issues, consider monitoring some catchments as indicators of conditions in larger areas. For example, if you are faced with a need to monitor four neighbouring catchments (all of which have similar pipe age, material, and soil conditions), consider monitoring just one or two as indicators of likely conditions in the others. 4. Decide on the base mapping to be used for catchment delineation. Access to a GIS database will produce the best results. A suggested mapping scheme is: Use an aerial photo with muted colours as the background image, to help you identify land use and large, unsewered areas such as regional parks; Colour pipes by type (AC, PVC, etc.) in order to help distinguish areas with similar pipe material. Alternately or as well, try colouring pipes by their age; Show manholes in order to assist with locating potential flow monitoring sites; Overlay subtly coloured contour lines to establish areas with steep grades from those in low lying or flat areas; If available, prepare a separate map, replacing the aerial photo with soil type to distinguish between fast and slow draining areas; KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT 5. With base mapping in hand, the goal is to establish catchments with similar pipe materials, age, slopes and soil types. Delineating catchments with these similar characteristics will increase the odds of finding smoking gun catchments. Choosing catchments with broadly mixed characteristics will likely just produce average I&I results. 6. To a lesser extent, consider land use when delineating catchments. Catchments that mix residential with significant industrial, commercial, or institutional sources can make identifying some components of the I&I difficult, as the dry weather components of the flow are often not as repeatable or predictable as residential areas. 7. Consider catchment size carefully. A good limit for the lower size is 20-30 hectares. While achievable, catchments much smaller than this tend to produce too little flow and have higher solids content. This can result in failure to flush debris from the flow monitoring equipment. Monitoring of a catchment smaller than this requires special equipment and techniques, and should only be used as necessary in specialized pilot projects. 8. On the opposite end of the spectrum, try to keep catchment size under 300 hectares. While there is no hard upper limit to the size of a catchment that can be monitored, eventually the results collected from an excessively large catchment become of little practical value aside from reporting a total I&I value (i.e. totals for each municipality). Factors such as travel times, attenuation, difference in rainfall distribution, and non-uniform pipe characteristics will yield little information to guide targeted repair and replacement programs. 9. Be aware of diversion pipes (both intentionally installed and undocumented), which can move water from one catchment to another during wet weather events. In such cases it may be necessary to monitor the diversion flow as well as the main outlet flow for a catchment. These monitors must be operated concurrently in order for the results to be conclusive. If you discover a diversion in a catchment which has already been monitored, you should consider re-monitoring the outlet along with the diversion simultaneously for true results to be obtained. 10. When drawing catchment boundaries, do not include large unsewered areas (such as regional parks, industrial areas such as gravel pits or large material storage yards), rail yards, etc. (especially when those areas are on the outside edge of the catchment). These areas do not contribute to I&I and will artificially reduce the stated I&I when expressed as an area-weighted value. 11. It is generally acceptable to leave in smaller neighbourhood parks and school yards in a catchment. A rule of thumb is that when a catchment is viewed as a whole on the map, it should not include visually obvious non-contributing areas. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT 12. Use other information such as planned upcoming developments, known replacement programs, and need for computer model calibration data to assist in prioritizing areas to monitor. Could others use the data for model calibration? Will flow estimates for bypass pumping be required during a replacement program? Alternate funding sources may be identified to assist in monitoring costs, which would also allow for the flow monitoring data to serve additional needs beyond I&I measurement. 1.3 TECHNOLOGY SELECTION When the process of delineating catchments is complete, begin to identify potential manholes for monitoring. A brief understanding of the usual measurement technologies is helpful for this, and can be broadly broken into four categories for temporary monitoring programs. 1. Area-velocity meters these units are intrusive (a sensor is placed in the flow, usually at the bottom of the pipe). Different sensors measure the depth and velocity of the sewage, and the meter then calculates the flow rate using the principle of continuity (cross sectional area of water multiplied by velocity equals flow rate). Uses: Generally works best in shallow grade pipes with uniform flow. Overall the most economical. Disadvantages: Will not work on steep sites with low depth and high velocity. Should be avoided in pipes above 600mm in diameter as velocity tends to underreport. Requires extensive field maintenance, as they are subject to debris fouling. 2. Weir/flume specially shaped weirs and flume inserts are available for temporary deployment, having proven fairly reliable at remaining clear of debris. The sensor used is often a downward facing ultrasonic to measure the water level behind the weir. Examples of these types of stations exist in the Lower Mainland that have been running continuously for years with little maintenance. Uses: Weirs generally work best at steeper slopes (has been used successfully at grades up to 15%). Shallow slopes are better suited for flumes. Tends to require less maintenance but with slightly more upfront cost; Weirs in particular have good low flow resolution. Disadvantages: Backwater pool can cause gravel and grease buildup on shallower grade sites; Requires more extensive installation at each site; KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT Not well suited for sites that surcharge; Weirs are not suitable for larger diameter pipes such as interceptors where head loss across the weir would be unacceptably high. 3. Radar Velocity non-invasive sensors hang in the manhole barrel and shine down on to the water surface to measure level and surface velocity, from which flow is computed. Uses: Most pipe grades where ease of maintenance is desired; Can handle larger diameter pipes; Disadvantages: Average velocity measurement is inferred from surface velocity. Requires calibration with manual site profiling measurements if high accuracy is required; Limited functionality in surcharge conditions; Relatively expensive when compared to options 1 and 2. 4. Acoustic Doppler Profiling Meter invasive sensor that sits at the bottom of the pipe, similar to an area-velocity meter. High power sensor and acoustic binning allow the unit to handle large diameter pipes and flow asymmetry. Uses: Large diameter (up to 6 metres), and/or significant flow asymmetry; Disadvantages: Expensive Choice of equipment is dictated by site conditions, available budget, and equipment availability (either rental or purchase). Ultimately, an experienced flow monitoring specialist should approve the technology selection for each site, based on their experience and professional judgement. 1.4 SITE SELECTION With catchments delineated, begin to select manholes for each site. following: Consider the 1. Regardless of which technology is used, all flow monitoring sites benefit from a straight through manhole with no contributing laterals or other disturbances. Always opt for this configuration if available. 2. Avoid manholes with significant bends. It is possible to monitor sharp bends, if necessary, by using weirs. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT 3. Avoid manholes with contributing laterals. It is possible to monitor in these manholes, if necessary, by using weirs to either include or exclude flow from the lateral. 4. Consider traffic control issues for installation, maintenance, and removal of the equipment. When possible choose a manhole that would not require traffic control to access. 5. In many areas within Metro Vancouver, the municipal collection system flows down a steep grade into the Metro Vancouver sewer, which is often laid at a flat grade. Many of the Metro Vancouver sewers were designed to surcharge, so choose sites that are high enough up the hill to stay out of the surcharge zone of the Metro Vancouver sewer. Look for any evidence of surcharge when doing the field check of each site (toilet paper and other debris hanging from the rungs is a common sign of a manhole that surcharges and should be avoided). 6. Never rely purely on the desktop site selection exercise. Always have a field inspection of each manhole done prior to final selection to ensure that any unforeseen circumstances are avoided prior to site installation. Sites that are particularly dirty or greasy should be power washed and flushed prior to site installation. 7. In many areas locating the manhole can be problematic. Some manholes have been covered over by repaving, while others may be lost in a right of way overgrown with blackberry bushes. In other locations, the manhole may simply never have been built even if it is shown on a GIS system. 8. Be wary of bolted manhole lids. On some systems (especially Metro Vancouver s), bolted lids are often a sign of a system that surcharges. Other lids may be bolted to eliminate odour complaints, or to prevent metal theft. 1.5 PERSONNEL SELECTION: CONTRACTOR OR IN-HOUSE Within Metro-Vancouver, there are municipalities that contract out their flow monitoring needs and others that use in-house staff. There are pros and cons to each, and in some cases a mixture of both may be useful. This decision is an individual choice for each municipality based on policy, staffing levels, and available budget. Consider the following when deciding to develop an internal flow monitoring services team: 1. Installing and maintaining sanitary flow monitoring sites is a 2-person job. During many phases of installation and removal, confined space entry procedures must be followed mandating 2 staff members. Additional crew may be needed if traffic control requirements for the site dictate. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT 2. Minimum equipment consisting of a vehicle, confined space entry tripod, blower with generator or invertor for ventilation, harness, traffic signage, and gas detector is required for confined space entry. In addition, each member of the crew should have undergone a confined space entry course and be currently certified as such. Gas detector maintenance must be undertaken and bump tests done daily. 3. Owning and maintaining sewage flow monitoring equipment is an ongoing cost that escalates as time goes on. It is not unusual for sensors to need calibration after every season, typically an ongoing cost that is best handled by shipping the equipment back to the factory for recertification. Loss of equipment due to theft, sewer surcharge, and even rats chewing cables is a common occurrence. 4. Specific staff should be dedicated to the task, otherwise poor quality data will likely the outcome. Ongoing maintenance including battery changes, calibration checks, site documentation, and inspection/cleaning must be undertaken ritually. If this work is being done in-house, timely data QA/QC must also be done by in-house staff to avoid collecting an entire season of poor quality data. 5. Many techniques including onsite calibration checks are best done by well-practised staff, both to ensure accuracy and repeatability of the data. Senior staff should oversee junior staff until satisfied that the knowledge gained through years of experience is passed on. 6. All staff that work around sewers should have Hepatitis A and B vaccinations and refer to WorkSafe BC for a list of additional health and safety precautions. 7. A rugged laptop is required to program and retrieve data from the flow meters. Even flow monitoring units that use wireless services to send their data to a central server still need initial programming that requires a laptop. 8. Train your staff to recognize and step back from a site or situation that is beyond their abilities, either due to safety concerns or lack of appropriate monitoring equipment. In these cases, it may make more sense to hire a dedicated flow monitoring contractor, to take advantage of their experience and specialized equipment. 9. A current safety plan must be prepared and kept onsite with staff at all times. The safety plan outlines the procedure to be performed, the conditions under which the crew can operate and those under which they must cease operations. A site permit must be filled out ahead of each installation during a tailgate meeting, and the completed documentation kept for auditing purposes. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX A I&IMP TEMPLATE DRAFT REPORT CONTRACTOR QUALIFICATIONS If the decision is made to hire a contractor to perform the flow monitoring services, consider the following: 1. Even if the project is small enough to sole-source, prepare a specification so that the contractor clearly understands the scope of the work. Important points to cover in the specification include: a. Table of the site locations, with alternates if the sites have not yet been inspected for suitability. Clarify if the contractor is permitted to select an alternate site with/without approval; b. Indication of which technology is suitable with or without approval; c. Period of monitoring; d. Format, method, and frequency of data delivery; e. Required reports; f. Quality control expectations; g. Payment terms relative to percentage of good data. 2. An appendix is provided which contains sample specifications for a typical temporary flow monitoring program. 3. If tendering the work, ensure an understanding of what each contractor is providing in order to ensure comparable pricing. Some contractors focus on raw data delivery with little or no data manipulation, while others employ dedicated engineers or technologists to scrub the raw data into a final product. If the latter is the case, always ensure that the unfiltered raw data is also delivered alongside the final data, along with clear explanations of what was done to the final dataset. 4. Request and check a recent list of references. 5. Verify your insurance requirements against the contractor s coverage well before the start of the monitoring season. Pay special attention to coverage for accidental and sudden environmental releases, and also to total amounts for comprehensive. Most contractors can obtain extra insurance as needed but this process takes time and additional funds. 6. Review the data in a timely manner, not just for payment purposes but to ensure that problems that occur are rectified early in the monitoring season. Utilize techniques from the next section to assist in your data review. KERR WOOD LEIDAL ASSOCIATES LTD.
Appendix B Flow Monitoring Contract Guidelines
APPENDIX B - FLOW MONITORING SPECIFICATION 1
SPECIFICATIONS 1.1 Scope of Work.1 The City is undertaking sanitary sewer flow monitoring as part of its sewer assessment and performance program..2 The Work to be performed is described as: o Installation and operation of temporary flow monitoring sites (and associated reporting of sanitary flow) at seven manholes for a period of five-months during the winter of 2010/2011. o Traffic control per site, as required..3 The sites are located within the City, and most are categorized as steep slope, high velocity sites (slopes from 3-15%, with full-pipe velocities from 2-5 m/s). Some sites require monitoring of the combined flow from two laterals. These sites are listed in the table in Section 1.6. The Tenderer shall visit each of the pre-selected sites prior to submitting their Tender..4 Pricing is required for the complete set of installations as described above as shown in the Schedule of Prices. 1.2 Schedule.1 The target date for having the seven temporary winter stations operational is November 1, 2010. The five-month operating period would then be from November 1, 2010 until March 31, 2011. 1.3 Basis for a Contractual Relationship.1 This document is a "performance specification". Within it, the City has defined what it requires as deliverables. The Contractor has the flexibility and discretion to determine how the Contract deliverables can be most effectively provided within the spirit of the guidelines presented herein. The Contract includes supply, installation, calibration, and operating of equipment (including data quality assurance) to collect reliable flow data for the operational duration. 1.4 Description of Contract Tasks.1 The "performance specification" as presented is comprehensive and detailed in describing the contract deliverables. The key points are summarized below to provide an overview of the program requirements: Commissioning of Stations: supply, installation and calibration of approved equipment to measure sewer flow for the operational period. Station Operation: maintenance and operation of flow monitors for the operational period. Flow Data Reporting: monthly reports in approved format of quality-assured data in graphical (hydrograph) and electronic form to the Engineer (both raw and corrected data to be provided, as well as documentation of calibration procedures)..2 The Contractor is encouraged to develop innovative and cost-effective ways of providing the deliverables. Approval of methods and equipment by the Engineer is required prior to proceeding with any proposed work. 2
1.5 Selection of Monitoring Sites.1 The Contractor is advised that most sites that will be encountered are steep slope, high velocity conditions (slopes from 2-15%, full-pipe velocities from 2-5 m/s). Some sites require monitoring the combined flow from two laterals. Traditional AV meters are not expected to work in most of the encountered sites. As a result, a limited number of approved technologies will be accepted, as detailed in Section 2..2 The City has identified the required monitoring sites based on field investigations and the City s information needs. Use of alternate manhole locations for pre-selected sites, or selection of new sites, must be approved in writing by the City. 1.6 Existing Field Conditions.1 Station numbers, manhole numbers, and pipe diameters are listed in the following table: STATION NAME Station Name # 1 MH # SM00890 LOCATION DESCRIPTION Slope Pipe Status Lane east of Street A s of Street B 5.0% 200mm Repeat Station Name # 2 SM00715 Street C at Street D 6.0% 200mm New Street E. south of Stree Station Name # 3 SM00956 4.0% 200mm New Station Name # 4 Avenure A, north of Str SM00633 G. 9.0% 250mm Repeat Station Name # 5 SM00150 Steet H at Street I 15.0% 375mm Repeat Street J, N of Highway Station Name # 6 SM00768 12.0% 300mm Repeat Station Name # 7 SM00300 Street K at Streek L 7.0% 200mm Repeat.2 Additional site information required to select equipment shall be collected by the Tenderer during a site visit prior to submitting their Tender. 1.7 Wet Weather Event Response Time.1 The Contractor will meet the performance specification for site visits during high flow events, local representation is required. Refer to clause 3.3. PART 2 PRODUCTS 2.1 Flow Measurement Methodologies.1 Due to the hydraulic conditions in many of the proposed sites, the Contractor may only use and install approved methodology and equipment for monitoring steep-slope, high velocity sewer flow. This is limited to weirs with elevated weir crests designed to dissipate the excessive velocity head, and to velocity-area meters that are capable of correctly measuring depth under high-velocity conditions. In either case, the Tenderer must demonstrate that they have successfully used the proposed equipment in previous multi-site, steep-slope, high-velocity conditions. The Contractor is required to submit laboratory documentation that the proposed equipment and methodologies are capable of operating under the anticipated range of conditions. Laboratory results shall be submitted in accordance with Section 1.4. 3
.2 Pre-Approved equipment is described in Section 2.7. 2.2 Electronic File Formats.1 Data shall be submitted in monthly comma-separated ASCII files. Tab-separated ASCII files will not be accepted..2 File names shall indicate STATION NAME AND MANHOLE NUMBER, month, and year of data contained within. Files shall contain homogeneous month-long data records, starting at the first day of each month at 00:00:00 and ending on the last day of each month at 23:55:00. File names shall indicate the station identification and the month and year of data contained in each file, and shall be of consistent format from month to month..3 Files shall be provided via email to johnsmith@abc.ca 2.3 Time and Date.1 All times and dates shall be reported in Pacific Standard Time, synchronised to coordinated universal time (1-303-499-7111). 2.4 Data Recording Frequency.1 All data shall be recorded at an interval of 5 minutes. 2.5 Data Reporting Frequency.1 All data shall be reported in electronic files at a frequency of 5 minutes, on even 5-minute increments (i.e. 00:05, 00:10, 00:15 etc.). 2.6 Sewer Flow Reports.1 Monthly reports shall be provided within two weeks of the end of each month..2 Each monthly report shall contain the following information: Site sketch and installation data sheet Monthly Data files for each site Documentation of quality assurance procedures, which may include but is not limited to scatter plots (for VA meters), manual flow profiling reports, offset tracking narratives, and site maintenance records Electronic files as specified containing both raw and corrected data, including correction information and flagging of all suspect data Confined space entry reports 2.7 Approved Equipment.1 Equipment pre-approved is outlined below. Any other equipment proposed is subject to the approval of the Engineer. Approval will not be unreasonably withheld, however the Engineer must be satisfied that the proposed equipment suits the needs of the City. The Contractor assumes responsibility for the appropriate operation of all equipment..2 Weirs pre-approved for use in flow monitoring include designs from the following manufacturers: Southwestern Flowtech and Environmental (SFE) 4
.3 V-A meter ( flow meter ) equipment pre-approved for use in flow monitoring includes equipment from the following manufacturers: Marsh-McBirney American Sigma ISCO ADS.4 The Contractor is reminded that these instruments typically have limitations in terms of velocity and depth ranges that must be considered prior to installation. Pre-approval does not warrant that these instruments are necessarily applicable for the sites to be monitored under this Contract..5 Equipment pre-approved for manual flow profiling includes: Marsh-McBirney Model 2000..6 Equipment pre-approved as ultrasonic level monitors include: PART 3 EXECUTION 1. American Sigma model 950 2. Telog RU33 with Massa ultrasonic module 3.1 Equipment Installation Approval.1 Design drawings shall be provided for approval by the City prior to installation of any non-temporary equipment..2 Provide information on confined space entry training of installation personnel..3 Provide safety plan, including details of confined space entry plan..4 Submit Equipment Installation Plan including items 3.1.1, 3.1.2 and 3.1.3. 3.2 Flow Site Calibration.1 All instruments used shall be calibrated by manual flow (velocity) profiling throughout the full range of flows recorded at each station. Documentation of profiling exercises shall be provided in the monthly reports..2 The full range of flows is defined as the range of recorded depths of flow from dry weather nighttime low flow conditions up to a minimum of 80 percent of the highest depth peak wet-weather event flow recorded. 3.3 Site Visits.1 The sites shall be visited at a frequency appropriate to ensure proper equipment operation to meet the Data Capture specified and for manual flow profiling during wet-weather events to confirm equipment calibration over the range of flows defined. 3.4 Data Capture.1 The Contractor is required to obtain a data capture of at least 95 percent of readings over each one-month period. This is calculated as the number of 5-minute recordings reported out of the total number of 5-minute intervals between the start and end of the billing month. 5
.2 Of the data captured, at least 95 percent of readings must accurately represent sewer flow after quality assurance and approved correction if required..3 The overall capture of approved and usable data is therefore 90 percent (95 percent * 95 percent = 90 percent). 3.5 Quality Assurance.1 Data shall be examined by the Contractor and corrected as necessary to provide an accurate representation of sewage flow for all readings. Both the raw and corrected data shall be provided in electronic and hydrograph (for sewer flow) or hyetograph (for rainfall) formats. Documentation of corrections made and reasons for corrections shall be provided in the reports..2 The data reported shall be of high calibre and should not require extensive examination or correction by the Engineer. However sufficient data shall be reported to allow the Engineer to fully audit all corrections made by the Contractor. 6
Appendix C QA/QC for Flow Monitoring Data
APPENDIX C I&IMP TEMPLATE DRAFT REPORT 2. APPENDIX C FLOW MONITORING DATA QA/QC PROCEDURES 2.1 QA/QC PROCEDURES The purpose of this section is to provide guidance and procedures for reviewing sewer flow monitoring data. Reviewing this type of data is both an art and a science; with regular review and practise it is possible to identify numerous issues with the data early on. Doing so avoids collection of data that would otherwise require complex repair or, worse, be unusable. SCATTER PLOTS A traditional method of reviewing flow monitoring data is to plot two variables (level vs. velocity, or level vs. flow) and establish a baseline for normal operation. Then, for example, if the site were to experience a sudden change such as backwatering or sensor shifting, the data would plot off of the normal curve. In the example in Figure 1, plotting level vs. flow yields a good scatter plot. A curve fit (such as a polynomial fit) can then be applied to a portion of good data to determine what is normal for this location. By plotting future data to be reviewed against the curve fit, variation from the norm is usually identifiable which can then trigger further investigation as to the cause. The scatter plot approach is of limited use for weirs and flumes, as plotting the level vs. flow curve will always yield a perfect fit, corresponding to the level vs. flow relationship for the weir or curve. However, were the relationship to accidently change partway through a season due to human error or a meter fault, the change would be obvious. See Figure 2 for an example. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT Figure 1: Example Scatter Plot of Level and Velocity Data Figure 2: Example Scatter Plot of a Weir or Flume TIME SERIES REVIEW With practise and enough examples, reviewing the data plotted directly as time series (i.e. flow vs. time) is a convenient and quick way to identify issues. The method looks for consistency in the data. If for example, on a weekly basis, one week of non-validated data is plotted along with the preceding 3-weeks of validated data, a reference point from which to view the new data is provided. Looking for inconsistencies in magnitude, baseline, etc. will routinely identify issues. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT The following sections outline the major issues that often appear in sanitary flow monitoring data. SUDDEN UPWARD BASELINE SHIFT A sudden upward baseline shift almost always indicates a weir or flume has become obstructed by an object. Common items can do this including blocks of wood and other types of debris. The clearing of the object (either by maintenance staff or self-clearing) should be clearly identifiable in the data as well. No rainfall Figure 3: Sudden Rapid Rise/Fall w/o Rainfall Indicates Likely Blockage and Removal BENCHING INTERFERENCE - SENSOR MISALIGNMENT A sudden flattening of the baseline at night almost always indicates that an ultrasonic sensor has been knocked out of alignment. If the sensor is not pointing directly downwards, it may be picking up the manhole benching instead of the sewage level. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT Figure 4: Sensor Echo Off of Benching from Misaligned Sensor GRADUAL UPWARD SHIFT Gradual upward shift is almost always caused by gradual debris build-up, which can include gravel, grease, rags, etc. The upward shift is easily identified by plotting the flow along with the rainfall signal. Baseline shifting due to Inflow & Infiltration (I&I) visually correlates very well with rainfall. A slow steady increase in the baseline with no identifiable rainfall pattern will usually indicate debris build-up. It is very important that this problem be addressed quickly, as it is very difficult to reconstruct data that has been impacted by a changing debris level. Figure 5: Gradual Baseline Increase Caused by Debris Build-Up KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT MAGNITUDE OF BASELINE FLOW The minimum flows that occur in the middle of the night are usually assumed to be about 85% groundwater, with only about 15% being sewage when the main land use upstream of the flow monitoring station is residential. Even with commercial and institutional uses, these are often focussed on serving people who are asleep at night. As a result, looking at the magnitude of the minimum base flow each night is often a good indicator of whether or not the flow data is correct. Specifically, a large base flow relative to the magnitude of the daily flow variation can indicate a problem. One exception is sites that serve industrial uses, which can operate during night shifts and hence the baseline magnitude is not necessarily a good indicator of issues where industrial is the primary use. The latter half of the previous Figure 5 is a good example of where the baseflow is too high relative to the magnitude of the daily fluctuations. MAGNITUDE OF DIURNAL VARIATION Similarly, there is a normal range of daily fluctuations in typical land-use applications. When the magnitude of these diurnal variations is too large or too small, or when it suddenly changes, it may be indicative of problems with the data. Figure 6: Issue with Different Diurnal Pattern Magnitude after Meter Repair YEAR-LONG GROUNDWATER TREND On sites where longer data collection is being conducted, a year s worth of data is worth reviewing to see how the minimum baseline flow (which is mostly groundwater) has varied over the course of the year. The minimum should occur in August and September. After the first rains in October and November, it is typical to see that the baseline has KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT risen to what could be called the winter value. This will often be noticeably elevated above the summer value. From generally April onwards the value will often decrease back down to the minimum summer value as groundwater levels decrease. Some sites may not show a noticeable change throughout the year, which depends on the ground conditions within the catchment. What is important to look for is a trend in the wrong direction (i.e. summer baseflows higher than winter). See the following figure for an example of a properly working station (the spurious zero readings in August were caused by a temporary meter failure). Figure 7: Typical Summer and Winter Baseflows RAINFALL: VISUAL COMPARISON OF MULTIPLE GAUGES By far the most common type of rain gauge failure is debris plugging. This is usually easily identified by comparing a given time period against other rain gauges, as shown in the following figure. When preparing such a figure, make sure that the axis scaling is set to the same value for each station, and stack the stations on top of each other for easiest visualization. Figure 8 shows an example. Another common indication of a plugged rain gauge is a slow, continual single rain tip repeated at fairly regular intervals, when other gauges clearly show a more dramatic response. This is caused by a very slow leakage of the plugged funnel, as shown in Figure 9. KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX C I&IMP TEMPLATE DRAFT REPORT Figure 8: Rainfall Signals from Multiple Stations Showing Missing Storm Figure 9: Rainfall Signals from Multiple Stations Showing Plugged Gauge KERR WOOD LEIDAL ASSOCIATES LTD.
Appendix D I&I Envelope Methodology
APPENDIX D I&IMP TEMPLATE DRAFT REPORT 3. APPENDIX D - I&I ENVELOPE METHODOLOGY This section explains the procedures to apply the I&I Envelope Methodology. It assumes that the dataset is quality controlled and corrected. In order to use the methodology, flow and rainfall data should both be at 5-minute intervals. The rainfall gauge should be the closest gauge that represents the rainfall for the sewer flow monitoring catchment. PURPOSE The purpose of the I&I Envelope Method is to use a collection of recorded storm events to create a correlation between the amount of rain that falls in a catchment and the amount of I&I that shows up at the flow monitoring site. Knowing the return period of the rainfall, combined with the assumption that rainfall return period correlates to I&I return, allows the correlation to be used to produce estimates for return period based I&I. This allows catchments that were monitored in different seasons with different storm events to be compared on an apples to apples basis. STEP 1: PREPARE DATA FOR STORM SELECTION To begin, prepare monthly graphs of flow with rainfall for the site to be analyzed. Keep the same y-axis scale for each graph, and lay them out end to end to see the entire season. In addition, if monthly rainfall summary tables exist lay these out as well. See the following figures for a monthly example of a graph and rainfall table. Figure 10: Typical Monthly Data Plot showing Flow and Rainfall KERR WOOD LEIDAL ASSOCIATES LTD.
APPENDIX D I&IMP TEMPLATE DRAFT REPORT Figure 11: Monthly Rainfall Summary Table For sites in Metro-Vancouver, ideally you should have 6 months of data covering the span October to March. In any case work with the data that you have. STEP 2: CHOOSE STORM EVENTS Using the graphs (and rainfall tables if available), begin to make a list of storm events. Here are some guidelines for selecting storm events: Start with the largest events, identifying them by both their visual response on the graphs as well as by rainfall totals on your rainfall tables. Identifying storms that stand out using their 6, 12, and 24 hour totals is a good starting point. Give first priority to storms that have one clearly defined peak, and which clearly return to pre-storm baseflow conditions after the rain event. Storms with multiple peaks or that do not return to baseflow conditions before the next storm are more difficult to analyze. KERR WOOD LEIDAL ASSOCIATES LTD.