Fall 2018
Environmental Engineering
San Diego State University
Proposal
The Greenacres City Council has just been informed that a local city park may have had a low-grade contaminant within the latest annual mosquito spraying. Testing of the contaminant and quantifying the health impact of exposure is required by the city’s health department.
Even though the department cannot yet quantify the effects, they have identified a chain of health problems associated with the contaminant. If the contaminated vegetation is burned, the contaminant is then released back into the air as a vapor. The health effects of this vapor is that it can irritate the eyes and can cause acute damage to anyone wearing contact lenses. Although the contaminant is irritable as a vapor, there is no problem if it is touched or eaten, thus the main danger of the contaminant would be campfires, disposal of windblown leaves (which could mix with the local residential area), or the possibility of wildfire in the park. The health department also stated that sunshine reduces the toxicity of the contaminant over a 2 to 3 year period, and after 4 years, the danger of the contaminant will be eliminated.
The city council expects that the publicity of the contaminant will be large and have decided that a benefit/cost analysis must be done immediately, before the health department supplies any results. The city manager must have preliminary results within 24 hours.
The city manager expects the council will want to have definitive conclusions for the two worst-case scenarios:
1.) Scenario 1: Removal of all vegetation and turning the park into a landfill
a. Step 1: Remove all vegetation and burn it in a specially controlled environment
i. The city is in an industrial area where hazardous waste facilities are available, costing approximately $2 million to $5 million.
b. Step 2: Create a substantial cover using the site as a temporary landfill
i. 20 homeowners will have to be bought out, costing $135,400 each.
ii. All other associated costs can be ignored since the city will be incurring them at another site.
c. Step 3: In 3 years, the cover would be deep enough that the landfill can be converted back into a park
i. The park currently emphasizes vegetation, jogging paths, and similar uses, but the plantings and regrowth are likely to be far to slow after the conversion.
1. Thus, the city engineer recommended the area could instead be used as a complex of playing fields for softball, baseball, soccer, and football.
a. The would cut the regrowth time and would only require $300,000 for construction
ii. The city engineer has suggested a “net benefit” stream of $125,000 annually for the field complex after maintenance costs. She also identified a 5% discount rate that the city council accepted for that study.
2.) Scenario 2: The maximum health cost in the complete absence of recovery efforts
a. This scenario is far less defined as there is difficulty in estimating the probability of different kinds of fires and then estimating how many people could be affected.
i. A wildfire is the least likely, but could affect the 35,000 people who live in proximity to the park
1. A wildfire has a probability of 0.002, but may increase to 0.01 due to publicity and arson.
b. Although, over a 3 year period, someone is almost certain to build a fire with vegetation containing the contaminant.
i. Over 20% of the park goers are picnickers
1. ¼ of those parkgoers use wood
ii. Leaves from this year in this scenario are less of an issue, but would still need to be collected and incinerated, costing about $1 million.
The possible danger is not exactly known, but it appears to be associated with park usage. There are approximately 250,000 visitor-hours per year and growing about 15,000 hours per year, which is slightly faster than the city’s population. Clearly, an exact answer is impossible, but nevertheless, an answer is required.
Analysis
This analysis will break broken into 2 parts which will examine the benefit-cost ratio analysis of present worth and annual cost then each scenario will be compared. Since scenario 2 is not as defined as scenario 1, the report will also do a probability analysis of scenario 2.
Scenario 1
Present Worth Analysis (Equivalent Present Consequences), using the most conservative estimates
With present worth analysis, reference Appendix A. As seen on that spreadsheet, it would take over 100 years for the new field complex to return a profit, thus, this present worth benefit-cost ration is < 0.
Annual Cost Analysis
With annual cost analysis, reference Appendix A. As seen on that spreadsheet, this analysis also shows that it will take over 100 years for the new field complex to have a positive annual return. This annual cost benefit-cost ratio is < 0.
Scenario 2
Present Worth Analysis (Equivalent Present Consequences), using the most conservative estimates
With present worth analysis, we see that the city will pay a onetime fee of $1,000,000 for the incineration of all contaminated leaves. This present worth benefit-cost ration is < 0 until the city returns enough money for this cost to be covered, probably allocated from another department.
Annual Cost Analysis
With annual cost analysis, reference Appendix A. As seen on that spreadsheet, this analysis also shows that it will take over 100 years for the new field complex to have a positive annual return as in this scenario, the park will not have a positive annual return. This annual cost benefit-cost ratio is < 0.
Probability of Fire
With the probability of contaminated vegetation being burned, reference Appendix B. In Appendix B, we see that out of all 4 years the contaminant is active, there is a 26% chance that the contaminated vegetation will be burned at any given time.
Recommendation/Conclusion
With scenario 1, the city will essentially be losing money on the park alone for over 100 years, if the money isn’t supplied by another department. Fiscally, this scenario is not ideal, but it protects the fraction of the public that wear contacts. Scenario 2 will only cost $1 million to the city, but the park will essentially be “off limits” to people that prefer to wear contacts. With this scenario, the probability that any contaminated vegetation could be burned within the four-year period is 26%.
Because the eye damage that can occur, the public must be notified immediately, of the source of the contaminant and what the general public can do to protect themselves. One option for obtaining the money for both scenarios is to investigate the company that administers the mosquito spray to see what exactly was at fault.
The risk with scenario 1 is that the money for this project is possibly not readily available, but it would protect the health of the general public. Risk with scenario 2 is that anyone who wear contacts and comes into contact with the contaminant vapor could get acute damage to their eye.
With public water systems, if any acute contaminants are detected, that water system is required to notify its customers within a 24 hour period, or even have their water shut off by their supplier. Any contaminants in the air should be held to the same standard. My recommendation is that if the money is readily available, continue with scenario 1. If the money is not, then close the park, and hold a public forum on what the citizens who live in proximity to the park think. To me, the safety of any citizen is priceless and would continue with scenario 1 as the citizens look to their government for protection.
References
Donald G. Newnan, Ted G. Eschenbach, Jerome P. Lavelle, and Mean A. Lewis. Engineering Economic Analysis. Oxford University Press, New York, 2017.
Appendix A
![]()
Appendix B
![]()
10
Years (n)(P/A, 5%, n Years)PW 1(A/P, 5%, n Years)EUAC 1EUAC 2
10.952-78890001.05-8283400-1050000
21.859-77756250.5378-4181702-537800
32.723-76676250.3672-2815538-367200
43.546-75647500.282-2133256-282000
54.329-74668750.231-1724848-231000
65.076-73735000.197-1452576-197000
75.786-72847500.1728-1258782-172800
86.463-72001250.1547-1113838-154700
97.108-71195000.1407-1001726-140700
107.722-70427500.1295-912036-129500
118.306-69697500.1204-839163-120400
128.863-69001250.1128-778302-112800
139.394-68337500.1065-727852-106500
149.899-67706250.101-683808-101000
1510.38-67105000.0963-646170-96300
1610.838-66532500.0923-614138-92300
1711.274-65987500.0887-585310-88700
1811.69-65467500.0855-559684-85500
1912.085-64973750.0827-537262-82700
2012.462-64502500.0802-517242-80200
2112.821-64053750.078-499624-78000
2213.163-63626250.076-483608-76000
2313.489-63218750.0741-468393-74100
2413.799-62831250.0725-455580-72500
2514.094-62462500.071-443568-71000
2614.375-62111250.0696-432357-69600
2714.643-61776250.0683-421946-68300
2814.898-61457500.0671-412337-67100
2915.141-61153750.066-403528-66000
3015.372-60865000.0651-396321-65100
3115.593-60588750.0641-388313-64100
3215.803-60326250.0633-381906-63300
3316.003-60076250.0625-375500-62500
3416.193-59838750.0618-369894-61800
3516.374-59612500.0611-364289-61100
4017.159-58631250.0583-341866-58300
4517.774-57862500.0563-325850-56300
5018.256-57260000.0548-313838-54800
5518.633-56788750.0537-305030-53700
6018.929-56418750.0528-297822-52800
6519.161-56128750.0522-293018-52200
7019.343-55901250.0517-289014-51700
7519.485-55723750.0513-285810-51300
8019.596-55585000.051-283408-51000
8519.684-55475000.0508-281806-50800
9019.752-55390000.0506-280205-50600
9519.806-55322500.0505-279404-50500
10019.848-55270000.0504-278603-50400
Total visitor-
hours to park
Visitor-
hours of
wood use
Probability
of wildfire
Total Probability
of Vegetation
being burned
Fraction of time
that vegetion being
burned is possible
2500006250025006500026
2650006625026506890026
2800007000028007280026
2950007375029507670026
jhayes
6.Sample-6.docx
0
