quantitative engineering questions

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CEE 350 Assignment 4

You have the option to work on this project alone, or in groups of 2 or 3. If work is done in a group, each member of the group should submit the complete assignment on Canvas.

A luxurious suburb region in Omaha, Nebraska will be transformed into an ecocity with initial funding from Berkshire Hathway Inc. The plan of the investor is to attract new talents to the Midwest to employ in a technology hub for 5G and green energy. Note that in all the calculations below no pipe leakage will be considered, thus water is conserved in the system.

There are 500 homes in the subdivision. The estimated family size is 5 people. Total lands of the subdivision cover 1.32 km2, with the following breakdown of land use.

Land type Area (m3) and attributes

Single family homes 500 homes, 1000 m2 (~1/4 acre) footprint on soils with low infiltration capacity: 150 m2 roof, 25 m2 paved driveway, and 825 m2 yard in good condition >75% grass.

Streets and roads (paved, with curbs and storm sewer)

200,000 m2

Commercial and business 125,000 m2 (85% impervious)

Parks and greenbelts,>75% grass, same as yards.

500,000 m2

The frequency distribution of rainfall depth for a mean number of observed storms of 55 in a year is given below (MAP is mean annual precipitation):

# of storms 55

MAP (mm) 789.25

rainfall (mm) Fraction Cum. (mm)

5 0.4 110

10 0.2 110

15 0.15 123.75

20 0.05 55

25 0.05 68.75

30 0.04 66

35 0.02 38.5

40 0.03 66

45 0.05 123.75

50 0.01 27.5

Cumulative: 1 789.25

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

5 1

0

1

5

2

0

2

5

3

0

3

5

4

0

4

5

5

0 Rainfall depth (mm)

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Water requirements:

• According to recent statistics a person in Lincoln, NE uses 320 L/(cap-day). This amount excludes irrigation of yards.

• Irrigation requirement of yards is 3 mm/d for a period of 60 days in the summer. Individual homeowners use this from the grid before the ecocity planning. Irrigation water in the parks are not part of ecocity calculations.

• Storm runoff in the common areas (schools, parks, roads, parking lots) are not included in the fee because they are subject to river discharge without treatment. Runoff from common areas can be captured and reused in homes with centralized treatment for this community.

• Runoff from individual yards can also be captured for reuse purposes with treatment.

• There is a creek that runs year-around with a flow discharge of 40 m3/h inside the development area. The Department of Ecology only allows the use of half of this creek discharge in order to leave sufficient flow for aquatic life.

Energy requirements:

• Energy needed for using water from the grid is 0.9 kWh/m3.

• Energy needed for wastewater removal and treatment by the city of Lincoln grid is 0.75kWh/m3. This amount is charged to each household regardless if the water is used in the house (and returned as wastewater) or used for watering plants (and not returned). The volume of overland flow from house roofs connected to the sewer system by downspouts is also subject to this rate.

• Estimated energy for pumping water from the creek and filtering is 0.51 kWh/m3.

• Energy for pumping and filtrating of roof runoff for irrigation is 0.25 kWh/m3.

• Estimated energy cost of treatment of runoff water from driveways and roofs for residential use is 0.65 kWh/m3.

• Energy cost of wastewater treatment is 1.2 kWh/m3 (for full recover and reuse). Cost of water:

• Cost of metered residential water from the grid is $2.00 per unit (a unit water is 748 gallons) applied as a uniform rate.

• Cost of residential wastewater discharge into the grid is $2.45 per unit. Carbon equivalent of energy: Nebraska obtains 63% of its net electricity generation from coal, 15% from nuclear power, and 14% from wind. The rest is generated from hydropower (4%) and natural gas (3%). Hydropower, nuclear and wind are considered green energy for this project. You can use the table below for CO2 release per kWh energy production.

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Task: The investor wants to develop a concept towards ecocity that:

• Reduce the current use of water from the grid by half

• Reduce its current CO2 footprint in half or more (if possible)

• Per-capita water reduction in houses should not exceed 15% of the current use.

• Reduce the cost of current energy cost in US$ by half. However, if the cost reduction cannot be met, the client still wants to see your scenarios that can reduce large amounts of emissions.

• Xeriscape is acceptable, however the client wants you to look into option of roof runoff for irrigation and keep yards at least for a certain fraction of the landscape.

They want to know if only using the runoff water in the land and partly from the creek can achieve this. You are asked to plan a water use strategy for this goal. You can suggest any changes on the driveway material or convert loan to xeriscape (see the related limitation below) that will not require irrigation. You will need to pay attention to the limitations listed above. If the proposed goal of the investor cannot be achieved, develop a solution that will come closest to what they ask for. Answer the following questions which will also help to organize your ideas.

Before development:

a) Calculate the total annual water requirement for the city before development. (Answer: 366,250 m3/yr) (1 point)

b) Calculate the cost (in US$) of water use and wastewater disposal (and their sum) for the city. (Answer: 626,600 dollars/yr) (1 point)

c) Estimate the energy use per capita per day in kWh/cap-day that includes both using the water from the grid and wastewater (including irrigation water although not returned). (Answer: 0.71 kWh/(cap-day)) (1 point)

d) Estimate the total CO2 emission in kg/year from this suburban region before development. (Answer: 404,150 kg/yr) (1 point)

For development consider the scenarios below. Report your results in a table that will include the name of the scenario, Water use m3/year; Emission in kg CO2 /year; Cost in US$. You will develop two plots with the data you will generate for different scenarios. You will plot Water use (m3/year) in x-axis in both plots. One of the plots will use kg CO2/year and the other plot $/year on y-axis. You will explore if your figure looks like Novotny (2011) hypothesis. Please address many alternatives as you can and plot your options.

e) Reduce water use in houses 15% (1 point) f) Reduce water use 15%, keep existing yard and supplement irrigation water with roof runoff (1

point)

g) Reduce water use 15% and convert all lawns to xeriscape (1 point) h) Reduce water use 15%, keep existing yard and supplement irrigation water with roof runoff (1

point)

i) Reduce water use 15%, convert all lawns to xeriscape, treat and use runoff from roof and driveways in residences (1 point)

j) One additional scenario of your choice (1 point)