1. DEPARTMENT OF
CIVIL ENGINEERING
TOWN OF HARTLAND
CLIMATE CHANGE RISK ASSESSMENT
FINAL DESIGN BRIEF
by
Ben Connolly
Tyler Harris
Nicholas Phelan
Ryan Steeves
Benjamin Taylor
A Report Submitted in Partial Fulfillment of the Requirements for
CE4973
Instructor: Dr. Bruce Wilson, P.Eng
April 9, 2012
2. Disclaimer
This report presents the work of a student project at the University of New Brunswick.
Although the studentsโ work was reviewed by a faculty advisor, that review does not
constitute professional certification of the work. Any design, analysis, or calculations
contained in this report must be reviewed by a professional engineer before
implementation. This report is made available without any representation or warranty and
on the strict understanding that the reader accepts full liability for the application of any
of the contents of the report.
3. Letter of Transmittal
Total Engineering
17 Dineen Drive
P.O. Box 4400
Fredericton, N.B.
E3B 5A3
April 9, 2012
Rory C. Pickard, P.Eng
Linda Brown, CAO, Town of Hartland
Dear Rory C. Pickard and Linda Brown:
RE: Town of Hartland-Climate Change Risk Assessment
Enclosed is the design brief for the above-captioned report. This report was prepared as
per the request to assess the risks that are associated with climate change and how these
risks are going to affect the Town of Hartlandโs municipal assets.
The project was initially introduced to Total Engineering in January 2013. With a
growing concern of a changing climate, municipalities are becoming more aware of the
need for mitigation techniques to reduce the effects of climate change. Total
Engineeringโs goal was to develop preliminary strategies that will help reduce the effects
on municipal assets due to a changing climate. Having a limited time frame to complete
the project, Total Engineering ranked the assets and came up with mitigation strategies
for the wastewater system (including the lagoon), storm water system, and lagoon.
This report outlines the scope of the project, methods for determining municipal assets
for the project, mitigation strategies developed for each potential asset, assumptions
made during the project, and any recommendations Total Engineering has for the Town
of Hartland.
Total Engineering aims at providing the Town of Hartland with innovative engineering
ideas that can be realistically implemented into the town to mitigate the effects of
climate change.
Sincerely,
Total Engineering
Ben Connolly
Tyler Harris
Nicholas Phelan
Ryan Steeves
Benjamin Taylor
4. ii
Executive Summary
The Town of Hartland wished to gain an understanding of the impact that climate change
will have on its municipal assets and operations. Gaining this understanding, an adaption
strategy was developed to mitigate the risks of climate change. With a proper risk
assessment and strategy in place, decisions can be made to effectively allocate public
funds to better prepare for the effects caused by climate change.
Total Engineering performed a climate change risk assessment that identified the
problems and vulnerability of the municipal assets within the Town of Hartland. Due to
the time constraint of the project, Total Engineering used a multi-criteria evaluation to
rank the assets that would be the most beneficial for further investigation for the town.
The results of the evaluation determined the storm water system and wastewater system
(including the lagoon) were to be further assessed for mitigation strategies.
The team developed a low-level storm water management system along McLean Avenue
that can also be installed on the New Brunswick walking trail. The implementation of this
will be done in three phases to reduce costs and gain the most benefits as early as possible.
This strategy will allow for the greatest amount of catchment of run-off to reduce soil
erosion, roadside pavement cracking and deterioration, maintenance costs and operations,
pooling of water in residential lots, sediment transfer (siltation), and increase traffic safety.
The team also recommended the use of Low Impact Design (LID). A LID is an upcoming
design philosophy being using to reduce the effects of climate change by having smaller
design placed more frequently over an area to reduce the effects to the environment. Some
of the types of LIDs that were recommended for the town were catch basin inserts and
filtration socks, tree box filter storm drains, rain gardens, grassy swales, and bovine
terraces.
The lagoon is a valuable asset to the Town of Hartland and has been in danger of being
breached. The two solutions that were implemented to protect the lagoon are a removable
floodwall (RFW) and a berm and concrete wall combination. The barriers were estimated
to be built at a height of 1.25m to 2.0m to reduce the risk of the flooding topping over the
barrier.
The team recommended that the storm water system and wastewater be separated where
the locations are interconnected. A total of four connections were found within the town
with the given network layout. The separation will provide a longer service life to the
force pumps, reduce costs for treatment, and reduced the risk of a combined sewage
overflow. With the implementations of the storm water system and LIDs, the wastewater
system will gain the same benefits from separation benefits from having reduced inflow.
5. iii
The team has recommended the following implementation strategy, in order, for the Town
of Hartland: Phase 1-Storm Water Management System, RFW or berm and concrete wall
combination, Phase 2-Storm Water Management System, storm water and wastewater
separation, Phase 3-Storm Water Management System, and while continually promoting
the use and implementation of LID around the town.
6. iv
Acknowledgments
Total Engineering would like to show its appreciation to Rory C. Pickard, a professional
engineer and Office Manager at Dillon Consulting in Fredericton, New Brunswick. Mr.
Pickard has provided the team with essential information required to complete the climate
change risk assessment, along with the sharing of engineering knowledge and local
knowledge of the town.
Appreciation is given to the mentors of the project, Dr. Eric Hildebrand and Dominic
Richard, for their time in providing their engineering knowledge from an academic and
industry perspective. Their additional time to review and provide suggestions to
documents proved to be detrimental in completing the project in a timely manner.
Total Engineering would also like to show its appreciation to Dr. Nassir El-Jabi, an
engineering professor at the Universitรฉ de Moncton in the Civil Engineering Department.
Nassie El-Jabi has provided the team with documents outlining predicted climate change
events in the Province of New Brunswick along with potential contacts if further
information was required.
Finally we would like the thank Linda Brown, CAO from the Town of Hartland for taking
the time for the site visit around town and identify some the current problems the town is
experiencing.
7. v
Table of Contents
Executive Summary ...................................................................................................ii
Acknowledgments ....................................................................................................iv
List of Tables.............................................................................................................vi
List of Figures ...........................................................................................................vi
1 Introduction........................................................................................................ 1
1.1 Background and Problem Statement........................................................................1
1.2 Goal and Objectives.................................................................................................2
1.3 Scope......................................................................................................................2
2 Evaluation of Municipal Assets............................................................................ 2
2.1 Information.............................................................................................................2
2.2 Constraint Methodology..........................................................................................3
2.2.1 Vulnerability to Climate Change............................................................................... 3
2.2.2 Public Safety.............................................................................................................. 4
2.2.3 Economics................................................................................................................. 4
2.2.4 Environmental........................................................................................................... 4
2.2.5 Adaptability............................................................................................................... 4
2.2.6 Political...................................................................................................................... 4
2.3 Methodology / Approach.........................................................................................5
2.4 Discussion and Summary of Results .........................................................................5
3 Potential Mitigation Strategies - Storm Water System ......................................... 5
3.1 Storm Water Management System With Detention Pond .........................................6
3.1.1 Information............................................................................................................... 6
3.1.2 Working Assumptions............................................................................................... 7
3.1.3 Methodology/Approach ........................................................................................... 8
3.1.4 Recommendations.................................................................................................. 10
3.2 Low Impact Designs...............................................................................................16
3.2.1 Information............................................................................................................. 16
3.2.2 Working Assumptions............................................................................................. 16
3.2.3 Potential Solutions.................................................................................................. 17
3.2.4 Recommendations.................................................................................................. 20
4 Potential Mitigation Strategies - Wastewater System and Lagoon.......................21
4.1 Information...........................................................................................................21
4.2 Working Assumptions............................................................................................22
4.3 Methodology/Approach ........................................................................................22
4.4 Potential Solutions ................................................................................................23
4.4.1 Removable Floodwall.............................................................................................. 23
4.4.2 Combination of Berm and Concrete Wall............................................................... 24
4.4.3 Separation of Storm Water System from Wastewater System.............................. 26
4.5 Recommendations.................................................................................................28
5 Recommendations for Implementation Strategy ................................................29
6 References.........................................................................................................31
Appendix A - Municipal Asset Selection
Appendix B - IDF Curves Used for Assessment
Appendix C - Rational Method Calculations
Appendix D - Preliminary Design for Ditches
Appendix E - Detention Pond Area Check
8. vi
List of Tables
Table 1-Listing of Assets to be Evaluated .........................................................................3
Table 2-Examples of Ditch Lining, Vegetation, and Ditch Checks.................................12
Table A1-Weighting and Scale for Constraints .............................................................A.2
Table A2-Results of Delphi Model................................................................................A.2
List of Figures
Figure 1-Location of Hartland, NB....................................................................................1
Figure 2-Map Showing Location of McLean Avenue and NB Walking Trail ..................6
Figure 3-Catchment Areas for McLean Avenue................................................................9
Figure 4-Storm Water Management System Layout for McLean Avenue......................10
Figure 5-Typical Ditch Cross Section for McLean Avenue ............................................11
Figure 6-Phase 1 Storm Water System ............................................................................13
Figure 7-Phase 2 Storm Water System ............................................................................14
Figure 8-Phase 3 Storm Water System ............................................................................15
Figure 9-Catch Basin Insert .............................................................................................17
Figure 10-Filtration Socks ...............................................................................................17
Figure 11-Tree Box Filter Storm Drains..........................................................................18
Figure 12-Land Development for Rain Gardens Section View.......................................19
Figure 13-Land Development for Rain Gardens Profile View ........................................19
Figure 14-Example of a Bovine Terrace..........................................................................20
Figure 15-Historical Flood Levels for Hartland, NB.......................................................22
Figure 16-Typical Profile/Cross Section of Removable Flood Wall...............................24
Figure 17-Concrete Cantilever Wall ...............................................................................25
Figure 18-Berm Cross Section ........................................................................................26
Figure 19-Combined Storm Water and Wastewater System Points ................................28
Figure 20-Overall Cost vs. Overall Impact of Solutions for Implementation..................30
Figure A1-Results of Multi-Criteria Evaluation ............................................................A.4
Figure B1-Modified IDF Curve for Prediction Mid-Century ........................................B.2
Figure B2-Modified IDF Curve for Prediction 2081-2100............................................B.3
Figure C1-Seeley Chart..................................................................................................C.7
9. 1
Figure 1-Location of Hartland, NB
1 Introduction
1.1 Background and Problem Statement
The Town of Hartland is a small rural community of approximately 1000 residents that is
located along the Saint John River in the western portion of New Brunswick. The green
dot, in Figure 1 below, identifies the location for the Town of Hartland. The town wishes
to gain an understanding of the impact that climate change will have on its municipal
assets and operations. Gaining this understanding, an adaption strategy can be developed
and implemented to mitigate the risks of climate change. With a proper risk assessment
and strategy in place, decisions can be made to effectively allocate public funds to better
prepare for the effects caused by climate change.
[Source: Wolterland Estates, 2011]
The significance of assessing the risks associated with climate change lies primarily in
public safety and the economic impact of ignoring these changes. After a record breaking
spike in warm temperatures in March of 2012, Perth-Andover experienced first-hand the
effects of climate change by a massive flood (CBC, 2012a). Perth-Andover is a town of
1700 residents located 60 kilometers north of Hartland. Over 500 residents were forced
to leave their homes and damages were over $25 million (CBC, 2012b). With
approximately half of its population living along the river, Hartland could be at risk for a
similar event if strategies are not taken to mitigate the associated risks.
10. 2
1.2 Goal and Objectives
The goal of the project was to conduct a preliminary assessment on the vulnerability of
municipal assets to climate change, followed by development of mitigation strategies to
reduce these effects. The goal was accomplished through the completion of the following
objectives:
๏ท Developed a general listing of the townโs assets that would be vulnerable to the
predicted climate changes in New Brunswick.
๏ท Developed a listing of constraints to rank/order the municipal assets for further
investigation.
๏ท Assessed, ranked, and chose assets using a Delphi model and a multi-criteria
evaluation method.
๏ท Proposed a range of adaptation strategies focused on the chosen municipal assets.
๏ท Developed a possible sequence of implementation for each mitigation strategy.
๏ท Developed and presented a final report outlining the strategies and adaption
procedures purposed to mitigate the climate change risks.
1.3 Scope
Total Engineering was to perform a climate change risk assessment that would identify
the problems and vulnerability of the municipal assets within the Town of Hartland. In
order to achieve this, the project team worked with officials from the town and a
consulting engineer from Dillon Consulting to identify the specific needs, expectations,
and resources that will aid in the assessment of the townโs assets.
Total Engineering aimed at creating innovative ways to adapt the current assets to mitigate
the effects of climate change, while considering the economical constraints of a rural
town. This project assessed the predicted climate change impacts on the storm water
system, wastewater system, and lagoon to provide mitigation methods to reduce the risks
associated with climate change. The team was also responsible for providing an
implementation/adaptation strategy. Special consideration was placed towards the
southern portion of the town due to the older infrastructure and current problems with
flooding and washouts in this area.
2 Evaluation of Municipal Assets
2.1 Information
11. 3
With the continuing trend of more frequently occurring intense storms, caused by climate
change, municipalities need to be aware of the risks facing their municipal assets. The
following are only a few of the climate change predictions presented in the document
Summary of Predicted Impacts of Climate Change in New Brunswick (Sciences and
Reporting Branch, Sciences and Planning Division, New Brunswick Department of
Environment, 2004): increase in temperatures, increased UV, increase ice free season,
extended duration of dry spells, higher frequency of intense storms, and more frequent
flooding for the region. These predictions of climate change present a great risk to the
economic state and well-being of the town by threatening its assets. Total Engineering
developed a general listing of the municipal assets, as shown in Table 1, which could be
affected by the predictions listed above. These assets were evaluated and ranked to
determine those of most importance with respect to the chosen constraints. These
constraints are explained in further detail under Section 2.2.
Table 1-Listing of Assets to be Evaluated
LISTING OF THE TOWN OF HARTLAND ASSETS
Roadways Municipal Buildings
Non-Municipal Buildings Recreational Facilities
Municipal Land Sewage Lagoon
Covered Bridge Culverts
Small Bridges Wastewater System
Storm Water System Drinking/Potable Water System
Sidewalks and Curbs Town Signage
Power Infrastructure
2.2 Constraint Methodology
The following six constraints were used in the evaluation for the ranking of the municipal
assets that would be most beneficial for the Town of Hartland to consider. The following
definitions of each of the constraints were used to allow for a consistent understanding
and ranking each alternative asset during the multi-criteria evaluation. A listing of the
constraints, along with the associated weighting factor from the Delphi model, can be
found in Appendix A in Table 5 and Table 6.
2.2.1 Vulnerability to Climate Change
Vulnerability to climate change was thought from the perspective of how much damage
could be done to the asset as a direct result of climate change. When deciding the amount
of weight to be place on the constraint, Total Engineering again used the document called
Summary of Predicted Impacts of Climate Change in New Brunswick (Sciences and
Reporting Branch, Sciences and Planning Division, New Brunswick Department of
12. 4
Environment by the government of New Brunswick, 2004). This allowed the team to look
at the predicted climate changes that are to occur, what the likelihood of the change is
going to be (High, Medium, Low), and if multiple climate changes are going to impact
the asset. This constraint was assigned a weighting factor, by Total Engineering, of 35 out
of 100 because it is the primary basis of the assessment.
2.2.2 Public Safety
Public safety is an engineerโs utmost responsibility to uphold and scored a weighting of
26 out of 100 by the team. When thinking about the public safety the team tried to answer
the question โif the asset were to be damage or lost how would the public be affected with
regards to mobility, health, and risk of injury?โ An example would be comparing the
townโs signage to the wastewater system. If the townโs signage fades quicker due to
increased UV exposure, the impact of people not seeing the signage would be minimal. If
the wastewater system were to go over its capacity and backup into peopleโs homes, the
risk of bacteria present would become a major health concern.
2.2.3 Economics
The economic constraint looks at the cost of changing the asset if it were to be damaged,
the cost of maintenance and operations the asset, and the frequency of changing the asset
due to its typical service life. The Town of Hartland did not have a budget for Total
Engineering to adhere to but the team felt, as in many engineering projects, money is an
important factor to consider. A weighting of 13 out of 100 was applied for this constraint.
2.2.4 Environmental
The environmental constraint considers what environmental impacts would result if the
asset were to be damaged/lost due to climate change or is not upgraded to meet the
predicted changes. This constraint was weighted the same as economics, 13 out of 100,
not for the purpose of being equal but rather for it to be placed just below public safety.
2.2.5 Adaptability
Adaptability looks at the ease of implementation to the Town of Hartland. This involves
the level of effort to learn about a new approach, the level of co-operation from the public,
and the level of maintenance that would be required by the townโs public services.
Adaptability was weighted with an 8 out of 100.
2.2.6 Political
13. 5
The political constraint was placed as the least weighted constraint but was still
considered. This is due to the requirement of the town to rely on the provincial and federal
government for funding of some of the projects done around the town. This would be
comparing the how responsive politicians are to an idea and how much political gain can
be achieved by implementation of the project. The constraint was given a 5 out of 100
weighting.
2.3 Methodology / Approach
The ranking of the municipal assets considered above was performed using a multi-
criteria evaluation model. A โmulti-criteria evaluation is a well-tried and effective
procedure for structuring and aiding complex decision-making processesโespecially
those involving environmental considerationsโ (Drechsler, M., Proctor, W., 2003). The
evaluation works by utilizing the weighted constraints, obtained from a method such as
the Delphi model, and applying a scale that determines the portion of the weighted
constraint to be applied to the asset. The scale allows each constraint to be evaluated on
the basis of (1) being the least desirable to the client while (10) being the most desirable
to the client. It also gives a quantitative solution that can be ranked to determine the best
approach as determined by the evaluation team. A breakdown of the evaluation can be
seen in Appendix A, Figure A.1 with a sample calculation located on the page following
the evaluation. The highest ranked municipal assets were chosen as the most preferable
assets to be considered for the client for this project.
2.4 Discussion and Summary of Results
Based upon the results of the evaluation, the highest ranked assets were chosen for further
investigation. The municipal assets of highest rank were the storm water system and the
wastewater system (including the lagoon) Due to the time constraints of the project, these
were the only assets chosen in order to give the Town of Hartland a more viable product.
These assets are significant due to the history of problems that the town has already
previously experienced. The problems include a near breach of the lagoon from flooding
and the backup of the storm water and wastewater systems during intense storms. The
development of mitigation strategies involved creating viable, economical, and adaptable
solutions that can be applied within the town to detour the effects of climate change within
these systems. The following sections give a breakdown of the mitigation strategies for
each asset and any recommendations that are involved with each.
3 Potential Mitigation Strategies - Storm Water System
With the prediction of an increase in intensity and frequency of rainfall, this can cause
problems with erosion, roadway shoulders, slope stability, siltation, and over capacity of
14. 6
the existing storm water system. This would require the Town of Hartland to increase
maintenance and also run the risk of replacement to existing systems. Total Engineering
aimed at mitigating these effects by: finding the location that would catch the greatest
amount of run-off, controlling the pathway/flow of the water, and slowing the travel time
of the water. This will distribute the effects of the intensity of the storm over a longer
period of time. These effects could be mitigated through the use of a storm water
management system with a possible detention pond and through the use of low impact
design (LID) methods that are growing in popularity across municipalities.
3.1 Storm Water Management System With Detention Pond
It was determined, through a water sensitivity analysis using AutoCad Civil 2013, that
McLean Avenue and the New Brunswick (NB) walking trail were the two most
appropriate locations to implement a low-level storm water management system. These
two locations can be seen in Figure 2, denoted by the blue and red lines for McLean
Avenue and NB walking trail respectively. The overall impact of climate change on the
existing storm water system with the town was unable to be determined due to the limited
information on the system. This prevented the team from running a full analysis to ensure
the current sizing of pipes was able to handle the predicted increase of the flow of water.
Total Engineeringโs focus of this project was to implement a low-level storm water system
over as much of the town as possible to try and alleviate some of the water going into the
current system before discharging into the Saint John River.
3.1.1 Information
Figure 2- Location of McLean Avenue and NB Walking Trail
[Source: Google, 2013]
15. 7
Currently, the storm water management system in these areas, McLean Avenue and the
NB Walking Trail, consists of a combination of natural ditches and culverts used under
roadways and driveways of local businesses. When developing strategies for the storm
water management system several sources were used. The Handbook of Steel Drainage
& Highway Construction (CSPI, 2007) provided details on how to develop a preliminary
design on hydraulic channels using current methods in practice today. AutoCad Civil 2013
was used to gather all the necessary information such as roadway profiles, catchment
areas, size of each flow regime, hydraulic lengths, and slopes to determine the flow rate
for each catchment. This flow rate was determined by using the Rational Method, which
has several assumptions that will be described in the following section. Additional
features such as ditch lining, vegetation, ditch checks, and the use of a detention pond
were also researched to be included the design of the storm water management system.
3.1.2 Working Assumptions
During the preliminary development of the storm water management system several
assumptions needed to be made. First, the Rational Method has three main assumptions
built into its formulation:
1. The rainfall intensity is uniform over the entire watershed during the entire storm
duration.
2. The maximum run-off rate occurs when the rainfall lasts as long or longer than the
time of concentration.
3. The time of concentration is the time required for the run-off from the most remote
part of the watershed to reach the point under design (CSPI, 2007).
It is also recommended that the rational method be used on areas less then 200 acres
(CPSI, 2007). From the level of design that is being proposed in this project, it was
deemed acceptable to use above 200 acres to make an approximation of the flow rate. The
impacts due to these assumptions could result in a more conservative number produced
for the flow rate that may lead to a larger design then required.
The climate change risk assessment deals with future predictions of climate change,
therefore, the current Intensity-Duration-Frequency (IDF) curves for the Hartland area
could not be used. The Canadian Standards Association (CSA) has predicted, in the
Technical Guide-Development, interpretation and use of rainfall intensity-duration-
frequency (IDF) information: Guideline for Canadian Water Resources Practitioners,
that โOver North America in general, extreme precipitation events which currently occur
once every 20 years are projected to occur once every 12 to 13 years by mid-century and
once every 8 to 9 years by 2081 to 2100โ (CSA, 2010). This assumption was used to
produce predicted IDF curves by providing a ~37.5% drop to the mid-century design years
and a ~57.5% drop to 2081-2100 design years. The IDF curves that were used can be
found in Appendix B in Figures 21 & 22. This potential impact from making this
16. 8
assumption will provide an over estimate of the predicted flow within each catchment
leading to a possible over design of the system.
It was also assumed that the AutoCAD file, provided by the client, contained the most up-
to-date information, correct layouts for the piping networks, and the contours of the land
were correct. Due to the age of the town there may be additional piping that was not
recorded or known of that could affect the assessment being performed. Better alternatives
may be available if further knowledge of actual field conditions were known.
An assumption that the run-off water will follow the contours of the land only and such
impedances as trees, roadways, crops, buildings, etc. do not deflect the flow path of the
water was implemented. This assumption could lead to a larger portion of the water
flowing into other catchments areas increasing the flow in that particular catchment.
3.1.3 Methodology/Approach
In order to effectively assess the flows needed to determine ditching, culverts, and catch
basins, the catchment areas along McLean Avenue were developed through the water
sensitivity analysis using AutoCAD Civil 2013 and are depicted in Figure 3. This analysis
allows the user to determine the location of flow for multiple droplets of water using the
provided contours to effectively determine the catchment area for a section of roadway.
The next step was to determine the approximate locations where ditches, culverts, and
catch basins would be able to catch and control the greatest amount of run-off possible.
This was done by creating a profile, using AutoCAD Civil 2013, to determine the
locations of ditches, catch basins, and rip-rapping, while GeoNB was used to determine
the location of driveways for culvert placement. The final location of the ditches, culverts,
drainage basins, and rip-rapping can be seen in Figure 4.
Once the location of the ditches was determined, a preliminary design of an engineered
ditch for each catchment along the roadway was conducted. This was done using simple
hydraulic design laid out in the Handbook of Steel Drainage & Highway Construction
(CSPI, 2007). Refer to Appendix C for calculations for determination of flow within each
catchment and Appendix D for the preliminary design calculations for the engineered
ditch. It was determined that the ditches along McLean Avenue should have a minimum
base of 1.0m to 1.2m in width given a side slope of 3:1, 60% flood stage depth, and a
normal-dense grass and weed mixture. This calculation is to provide the Town of Hartland
with a general idea of the size of ditch that would be required for implementation.
Additions, such as vegetation, linings, and ditch checks, were added to aid in reducing the
flow of the water. Due to the time constraint, the sizing of the culverts and catch basin
17. 9
Legend
Engineered Ditching
Culvert/Piping
Rip-Rapping Ditch
Completed Engineered Ditch
Catch Basin
Detention Pond
Figure 3-Catchment Areas for McLean Avenue
along McLean Avenue was not performed and would need to have further investigation
if implementation of the recommendation were to be considered.
Catchment 1
Catchment 2
Catchment 2b
Legend
Catchment 1
Catchment 2
Catchment 2b
Catchment 3
Catchment 4
Residential Area
Commercial
Area
Forest Area
Agricultural/Low
Vegetation Area
McLean Avenue
Catchment 3
Catchment 4
18. 10
When looking at catchment 3 in Figure 3, it was noticed that this area contains a large
portion of cropland. Due to the prediction of increased erosion due to precipitation, the
run-off in this catchment will be carrying large amounts of sediment, fertilizers, and any
other chemicals used on those particular crops. The intersection of McLean Avenue and
Route 575 provides a possible location for the detention pond to be implemented. This
will detain the run-off water for a period of time to allow the suspended particulates to
settle. An approximation to the size of the detention pond required can be found in
Appendix E. The detention pond would be connected into the existing storm water system
along Route 575 to allow for a controlled release after settlement has occurred and the
storm has passed.
3.1.4 Recommendations
It is recommended that the typical cross-section for the engineered ditch, seen in Figure
5, be constructed along McLean Avenue and NB walking trail. With the implementation
of vegetation before entering the ditch, maximizing the side slopes to 3:1, and
implementing a trapezoidal shape, the following benefits will occur:
Figure 4-Storm Water Management System Layout for McLean Avenue
[Source: GeoNB, 2013]
19. 11
๏ท Decrease erosion of ditch,
๏ท Increase slope stability,
๏ท Increase safety to drivers,
๏ท Increase catchment of sediments/debris (Stallings, 1999).
All of these features will in turn reduce the amount of maintenance and replacement costs
to the Town of Hartland to upkeep the ditch due to the predicted increased in precipitation.
One of the major goals of storm water management is to lengthen the time required for
the water to travel to its discharge point. This allows the entire storm water system to see
a more โuniform stormโ rather than a very intense storm that would cause the system
overloaded for a short duration. Through a literary review, several of the more popular
method associated with lining, vegetation, and ditch checks are provided in Table 2 that
will lengthen the travel time and result in a more uniform storm so the storm system will
have less risk of becoming overloaded (Association of Illinois Soil & Water Conservation
Districts, n.d., British Columbia-Ministry of Agriculture, Food and Fisheries, 2004,
Schneider, 2010, Tennessee Department of Transportation, 2011). It is recommended that
a form of lining should be applied, as indicted in Figure 5 and Table 2, due to the velocity
check performed for each catchment during the preliminary design of the engineered
ditch. Refer to Appendix D for velocity check computations for each catchment.
Table 2-Examples of Ditch Lining, Vegetation, and Ditch Checks
LINING VEGETATION DITCH CHECKS
Turf Reinforcement Mats Thick Grasses (Depending on the
composition of the current soil)
Straw Bails
Geotextiles (Woven Mats) Sod Sediment Control Wall Mats
Rip-Rap (Rocks,
Boulders)
Small Shrubs Wire-Enclosed Stone
Grouted Rip-Rap Weeds Plastic Permeable Checks
Urethane Vertical Foam Mats
Figure 5-Typical Ditch Cross Section for McLean Avenue
20. 12
It is recommended, by Total Engineering, that the use of temporary ditch checks (wall
mats, foam mats, etc) should be used as temporary measures for ditch checks to reduce
the velocity of run-off. These should be placed into the ditch during the early spring and
removed prior to winter to mitigate the risk of damage during snow removal operations.
This will reduce the cost of replacement for the ditch checks each year. When using lining,
it is recommended to use it as an underlay along the edge of the roadway. This will
decrease the amount of erosion and will also reduce the risk of pavement deterioration
along roadside edges. Total Engineering recommends the following three-phase process,
located on the following pages, for the implementation of this storm water management
system.
Phase 1-Water Storage Tank to McMullin Road
The first phase to be conducted is from the water storage tank to McMullin Road as seen
in Figure 6 below. The town has already experienced problems along this section with
storm water run-off, so upgrading of this section is currently required. This area is
comprised mostly of industrial occupancy, with large paved lots, resulting in increased
velocity and volume of run-off due a reduced of absorption rate into the ground. This
phase includes implementing the recommended ditch as shown in Figure 5 above,
21. 13
culverts, a catch basin (indicated by the green square) along McLean Avenue, and ditches
with rip-rap and piping along the length of McMullin Road for the outflow into the Saint
John River.
Phase 2- Water Storage
Tank to Rockland Rd. &
McMullin Rd. to Walton Ct.
Phase two would be completing the remaining ditching and culverts along the entire
length of the McLean Avenue. Shown in Figure 4, the lower section on McLean Avenue
has recently been engineered and rip-rapped and therefore construction on this portion
Figure 6-Phase 1 Storm Water System
[Source: GeoNB, 2013]
22. 14
may not be required. During this phase, the Town of Hartland should also present a request
to the provincial government to implement a similar ditching strategy along the NB
walking trail, as it is provincially owned. This will have all the same benefits as the
ditching and culvert system along McLean Avenue with the addition of divirting the water
away from the foundations of residential housing along Main Street. This will allow the
economic costs to be spread slightly more evenly across the three phases.
Phase 3-Addition of Detention Pond
Phase three would be the highest cost phase and would require the following:
๏ท Implementing a water passage over the brook at the bottom of McLean Avenue
23. 15
๏ท Designing and constructing a detention pond to hook up to the existing system on
Route 575
๏ท A diversion channel for the small brook during peak flows of intense storms.
This phase is aimed at mitigating the risk of flooding near the back of the lagoon due
overflow of the brook, while enhancing the environmental impact due to the increased
sediment loads from the large agricultural areas. The area between McLean Avenue and
Route 575 was checked to ensure the detention pond could fit within this suggested area.
The area required was calculated to be 2.5 acres while the proposed lot is 3.1 acres. Refer
to Appendix E for calculations and assumptions made to achieve this area. Once the
detention pond is in place, regular maintenance would need to be completed. This would
have a carry additional cost to the town but would be beneficial when considering the
impact caused by the release of sediments and chemicals into the waterways (United
States Environmental Protection Agency, 1999). This would also alleviate some of the
capacity from the system along Route 575 during heavy rainfall that may overload the
system causing damage or flooding.
Figure 8-Phase 3 Storm Water System
[Source: GeoNB, 2013]
24. 16
Overall, having these low-level storm water systems in place on McLean Avenue and the
NB walking trail will:
๏ท Reduce the volume of uncontrolled run-off,
๏ท Reduce the velocity of run-off water,
๏ท Reduce soil erosion,
๏ท Reduce ponding near foundations of houses along Main Street,
๏ท Increase traffic safety to motorists,
๏ท Reduce operations and maintenance costs to the towns public works,
๏ท Reduce the deterioration of the pavement along the sides of the roadway,
๏ท Enhance environmental quality.
3.2 Low Impact Designs
Total Engineering searched for a relatively inexpensive, environmentally friendly and
innovative alternative to storm water run-off mitigation. The scope of the climate change
risk assessment had to go beyond current threats and promote continuous sustainable
development in the Town of Hartland. Low Impact Designs (LID) provide sustainable,
cost efficient improvements to reduce the burden on the storm water system, and
indirectly the wastewater system, and can be implemented continually over an extended
period of time.
3.2.1 Information
LID is a new storm water drainage design philosophy being adopted by municipalities
around the world. The design philosophy promotes low environmental impact through the
use of more natural processes and small changes to the local environment (Green BuiltTM
Michigan, 2012). This section contains a variety of simple LID solutions that could be
implemented around the Town of Hartland. LIDs create an opportunity to provide a low
cost and environmentally friendly solution to the Town of Hartlandโs ageing storm water
system.
3.2.2 Working Assumptions
When selecting a LID, it was important to select solutions suitable for the Town of
Hartland. It was assumed that the designs needed to be low cost, versatile, and suitable
for the Town of Harlandโs climate. These parameters would allow the LID to be
community based, privately implemented, and affordable for a small municipality.
It was also assumed the Town of Hartland would be interested in gaining LEED
(Leadership in Energy and Environmental Design) certification for the neighbourhood.
LEED is a third party certification program that has become the global standard in
25. 17
definition of quality in environmental design (CaGBC, 2013). LEED design certifications
are awarded through the Canadian Green Building Council and must undergo a
certification process in order to be awarded a rating (CaGBC, 2013). The implementation
of several LID solutions could be a step towards the Town of Hartland in becoming a
certified LEED neighbourhood.
3.2.3 Potential Solutions Catch basin
Catch Basin Inserts and Filtrations Socks
Catch basin inserts and filtrations socks are a low cost and easily installed solution to
reduce surface run-off pollution from entering the storm water system. Sediment, debris,
oil, and grease are caught in the inserts and filtration socks will reduce pollutants that
would otherwise flow into the Saint John River (UltraTech, 2013). The inserts are non-
woven screens that are inserted under the storm water drain. These inserts have built-in
overflow ports in the case of extreme surface run-off conditions. Filtration socks wrap
around the exterior of curb side storm drains, or can be implemented inside with lock-in-
place system, and act as a barrier from debris and heavy metals (UltraTech, 2013).
This will reduce the amount of debris build up with the storm water system that would
reduce the overall capacity of the system. Regular drive-by maintenance checks to ensure
the inserts or socks are not at capacity, or require servicing, would be required depending
on the level of run-off experienced of a time period. These are to be installed during the
spring and summer months to reduce the amount of damage that may be done by snow
operations and ice build-up.
Figure 9-Catch Basin Insert
[Source:UltraTech ,2013]
Figure 10-Filtration Socks
[Source: UltraTech, 2013]
26. 18
Tree Box Filter Storm Drains
Tree box filters slow down surface run-off, aid in water quality treatment through natural
processes, and create a more aesthetically pleasing design solution. Tree box filters may
be used in the place of curb side storm drains and are ideal for the town centre to add an
aesthetic appeal. This may be appealing to the downtown area of Hartland since there are
over 90,000 tourists annually visiting the town as mentioned by Linda Brown during the
site visit. A perforated pipe should be placed in a base layer of crushed rock, with an
overflow pipe leading to the surface if heavy flows in the implementation area are
anticipated, as shown Figure 11. The second layer of soil should be a bio-retentive soil
(20% compost, 80% sand), with local tree species planted. Tree box filters can remove
nitrogen and petroleum hydrocarbons from surface run-off. The bio-retentive soil has a
high absorption rate that will allow run-off to penetrate into the soil, decreasing the
amount of run-off over the given area, slow the flow of water over the system, and
decrease the amount of water entering the current system (University of New Hampshire-
Storm water Center, 2013).
Rain Gardens
Figure 11-Tree Box Filter Storm Drains
[Source: University of New Hampshire, 2007]
27. 19
Rain gardens, as shown in Figure 12 and 13, are sunken gardens designed to catch and
absorb water. They are ideal for, but not limited to, commercial parking lots with large
areas of pavement such as the industrial buildings along McLean Avenue. Rain gardens
can reduce and filter storm water run-off through natural processes and should be installed
on level surfaces with a small depression to promote infiltration (Dhalla & Zimmer, 2010).
The soil should remain un-compacted and should be unlined to promote infiltration into
native soil. A perforated pipe under the garden may be necessary depending on the
saturation or permeability of the native soil. They can support very diverse plant life,
ranging from grasses to trees and should be designed to have a combination of wet and
dry plants (City of Santa Rosa, 2011). The addition of rain gardens can be implemented
into residential and commercial areas to not only detour the effects caused by climate
change, but to also increase the aesthetics around the Town of Hartland.
Grassy Swales
Grassy swales are alternatives to roadside storm drains that run on the surface of grassy
land that experience low flows. They are effective at slowing groundwater flow, and
increasing the filtration of surface run-off. Swales should have gradual side slopes ranging
from 1.0% to 2.5% and a max longitudinal slope of 8.0%. In steep areas, check-dams
should be placed to slow water velocity. Grassy swales in the Town of Hartland will
require a permanent geotextile liner due to the severity of velocity of the projected 1 in
62.5 year storm for mid-century. Swales should be designed so that the water level does
not exceed two-thirds the depth of the swale. Swales must also be designed to have a
minimum retention time of twelve minutes (City of Santa Rosa, 2011).
Bovine Terrace
Figure 12-Land Development for Rain
Gardens Section View
[Source: CMHC, 2011b]
Figure 13-Land Development for Rain Gardens
Profile View
[Source: CMHC, 2011a]
28. 20
Bovine terraces (also known as cow terraces) are contoured ruts on a hillside, as shown
in Figure 14. The benefits of bovine terraces include reducing run-off speed, erosion, and
increasing infiltration into the soil with an aesthetically pleasing solution. The terraces
should only protrude up to one meter out from the hillside and spaced two to five meters
apart vertically. When designing the terraces, they should be supported with vegetation
and trees to maintain slope stability. This solution is ideal for larger open areas. (City of
Santa Rosa, 2011).
3.2.4 Recommendations
It is recommended that the catch basin inserts and filtration socks be installed along the
routes where heavy equipment (tractor trailers, city equipment, garages, etc.) are most
Figure 14-Example of a Bovine Terrace
[Source: City of Santa Rosa, 2013]
29. 21
predominantly used. This will give the town the largest impact per dollar spent for cost of
material and routine maintenance instead of implementation for every inlet around the
town.
Tree box filter drains would be ideally located in the downtown area along Main Street
and the Hartland Covered Bridge. With this area having the largest portion of tourists, it
would be beneficial to add this LID to add aesthetics, while naturally filtering any
sediment, debris, or chemicals flowing down off the hillside before entering into the Saint
John River.
Rain gardens are an excellent choice of LID and are highly recommended by Total
Engineering due to their adaptability into practically any environment. They are highly
sought out for industrial parking lots to slow the velocity of water and reduce the amount
of run-off into the storm water system. These can be used as a community event to
promote the use of LIDs, while reducing the costs of construction by having volunteers
help construct and maintain the gardens. This will also encourage the implementation of
rain gardens into residential housing as an alternative to flower gardens to help the town
while still making residential lots aesthetically pleasing.
The Town of Hartland may consider adopting a bovine terrace along the hillside at the
end of Walton Court towards McMullin Road. It was expressed, during the site visit, that
the flow of run-off over the hillside of Walton Court area was causing minor flooding at
the back of residential lots. The implementation of a bovine terrace would aid in correcting
this problem while increasing the slope stability by the addition of trees. It would also
increase infiltration potential, increase time of concentration, decrease erosion, and
provide an aesthetically pleasing solution to the hillside.
4 Potential Mitigation Strategies - Wastewater System and Lagoon
4.1 Information
In 2012, the Town of Hartland experienced one of the worst flooding events recorded in
the townโs history. Due to several ice jams occurring in the Saint John River, the town
saw water levels rise to 48.23 meters above mean sea level (AMSL). These water levels
30. 22
nearly caused a breach of the lagoon, which could have led to structural damage and
environmental implications. To protect the lagoon from expected future flooding, the use
of barriers should be considered for implementation.
4.2 Working Assumptions
During the investigation into potential
solutions for protecting the lagoon from
flooding, an assumption had to be made
regarding future flood levels. These flood
levels are highly variable and are very
difficult to accurately predict. The
assumption may result in a higher cost of
construction due to an increase in
materials required. The team choose a
barrier height of 1.25m to 2.0m to be
slightly conservative, as a flood of this
height would have devastating effects on
other portions of the town. This report
assumed that flood levels would not increase significantly over the life of the lagoon. This
assumption is based on the fact that over the past 50 years, there has been no obvious
trend in the flood levels for the St. John River at Hartland as shown in Figure 15. This
figure only shows the years in which the town reached its flood level, years which the
town did not reach its flood level are not shown.
4.3 Methodology/Approach
Part of the potential solutions for the lagoon was to determine the necessary height of the
protective barriers needed to be to ensure over topping of flooding was not incurred. While
the maximum historical flood level for Hartland was determined to be 48.23 meters
AMSL (GNB, 2013), this measurement is only accurate for the location at which it was
measured. Flood level readings vary based on where they are taken and a reading taken
upstream would be higher than one taken downstream. Using GeoNB flood information
for the 2008 flood, where levels reached 47.91 meters, and along with the elevation map
provided by the client, the team was able to approximate the elevation for the 2008 flood
at the lagoon. To find the maximum historical flood height, which occurred in 2012, the
2008 elevation was increased by 0.3 meters to determine a maximum historical flood level
at the lagoon of approximately 45 โ 46 meters ASL. Using this value, a height of 1.25
meters to 2 meters for potential solutions is recommended in order to ensure adequate
protection against flooding.
47.68
48.01
47.72
45.82
46.97
47.91
45.81
48.23
45.5
46
46.5
47
47.5
48
48.5
1970 1980 1990 2000 2010 2020
WaterElevationASL(m) Year
Figure 15-Historical Flood Levels for Hartland, NB
[Source: GNB, 2013]
31. 23
4.4 Potential Solutions
Two types of barrier solutions are provided below that could be constructed to protect the
lagoon from a breach due to flooding. The first option is a removable floodwall that will
only be in place during the flood season to keep the aesthetics of the town while still
performing the protection of the lagoon. The second solution is a combination of
cantilever concrete wall and asymmetrical berm for a more permanent solution. This
option would reduce the yearly implementation of the removable floodwall.
4.4.1 Removable Floodwall
A removable floodwall (RFW) would consist of a permanent concrete base along with
removable columns and wall components that are erected prior to a flood. This pre-
engineered solution would allow for complete flood control while still preserving the
aesthetics of the townโs Main Street and waterfront area.
The most critical component of the wall is the concrete base. This permanent base goes
along the entire length of the wall and is flush or slightly above ground level. The base
would need to be designed to ensure that at the maximum flood height, it will not slide or
overturn from the force of the water. Spaced along the base are anchor plates that are
embedded in the concrete and used to secure the wall posts, which are attached using
bolts. The wall components have a rubber seal that ensures the wall will not be penetrated
in the event of a flood. These components simply slide between the posts and are secured
to each other in a tongue and groove fashion (IBS, 2012). While pre-engineered solutions
exist where it is not required, it may be advisable to provide additional wall support with
45o
bracing at regular intervals to ensure the wall does not over-turn due to the additional
pressure from ice flow (Sovran, 2003). For a visual of the typical profile/section of
removable wall see Figure 16.
Since a RFW takes time to deploy, it is critical that a reliable flood warning system is in
place (Ogunyoye, 2002). While such a system does exist in New Brunswick for the Saint
John River, the system may not be able to provide adequate advanced warning (GNB,
2013). In addition, it would not be feasible to setup and remove the wall each time a flood
warning is issued as this may occur multiple times each flood season. Due to this, the best
option would be to install the RFW in late-February and only remove it in May. This
would ensure that the lagoon is protected throughout the duration of the flood season and
the townโs limited manpower and resources will not be inaccessible during a critical event.
Given a similar construction of a floodwall for a 100.6m long, with a distance between
supports of 3.05m, and approximately 1.2m high required 1-2 hours with 4-8 instructed
workers (IBS, 2012). This translates into a set up time of approximately 6 to 10 hours for
the town for the required length and height of the removable floodwall.
32. 24
While it is a very effective, proven solution, the costs of a RFW are quite significant. In
2009, a 5 meter high, 1000 metre long RFW was constructed at the St. Paul downtown
airport in Minnesota. The wall was completed at a cost of $24 million (Johnson, 2010).
Based on that, it would be expected that a similar project for the town would cost
approximately $3-6 million for a wall of 400 meters in length by 2 meters high. It is
difficult to determine a more accurate value as each individual project is highly varied.
The RFW could also be used in addition to a berm. Instead of a permanent concrete wall
structure, the RFW would provide a more aesthetically pleasing solution, leaving the front
open until a flood event occurs. It would also allow vehicles and equipment much easier
access to the lagoon in the event that inspections or work needs to be completed.
4.4.2 Combination of Berm and Concrete Wall
The second solution for protection of the lagoon is a combination of a cantilever concrete
wall and an asymmetrical berm. The initial approach was to construct a berm along the
entire perimeter of the lagoon, however, this alternative was dismissed as it was quickly
discovered there is insufficient space to construct a berm along side of Main Street due to
the recommended 4:1 width to height ratio. The alternative solution, proposed by Total
Engineering, was to construct a cantilever concrete retaining wall along Main Street and
the end portions of the lagoon due to redistricted space. The remaining perimeter would
Figure 16-Typical Profile/Cross Section of Removable Floodwall
33. 25
consist of an asymmetrical berm, as there is plenty of room along the east side of the
lagoon. The concrete wall would be approximately 265 linear meters and constructed to
a height of 1.25-2.0 meters, while the berm would be 150 linear meters at the same height.
The most appropriate retaining wall for this situation would be a concrete cantilever
retaining wall. As shown in Figure 17, cantilever retaining walls are constructed of
reinforced concrete, which can be precast or cast in place. The wall is divided into two
sections, a narrow stem and a base slab. The base consists of a heel, which lies underneath
the soil, and a toe that sits on the outer portion of the wall base (Assakkaf, 2004). The
cantilever retaining wall will provide a more economical solution when compared to the
traditional gravity wall. The benefits include providing the best support to resist against
overturning, sliding and bearing resistance for the allocated area (Craig, 2012).
Aesthetics may be of concern to the town so options for this have been developed. Options
for improving the look of the retaining wall vary considerably depending on the level of
detail the customer is looking to achieve. The most popular are stone, brick veneer, and
stain.
To provide a stable berm, the berm should be built at a 4:1 slope. Due to the expected
flooding patterns the berm should be built between 1.25m to 2m in height, and 8.5m to
Figure 17-Concrete Cantilever Wall
34. 26
13m in width. This means the Town of Hartland will require 1600 m3
to 3900 m3
of
material. A simplified diagram of the type of berm to implement can be seen in Figure 18.
Figure 18-Berm Cross Section
[Source: Wilson, 2006]
The berm should be an asymmetrical berm that is consistent with the surrounding
environment and to appear as natural as possible. One option to improve the natural
appearance of the berm is by applying gradual transitions in the elevation. Trees may be
planted on slopes no steeper than 5:1, other types of plants may be planted on steeper
slopes although water will not be effectively absorbed in steeper slopes (Wilson, 2006).
Due to the size of the lagoon, the berm will require a large amount of soil. Great care
should be taken when deciding what type of soil is to be used in the berm. When looking
for a cost effective solution to a permanent berm, three layers should be used. The top
layer should consist of high quality topsoil at approximately one foot in depth to promote
vegetation growth to promote stability and absorption. The next layer should be an
impervious layer of clay at about one foot in depth, which acts as an adhesive and barrier
between the first and third layer. The third and final layer should consist of fill material;
whatever is readily available and affordable. Gravel should not be used directly
underneath the high quality topsoil, as it has a high likelihood of the soil to wash through
the gravel and a clay layer promotes adhesion for slope stability (Wilson, 2006).
With the implementation of these barriers, an alternative entrance must be constructed in
order to accommodate for vehicles and maintenance equipment. The most viable option
is to construct a gradually raised driveway on the South East corner of the lagoon off
Route 575. The area has enough room to provide a proper grade and side slope to ensure
stability during flooding.
4.4.3 Separation of Storm Water System from Wastewater System
During the site visit and from the AutoCAD files provided by the client, it was determined
there are several identifiable locations where the storm water system is directly connected
35. 27
to the wastewater system. Separating these two systems will impact the longevity and
effectiveness of the wastewater system components (Xylem, 2011).
The red circles in Figure 19 denote the locations that are interconnected. There may also
be other locations of interconnectivity but from the information provided these were the
only locations that could be identified. If other places exist, they should be disconnected
as well.
The risk of the wastewater system being overwhelmed is increased by the burden of the
extra storm water entering the system and may lead to a discharge of wastewater through
the storm water outlets. The wastewater system should be a closed system to ensure this
does not happen, as this would be considered a combined sewage overflow, and should
be avoided due to obvious environmental and health concerns (Government of Canada,
2013).
The increased in flows cause higher stresses on the forced water pumps and the
wastewater piping system (Xylem, 2011). These pumps and pipes will wear faster and it
will also cost the town more money for the treating of the increased volume of water. This
will, in the end, increase the frequency of maintenance with the system and affect the
longevity of the entire system. A cost analysis should be carried out to verify if the cost
to alleviate the burden is less than the cost to make the increased repairs on the pumps and
piping.
36. 28
4.5 Recommendations
The recommendation by Total Engineering for the protection of the lagoon would be to
construct the RFW. This option will allow the town to remain within its original setting
during tourist season while having the security of being able to provide protection of the
lagoon during flood season. The initial costs may seem higher than the concrete wall and
berm option, but it has been proven to work and is also pre-engineered. This will decrease
the amount of design required and the amount of material required for construction. It is
to the discretion of the town which option to pick depending on the level of aesthetics and
routine yearly work required for each option.
It is recommended that the Albert Street and Elm Street connections be disconnected and
create a separate storm water pipe connecting into the existing system on Rockland Road,
denoted by the dashed line. Another option for this area, if construction costs would be
too high, is the use ditching or grassy swales to carry the run-off water along Albert Street
and Elm Street and flow to an inlet on Rockland Road through simple gravity feed. This
can be seen in Figure 19 using the contours as a visual to show the slope of the land in the
area. Finally the disconnection of the School Street is to be done in similar fashion with
connection onto the existing system on Hillcrest Avenue. A cost analysis should be
performed to verify if this is a worthwhile venture.
Figure 19-Combined Storm Water and Wastewater System Points
37. 29
5 Recommendations for Implementation Strategy
Total Engineering has developed an implementation strategy based on the relative cost
compared to the overall impact for each possible solution recommended above. Figure 20
shows a visual representation of this comparison. Overall impacts include mitigation of
climate change effects, increased public safety, reduced maintenance, and environmental
benefits with implementation. The solutions should be implemented beginning with the
solutions in the green portion of the table and moving towards the red. This strategy will
allow the Town of Hartland to have the greatest amount of impact to reduce the risk of
climate change per dollar invested toward each strategy.
The first recommended solution is to implement phase one of the storm water system. The
area along McLean Avenue already has ditching and culverts in place, thus the cost of
excavation during the construction for the engineered ditches will be minimized. Phase
one would have a high impact by alleviating the burden on the storm water drains below
the hill, reducing erosion in the industrial area, increasing traffic safety, and reducing
deterioration of the pavement along the sides of the roadway.
The second recommended solution would be to implement either the removable floodwall
or the berm and concrete wall combination. Due to the recent near breach of the lagoon,
the lagoon needs to have protection against structural damage as well as protecting the
town from environmental cost due to clean up from a breach and the cost of not having
the system available for an extended duration of time.
The third recommendation would be to implement phase two of the storm water system.
This would have a low to medium cost due to the small portion of roadway to be
completed and provincial funding to complete the NB walking trail. Due to a smaller
industrialized area of implementation, the amount of erosion and deterioration of the
roadway, when compared to phase one, would have less impact overall.
The storm water system and wastewater separation recommendation would have a higher
cost associated with it due to the level of excavation and construction required to
implement its own piping system within the area. The overall impact would be minimal
since there were only several areas identified that would alleviate the burden on the
wastewater system. It is also assumed that the wastewater system can currently hold a
small increase due to the increase in run-off so implementation of this may not be required
until a future date. A full analysis would need to be completed to confirm this.
Phase three would have the highest cost associated with it due to the level of design,
construction, and possible purchasing of land. Its purpose and impact would be solely to
38. 30
increase the environmental aspects by allowing the sediment and chemicals to settle and
not be released into the environment. It also alleviates some of the flooding from occurring
in back portion of the lagoon during peak flows of the brook.
LIDs are considered to be of low cost for implementation in their nature. These types of
solutions should be a part of an ongoing program within the town. The overall impact
depends on the magnitude and frequency used with the town.
OVERALLCOSTS
OVERALL IMPACT
LOW MED HIGH
HIGHMEDLOW
Figure 20-Overall Cost vs. Overall Impact of Solutions for Implementation
STORM WATER
&
WASTEWATER
SEPARATION
PHASE 2-STORM
WATER SYSTEM
LOW IMPACT
DESIGN
BERM &
CONCRETE
WALL
REMOVEABLE
FLOODWALL
PHASE 1-STORM
WATER SYSTEM
PHASE 3-STORM
WATER SYSTEM
39. 31
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http://www.assakkaf.com/Courses/ENCE454/Lectures/HANDOUTa.pdf [cited 14
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2013]
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Cantilever Retaining Walls. (2001). Retrieved from Concrete Network:
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44. A.2
Table A1-Weighting and Scale for Constraints
CONSTRAINT WEIGHT SCALE
Vulnerability to Climate
Change
35 1=Not
Vulnerable
10=Highly
Vulnerable
Economical Impact 13 1=High Cost 10=Low Cost
Adaptability 8 1=Hard To
Adapt
10=Easy To
Adapt
Environmental 13 1=Low Impact 10=High Impact
Public Safety 26 1=Low Concern 10=High Concern
Political Influence 5 1=Low
Influence
10=High
Influence
Total 100
Table A2-Results of Delphi Model
ROUND 1
Vulnerability Public
Safety
Cost Environment Adaptability Political Total
BC 35 25 15 10 10 5 100
BT 45 25 3 7 15 5 100
T 40 20 15 10 10 5 100
N 30 40 10 10 5 5 100
R 35 30 15 10 7 3 100
Round 2
Vulnerability Public
Safety
Cost Environment Adaptability Political Total
BC 35 25 15 10 10 5 100
BT 35 25 15 10 10 5 100
T 40 25 10 15 5 5 100
N 35 30 10 15 5 5 100
R 35 30 15 10 5 5 100
Round 3
Vulnerability Public
Safety
Cost Environment Adaptability Political Total
BC 35 25 15 15 5 5 100
BT 35 25 15 10 10 5 100
T 35 25 10 15 10 5 100
N 35 25 15 15 5 5 100
R 35 30 10 10 10 5 100
Avg 35 26 13 13 8 5 100
45. A.3
The above average have been rounded to the nearest 0.5 and adjusted based on the groupโs
decision.
BC=Ben Connolly
BT=Ben Taylor
T=Tyler Harris
N=Nicholas Phelan
R=Ryan Steeves
52. C.7
List of Symbols
๐ด ๐ = Total catchment area
๐ด ๐ = Residential area within catchment
๐ด ๐ = Commercial area within catchment
๐ด ๐ = Agricultural/Flat area within catchment
๐ด๐ = Forest area within catchment
๐ถ ๐ค = Weighted average for hydraulic coefficient
๐ถ๐ = Residential hydraulic coefficient
๐ถ๐ = Residential hydraulic coefficient
๐ถ ๐ = Residential hydraulic coefficient
๐ถ๐ = Residential hydraulic coefficient
๐ฟโ = Hydraulic length for catchment
๐6.25= Predicted intensity of rain during 6.25 year storm for mid-century
๐62.5= Predicted intensity of rain during 62.5 year storm for mid-century
๐ = Average slope of flow in catchment
๐6.25= Peak flow 6.25 year storm for mid-century
๐62.5= Peak flow 6.25 year storm for mid-century
๐๐ = Time of concentration
โ๐ฅ = Change in horizontal distance
๐ฅ1 = Horizontal position for starting point of segment
๐ฅ2 = Horizontal position for starting point of segment
โ๐ฆ = Change in vertical distance
๐ฆ1 = Vertical position for starting point of segment
๐ฆ2 = Vertical position for starting point of segment
53. C.7
Drainage Areas:
The drainage areas were measured using AutoCAD Civil 3D water catchment area tool.
The total capture zone was then divided into categories: residential, agricultural/field,
commercial, and forest. The sub areas were measured using the AutoCAD polyline tool.
C values for areas:
The C values were assumed to be of an average value for the types of areas. The average
C value for each area was determined from Hydraulics and Hydrology Engineering-UNB
Fredericton CE 3713 textbook Chapter 6-Hydrology for Hydraulic Design in Table 10.
Equation 1 ๐ด ๐ = ๐ด ๐ + ๐ด ๐ + ๐ด ๐ + ๐ด ๐น
Equation 2 ๐ถ ๐ค =
[(๐ถ ๐โ๐ด ๐)+(๐ถ ๐โ๐ด ๐)+(๐ถ ๐โ๐ด ๐)+(๐ถ ๐โ๐ด ๐)]
๐ด ๐
Flow Calculations
Hydraulic length
The Hydraulic length is the length of the longest catchment path. This was measured using
AutoCAD Civil 3D in meters and converted into feet in order to use it with the Seeley
graph.
Slope of the Road
The slope of the road, also known as the grade was measured by averaging the slope of
the segment.
Equation 3 โ๐ฅ = ๐ฅ2 โ ๐ฅ1
Equation 4 โ๐ฆ = ๐ฆ2 โ ๐ฆ1
The slope for the segment can be calculated.
Equation 5 ๐ =
โ ฮ๐ฆ
โ ฮ๐ฅ
Time of Concentration
In order to find the time of concentration the Seeley chart was used. To use the Seeley
chart, start off with the hydraulic length, make a straight line to the hydraulic coefficient
and continue to the midway line. The point on the midway line acts as a pivot. A straight
line is then made to the percent grade, which then continues to the right scale that
identifies the time of concentration in minutes.
54. C.7
Intensity of the Storm
Using the time of concentration we then make reference to IDF curves to find the intensity
of rainfall in feet squared per second, which is then converted to meters squared per
second. The run-off is then calculated using Equation 6 below. The Mid-Century IDF
curve was used for the calculations for this project.
Equation 6 ๐ = ๐ถ ๐ค โ ๐ โ ๐ด ๐
Example Calculation for Catchment 1
The first objective is to determine the run-off area for each flow regime. The areas for this
project were measured with AutoCAD Civil 3D
Drainage areas Area(m2
)
Residential 147103.73
Agricultural/field 110873.57
Commercial 0.00
Forest 21553.25
Total Area 279530.55
Using equation 1, the total area is found.
๐ด ๐ = ๐ด ๐ + ๐ด ๐ + ๐ด ๐ + ๐ด ๐น
๐ด ๐ = 147103.73 + 110873.57 + 21553.25 = 279530.55
1. The areas are converted from meters squared to acres.
๐ด ๐* 0.000247105381 = ๐ด ๐ (in acres)
147103.73*0.000247105381 = 36.4 ac.
2. The weighted C value is calculated using Equation 2.
๐ถ ๐ค =
[(๐ถ๐ โ ๐ด ๐) + (๐ถ๐ โ ๐ด ๐) + (๐ถ ๐ โ ๐ด ๐) + (๐ถ๐ โ ๐ด๐)]
๐ด ๐
๐ถ ๐ค =
[(0.55 โ 147103.73) + (0.4 โ 110873.57) + (0.2 โ 21553.25)]
279530.55
๐ถ ๐ค = 0.46
3. The hydraulic length is measured with AutoCAD 3D and converted to feet.
55. C.7
๐ฟโ = 440.0๐ ๐ฟโ = 440.0 โ 3.28084 = 1443.7๐๐ก
4. The Slope of the road is determined using elevations taken from the AutoCAD
3D file. Equations 3, 4, and 5 are used.
๐ =
6.14+1.25+0.15
176.703+78.467+73.491
=0.022942
Part โ๐ฅ ๐ฆ2 ๐ฆ1 โ๐ฆ
โ๐ฆ
โ๐ฅโ
1 176.703 92.14 86 6.14 0.034748
2 78.467 85.3 84.05 1.25 0.01593
3 73.491 84.2 84.05 0.15 0.002041
Total 328.661 261.64 254.1 7.45 0.022942
5. The time of concentration is determined using a seeley graph.
In the Figure 23 below, the blue that starts at approximately 1400 feet on the left passes
through a 0.46 point of the coefficient bar and heads to the center. The line then passes
the 2.3% slope point and continues straight to just under the 26.0 minutes mark.
๐๐ = 26.0 ๐๐๐๐
Figure C1-Seeley graph
[Source: Mountain Empire Community College, n.d]
56. C.7
6. The intensity of a 1 in 6.25 year and a 1 in 62.5 year storms are determined using
the Mid-Century IDF curve that has the most up to date predictions based on
climate change data in New Brunswick. The intensity is then converted to inches
per hour.
๐6.25 = 45.0 ๐๐/โ๐ ๐62.5 = 75.0 ๐๐/โ๐
๐ * 0.0393701= ๐ (in/hr)
๐6.25 = 1.8 ๐๐/โ๐ ๐62.5 = 3.0 ๐๐/โ๐
7. The Peak run-off is calculated using equation 6, and then converted into meters
cubed per second.
๐ = ๐ถ ๐ โ ๐ โ ๐ด ๐
๐6.25 =0.46*1.8*69.1=57.2 ft3
/s
๐62.5 =0.46*3.0*69.1=95.4 ft3
/s
Q * 0.028316847 = Q (m3
/s)
๐6.25 =57.21*0.028316847 =1.6 m3
/s
๐62.5 =95.4*0.028316847 =2.7 ft3
/s
These values can now be used as approximate peak run-off for ditch and culvert design.
NOTE: All calculations were done using the modified Mid-Century IDF curves.
57. C.7
Catchment 1
Drainage areas Area(m2
) Area(acres) C value
Residential 147103.73 36.4 0.55
Agricultural/field 110873.57 27.4 0.4
Commercial 0.00 0.0 0.8
Forest 21553.25 5.3 0.2
Total Area 279530.55 69.1
weighted C
value 0.46
Hydraulic length(m) 440.0
Hydraulic length(ft) 1443.7
Slope of Road 2.3
Time of concentration
(min) 26.0
Intensity 6.25 year (in/hr) 1.8 Intensity 62.5 year (in/hr) 3.0
peak run-off 6.25 year(ft3
/s) 56.7 peak run-off 62.5 year(ft3
/s) 94.5
peak run-off 6.25 year(m3
/s) 1.6
peak run-off 62.5
year(m3
/s) 2.7
58. C.8
Catchment 2a
Drainage areas Area(m2
) Area(acres) C value
Residential 0.00 0.0 0.55
Agricultural/field 59281.51 14.6 0.4
Commercial 80479.22 19.9 0.8
Forest 225191.68 55.6 0.2
Total Area 364952.41 90.2
weighted C value 0.36
Hydraulic length 591.73
Hydraulic length(ft) 1941.38
Slope of Road 2.61
Time of concentration 29.00
Intensity 6.25 year (in/hr) 1.65 Intensity 62.5 year 2.8
peak run-off 6.25 year (ft3
/s) 54.40 peak run-off 62.5 year (ft3
/s) 90.7
peak run-off 6.25 year(m3
/s) 1.54 peak run-off 62.5 year(m3
/s) 2.6
Catchment 2b
Drainage areas Area(m2
) Area(acres) C value
Residential 0.00 0 0.55
Agricultural/field 5611.89 1.386727969 0.4
Commercial 10943.57 2.704214046 0.8
Forest 4099.43 1.012990224 0.2
Total Area 20654.88 5.103932239
weighted C value 0.57
Hydraulic length 153.39
Hydraulic length(ft) 0.00
Slope of Road 1.96
Time of concentration 16.00
Intensity 6.25 year (in/hr) 2.36 Intensity 62.5 year (in/hr) 4.13
peak run-off 6.25 year (ft3
/s) 6.90 peak run-off 62.5 year(ft3
/s) 12.07
peak run-off 6.25 year(m3
/s) 0.20 peak run-off 62.5 year(m3
/s) 0.34
59. C.9
Catchment 3
Drainage areas Area(m2
) Area(acres) C value
Residential 0.00 0 0.55
Agricultural/field 128086.69 31.65090984 0.4
Commercial 36838.60 9.103015547 0.8
Forest 59483.70 14.69874112 0.2
Total Area 224408.98 55.4526665
weighted C value 0.41
Hydraulic length 711.77
Hydraulic length(ft) 0.00
Slope of Road 2.76
Time of concentration 28.00
Intensity 6.25 year (in/hr) 1.69 Intensity 62.5 year (in/hr) 2.95
peak run-off 6.25 year (ft3
/s) 38.74
peak run-off 62.5 year
(ft3
/s) 67.6
peak run-off 6.25 year(m3
/s) 1.10
peak run-off 62.5
year(m3
/s) 1.91
Catchment 4
Drainage areas Area(m2
) Area(acres) C value
Residential 0.00 0 0.55
Agricultural/field 70947.28 17.53145391 0.4
Comercial 0.00 0 0.8
Forest 84393.84 20.854171 0.2
Total Area 155341.11 38.38562491
weighted C value 0.29
Hydraulic length 330.31
Hydraulic length(ft) 1083.71
Slope of Road 4.36
Time of concentration 30.00
Intensity 6.25 year (in/hr) 1.65 Intensity 62.5 year (in/hr) 2.83
peak run-off 6.25 year(ft3
/s) 18.49
peak run-off 62.5
year(ft3
/s)
31.7
0
peak run-off 6.25 year(m3
/s) 0.52
peak run-off 62.5
year(m3
/s) 0.90