Island Lake- Baptiste Lake Wastewater Collection Feasibility Study
Final report
Prepared for:
Island Lake- Baptiste Lake Wastewater Collection Feasibility Study
724 Baptiste Drive West Baptiste, AB, T9S 1R7
Prepared by:
Stantec Consulting Ltd. 10160 – 112 Street Edmonton, Alberta T5K 2L6
File: 1101 26009 Copyright© Stantec Consulting Ltd., 2010
25 January 2010 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
Executive Summary
The Island Lake- Baptiste Lake Wastewater Collection Feasibility Study was conducted by Stantec Consulting Ltd. to identify and evaluate domestic wastewater servicing alternatives for the Summer Villages and other areas located on Island and Baptiste Lakes. The service areas include Summer Villages of Island Lake, Island Lake South, South Baptiste, West Baptiste, Sunset Beach and Whispering Hills, as well as County communities of White Gull, Poplar Point and Pac Beach.
Population census data for the Summer Villages for years 2004 to 2008 was obtained from the Alberta Municipal affairs website. The data indicated an average annual population growth rate of 12.33% in the Summer Villages for this period. This growth rate is significantly higher than the average rate used by the municipalities in their development planning and may not be adequate for use in this study for estimating ultimate growth in the Summer Villages. Based on discussions with the Summer Villages representatives, an average occupancy rate of 3.0 persons per lot was agreed for use in this study. A total 1358 lots in Baptiste and Island Lakes were identified that will need wastewater servicing based on the most recent planning layout and assumptions made for the number of lots in some new subdivisions being planned in the area. This resulted in an ultimate population of 4,071 people in the service areas.
Sewage generation rates and peaking factors used in this study are based on the guidelines in Alberta Environment’s Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems (January 2006) and Alberta Private Sewage Systems Standard of Practice (2009).These guidelines specify daily average and peak flow rates of 228 L/person and 340 L/person, respectively, for wastewater generation in residential land uses.
No wastewater sewer system currently exists in the study areas. Majority of lots in the study areas collect domestic wastewater in on-lot tanks from where it is periodically pumped and hauled to the existing evaporation lagoon located in SE-23-67-24-W4.
Three alternatives were identified and evaluated in this study for providing centralized wastewater sewer servicing for the study areas. These alternatives included:
1. Conventional gravity/pressure sewer system,
2. Small diameter gravity/pressure – STEG system, and
3. Low pressure sewer – STEP system.
Preliminary hydraulic calculations indicated that several pumping stations and lengthy force mains would be required for both conventional gravity and small diameter gravity sewer system
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc E.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT EXECUTIVE SUMMARY February 24, 2010 alternatives. Significant capital and operational costs would be associated with these pumping stations resulting in substantial increase to the project’s overall costs.
Preliminary calculations resulted in opinion of probable costs of approximately $28,474,200 for Alternative 1; approximately $22,882,400 for Alternative 2; and approximately $9,696,300 for Alternative 3. All these costs include 30% contingency and 15% engineering costs. The opinion of probable costs for Alternatives 2 and 3 do not include costs for the on-site facilities which are anticipated to be handled on individual basis.
Based on the preliminary calculations, Alternative 3 – Low Pressure STEP System was found to be the most economical alternative for providing long term sanitary servicing for the service areas. This alternative would not require any pumping stations on the main sewer system. However, small pumping units will be required on individual lots to discharge filtered-out sewage to the main pressure sewer system. Based on the comparative analysis, low pressure STEP system has been selected as this study’s recommended alternative.
The proposed low pressure system would comprise of a network of small diameter pressure sewers that collects wastewater from private pumping units for discharge at the existing Baptiste - Island Lake evaporation lagoon. The design flow rates are calculated based on the equation developed in the US Environmental Protection Agency’s publication “Alternative Wastewater Collection Systems Design Manual (October 1991). This equation calculates design flows corresponding to the required number of connections serviced by the pressure sewer. Preliminary hydraulic calculations resulted in design flows of 27.8 L/s and 16.9 L/s for the Baptiste Lake and Island Lake areas, respectively. Sewer sizes ranging between 50 mm to 250 mm would be required for the main system. The proposed system would not require any manholes on the main sewers. This would eliminate any inflow and infiltration from surface stormwater or groundwater into the system, thus, considerably reducing design flow rates.
The proposed low pressure sewers would generally follow the land contours and would have a shallow burial depth between 2.5 m to 3 m. The horizontal alignment of the sewers is proposed along the service areas’ internal streets and regional roads. However, final horizontal and vertical alignments of the proposed system should be decided at the detail design stage based on geotechnical recommendations and information on existing utilities etc. The proposed sewer would require crossings at the existing Baptiste Lake Creek and Highway 2. An inverted siphon crossing would be required at the Baptiste Lake Creek whereas trenchless installation of the pressure sewer would be needed at the Highway 2 crossing. All other regional roads are currently gravel where open cut installation of the sewers would be feasible.
The proposed system will require installation of on-site facilities such as septic tanks, pumps, alarms, control panels and service connections by the homeowners. Typically, 1000 to 1500 gallons septic tanks would be required depending on the type of pumping units and number of dwelling units served by each facility.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc E.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT EXECUTIVE SUMMARY February 24, 2010
Based on preliminary hydraulic calculations and existing topography, standard 1 horsepower effluent pump would be adequate to service each dwelling unit in the study area. This pump would be capable of discharging a minimum rate of 0.31 L/s (5 gpm) at a total dynamic head (TDH) of up to 100 m. The pumping rate would vary depending upon the hydraulic conditions in the pumping unit and downstream main sewer system. Each pumping unit will be equipped with appropriate alarms and controls, such as level sensors, pressure sensors etc., which can be configured according to the operational demands of the system.
Average cost of on-lot facilities would depend on the type and configuration of the pumping units and system controls used in the proposed system. Some existing tanks would need modifications or decommissioning based on the requirements of the selected system. Opinion of probable costs for the supply and installation of typical on-lot facilities having a standard STEP pumping unit would be approximately $10,000. Based on opinion of probable cost of approximately $9,696,300 for the proposed collection system, average cost share per lot would be $7,140.
The existing Baptiste - Island Lake lagoon operates as an evaporation lagoon. According to the as-built data, the lagoon has an operating capacity of 24,400 m³ and surface area of 17,890 m² at a maximum operating depth of 1.5 m. Based on the this surface area and weather data, with the implementation of a collection system, the current lagoon size would only be able to service a very small population (less than 100). It is anticipated that with implementation of the proposed collection system, an alternative method of wastewater treatment to an evaporation lagoon will be required to service the design population. It is recommended that detailed assessment of the wastewater treatment system needs for the service areas should be conducted as part of a separate study.
An alternative to a single regional wastewater collection system is the installation of decentralized collection systems to service specific areas. In an effort to evaluate the potential benefits of a decentralized approach for this project, the South Baptiste Lake area was evaluated for the use of a decentralized system against the regional gravity/pressure sewer system analyzed in this study. The evaluation process indicated that a decentralized system would eliminate approximately 3,500 m of forcemains and one pumping station while it would add a small treatment and disposal system to service the South Baptiste Lake area.
Preliminary assessment of the decentralized system indicated that if a surface water discharge is utilized for the disposal of treated wastewater from the South Baptiste Lake area, the estimated costs would be the same for the regional collection system and the decentralized system alternatives. If a land disposal system (infiltration beds, trenches or drip disposal) were utilized, the estimated cost for the decentralized alternative would be between $100,000 and $200,000 higher than the regional alternative depending on the area utilized for the disposal system. Based on this evaluation, a decentralized system does not provide an economically feasible alternative and has not been recommended in this study.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc E.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT EXECUTIVE SUMMARY February 24, 2010
It is anticipated that after the installation of a community collection system, wastewater generation may temporarily trend upward, because system users may not perceive the same level of importance with water conservation as they did with their individual system. However over time the water usage should trend down again. It is difficult to estimate what the end liter per capita per day (lcd) will result and is influenced by community initiatives and education. Wastewater generation values used in the design basis must be defendable and supported in order for regulatory approval. It is important that the RME sets the cost for the collection, treatment and discharge of the wastewater at rates that are appropriate for the provision of these services, as well as including the long term costs to operate and maintain this infrastructure.
Potential environmental impacts of the proposed collection system route will include a stream crossing, a wetland crossing, and potentially crossing through areas of potential habitat for rare plants or animals. In order to identify the magnitude of these impacts, a biophysical evaluation of the proposed collection sewer system routes, as well as the treatment system site, will be required once the alignment is solidified. Other impacts associated with the project construction, such as crossing of existing utilities, crossing of railroad lines, and crossing of major roads, should be identified and considered.
The existing individual septic systems are potentially negatively impacting the environment due to the age of some of the systems, as well as the potential for lack of operational care of the existing systems. The evaluation should also consider the positive impact to the environment that will result with a proposed community wastewater system, including the reduction in pollution that will occur when the individual septic systems are removed from service and a community wastewater system is installed under professional management.
A Responsible Management Entity (RME) should be identified for managing the infrastructure established. Typically the RME is a governmental agency such as a County or a Municipal District, however the RME can also be a private entity if this model is selected by the project owner. The RME will be responsible for the operation and maintenance of the collection and treatment system, with the goals of maximizing the life of this infrastructure and providing cost effective wastewater servicing over long term. The RME should administer the sewer use ordinance and collect fees necessary to support the operation and maintenance of the infrastructure. The RME should select a competent operator, who is certified in Alberta, to operate and maintain the wastewater system. The RME should administer a program to maintain the infrastructure, and rely on input from the operations staff on the condition of the system and the projected capital needs.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc E.4 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
Table of Contents
LETTER OF TRANSMITTAL CORPORATE AUTHORIZATION EXECUTIVE SUMMARY E.1 TABLE OF CONTENTS i LIST OF TABLES ii LIST OF FIGURES iii
1.0 INTRODUCTION ...... 1.1 1.1 PROJECT BACKGROUND AND ISSUES...... 1.1 1.2 SCOPE OF WORK ...... 1.1
2.0 GENERAL ...... 2.1 2.1 SITE DESCRIPTION ...... 2.1 2.1.1 Location ...... 2.1 2.1.2 Existing Topography ...... 2.1 2.1.3 Land Use...... 2.1
3.0 DATA COLLECTION AND REVIEW...... 3.1 3.1 EXISTING DOCUMENTS REVIEWED...... 3.1 3.2 STAKEHOLDER CONSULTATION ...... 3.2
4.0 DESIGN CRITERIA ...... 4.1 4.1 WASTEWATER CONSUMPTION RATES AND PEAKING FACTORS ...... 4.1 4.2 DESIGN POPULATION AND DEVELOPMENT INTENSITY ...... 4.1 4.3 HYDRAULIC CRITERIA ...... 4.2
5.0 WASTEWATER COLLECTION ALTERNATIVES...... 5.1 5.1 GENERAL...... 5.1 5.1.1 Alternative 1 - Conventional Gravity/Pressure Sewer System...... 5.1 Note: Unit costs for gravity sewers are based on weighted average burial depth ...... 5.3 5.1.2 Alternative 2 - Small Diameter Gravity Sewer System – Septic Tank Effluent Gravity (STEG) System ...... 5.3 Note: Unit costs for gravity sewers are based on weighted average burial depth ...... 5.5 5.1.3 Alternative 3 - Low Pressure Sewer - Septic Tank Effluent Pumping (STEP) System...... 5.5 5.2 EVALUATION OF COLLECTION ALTERNATIVES ...... 5.7
6.0 CONCEPTUAL DESIGN ...... 6.1 6.1 GENERAL...... 6.1 6.2 ON – LOT FACILITIES ...... 6.1 6.2.1 Septic Tanks ...... 6.1
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc i ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
Table of Contents 6.2.2 Pumps...... 6.2 6.2.3 Control Systems...... 6.2 6.2.4 Opinion of probable Costs for On-Lot Facilities ...... 6.2 6.3 LOW PRESSURE SYSTEM HYDRAULIC DESIGN...... 6.3 6.4 PIPELINE ALIGNMENT...... 6.4
7.0 DECENTRALIZED COLLECTION ALTERNATIVE ...... 7.1 7.1 GENERAL...... 7.1 7.2 DECENTRALIZED COLLECTION SYSTEM ...... 7.1 7.2.1 Financial Impacts...... 7.1
8.0 POTENTIAL SOCIAL AND ECOLOGICAL IMPACTS ...... 8.1 8.1 IMPACTS ON WATER USE ...... 8.1 8.2 IMPACTS ON NEW DEVELOPMENT ...... 8.1 8.3 POTENTIAL ENVIRONMENTAL IMPACTS ...... 8.2 8.4 MANAGEMENT AND OPERATIONS FRAMEWORK FOR THE PROPOSED WASTEWATER SYSTEM ...... 8.2
9.0 EXISTING SEWAGE LAGOON ASSESSMENT...... 9.1 9.1 GENERAL...... 9.1 9.2 LAGOON SITE INSPECTION...... 9.1 9.2.1 Observations...... 9.1 9.2.2 Discussions...... 9.2 9.2.3 Recommendations...... 9.3 9.3 CAPACITY ASSESSMENT OF EXISTING SEWAGE LAGOON ...... 9.3 9.4 TREATMENT AND DISPOSAL CONSIDERATIONS ...... 9.4 9.4.1 Treatment...... 9.4 9.4.2 Disposal ...... 9.4 9.4.3 Additional considerations...... 9.5
10.0 CONCLUSIONS AND RECOMMENDATIONS ...... 10.1
LIST OF TABLES
Table 4.1 Population Census Record for Summer Villages (2004 – 2008)...... 4.1
Table 5.1 Alternative 1 – Wastewater System Design Calculations...... Following Page 5.2
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc ii ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
Table of Contents Table 5.2 Alternative 1 – Opinion of Probable Costs...... 5.3 Table 5.3 Alternative 2 – Wastewater System Design Calculations...... Following Page 5.4 Table 5.4 Alternative 2 – Opinion of Probable Costs...... 5.5 Table 5.5 Alternative 3 – Wastewater System Design Calculations...... Following Page 5.6 Table 5.6 Alternative 3 – Opinion of Probable Costs...... 5.7 Table 5.7 Estimated Cost Share Per Lot for the Collection System Alternatives ...... 5.9
Table 6.1 Opinion of Probable Costs for On-Lot Facilities ...... 6.3
LIST OF FIGURES
Figure 2.1 Existing Topography Figure 2.2 Service Area Legal Survey Plan
Figure 5.1 Alternative 1 – Conventional Gravity/Pressure Sewer System, Baptiste Lake Figure 5.2 Alternative 1 – Conventional Gravity/Pressure Sewer System, Island Lake Figure 5.3 Alternative 2 – Small Diameter Gravity Sewer System, Baptiste Lake Figure 5.4 Alternative 2 – Small Diameter Gravity Sewer System, Island Lake Figure 5.5 Alternative 3 – Low Pressure Sewer – STEP System, Baptiste Lake Figure 5.6 Alternative 3 – Low Pressure Sewer – STEP System, Island Lake
LIST OF APPENDICES Appendix A Existing Lagoon Field Inspection Report
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc iii ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
1.0 Introduction
Stantec Consulting Ltd. prepared the Island Lake – Baptiste Lake Wastewater Collection Feasibility Study to identify and evaluate alternatives for the domestic wastewater servicing for the Summer Villages and County areas located on and adjacent to Island and Baptiste Lakes. The purpose of this study is to identify and develop community wastewater collection system requirements on a conceptual level to establish budgetary costs for the future development in the study areas. The proposed community wastewater collection and disposal system would replace individual collection systems currently practiced on existing residential lots in these areas.
1.1 PROJECT BACKGROUND AND ISSUES
The Baptiste Lake and Island Lake Summer Villages created a legal entity “Baptiste – Island Lake Sewage Lagoon Committee” in 1988 for the purpose of constructing and operating a sewage lagoon serving the County of Athabasca and the summer villages in the region. In a meeting of the Summer Villages and Councilors held on September 8, 2007, the Summer Village of Island Lake was designated as the managing partner to submit an application for an inter-municipal grant for the development of an engineering plan and feasibility study for a water/wastewater/solid waste management system. The study would involve a feasibility analysis for installation of a regional and/or decentralized sewer collection system with discharge to a wastewater treatment facility.
The proposed wastewater collection system will service Summer Villages of Island Lake, Island Lake South, South Baptiste, West Baptiste, Whispering Hills and Sunset Beach, as well as County areas of White Gull, Poplar Point and Pac Beach. A legal survey plan of the region showing property boundaries, roads and right of way information for the study areas was prepared for use in this study.
1.2 SCOPE OF WORK
The scope of services for this feasibility study is as follows:
• Collect available mapping, topographic information, soils hydrology and land cover and land use information. Also collect available information on the existing summer villages water use, population, collection treatment and disposal practices, commercial and other business uses and unique concerns.
• Collect information on the design, current capacity, condition and need for upgrading of the existing lagoon. Identify the site for potential to upgrade and expand.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 1.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Introduction February 24, 2010
• Work with the summer villages in identifying their concerns, needs and preferences in the development of wastewater services. Provide information on options for centralized and decentralized services so that decisions can be made with good information on options and benefits.
• Identify potential routes for a sewer collection system. Consider public right of way, private land options and constraints.
• Evaluate sewer collection options with emphasis on low pressure sewer systems including the benefits and disadvantages, and prepare cost estimates for installation and operation. Identify whether additional lift stations are needed with sewer options.
• Where circumstances warrant, consider decentralized approaches to a full collection system servicing all of the summer villages. These circumstances may include high cost, physical and environmental constraints and other wastewater management concerns.
• Identify the potential impacts on water use practices and the mitigation measures that may be applied to minimize impacts.
• Conduct a desktop study of potential environmental impacts of the selected collection system. Identify the scope of a biophysical investigation of the most feasible sewer route(s). Upon selection of the route and upgrade needs provide a scope and budget for performing the necessary environmental studies for permit approvals from Alberta Environment.
• Based on similar lake sewer servicing projects identify the secondary impacts of the potential for increased development stimulated by the availability of wastewater services. Identify mitigation measures to manage secondary impacts.
• Provide a project manager to work directly with the summer villages and coordinate the needs and special concerns of each.
• Provide leadership to the project team and the client in selection and securing approvals to move the project forward.
• Assist in funding options including grant and loan assistance. Provide budgeting and financial management.
• Assist in identifying the needs and options for the management and operations framework and authority for managing a wastewater system.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 1.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
2.0 General
2.1 SITE DESCRIPTION
2.1.1 Location
Baptiste Lake is located approximately 16 km west of the town of Athabasca and is bounded by Twp. Road 672 on the north, Range Road 663 to the east, Twp. Road 663 to the south and Range Road 243 to the west. Island Lake is located approximately 4 km north of Baptiste Lake and is bounded by Twp. Road 682 on the north, Range Road 235 on the east, Twp. Road 674 on the south and Range Road 242 to the west.
The lakes can be found on the 1:50,000 scale NTS map sheets 83I/13 and 83I/12.
2.1.2 Existing Topography
Figure 2.1 shows the existing topography within the study area. The area contours indicate that the existing ground surface elevation around the Baptiste Lake ranges from approximately 580 m to 618 m sloping towards the lake. The existing ground elevation west and south of the Island Lake ranges from approximately 603 m to 620 m sloping towards the lake.
2.1.3 Land Use
The majority of lots in the Summer Villages are intended for residential land use purposes. The occupancy of these units is a mix of permanent and seasonal residences. No information is currently available for determining the exact proportion of permanent and seasonal dwelling units in the Summer Villages.
Figure 2.2 shows the legal survey plan for all the Summer Villages on Island and Baptiste Lakes. The plan shows lots in all the Summer Villages and County areas of White Gull, Poplar Point and Pac Beach. Discussions with the Summer Villages indicated that some new subdivisions are currently being planned in the study area. These new subdivisions have not been shown in the survey plans. Further information on the exact location and number of lots in these new subdivisions was not available at the time of this study. Therefore, for the purpose of this study, assumptions were made for the number of lots in these new areas to estimate corresponding sewage flow rates and servicing requirements. Actual number of lots in these new subdivisions should be confirmed in the later stages of the project development.
The area planning layout and above assumptions made for the new subdivisions resulted in a total of approximately 852 and 506 residential lots in the Baptiste and Island Lakes, respectively, that will require wastewater servicing. These include lots in all the six Summer Villages, and in County areas of White Gull, Poplar Front and Pac Beach etc. It is understood that the County and Summer Villages will carry out a consultation process at a later stage to
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 2.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT General February 24, 2010 determine which communities will require wastewater servicing and connection to the proposed regional wastewater collection system. For the purpose of this study, these numbers were assumed to represent ultimate build-out in the study areas. It is anticipated that planning layout in the service area may undergo changes as more accurate information on number of lots in the new subdivisions is available.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 2.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
3.0 Data Collection and Review
This section describes the data collection and review completed for the preparation of this feasibility study. The following data was collected and reviewed:
• Relevant previously completed reports • Land ownership information • Topographic Maps • Stakeholder consultation
3.1 EXISTING DOCUMENTS REVIEWED
The following documents were reviewed to familiarize the project team with the project, and extract relevant data for use in this study:
• State of Baptiste Lake Watershed Report, Matt Carlson, Terra Ecological Consulting, June 2008: this report investigated existing conditions at the Baptiste Lake and its watershed, and assessed potential strategies to improve the health of the lake and watershed. The environmental issues discussed in this report included water quality, fisheries, shoreline conditions, and water level etc.
• A legal survey plan was provided by the Summer Village Representatives in digital format. The plan shows property boundaries, roads and right-of-way information for the service areas including all the Summer Villages, and County areas of White Gull, Poplar front and Pac Beach.
• County of Athabasca No. 12; By-Law No. 25-1990. The by-law provides for the Regulation and Control of the Baptiste/Island lake sewage lagoon.
• Land Title Certificate for the SE-23-67-24-W4 where the existing sewage lagoon is located.
• Topographic map for the area including 1 m contours for the study area.
• County of Athabasca documents pertaining to the operation and management of the existing sewage lagoon.
• Part of the As-built drawing showing design data for the existing sewage lagoon.
• County of Athabasca land ownership map showing information on the land ownership in the service areas.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 3.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Data Collection and Review February 24, 2010
3.2 STAKEHOLDER CONSULTATION
As part of our evaluation, we engaged the Island Lake and Baptiste Lake Council Representatives to help us better understand specific needs of the project. The summary below identified these concerns:
Ecological impacts • Reduced trucking and related use of diesel fuel • Depending on collection options – eliminate leaking septic tanks, pipes and failed septic mounds. This will have a positive effect on the ground water from which much potable water is obtained. • Ground water usage may increase as a result of collection system • Average pump-out frequency is 1500 gal/ month at a cost of $75.00 per load.
Social Impacts • Wastewater collection and treatment infrastructure can drive development in the area. Land use planning and ASP’s (Area Structure Plans) are required to guide growth. • Sewage bylaws will need to be developed to ensure compliance • Water conservation guidelines and/or bylaws may need to be developed • A growth rate of 1.5% described for several areas of the County is not reasonable for this community. • Several new and proposed subdivisions are not on the map provided and will be considered moving forward. • Assumptions will be made for this exercise and noted in the report.
Financial Impacts • Property values will increase. • Depending on collection option, septic tank and field maintenance will decrease or be eliminated • Depending on collection option, a monthly service fees is likely • Depending on collection option, the property owner will be responsible for some part of the system connection to the home or property. In the event that property is vacant, a variety of payment concepts exist. • Overall system cost and funding mechanisms are a concern.
Potable Water • At some point in time community potable water will need to be considered. This is not part of Stantec’ scope and can be proposed if requested. It is our experience that doing both water and wastewater at the same time can be difficult to achieve. Separating the projects into two distinct entities is recommended. There are little to no cost savings to doing both at the same time. • A future potable water system will be considered in the feasibility study for lagoon sizing purposes.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 3.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Data Collection and Review February 24, 2010
Appliances • It was noted that most permanent residents have laundry and dishwashers in their homes.
Long term considerations • Future upgrading may be required and therefore additional land must be considered. • Secondary treatment may be required and therefore additional land must be considered. • On-site inspection of condition of the lagoon is important in determining its future if a collection system is built.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 3.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
4.0 Design Criteria
The study area falls within the County of Athabasca No. 12. Currently, the County has not developed any engineering standards for the design of wastewater systems. Alberta Environment’s Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems (January 2006) and Alberta Private Sewage Systems Standard of Practice (2009) developed by the Safety Codes Council, Alberta Municipal Affairs were consulted for the design of wastewater collection system alternatives in this study.
4.1 WASTEWATER CONSUMPTION RATES AND PEAKING FACTORS
Guidelines in Alberta Private Sewage Systems Standard of Practice were used to determine expected sewage generation rates for the residential units in the Summer Villages and County areas. For residential land uses, these guidelines specify sewage generation rates of 228 L/day/person and 340 L/day/person for the expected median and peak flow conditions, respectively.
4.2 DESIGN POPULATION AND DEVELOPMENT INTENSITY
Population census data for the Summer Villages for years 2004 to 2008 was obtained from the Alberta Municipal affairs website. The data also included information on the number of total dwelling units in each summer village. This data is summarized in Table 4.1.
Table 4.1 Population Census Record for Summer Villages (2004 – 2008) 2008 Dwelling 2008 Occupancy Summer Village 2004 Population 2008 Population Units Rate/Unit Island Lake 216 351 102 3.44
Island Lake South 72 105 76 1.38
South Baptiste 44 69 23 3.00
West Baptiste 46 104 18 5.78
Whispering Hills 118 125 55 2.27
Sunset Beach 50 88 24 3.67
Total 546 842 298 3.26
Note: Population census data for the County areas of White Gull, Poplar front and Pac Beach were not available at the time of this study.
Table 4.1 indicates an average annual population growth rate of 12.33% for the Summer Villages from 2004 to 2008. This growth rate is significantly higher than the average rate used
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 4.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Design Criteria February 24, 2010 by the municipalities in their development planning and may not be appropriate for use in this study for estimating design population in the Summer Villages.
The census data indicates an average occupancy rate of 3.26 persons per lot for the 2008 year. Based on discussions with the Summer Villages representatives, an average occupancy rate of 3.0 persons per lot was agreed for use in this study. As previously discussed, an estimated 1358 lots in the Summer Villages and County areas will require wastewater servicing based on the legal survey plan and assumptions made for the number of lots in the proposed new subdivisions. This resulted in a total design population of 4,074 people in the service areas.
4.3 HYDRAULIC CRITERIA
The hydraulic design criteria used in this study for the gravity sewer systems are based on the Alberta Environment’s Standards, January 2006. A summary of the key design criteria used for this study is as follows:
a) The gravity sanitary sewers are sized using Manning’s Equation with a Manning’s roughness coefficient (n) of 0.013.
b) A combined flow of 0.4 L/s/ha is used for inflow/infiltration and sag location allowances in the gravity sewer systems.
c) The Alberta Environment’s Standards require that the sanitary pipes be sized to convey the total design flow at no more than 80% of the full flow pipe depth. Therefore, the required flow capacity for sizing the sewers was computed using the following relationship:
Flow Design Estimated Design Flow Required full flow pipe capacity = 86.0
d) For the low pressure – STEP system, the design flow rates are calculated based on the equation developed in the US Environmental Protection Agency’s publication “Alternative Wastewater Collection Systems Design Manual (October 1991). This equation calculates the design flows corresponding to the required number of connections serviced by the pressure sewer. The equation has been derived by drawing a best fit on the results from some other relationships currently used by various manufacturers of the STEP systems. The simplified form of this equation is listed as follows:
Q = A x N +B
Where
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 4.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Design Criteria February 24, 2010
Q is the peak flow in gallons per minute
A is a coefficient selected based on the occupancy rate used, typically it is 0.5
N is the total number of dwelling units serviced by the pressure sewer, and
B is a constant used to establish a minimum flow rate in the system. Typical value of this constant varies from 15 to 20 depending on the total number of dwelling units.
e) A Hazen-William’s coefficient of 140 was used to estimate friction head loss in the pressure pipe lines.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 4.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
5.0 WASTEWATER COLLECTION ALTERNATIVES
5.1 GENERAL
No sanitary sewer system currently exists within the study area. Presently, domestic wastewater is collected in private holding tanks and then hauled to the existing Baptiste – Island Lake lagoon located in SE 23-67-24-W4.
Three main alternatives were identified and evaluated in this study for providing wastewater servicing for the study area. These options included:
• Conventional Gravity/Pressure Sewer System • Small Diameter Gravity Sewer System – Septic Tank Effluent Gravity (STEG) System • Low Pressure Sewer - Septic Tank Effluent Pumping (STEP) System
5.1.1 Alternative 1 - Conventional Gravity/Pressure Sewer System
Under this alternative, domestic sewage from individual units will be collected through a network of gravity sewers that will eventually discharge at the existing sewage lagoon. Minimum slope, velocity and size requirements (as specified by the AENV Standards) will apply for all the sewers to facilitate self-cleaning and prevent accumulation of sediments in the pipelines. Manholes would be required at regular intervals and at all the bends and junctions in the sewer system.
Typical to a lake side development, the majority of lots in the study area are located along the shoreline where ground elevations are generally lower compared to the adjacent lands. High ground water table adjacent to the lakes limits excavation depths for the pipelines. This would mean the gravity sewers can be installed up to a certain distance beyond which lift stations would be required on the system. Preliminary design calculations and existing topography indicate that approximately 14 pumping stations and force mains would be needed on the proposed sewer system. The proposed conveyance system under this alternative will, thus, comprise of a mix of gravity and pressure sewers.
A conceptual layout of the proposed gravity/pressure sewer system for the study area is illustrated on Figures 5.1 and 5.2. Table 5.1 includes preliminary design calculations for the proposed system under this alternative. These calculations indicate that approximately 60,000 m long sewers would be required which include approximately 27,330 m of force mains.
Each pumping station will house two pumps; one duty and one standby, both of which will be of the same size. All the pumps will be equipped with variable frequency drive (VFD) as a means to adjust the pumping flow and head according to the system demand, thereby reducing power consumption and pumping costs. Most of the required pumping stations can be a wet well
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010 configuration with the control box located on the surface in a small heated chamber. However, Pumping Station K (see Figure 5.1) on the Baptiste Lake system may require a small building due to its larger pumps and operational requirements. The building would be adequately sized to accommodate all pumps, an emergency back-up generator and related mechanical and electrical equipment including unmanned automatic controls. The emergency generator would be sized to handle all pumps and building loads during a power interruption or outage to the station. For the purpose of this study, it has been assumed that electric pumps would be provided on this system.
Table 5.2 shows the opinion of probable cost for Alternative 1. The order of magnitude opinion of probable cost for Alternative 1 is approximately $28,474,200, which includes 30% contingency and 15% engineering costs.
The above costs do not include operation and maintenance (O&M) costs for the wastewater system. For the sewer system, occasional inspection and cleaning of the manholes and pipes would be required. However, substantial O & M costs will be associated with the pumps and lift stations operations.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010
Table 5.2 Alternative 1 – Opinion of Probable Cost Description Unit Quantity Unit Costs Costs Baptiste Lake System 75 mm Dia. Force Mains l.m. 3,610 $90 $324,900 100 mm Dia. Force Mains l.m. 5,860 $120 $703,200 125 mm Dia. Force Mains l.m. 3,080 $150 $462,000 150 mm Dia. Force Mains l.m. 5,130 $190 $974,700 200 mm Dia. Force Mains l.m. 3,560 $200 $712,000 200 mm Dia. Gravity Sewers l.m. 22,390 $350 $7,836,500 Manholes v.m. 1,077 $2,000 $2,154,100 Pumps – 20 nos. Lump sum 1 $622,000 $622,000 Pump House Building Lump sum 1 $350,000 $350,000 Instrumentation and Controls Lump sum 1 $700,000 $700,000 Total Construction Costs $14,839,400 Contingencies (at 30% of Construction Costs) $4,451,800 Engineering (at 15% of Construction Costs) $2,225,900 Sub-Total $21,517,100 Island Lake System 100 mm Dia. Force Mains l.m. 2,220 $120 $266,400 150 mm Dia. Force Mains l.m. 3,880 $190 $737,200 200 mm Dia. Gravity Sewers l.m. 10,310 $300 $2,474,400 Manholes v.m 370 $2000 $740,000 Pumps – 20 nos. Lump sum 1 $200,000 $200,000 Instrumentation and Controls Lump sum 1 $380,000 $380,000 Total Construction Costs $4,798,000 Contingencies (at 30% of Construction Costs) $1,439,400 Engineering (at 15% of Construction Costs) $719,700 Sub-Total $6,957,100 Total Cost $28,474,200 Note: Unit costs for gravity sewers are based on weighted average burial depth
5.1.2 Alternative 2 - Small Diameter Gravity Sewer System – Septic Tank Effluent Gravity (STEG) System
Small diameter gravity sewer systems are also known as Septic Tank Effluent Gravity (STEG) systems. Under this alternative, raw sewage from the dwelling units will be collected in underground septic tanks located on the private property. For typical STEG systems, most of the sediments, oil and grease are retained in the septic tanks while the relatively filtered-out effluent is drained via gravity or pressure service connection to the main gravity sewer system.
As effluent from the septic tanks is generally free of solids, the gravity mains will have less hydraulic velocity and longitudinal slope requirements. Moreover, the main sewers will be of
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010 smaller size, typically ranging from 75 mm to 250 mm, depending on the design peak flow from the service areas entering in the system. The spacing between the manholes would also increase due to less maintenance requirements for this system. Reduced slope and velocity requirements would generally increase the length of gravity pipelines. However, due to relatively lower ground elevations and high groundwater table in the service areas, pumping stations and force mains would be required at several locations in the system. A conceptual layout of the small diameter gravity sewer system for the service areas is illustrated on Figures 5.3 and 5.4.
Table 5.3 shows preliminary design calculations for the collection system under this alternative. These calculations indicate that a total of approximately 13 pumping stations would be required for this alternative. Most of the pumping stations would be a wet well configuration with the control box installed at the top in a heated chamber. However, proposed Pumping Station J on the Baptiste Lake system would need a small building due to its larger pump sizes and operational requirements. Each pumping station would comprise two pumps (one duty and one stand-by) equipped with VFD’s, and all electrical and mechanical controls. Preliminary calculations indicate that approximately 60,000 m long pipelines would be needed for this alternative including approximately 26,370 m of pressure mains.
The order of magnitude opinion of probable cost for Alternative 2 is approximately $22,882,400, which includes 30% contingency and 15% engineering costs. The opinion of probable cost for this alternative is shown in Table 5.4.
This alternative will require installation of on-lot facilities such as septic tanks, building sewer connection and service connection etc. by the homeowners. Operation and maintenance costs for the pumping stations would be approximately similar to those under alternative 1. However, routine maintenance and cleaning requirements for the sewer system would be considerably less under this alternative.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.4 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010
Table 5.4 Alternative 2 – Opinion of Probable Cost Description Unit Quantity Unit Costs Costs Baptiste Lake System 75 mm Dia. Gravity Sewers l.m. 18,320 $170 $3,114,400 75 mm Dia. Force Mains l.m. 2,640 $90 $237,600 100 mm Dia. Gravity Sewers l.m. 4,450 $350 $1,557,500 100 mm Dia. Force Mains l.m. 5,860 $120 $703,200 125 mm Dia. Force Mains l.m. 3,080 $150 $462,000 150 mm Dia. Gravity Sewers l.m. 440 $720 $316,800 150 mm Dia. Force Mains l.m. 5,130 $190 $974,700 200 mm Dia. Gravity Sewers l.m. 150 $280 $42,000 200 mm Dia. Force Mains l.m. 3,560 $200 $712,000 Manholes v.m. 990 $2,000 $1,980,000 Pumps – 18 nos. Lump sum 1 $592,000 $592,000 Pump House Building Lump sum 1 $350,000 $350,000 Instrumentation and Controls Lump sum 1 $700,000 $700,000 Total Construction Costs $11,742,200 Contingencies (at 30% of Construction Costs) $3,522,700 Engineering (at 15% of Construction Costs) $1,761,300 Sub-Total $17,026,200 Island Lake System 75 mm Dia. Gravity Sewers l.m. 7,750 $100 $775,000 100 mm Dia. Gravity Sewers l.m. 2,160 $170 $367,200 100 mm Dia. Force Mains l.m. 2,220 $120 $266,400 150 mm Dia. Gravity Sewers l.m. 300 $1,310 $393,000 150 mm Dia. Force Mains l.m. 3,880 $190 $737,200 Manholes v.m 460 $2000 $920,000 Pumps – 20 nos. Lump sum 1 $200,000 $200,000 Instrumentation and Controls Lump sum 1 $380,000 $380,000 Total Construction Costs $4,038,800 Contingencies (at 30% of Construction Costs) $1,211,600 Engineering (at 15% of Construction Costs) $605,800 Sub-Total $5,856,200 Total Cost $22,882,400 Note: Unit costs for gravity sewers are based on weighted average burial depth
5.1.3 Alternative 3 - Low Pressure Sewer - Septic Tank Effluent Pumping (STEP) System
Low pressure – STEP system comprises of a network of pressure sewers which collects wastewater from the service areas for disposal to a central wastewater treatment facility. Under this alternative, raw sewage from the dwelling units will be collected in private underground
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.5 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010 septic tanks where most of the settleable solids and grease will be filtered out. The filtered wastewater will be then pumped to the main pressure sewer system that will ultimately discharge to the existing sewage lagoon. Since most of the solids would be retained in the septic tank, the pressure mains would require less hydraulic velocity. No manholes will be needed on the pressure sewer system. This would eliminate any inflow and infiltration from high stormwater and groundwater flows, considerably reducing design flows in the sewer system. According to preliminary design calculations, the pressure mains would range in size between 50 mm to 200 mm. Vertical alignment of the sewers would generally follow the land contours with their burial depth just below the frost line. This would result in considerable savings in the pipe excavation costs. A conceptual layout of the proposed low pressure sewer system for the service areas is illustrated on Figures 5.5 and 5.6.
Table 5.5 shows preliminary design calculations for the proposed low pressure system. The design flows are calculated using method developed by the United States Environmental Protection Agency (US EPA) for estimating design flows for low pressure systems. Preliminary hydraulic analysis and existing topography indicate that no lift stations would be required on the proposed conveyance system. The proposed hydraulic design utilizes a standard STEP pumping unit (serving single or multiple dwelling units), comprising 1 horsepower pump capable of discharging a minimum flow rate of 0.31 L/s (5 gpm) at a total dynamic head (TDH) of 100 m. The pump discharge rates would vary depending on the hydraulic conditions in the pumping unit and in the downstream sewer system. Total estimated length of the effluent mains for this system is approximately 51,000 m. Cleanouts, flushing stations and other appurtenances like air valves, pressure release valves etc. will be provided on the system at required locations.
This alternative will require installation of on-lot facilities by the homeowners including underground septic tanks, effluent pumping units, control panels and service connections. The existing septic tanks may require decommissioning or modifications depending on the type of pumping unit employed for this system. Septic fields would also be eliminated under this alternative.
Table 5.6 shows the order of magnitude opinion of probable cost for Alternative 3 which is approximately $9,696,300 including 30% contingency and 15% engineering costs. This opinion of probable cost does not include costs for the on-lot components of the system such as septic tanks, pumping units, control systems and servicing connections. The operation and maintenance costs associated with the main sewer systems would be minimal due to relatively filtered out effluent and elimination of extraneous flows into the system. The operation and maintenance costs for the on-lot pumping units can also be minimized by employing efficient water use practices by the homeowners.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.6 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010
Table 5.6 Alternative 3 – Opinion of Probable Cost Description Unit Quantity Unit Costs Costs Baptiste Lake System 50 mm Dia. Pressure Mains l.m. 5,040 $70 $352,800 75 mm Dia. Pressure Mains l.m. 11,800 $90 $1,062,000 100 mm Dia. Pressure Mains l.m. 5,760 $120 $691,200 150 mm Dia. Pressure Mains l.m. 13,960 $190 $2,652,400 200 mm Dia. Pressure Mains l.m. 2,240 $200 $448,000 Air Valves Each 30 $750 $22,500 Pigging Ports Each 5 $450 $2,250 Clean-Outs Each 30 $300 $9,000 Total Construction Costs $5,240,200 Contingencies (at 30% of Construction Costs) $1,572,100 Engineering (at 15% of Construction Costs) $786,000 Sub-Total $7,598,300 Island Lake System 50 mm Dia. Pressure Mains l.m. 2,170 $70 $151,900 75 mm Dia. Pressure Mains l.m. 4,770 $90 $429,300 100 mm Dia. Pressure Mains l.m. 2,210 $120 $265,200 150 mm Dia. Pressure Mains l.m. 3,090 $190 $587,100 Air Valves Each 10 $750 $7,500 Pigging Ports Each 3 $450 $1,350 Clean-Outs Each 15 $300 $4,500 Total Construction Costs $1,446,900 Contingencies (at 30% of Construction Costs) $434,100 Engineering (at 15% of Construction Costs) $217,000 Sub-Total $2,098,000 Total Cost $9,696,300
5.2 EVALUATION OF COLLECTION ALTERNATIVES
All the three alternatives discussed in the preceding section provide potential solutions for servicing the wastewater collection and conveyance system needs of the Summer Villages and County areas in Baptiste and Island Lakes. These alternatives have been analyzed on the basis of most recent planning layout for the service areas which has been assumed to represent ultimate development in these areas.
A conventional gravity sewer system (Alternative 1) will not require installation of on-lot facilities such as septic tanks and private pumping units by the homeowners. This relieves the homeowners from bearing the capital and operating costs for these on-lot facilities. The system would require decommissioning of any existing private collection systems whereas the service connection points may change from back to the front of houses. This alternative will require
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.7 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010 installation of several pumping stations and force mains on the conveyance system which will add significant capital and operating costs to the overall collection system. Since, the domestic sewage is collected in raw form, the gravity sewers will have to be a minimum 200 mm size whereas minimum hydraulic velocity and slope requirements will apply to achieve self-cleaning in the sewers. Manholes will be required at regular intervals and at all bends and junctions in the system to facilitate inspection and cleaning of the sewers. Inflow and infiltration through these manholes will considerably increase the design peak flows as well as add costs to the system.
A small diameter gravity system (Alternative 2) includes installation of underground septic tanks on the private property. Relatively filtered out effluent from these septic tanks is drained to the main gravity sewer system. The minimum size, velocity and slope requirements are accordingly reduced for the sewer systems. Also, manholes can be placed at larger intervals due to less maintenance requirements for this system. Moreover, effluent from these systems would typically require less treatment at the treatment facilities. This would result in some savings for the overall capital and operational costs of the collection and treatment systems. However, similar to alternative 1, this alternative will require installation of pumping stations and force mains on the main sewer system resulting in substantial capital and operational costs. Decommissioning or modifications to the existing tanks may be required for this alternative whereas the service connection points may change from back to the front of houses. Preliminary calculations indicate that this alternative would be more cost effective in comparison to alternative 1.
The alternative of low pressure STEP system offers certain advantages over the other two wastewater servicing alternatives evaluated in this study. Based on preliminary hydraulic calculations, this alternative would not require any lift stations and force mains on the proposed collection systems for the two lakes. This provides significant cost savings in terms of installation and operation of the overall conveyance system. However, installation and operational costs for the on-lot components of the collection system such as septic tanks, pumps, control systems and service connections etc. will be borne by the homeowners. These costs can be minimized by implementing pumping units to service multiple lots in the service areas. Existing lots may require decommissioning or modifications to their on-lot septic tanks depending on the type of pumping units employed for this system. Preliminary hydraulic analysis indicates that standard 1 horsepower effluent pumps would be adequate to service all the connections in this system. The STEP system primary receiving cell will require a pump –out based on usage and tank sizing. Typical installations require a pump-out every 1-2 years.
No manholes would be required on low pressure sewer systems which would prevent entry of any inflow/infiltration from surface flows or groundwater into the system. Effluent from the septic tanks would be essentially free of solids and would thus reduce treatment and overall maintenance requirements of the system. Preliminary calculations indicate that the main pressure sewers would range in size between 50 mm to 200 mm. The sewers would be laid at shallow depths below the frost line causing significant reduction in the excavation costs.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.8 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010
Installation of low pressure laterals can be implemented to coincide with the ongoing growth and development in the service areas. Service laterals from new subdivisions can be adequately connected to the main system as these areas are developed.
Based on ultimate 1358 lots estimated for the service areas, the cost share per lot under each servicing alternative is summarized in Table 5.7.
Table 5.7 Estimated Cost Share Per Lot for the Collection System Alternatives Alternatives Opinion of Probable Cost Cost Share Per Lot Conventional Gravity/Pressure Sewer System $28,474,200 $20,968 Small Diameter Gravity Sewer System $22,882,400 $16,850 Low Pressure Sewer System $9,696,300 $7,140
Evaluation of the above three alternatives indicates that Alternative 3 – low pressure STEP system provides the most cost effective and feasible solution for long term servicing needs of the Summer Villages and other County areas. Main factors leading to the selection of low pressure system as the most preferred alternative are listed as follows:
• Overall capital cost for the low pressure alternative is significantly less compared to the other two alternatives.
• Expensive lift stations and force mains would not be required.
• No manholes would be required on the conveyance systems.
• The overall system would be typically water-tight due to elimination of manholes and installation of water-tight septic tanks. Therefore, no provision for the inflow and infiltration from surface stormwater flows or groundwater would be required. This would significantly reduce the design flows in the sewer system and would subsequently reduce required sewer sizes and capacity for the wastewater treatment facilities.
• The pressure mains would generally follow the land terrain and would be installed at shallow depths, just below the frost line. This would provide significant savings in pipe installation costs and time.
• The low pressure sewers would be less sensitive to groundwater table.
• The homeowners will have to bear the costs of installation and operation of underground tanks, pumping units and lot service connections. Septic tanks on the existing lots will either have to be decommissioned or require modifications depending on the type of pumping units employed for this system. Preliminary analysis indicates a 1 horsepower effluent pump will be adequate for all the connections in this system. Standard STEP pumps of this size are expected to incur minimal energy costs. As a cost-saving
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.9 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT WASTEWATER COLLECTION ALTERNATIVES February 24, 2010
measure, community based pumping units can be installed to service multiple lots in the service areas and their costs shared among the respective customers. Moreover, pumping costs may act as an incentive for the homeowners to reduce flows.
• A centralized collection system would save the homeowners the costs of pumping and hauling sewage from their underground tanks to the sewage lagoon. Moreover, the practice of septic fields will be eliminated causing positive impact on the environment.
• A low pressure system would provide more flexibility with reference to the development and growth in the servicing areas. New subdivisions can be adequately connected to the system as they are developed, without impacting the operation of the main system.
Based on the above analysis, low pressure STEP system has been selected as this study’s recommended alternative for providing wastewater servicing to the Summer Villages and other communities around the Baptiste and Island lakes. This alternative will be further discussed in the following sections.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 5.10 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
6.0 Conceptual Design
6.1 GENERAL
No centralized wastewater collection system currently exists in the service areas. Growing awareness about the environmental issues and anticipated more stringent regulations from Alberta Environment have triggered the needs for implementation of a community collection system to service the wastewater requirements of these areas on a sustainable and more environmentally friendly basis. Several wastewater collection alternatives were evaluated under this study. A low pressure STEP system was recommended as the preferred alternative which provides a more economical and technically feasible solution to meet the existing and future servicing demands of these areas.
A low pressure system would comprise of a network of small diameter pressure sewers which would collect wastewater effluent from private pumping units for discharge to the existing sewage lagoon located on SE 23-67-24-W4.
6.2 ON – LOT FACILITIES
On-lot facilities would typically include underground septic tank, pump, alarms and control panels, building sewer connection, and service connection to the main sewer.
6.2.1 Septic Tanks
Septic tank sizing depends on the required reserve capacity, type of pumping units and number of dwelling units serviced by each facility. A septic tank servicing multiple dwelling units can provide a more cost effective arrangement if the units are located within reasonable proximity. However, this may result in issues between the homeowners like maintenance, ownership and pumping costs which can possibly be resolved through proper management and coordination between the homeowners.
It is estimated that 1000 to 1500 gallons septic tanks would be adequate to service single or multiple connections on the proposed system. These tanks should be completely water tight and should not allow any inflow and infiltration from surface stormwater or groundwater. Due to corrosive nature of the wastewater ingredients, the septic tank material must be highly resistant to corrosion. Typically septic tanks are available in materials of concrete, plastic, thermoplastic, fiberglass and coated steel.
Two-compartment septic tanks are commonly installed as part of on-site collection systems. However, more advanced tank designs are also commercially available as part of a complete pumping package. The design of these tanks allows retention of most of the settleable solids, grease and oil in the first cell whereas the filtered out water is drained into the second cell. This filtered wastewater is then pumped into the main sewer system.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 6.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conceptual Design February 24, 2010
Septic tanks would be equipped with required internal piping and appurtenances such as check valves, gate or ball valves, hose connections, level sensors etc.
6.2.2 Pumps
Each underground tank will be equipped with an effluent pumping system. The system hydraulic design has been based on provision of a standard effluent pump capable of discharging a minimum rate of 0.31 L/s (5 gpm) at a total dynamic head (TDH) of up to 100 m. Preliminary hydraulic calculations based on existing topography indicate that a 1 horsepower pump will be adequate to service each dwelling unit in the service area.
Various types of the STEP pumping packages are currently available in the market. An example would be the “ProSTEP” effluent pumping package manufactured by Orenco Systems which comes complete with fiberglass tank, filter wall, effluent pump, piping and control panels. However, final determination of the type and model of the pumping units for the proposed system should be made during the detailed design or tender stages of the project.
6.2.3 Control Systems
Typical pumping units are equipped with basic operational controls which can be configured according to the operational demands of the system. These control systems can include level sensors, alarms, pressure sensors etc. More advanced control systems have smart features such as digital programmable panels and remote telemetry panels. These advanced controls can allow setting of multiple parameters, and monitoring and communication system operation to suit the system requirements. However, the selection on type of control systems should be made based on detailed hydraulic analysis results for the proposed system and subsequent consultations with the stakeholders.
6.2.4 Opinion of probable Costs for On-Lot Facilities
The cost of on-lot facilities depends on the type and configuration of the pumping units and system controls used in the collection system. Some existing tanks will need modifications or decommissioning based on the requirements of the selected pumping units. This assessment should be done on case to case basis after final system design and thorough stakeholder consultation process.
Opinion of probable costs for the supply and installation of a typical STEP pumping unit is illustrated in Table 6.1.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 6.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conceptual Design February 24, 2010
Table 6.1 Opinion of Probable Costs for On-Lot Facilities Description Unit Quantity Unit Costs Costs
Septic Tank (1,000 gallons) Each 1 $4,500 $4,500
Effluent Pumping Unit c/w 1 hp pump, control Each 1 $4,500 $4,500 system, risers and accessories
Service Connections Each 1 $500 $5,00
Electricals and Accessories Each 1 $500 $500
Total Opinion of Probable Costs $10,000 Notes: 1). The opinion of probable costs is based on Orenco’s standard “ProSTEP” effluent pumping system. 2). Additional costs may be required for the decommissioning of existing tanks that are found incompatible with the selected pumping units.
6.3 LOW PRESSURE SYSTEM HYDRAULIC DESIGN
The design flows for the proposed low pressure system were calculated based on the equation developed in the US Environmental Protection Agency’s publication “Alternative Wastewater Collection Systems Design Manual (October 1991). This equation calculates the design flows corresponding to the required number of connections serviced by the pressure sewer. The equation has been derived by drawing a best fit on the results from some other relationships currently used by various manufacturers of the STEP systems. The simplified form of this equation is listed as follows:
Q = A x N +B
Where
Q is the peak flow in gallons per minute
A is a coefficient selected based on the occupancy rate used, typically it is 0.5
N is the total number of dwelling units serviced by the pressure sewer, and
B is a constant used to establish a minimum flow rate in the system. Typical value of this constant varies from 15 to 20 depending on the total number of dwelling units.
Preliminary hydraulic calculations resulted in design flows of 27.8 L/s and 16.9 L/s for the Baptiste Lake and Island Lake areas, respectively.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 6.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conceptual Design February 24, 2010
The sewer system is designed using Hazen-William’s equation for calculating friction head loss in the pipes. A friction coefficient of 140 was used in the calculations for plastic pipes (PVC or HDPE). A PVC or HDPE pipe with a pressure rating of 160 psi should be sufficient to meet the pressure requirements for the proposed system. Both types of pipes are currently used in wastewater applications and have essentially identical hydraulic characteristics. However, final determination of the material and type of the pipe should be made at the detail design stage of the project.
Pipe sizes have been selected based on preliminary hydraulic analysis results while maintaining the total dynamic head and minimum hydraulic velocity values within allowable limits.
6.4 PIPELINE ALIGNMENT
The proposed low pressure sewers have been proposed along the internal streets of the service areas and County roads, as shown in the most recent legal survey plan. The proposed Baptiste Lake system is routed to the existing sewage lagoon from two different directions. One main line starts from the northern end of the South Baptiste and first runs south, then east and then travels north along the County roads towards villages of Sunset Beach and Whispering Hills. The pipeline will have a crossing at the Baptiste Lake Creek through an inverted siphon. The pipe installation technique at this creek should be decided at the detail design stage when results from the geotechnical investigation become available.
The second main line runs north along the west side of the Baptiste Lake, originating from the southern end of the West Baptiste and then joins the pressure main coming from the east side of the Baptiste Lake at the intersection of Twp. Road 672 and RR 241. The combined main then travels north along the west side of Highway 2 to terminate at the existing sewage lagoon.
The proposed low pressure pipeline in the Island Lake area will run along the area internal roads to join the main line at Tranquille Drive which will run south to travel through the Beaver Avenue in the summer village of Island Lake South. This proposed 150 mm main sewer will then run west along the Twp. Road 674 to cross Highway 2 via trenchless installation. This pressure main will then travel south along the west side of Highway 2 to terminate at the existing sewage lagoon.
County of Athabasca land ownership map indicates that the majority of land along the west side of Highway 2 belongs to the Hutterian Brethren Church of Athabasca and the County of Athabasca. Since, an open cut method is recommended for sewer installation, conservation and reclamation practices will need to be employed to restore the land to its original use. Also proper agreements will have to be adopted for sewer crossing through private lands.
Majority of existing area roads are gravel. The pipelines, therefore, can be installed using open cut methods. The pipes would be installed at shallow depths, typically 2 to 3 m below the ground elevation. No information is currently available regarding existing utilities and other
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 6.4 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conceptual Design February 24, 2010 services in the study area. It is recommended that horizontal and vertical alignments of the proposed pipelines should be determined at the detail design stage after reviewing data on existing utilities and geotechnical investigations.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 6.5 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
7.0 Decentralized Collection Alternative
7.1 GENERAL
Where circumstances warrant, consider decentralized approaches to a full collection system servicing all of the Summer Villages. These circumstances may include high cost, physical and environmental constraints and other wastewater management concerns. If decentralized options are pursued, a scope and budget will be provided for approval.
7.2 DECENTRALIZED COLLECTION SYSTEM
The installation of a community wastewater system has the benefit of providing wastewater service through a single wastewater system. An alternative to a single regional system is the installation of decentralized systems to service specific areas. The benefit of the decentralized system alternative is that this alternative typically doesn’t require the pumping stations and pressure mains necessary for a regional system. In an effort to evaluate the potential benefits of a decentralized approach for this project, the South Baptiste Lake area was evaluated for the use of a decentralized system. This alternative was evaluated in comparison to the conventional gravity/pressure system analyzed in preceding sections for a regional wastewater system.
If a decentralized system were installed in this area it would have the following impact on the infrastructure requirements:
1. Elimination of approximately 3,500 meters of forcemain
2. Elimination of one lift station
3. Addition of a small treatment and disposal system to service the South Baptiste Lake area
7.2.1 Financial Impacts
The financial impacts to the project that would result from removing the South Baptiste Lake wastewater from the regional system and treating this wastewater in a system specifically for the South Baptiste Lake area are as follows:
• If a surface water discharge is utilized for the disposal of the treated wastewater, the estimated costs would be the same for the regional alternative and the decentralized alternative.
• If a land disposal system (infiltration beds, trenches, or drip disposal) were utilized for the disposal of the treated wastewater, the estimated cost for the decentralized
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 7.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Decentralized Collection Alternative February 24, 2010
alternative would be between $100,000 and $200,000 higher than the regional alternative depending on the area utilized for the disposal system.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 7.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
8.0 Potential Social and Ecological Impacts
8.1 IMPACTS ON WATER USE
With the current individual systems, Owners are very aware of how long the system can go between pumping episodes, particularly if this system is a holding tank. Along with this awareness is a sense of how water usage impacts the pumping interval of the individual system. After the installation of a community collection system, water use may temporarily trend upward, because system users may not perceive the same level of importance with water conservation as they did with their individual systems. Ultimately the use of water by individuals will be most likely impacted by actions taken by the Responsible Management Entity (RME) the requirements for low flow fixtures and a campaign to educate the public on the smart use of water. Finally, the cost of water charged to the system users will likely be the biggest determinant in the amount of water utilized by the individual users. It is important that the RME sets the cost of wastewater, and the cost for collection and treatment of discharged wastewater, at rates that are appropriate for the provision of these services, as well as including the long term costs to operate and maintain this infrastructure.
8.2 IMPACTS ON NEW DEVELOPMENT
When lake areas are developed, it is not unusual for individual lot owners to purchase additional lots for future development, or to leave as a buffer between homes. It may also be the case that the original land owner retained tracks of the land for agricultural use or future development. When community sewers are installed, the cost for this installation, as well as the cost for operation of the facilities, is typically assessed against lot owners. In situations where all lots are assessed a similar amount, the undeveloped lots are forced to develop in order to justify the cost for the water and wastewater system charges. One way to mitigate this impact is to delay charging undeveloped lots until these lots are developed. This strategy results in a larger burden being placed on the development authority because the capital costs and operational costs will typically need to be borne by the development authority until these lots are developed and the costs repaid.
In addition to residential development, the installation of a community system may also stimulate commercial development. Some commercial development requires the treatment typically provided by a community system, and the installation of community collection, treatment and disposal systems may stimulate some commercial development.
Finally, the development of a wastewater collection system around a lake may stir secondary development away from the lake. A large cost of a wastewater system is the installation of the collection system. In some areas, adjacent tracks of land may choose to develop if they are allowed to connect to the community wastewater system.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 8.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Potential Social and Ecological Impacts February 24, 2010
Mitigation measures for the commercial development and adjacent residential development is typically handled through zoning ordinances and the sewer use ordinance. These ordinances can encourage or discourage commercial and secondary residential development, as well as vacant lot development. The sewer use ordinance should allow the Responsible Management Entity (RME) to control access to the wastewater system based on procedures established in the sewer use ordinance.
8.3 POTENTIAL ENVIRONMENTAL IMPACTS
Based on the proposed route for the collection system, some environmental impacts will occur. These potential impacts will include a stream crossing, a wetland crossing, and potentially crossing through areas with rare plant and/or animals existing. In order to identify the extent of these impacts, a biophysical evaluation of the proposed collection sewer system routes, as well as the treatment system site, will be required once the alignment is finalized. In addition to the environmental impacts, other impacts associated with the project construction should be identified and considered. These impacts include crossing of existing utilities, crossing of railroad lines, and crossing of major roads.
The existing individual septic systems are potentially negatively impacting the environment due to the age of some of the systems, as well as the potential for lack of operational care of the existing systems. The evaluation should also consider the positive impacts to the environment that will result with a proposed community wastewater system, including the reduction in pollution that will occur when the individual septic systems are removed from service and a community wastewater system is installed under professional management.
Through the implementation of a collection system, the environmental impact of pumping out tanks and hauling them to the septage receiving lagoon will decrease dramatically. Areas of concern that be affected are a reduction in traffic noise, reduction in fuel consumption and exhaust to transport the wastewater, reduced impact on road infrastructure and a reduction in odours that can be generated from pumping and transporting.
After these impacts are identified, a summary report should be prepared that discusses the various impacts, and the mitigation measures that will be taken to minimize these impacts. Moreover, costs associated with these impacts should also be identified.
8.4 MANAGEMENT AND OPERATIONS FRAMEWORK FOR THE PROPOSED WASTEWATER SYSTEM
A Responsible Management Entity (RME) should be identified for managing the infrastructure established. Typically the RME is a governmental agency such as a County or a Municipal District, however, the RME can also be a private entity if this model is selected by the project owner. The RME will be responsible for the operation and maintenance of the collection and treatment system, with the goal of optimizing service to the community over long term. The RME
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 8.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Potential Social and Ecological Impacts February 24, 2010 should administer the sewer use ordinance and collect fees necessary to support the operation and maintenance of the infrastructure. The RME should select a competent operator, who is certified in Alberta, to operate and maintain the wastewater system. The RME should administer a program to maintain the infrastructure, and rely on input from the operations staff on the condition of the system and the projected capital needs.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 8.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
9.0 Existing Sewage Lagoon Assessment
9.1 GENERAL
The Island – Baptiste Lake sewage lagoon was constructed in 1988-1990 by the County of Athabasca in conjunction with the Summer Villages of Island Lake, Island Lake South, Whispering Hills, West Baptiste, South Baptiste, Sunset Beach and White Gull. The lagoon is located in the land between the two lakes in the SE-23-67-24 W4. The lagoon is currently under direct management and control of the County and serves the wastewater collection and treatment needs of the County and all the Summer Villages in the region.
According to the as-built data, the existing facility operates as an evaporation lagoon. The lagoon has an operating capacity of 24,400 m³ at a maximum operating depth of 1.5 m. The lagoon’s bottom elevation is 615.0 m, the top of berm elevation is 617.1 m, and a freeboard of 0.6 m. The lagoon has a surface area of 17,890 m² at the design high water level.
9.2 LAGOON SITE INSPECTION
Stantec visited the existing lagoon site on November 20, 2009 to become generally familiar with the work and to determine existing conditions. The following Field Review Report is broken down into 3 parts. The Observations section is a list of deficiencies or observations noted during the visit. The Discussions section is a summary of items discussed with a local hauler who unloaded during the site visit. The Recommendations section pertains to work that appears to be required for the continued operation of the lagoon under the current conditions. Photographs taken during the site inspection have been included in Appendix A.
9.2.1 Observations
Following observations were noted by Stantec during visit to the existing lagoon site on November 20, 2009:
• Official truck unloading facility was clean at surface.
• Small cell has some sludge and willows.
• Main cell around the small cell appears to have sludge deposits. Small willows and cattails are growing.
• The berms appear to be in good condition. There is a good growth of grass on the berms. Cattails at the water line appear to provide some erosion protection.
• The perimeter fence is generally in good condition but needs some maintenance. The fence at the small cell has been removed to facilitate truck unloading.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 9.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Existing Sewage Lagoon Assessment February 24, 2010
• There was no evidence of seepage at the berms or in the surrounding fields. There were no obvious wet spots or locations where the vegetations looked unusually lush or typical of wet ground conditions.
• One of the two culverts appeared to be at least partially blocked with dirt.
• There was some erosion evident in the ditch south of the south berm of the lagoon.
• The lagoon appeared to have about a 300 mm depth of effluent. The depth appeared to be about typical for the year round operation under current loading.
• The Southeast corner of the lagoon berm was eroded due to turbulence from truck unloading operations. There was evidence of large rip rap being dumped into the scour hole. The riprap alone has not appeared to have stopped the scour.
• The existing gravel road appeared to be well maintained, graveled and in good condition.
9.2.2 Discussions
Following is a summary of items discussed with a local hauler who unloaded sewage at the lagoon during the site visit:
• The truck driver indicated that there were two main commercial haulers of domestic septage who used the lagoon and one oilfield hauler who occasionally brought sanitary wastes from oil field facilities. These large trucks dump directly at the lagoon.
• The truck driver also said there or a few residents who haul their own sewage to the facility. The residents tend to dump at the facility at the top of the hill. He indicated that this worked during the summer but during the winter the sewage tends to back up, overflow the manhole and flow down to road causing an ice build-up.
• The truck driver stated that there was rarely more than 300 to 450 mm of effluent in the lagoon and that capacity did not seem to be a problem with current loading.
• The truck driver would like to see the unloading facilities at the lagoon improved so erosion was not an issue.
• He indicated that small poplars and willows growing in the lagoon had periodically been cut back or removed as required.
• He believed that the lagoon was built in an extensive deposit of clay or clay till.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 9.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Existing Sewage Lagoon Assessment February 24, 2010
9.2.3 Recommendations
Following are the recommendations pertaining to the work that appears to be required for the continued operation of the lagoon under the current conditions:
• The existing layer of sediment in the small cell should be removed and the discharge pipe from the unloading facility located. This could likely be done by carefully excavating with a backhoe or Gradall from the berm. Care should be taken to prevent damage to the berms, clay liner, or the inlet piping.
• The pipe from the truck unloading facility should be cleaned. This could include flushing with a power flusher, CCTV camera inspection etc.
• The existing layer of sediment main cell could be cleaned to maintain capacity. Part of the sediment could be removed from the berm. Sediment further from the berm may possibly be removed during winter conditions from the ice.
• The barbed wire fence should be repaired. If truck unloading is to continue at the lagoon the fence needs to be adapted to accommodate this activity while maintaining the security of the site.
• The blocked culvert should be cleaned to maintain drainage and prevent a road washout.
• Some restoration and additional erosion protection measures should be taken to protect the toe of the berm. This could include filling the scour channel with topsoil, adding some erosion control blanket and seeding and perhaps adding a few synthetic ditch checks.
• If truck unloading is expected to continue at the lagoon, modifications are required to accommodate the practice.
• Tree and willow growth within the lagoon should be controlled. Shallow rooted vegetation can withdraw nutrients and promote evapotranspiration. Plants such as poplar and willow, with deep or extensive root systems can be considered as a threat to the liner and are therefore discouraged.
9.3 CAPACITY ASSESSMENT OF EXISTING SEWAGE LAGOON
The existing facility currently operates as an evaporation lagoon. Based on the criteria in “Alberta Private Sewage Systems Standard of Practice (2009)”, the existing lagoon surface area of 17,890 m² would be able to service a very small population. It is anticipated that with implementation of the proposed collection system, an alternative method of wastewater treatment to an evaporation lagoon will be required to service the design population. It is
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 9.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Existing Sewage Lagoon Assessment February 24, 2010 recommended that detailed assessment of the wastewater treatment system needs for the service areas should be conducted as part of a separate study.
9.4 TREATMENT AND DISPOSAL CONSIDERATIONS
Based upon our design criteria in section 4, the existing evaporative lagoon capacity is not sufficient to treat the expected flows that will be generated once a collection system is implemented. Should a collection system be constructed, a new treatment facility and disposal strategy will need to be evaluated. In order to determine the most appropriate treatment and disposal strategy, a Treatment and Disposal Feasibility Study will need to be preformed. In consideration of this work, the following are the comments on treatment and disposal options.
9.4.1 Treatment
Waste water lagoons – There are 3 basic waste water lagoon designs. An evaporative lagoon is designed in such a way to maximize the water surface area to promote evaporation as a means of water disposal. Evaporative lagoons do not provide a level of treatment where discharge is permitted. The land required is significantly more than other lagoon designs. The advantage is that they are simple to operate and depending on the cost to purchase land they can be the least expensive to construct. Facultative lagoons offer a higher level of treatment in that wastewater is conveyed (typically by gravity) from an anaerobic cell to a facultative cell then to a storage cell from which the water can be released seasonally to the surrounding environment. These lagoons are slightly more expensive to construct and more complex in their treatment process, however still quite easy to operate. Aerobic lagoons differ from evaporative and facultative lagoons in that they are oxygenated via large blowers. They are the most complex and have the highest operation and maintenance costs of the 3 types of lagoon systems. They provide a high level of treatment in a small area and can be discharged continually or seasonally depending on the receiving environment.
Mechanical treatment plants - Mechanical treatment plants offer many advantages over wastewater lagoons. They can treat very large volumes and loadings in a very short period of time and produce a higher quality effluent that can be discharged into more sensitive receiving environments or reused for irrigation. Mechanical treatment plants are more expensive to construct than lagoon systems and require a higher level of operations.
9.4.2 Disposal
There are several options available to dispose off the treated wastewater. Depending on the type of disposal, different treatment options are appropriate. Some disposal options to consider are:
• Subsurface Soil Disposal • Wetland Discharge
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 9.4 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Existing Sewage Lagoon Assessment February 24, 2010
• Spray Irrigation • Surface Water Discharge
Each of these options has advantages and disadvantages associated with them and require different levels of treatment of the wastewater prior to disposal. In some disposal situations additional treatment may be required to achieve higher levels of treatment prior to disposal. Each disposal option also comes with regulatory considerations and the requirement for approval. Approvals can have varying levels of complexity depending on the receiving environment
9.4.3 Additional considerations
The items listed below are additional considerations that one must evaluate before selecting a treatment and disposal strategy. A treatment and disposal feasibility study will be required to identify the advantages and disadvantages as well as the best course of action to take based on the community needs.
• Proximity to neighbouring lands, dwellings and water bodies
• Proximity to receiving soils or water course.
• Cost to purchase land
• Operational capability of the user
• Regulatory considerations
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 9.5 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
10.0 Conclusions and Recommendations
The conclusions and recommendations for the wastewater servicing of the Summer Villages of Island - Baptiste Lakes are outlined below:
• A total 1358 lots in Baptiste and Island Lakes were identified that will need wastewater servicing based on the most recent planning layout and assumptions made for the number of lots in some new subdivisions in the area. Based on discussions with the Summer Villages, an average occupancy rate of 3.0 persons per lot was used in this study to estimate design peak flows for the study areas. This resulted in an ultimate population of 4,071 people in the service areas.
• Sewage generation rates and peaking factors used in this study are based on the guidelines in Alberta Environment’s Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems (January 2006) and Alberta Private Sewage Systems Standard of Practice (2009).These guidelines specify daily average and peak wastewater generation rates of 228 L/person and 340 L/person, respectively, for the residential land uses.
• No wastewater sewer system currently exists in the study areas. Majority of lots in the study areas collect domestic wastewater in on-lot tanks from which it is periodically pumped and hauled either to the existing evaporation lagoon located in SE-23-67-24-W4 or to the septic fields in the area.
• Three alternatives for centralized wastewater collection system were identified and evaluated in this study, which included: (1) Conventional gravity/pressure sewer system, (2) Small diameter gravity/pressure system, and (3) Low pressure sewer – STEP system.
• Preliminary hydraulic calculations indicated that several pumping stations and lengthy force mains would be required for both conventional gravity sewer and small diameter gravity sewer system alternatives. Significant capital and operational costs would be associated with these pumping stations resulting in substantial increase to the project’s overall costs.
• Preliminary calculations resulted in opinion of probable costs of approximately $28,474,200 for Alternative 1; approximately $22,882,400 for Alternative 2; and approximately $9,696,300 for Alternative 3. All these costs include 30% contingency and 15% engineering costs. The opinion of probable costs for Alternatives 2 and 3 do not include costs for the on-lot facilities which are anticipated to be handled on individual basis.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 10.1 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conclusions and Recommendations February 24, 2010
• Based on the preliminary calculations, Alternative 3 – Low Pressure STEP System was found to be the most economical alternative for providing long term sanitary servicing for the service areas. This alternative would not require any pumping stations on the main sewer system. However, small pumping units will be required on individual lots to discharge filtered-out sewage to the main pressure sewer system. Based on the comparative analysis, low pressure STEP system has been selected as this study’s recommended alternative.
• The proposed low pressure system would comprise of a network of small diameter pressure sewers that collects wastewater from private septic tanks for ultimate discharge to the wastewater treatment facility. Preliminary hydraulic calculations indicate that required sewer sizes would range between 50 mm to 250 mm for the proposed collection system.
• The design flows for the proposed low pressure system were calculated based on the equation developed in the US Environmental Protection Agency’s publication “Alternative Wastewater Collection Systems Design Manual (October 1991)”. This equation calculates the design flows corresponding to the required number of connections serviced by the pressure sewer. The equation has been derived by drawing a best fit on the results from some other relationships currently used by various manufacturers of the STEP systems. The simplified form of this equation is listed as follows:
Q = A x N +B
Preliminary hydraulic calculations resulted in design flows of 27.8 L/s and 16.9 L/s for the Baptiste Lake and Island Lake areas, respectively.
• No manholes would be required on the proposed low pressure system. This would eliminate any inflow and infiltration from surface stormwater or groundwater into the system resulting in considerable reduction in the design flow rates.
• The proposed low pressure sewers would generally follow the land contours and would have a shallow burial depth between 2.5 m to 3 m. The horizontal alignment of the sewers is proposed along the service areas’ existing streets and regional roads. However, final horizontal and vertical alignments of the proposed system should be decided at the detail design stage based on geotechnical recommendations and existing utilities information.
• The proposed sewer would require crossings at the existing Baptiste Lake Creek and Highway 2. An inverted siphon crossing would be required at the Baptiste Lake Creek whereas trenchless installation of the pressure sewer would be needed at the Highway 2
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 10.2 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conclusions and Recommendations February 24, 2010
crossing. All other regional roads are currently gravel where open cut installation of the sewers would be feasible.
• The proposed system will require installation of on-lot facilities such as septic tanks, pumps, alarms, control panels and service connections by the homeowners. Typically, 1000 to 1500 gallons septic tanks would be required depending on the type of pumping units and number of dwelling units served by each facility.
• Based on preliminary hydraulic calculations and existing topography, standard 1 horsepower effluent pumps would be adequate to service each connection in the study area. This pump would be capable of discharging a minimum rate of 0.31 L/s (5 gpm) at a total dynamic head (TDH) of up to 100 m. The pumping rate would vary depending upon the hydraulic conditions in the pumping unit and downstream main sewer system.
• Each pumping unit will be equipped with appropriate alarms and controls, such as level sensors, pressure sensors etc., which can be configured according to the operational demands of the system. More advanced control systems have smart features like digital programmable panels and remote telemetry panels. However, the type of pumping units and control systems should be selected based on detailed hydraulic analysis and stakeholder’s consultation.
• Average cost of on-lot facilities would depend on the type and configuration of the pumping units and system controls used in the proposed system. Some existing tanks would need modifications or decommissioning based on the requirements of the selected system. Opinion of probable costs for the supply and installation of on-lot facilities with a standard STEP pumping unit would be approximately $10,000.
• The existing Baptiste – Island Lake lagoon operates as an evaporation lagoon. According to the as-built data, the lagoon has an operating capacity of 24,400 m³ at a maximum operating depth of 1.5 m. Based on the criteria in “Alberta Private Sewage Systems Standard of Practice (2009)”, the existing lagoon surface area of 17,890 m² would be able to service a very small population. It is anticipated that with implementation of the proposed collection system, an alternative method of wastewater treatment to an evaporation lagoon will be required to service the design population. It is recommended that detailed assessment of the wastewater treatment system needs for the service areas should be conducted as part of a separate study..
• An alternative to a single regional wastewater collection system is the installation of decentralized collection systems to service specific areas. In an effort to evaluate the potential benefits of a decentralized approach for this project, the South Baptiste Lake area was evaluated for the use of a decentralized system and the results were compared against a conventional gravity/pressure sewer system analyzed under the regional collection system alternatives. The evaluation process indicated that a
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 10.3 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT Conclusions and Recommendations February 24, 2010
decentralized system would eliminate approximately 3,500 m of forcemains and one pumping station while it would add a small treatment and disposal system to service the South Baptiste Lake area.
• Preliminary assessment of the decentralized system indicated that if a surface water discharge is utilized for the disposal of treated wastewater from the South Baptiste Lake area, the estimated costs would be the same for the regional collection system and the decentralized system alternatives. If a land disposal system (infiltration beds, trenches or drip disposal) were utilized, the estimated cost for the decentralized alternative would be between $100,000 and $200,000 higher than the regional alternative depending on the area utilized for the disposal system. Based on this evaluation, a decentralized system does not provide an economically feasible alternative and has not been recommended in this study.
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 10.4 ISLAND LAKE- BAPTISTE LAKE WASTEWATER COLLECTION FEASIBILITY STUDY
FINAL REPORT
Appendix A EXISTING LAGOON FIELD REVIEW REPORT
rd v:\1101\active\110126009_island lake\5.0 planning\final report\final_report-feb222010_rbd rev 4.doc 10.1