CVEN30010 System Modelling and Design
CVEN30010 System Modelling and Design 2017
A new township is proposed in Western Tasmania, Australia. The township is planned for 200 households and 15 small business outlets (cafes, a child care, a service station, etc.). Several dairy farms with up to 30,000 dairy cows will be operating near the township. To provide water to the township and the dairy farms, a water storage reservoir is proposed to be constructed not far from the future township. The reservoir will be constructed in an existing valley. Water will be supplied from the reservoir to the townships and farms through two separate water supply systems.
Figure 1 shows preliminary design decisions for the township, the dairy farms and the reservoir.
As an engineering design consultant, you are asked to provide a conceptual design of the water storage reservoir and the water supply systems. The conceptual design has to address several key aspects of these facilities that are outlined as separate tasks below. The conceptual design has to be presented as a design report with appendices.
Propose names for the township and the water storage reservoir and use these names in your design report.
Embankment distribution centre Dam
Figure 1: Preliminary design decisions for township, dairy farms and reservoir (not to scale)
Task 1. Ground Model
Prepare a critical geological cross-section BH1 – BH8 of the ground model using the site investigation data provided in Appendix A. The cross-section has to show the ground surface level, ground layers with depths and the location of the ground water table.
Task 2. Water Storage and Catchment
Calculate the reservoir storage volume and the catchment area required to provide reliable water supply to the township and dairy farms. For water supply reliability, the volume of water in the reservoir cannot be less than 1,000,000 m3 at any time.
In your calculations, you should use the site investigation data presented in Appendix A and the water consumption information for the township and the dairy farms presented in Appendix B.
In the estimation of the seepage through the embankment dams, the total length of the dams can be assumed as not more than 500 m.
Consider rainfall and evapotranspiration data for 2010-2012 in your calculations. You can assume that the initial water volume in the reservoir on 1 January 2010 is 2,500,000 m3.
Task 3. Water Supply Systems for Township and Farms
Propose a conceptual design of water supply systems to deliver water from the water storage reservoir to the township and the dairy farms. This task is split into three subtasks.
Subtask 3.1. Town water supply system
Propose a reliable and cost-effective system to supply water from the water storage reservoir to a water distribution station of the township. This system has to be designed to supply water for the residential properties and local businesses only. The design should consider capital investment into the system (or its installation cost) and an operating cost (or a pumping cost) during 20 years of the lifetime of the system.
A pipeline route of the water supply system has been identified. The route can be assumed to be a straight line going 12 m uphill from the reservoir to the water distribution station of the township. The length of the pipeline is estimated as 4,000 m.
Your design should include:
- The water supply pipework diameter selected (a single diameter pipework should be proposed);
- The schematic diagram of pump/s arrangements showing number of pumps and their configuration (for example parallel, in series or combined);
- The preliminary installation cost of the town water supply system proposed and its operating (pumping) cost for 20 years.
Appendix C provides a list of available materials and equipment for the design equipment and other information about the system.
Subtask 3.2. Water tower
Propose a reliable and cost-effective design of a water tower to store water for the township for the cases of power outrage or other emergencies. The water tower has to store a 3-day supply of water for the households and local businesses. The farms will have local water storage facilities (such as ponds and water storage tanks), so they will not be connected to the water tower.
Your conceptual design of the water tower should show the geometry of the tower that you propose including its height, shape and water reservoir dimensions. In your design, consider the technical requirements to the water tower provided in Appendix C.
Subtask 3.3. Water supply system for farms
Propose a reliable and cost-effective system to supply water from the water storage reservoir to the farm water distribution centre.
All farms have local water storage facilities such as pounds and water storage tanks. Water to the farms will be supplied from the reservoir each second day over a 2-hour period. The water supply will be organised through a main concrete open flow channel.
The main channel path has two straight legs:
- The first one from the reservoir is 1,200 m long with 4 m drop in height;
- The second one is 1,500 m long with 1 m drop in height.
Up to two different cross-sections (one per leg) of the main channel can be proposed. It can be assumed that all possible shapes of the main channels have the same 100 mm thickness of their walls for structural purposes.
Task 4. Stability of Existing Slopes
It was identified that the cross-section BH1 – BH8 shows the two most critical existing slopes of the reservoir for sliding. Assess stability of these existing slopes against sliding before and after the reservoir is constructed and propose adjustment of the slopes if necessary. When the water storage reservoir is constructed, the valley will be filled with water up to 213 m from RL.
A slope is considered stable against sliding if its factor of safety (FoS) against sliding is more than 1.2.
If slope/s are not stable, propose slope stability improvement measures using available methods. You can use cut-and-fill, removal of soil and placement of imported fill methods to improve stability of the slope/s.
To address this task, you should:
- Model both slopes in SLOPE/W and find critical failure surfaces and the minimum FoS against sliding using Bishop’s method.
- For one slope of your choice, perform hand calculations using Bishop’s method and compare the calculation result with the SLOPE/W result. In your hand calculations, use the critical slipe surface identified by the SLOPE/W modelling.
- Check the stability of slopes against sliding for the case when the valley is filled with water.
- If necessary, propose slope stability improvement measures using available methods. Your solution must be cost-effective, constructible and should not considerably reduce the volume of the future reservoir. The level of the bottom of the reservoir should not be changed.
Appendix D provides costs of slope stability improvement measures for your calculations and geotechnical parameters of imported fill.
Task 5. Embankment Dam
Embankment dams were proposed to restrict water flow from the water storage reservoir. To preserve water within the reservoir, seepage through the dams (including through the underlining soil) must be not more than 0.85 m3/day per metre length of dam. Propose a cost-effective conceptual design of the dams.
Appendix E provides two preliminary design options of the critical cross-section of the dams. Use these options as a starting point for your design. In addition, Appendix E provides the information about design requirements and costs of available materials.
At this conceptual design stage, you are asked to consider seepage through the dams only. The overall (global) dimensions of the dams are fixed for stability purposes and cannot be changed. One optimum cross-section has to be proposed as the recommended design option.
In the report, you should present:
- estimated daily seepage rates (in m3/day per metre length) through the dams and the underlining soil for the two preliminary design options of the dam cross-section using SEEP/W software,
- the sketch of the cross-section through the dams you recommend for construction showing layers,
- the preliminary installation cost of the dams (per metre length of dam) for the design you propose.
- Task 6. Environmental and Social Impact Assessment
Identify potential environmental and social impacts (both negative and positive) of construction and operation of the water storage reservoir proposed and outline measures to mitigate negative impacts.
This task should be completed by conducting a literature review and internet search of reputable sources. Identify the main potential impacts (up to seven) and present the results of your review in a table. Since you do not know the exact location of the reservoir, consider the impacts that would likely be applicable for Western Tasmania conditions.
It is expected that up to 2 pages of the report will be enough to address this task. Use Table 6.1 as a template.
Table 6.1: Environmental and Social Impacts
|Item||Impact Description||Proposed mitigation measures (if|
This assignment is to be undertaken on an individual basis and summarised in a design report. The report has to be not more than 20 pages excluding a title page, table of contents, references and appendices.
A suggested outline of the design report is given below.
Table of Contents
Water Storage and Catchment
Water Supply Systems for Township and Farms
Stability of Existing Slopes
Environmental and Social Impact Assessment
The main body of the report should present only key design decisions with concise justification and/or explanation. Where appropriate, summarise technical information into tables. The key design decisions should be illustrated with sketches/drawings where appropriate. Calculations, supplementary sketches/drawings, software calculation reports and other additional information should be presented in Appendices.
It is recommended to work on the assignment throughout semester. To help you to plan your time wisely, a suggested design project timeline is provided in Appendix F.
Please take very careful note that where copying and plagiarism is detected, penalties will be severely applied. This was clearly identified in some of the reports presented during last years for this subject and the penalties were applied.
The report is to be submitted online through a Turnitin link on the subject LMS website. The deadline of the submission is Sunday, 22 October, 5:00 pm. Late submissions without notification and justification will not be assessed.
GeoStudio 2016 Software
The Department has 50 site licences for the full commercial version of GeoStudio 2016 program, which includes SLOPE/W and SEEP/W. Students should be aware that there is a free 30-day trial version of the software available to download from the www.geo-slope.com website.
Because of the limited number of site licences, it is important that during the day, you keep to your allocated time in the computer laboratories
Site Investigation Results
During site investigation, eight boreholes were drilled down to 30 metres. The location of the boreholes and borehole logs are given in Figures A.1 and A.2 respectively.
The ground surface levels and ground water depths in the boreholes are given in Tables A.1.
Geotechnical parameters of the soil recorded on the site are summarised in A.2.
Table A.1: Ground surface levels and ground water depths
|Item||Ground surface||Ground water depth|
|level, m*||from the ground|
|* from reference level RL|
|Table A.2: Geotechnical parameters of soil|
|Material||Cohesion, c’||Friction angle, ?’,||Unit weight, ?|
|Dense silty sand||4||36||20|
|Stiff silty clay||16||21||19|
|Soft silty clay||8||18||17|
Preliminary site investigations show that the pan evaporation area of the reservoir will be approximately 500,000 m2.
The nearest Australian Government Bureau of Meteorology (BOM) weather station to the township location is Luncheon Hill, Tasmania. The daily evapotranspiration and rainfall data recorded by BOM during 2010 – 2012 is provided along with the Design Brief as a separate Excel file.
The ground properties of the catchment area are given in Table A.3. A1
Figure A.1: Relative location of boreholes
Table A.3: Ground properties of catchment area
Figure A.2: Borehole logs
Water Consumption Information
On average, water consumption of one household is estimated to be 500 l/day during April-October and 700 l/day during November-March. On average, each business outlet is estimated to consume about 400 litres of water daily.
The dairy farms will implement water efficiency measures to reduce their water consumptions. It is planned that the farms will use 10,000 litres of water per cow each year for general operational purposes (cleaning of equipment, cooling towers, irrigation, etc.). It can be assumed than this water usage is equality distributed throughout the year.
Each cow consumes 90 litres of water per day during April-October and up to 210 litres of water per day during November-March.
Other minor water needs of the households, the business outlets and the farms can be assumed to be of around 15% of their total daily consumptions.
Table B.1: Hourly water consumption distribution of households
|% of daily usage|
|12 am – 3 am||5|
|3 am – 6 am||5|
|6 am – 9 am||15|
|9 am – 12 pm||15|
|12 pm – 3 pm||10|
|3 pm – 6 pm||30|
|6 pm – 9 pm||15|
|9 pm – 12 am||5|
Table B.2: Hourly water consumption distribution of business outlets
|% of daily usage|
|12 am – 3 am||0|
|3 am – 6 am||0|
|6 am – 9 am||10|
|9 am – 12 pm||30|
|12 pm – 3 pm||30|
|3 pm – 6 pm||20|
|6 pm – 9 pm||5|
|9 pm – 12 am||5|
Town Water Supply System and Water Tower
The town water supply system has to maintain the minimum water pressure of 500 kPa at the water distribution station. For temporary water supply from the water tower, a minimum water pressure of 250 kPa has to be maintained at all households and business outlets.
HDPE pipework is proposed to be used for the town water supply system. The possible pipe sizes to be used in the design and their costs are given in Table C.1.
Table C.1: Pipe sizes and costs
|Inside pipe diameter, mm||Cost, $/m|
Excavation of trenches, pipework installation and backfilling are estimated to be $50 per metre length of pipeline for all pipe diameters. The cost of 1 kWh of electricity to power the pump/s can be assumed as $0.20.
The pump type available for the town water supply system is PLMGH 3-11. The pump performance curve is given in Figure C.1. The minor head losses can be assumed to be 1.5 m and the pump efficiency is 55%. One pump costs $4,000.
One of the most elevated location close to the township was selected to build the water tower. The minimum difference between the levels of the selected water tower location and residential dwellings is 15 metres (the tower location is higher than the locations of the dwellings).
In the design of pipework and pump/s as well as in the cost calculations, you do not need to consider water supply arrangement from the reservoir to the water tower.
Figure C.1: Pump performance curve
Slope Stability Improvement Measures
The costs of available slope stability improvement measures are given in Table D.1. The geotechnical characteristics of the compacted imported fill are given in Table D.2.
Table D.1: Unit costs of materials
|Sourcing, placement and compaction of imported fill||36|
|Excavation and local recompaction of soil from slope||24|
|Excavation and removal of soil from slope||20|
|Table D.2: Geotechnical parameters of imported fill|
|Material||Cohesion, c’||Friction angle, ?’,||Unit weight, ?|
|Compacted imported fill||3||34||21|
CVEN30010 System Modelling and Design
Two preliminary design options of a cross-section of the proposed dams are shown in Figure E.1.
The unit costs of the materials available for dam construction are given in Table E.1.
For constructability, it is recommended to use only one type of core material for the dams.
Hydraulic conductivities of the dam materials are given in Table E.2.
Figure E.1: Two preliminary design options of a cross-section of the proposed dams
Table E.1: Unit costs (installed) of materials
|Clayey core material, medium hydraulic conductivity||28|
|Clayey core material, low hydraulic conductivity||42|
Table E.2: Hydraulic conductivity of dam materials and sand
|Embankment backfill||2 x 10-5|
|Clayey core material, medium hydraulic conductivity||5 x 10-7|
|Clayey core material, low hydraulic conductivity||1 x 10-8|
|Drain material||5 x 10-4|
|Dense silty sand||5 x 10-6|
Suggested Design Project Timeline