300798 Tutorial Assignment 2: Sustainability and Risk Engineering

This document presents a detailed solution to a Sustainability and Risk Engineering tutorial assignment. The assignment covers several key areas, including calculating average rainfall intensity, determining rainfall intensity for a given duration and recurrence interval, and calculating annual exceedance probability. It also involves stormwater management, specifically calculating the reduction capacity of a treatment device for suspended solids in stormwater. Furthermore, the assignment includes a channel design problem requiring the determination of dimensions for a rectangular channel. The solution provides step-by-step calculations, formulas, and references to support the answers, making it a comprehensive resource for students studying environmental engineering and related fields. The assignment uses various parameters such as total water accumulation, area, time, recurrence intervals, and suspended solids to arrive at the solutions for each question. The solution provides a clear and concise approach to tackling each problem within the assignment brief.

Question 1
Given:
Total amount of water = 17 litres
Area = 1.27 m2
Time = 2 hrs 30 min
i) Needed: Average rainfall in mm/hr
Average rainfall= 17∗10−3
1.27∗10−4∗2.5 =53.54 mm/ hr (Bonnin, 2010)
ii) Rainfall intensity for 5 minute duration
Given:
Total amount of water = 1.8 litres
Rainfallintensity = 1.8∗10−3
1.27∗10−4∗5
60
=170.08 mm/ hr (Newby, 2015)
iii) Required: Annual Exceedance Probability (AEP)
Given:
Average Recurrence Interval ARI=50 years
Annual Exceedance Probability AEP= 1
ARI ∗100 % (Bonnin, 2011)
AEP= 1
50∗100 %=2%
iv) Required: Rainfall Intensity
Given:
ARI=20 years
5-minute duration
ln ( I ) =4.978+0.7533 ln 5−0.2796 ( ln 5 ) 2+0.0166 ( ln 5 ) 3
I =253.50 mm/hr
Question 2
Given:
Stormwater generated = 300 ML
Suspended solids = 12 mg/l
Amount of solids discharged = 2.16 tonnes
Needed: Reduction capacity

Amount of suspended solids in stormwater ¿ 12∗300∗106 =3.6∗109 mg
¿ 3.6 tonnes
Reduction capacity ¿ 2.16
3.6 ∗100 %=60 % (Moore, 2016)
Question 3
Q= AV
V = 1
n R
2
3 S
1
2
R= A
P = 10
155∗2 =0.032 m
s=0.021
n=0.013
V = 1
0.013∗0.032
2
3 ∗0.021
1
2 =1.124 m/s
Thus,
Q=10∗1.124=11.24 m3 /s
Working for dimensions;
A R
2
3 =10∗0.032
2
3 =1.008
1.008= √3∗( y8
4 )1
3
y=0.97 m
A=2 y2 =2∗0.972=1.885 m2
Breadth B=2 y=2∗0.97=1.94 m
Q= AV
V = Q
A = 11.24
1.885 =5.963 m/s
Drawing representation
V = 5.963 m/s H = 0.97 m
B = 1.94 m

Question 4
Given:
Initial investment ¿ $ 120000
Annual Benefits = $ 13200
T = 7 years
Salvage value = $ 34000
Interest rate r =7.5 %
Needed: Net present worth NPV
NPV =∑ cashflow
( 1+i )t −initial investment +salvage value (Siddique, 2014)
NPV =∑
t=1
7 13200
( 1+ 0.075 ) t −120000+34000
NPV =−$ 16084.86
Question 5
Given:
Capacity = 230 KW
Capital cost = $5500/KW
Interest rate = 3.8%
T = 25 years
Capacity factor = 0.72
Required: Annualised capital cost and levelised cost.
Annualised capital cost At = Asset prices∗interest rate
1− ( 1+interest rate )−t (Zakeri, 2015)
¿ ( 230∗5500 )∗0.038
1− ( 1+0.038 )−25
¿ $ 79271.11

Levelised cost=
I +∑
t =1
25 At
( 1+i ) t
∑
t =1
25 M
( 1+i ) t
(Larsson, 2014)
¿
( 230∗5500 )+∑
t =1
25 79271.11
( 1+0.038 )t
∑
t =1
25 230∗0.72
( 1+0.038 )t
¿ $ 984.74
References
Bonnin, G. M. (2010). Trends in heavy rainfalls in the observed record in selected areas of the
US. In World Environmental and Water Resources Congress 2010: Challenges of Change (pp.
2432-2440).
Bonnin, G. M., Maitaria, K., & Yekta, M. (2011). Trends in Rainfall Exceedances in the
Observed Record in Selected Areas of the United States 1. JAWRA Journal of the American
Water Resources Association, 47(6), 1173-1182.
Larsson, S., Fantazzini, D., Davidsson, S., Kullander, S., & Höök, M. (2014). Reviewing
electricity production cost assessments. Renewable and Sustainable Energy Reviews, 30, 170-
183.
Moore, T. L., Gulliver, J. S., Stack, L., & Simpson, M. H. (2016). Stormwater management and
climate change: vulnerability and capacity for adaptation in urban and suburban contexts.
Climatic change, 138(3-4), 491-504.
Newby, M., Franks, S. W., & White, C. J. (2015). Estimating urban flood risk–uncertainty in
design criteria. Proceedings of the International Association of Hydrological Sciences, 370, 3-7.
Siddique, A. R. M., Khondokar, A. A., Patoary, M. N. H., Kaiser, M. S., & Imam, A. (2014,
February). Financial feasibility analysis of a micro-controller based solar powered rickshaw. In
2013 International Conference on Electrical Information and Communication Technology
(EICT) (pp. 1-5). IEEE.
Zakeri, B., & Syri, S. (2015). Electrical energy storage systems: A comparative life cycle cost
analysis. Renewable and sustainable energy reviews, 42, 569-596.