Pre-Feasibility Report
Detroit (Zug Island) CSO Control Project
Eastern Outfall (DRO-1)
Prepared For:
City of Detroit
Detroit, Michigan
Prepared By:
GMMN Consultants
July 20, 2009
Table of Contents
Summary:
Introduction:
The Detroit Combined Sewer Overflow (CSO) Control Project – involves the design and construction of CSO control measures for one outfall, in the City of Detroit, MI. On July 20, 2009, GMMN submitted a Design Report to the Michigan Department of Environmental Quality (MDEQ) on behalf of the City of Detroit for the Detroit CSO Control Project. The Design Report developed new alternatives and evaluated previously developed CSO control alternatives. The recommendation from the Basis of Design Report calls for the construction of one treatment shaft to capture and treat CSO prior to discharge into the Detroit River. This CSO control program will be completed to meet existing National Pollution Discharge Elimination System (NPDES) permit requirements as set forth by the MDEQ.
The City of Detroit has retained GMMN Consultantsto provide design services for the Detroit CSO Control Project. This report includes a project background, an explanation of the economic and health indicators, resources and control, sector organization and developments, past projects, the people and project area and the overall need for this project.
PART I:
Detroit Michigan, like many other older cities was built using a combined sewer overflow system (CSO). CSO’s are notorious for not meeting the requirements put into place by the clean water act, and therefore there are specific guidelines for what must be done to a CSO put into place by the EPA. Detroit is the major urban center of Michigan, with almost the entire city developed over in some way. Detroit has many CSO’s which all dump into the Detroit river when substantial amounts of rain falls.
It is important to note the population and economic standards of Detroit’s current status. As of April 2009 Detroit’s unemployment rate is 22.8%. The economy here tends to go hand and hand with the fluctuations of the American automaker. In 2008 Detroit ranked 11th nationally in population with 912,062 residents living in the city. 81.6% of the population is African American. 21.7% of residents are below the poverty line, with the average income being around $29,500 per year.
The project we would be undertaking requires a large amount of concrete and the expertise necessary to build a structure like this that will perform up to the necessary standards. The Detroit area is quite capable of producing both, with concrete being readily available and a large amount of engineers located within just miles of the site, producing the product should not be limited because of materials or lack of qualified personnel.
Many parties will be involved with the oversight of this project including the army core of engineers, Detroit city council and other politicians, the EPA and MDEQ.
The core of engineers will likely have to decide whether this addition will change the Detroit River in any way that may be harmful to economics or the environment. The city council controls the budget for such projects and ultimately lets the public know what is going on in their city. The EPA and MDEQ will be on site during construction to make sure all goes well and that the project does what it is supposed to once complete.
Very few projects have been even considered in the area over the past 10 years. The city of Detroit is in serious debt and this project will only take place because of the EPA mandate. In cities with similar projects, such as Indianapolis where a 2 billion project is in place to store all overflow underground in a large horizontal pipe, costs are expected to be much greater simply because of their picking other options. Unfortunately government money has nearly dried up, as this mandate was passed over 15 years ago now.
PART II:
The general purpose of our proposed solution is to eliminate a substantial amount of pollutants contributed by combined sewage overflow. The end result of our report will be the culmination of the work of our immediate team members. However, the successful implementation of our solution also relies on external institutions such as the Detroit city council, contractors, the general public, and some commercial establishments. The roles of each, with respect to our proposed solution, will now be outlined.
The city of Detroit has retained us, the GMMN consultants, in order to provide design services for the Detroit CSO Control Project. As such, our function is to provide the background for the project, an explanation of economic and health issues relative to the problem at hand, resources available and needed,explanation of past projects undertaken related to CSO, and an overall need for this project. The combined work of the team members will be the document that will be presented to the Detroit city council, and also the general public. The latter, to raise awareness of the situation, approve the required costs, and the former to facilitate this process, and implement our recommended solution. Once this stage of the process is complete, contractors may be hired to construct the structure. Once this process is complete, a countermeasure to the pollution as a result of CSO will be in place at Zug Island, our area of interest.
Zug Island is located near the southern city limits of Detroit. At this location, the mouth of the Rouge River spills into the Detroit River, making it an effective location for our structure. The area is highly industrialized and is off limits to the general public. Wildlife are the only inhabitants of the island. The areas along the south and west shores of the island provide habitat them. Carrying out construction in this area does not present any foreseeable disadvantages to any parties involved.
PART III:
PROJECT ALTERNATIVES:
A number of alternatives had been presented in the past for the control of such overflows devices, some successful, some ill-fated. During the initial concept of the control system, we looked at a few of these alternatives and weighed the economic, social, financial, environmental, and technical feasibility of each.
Rock Tunnel:
Construction work for a prior project (DWSD Contract PC-709) was undertaken in November, 1999 and was planned to be operational in May 2005. That project consisted of an approximately 1-mile-long, 21-foot finished diameter rock tunnel approximately 300 feet below ground surface with associated shafts and terminal effluent diffusers. It was designed to transport and discharge during the critical design flood condition 1,000+/- million gallons per day (mgd) of treated wastewater from the existing Rouge River Outlet conduit to the Detroit River and would meet current NPDES requirements. However, construction of this initial project was halted following a flood event during tunneling activities in April 2003. In 2006, a salvage effort was planned at a cost of over 200 million dollars, however; the plan was abandoned when underlying geological problems discovered during the geological investigations, performed during the study phase, dictated a great risk factor at the installation depth of 200 feet. (DWSD.1)
Increase Capacity of Waste Water Treatment Plant:
The current Detroit Water and Sewer (DWSD) water treatment plant is the largest single-site wastewater treatment facilities in the United States. Of the more than $22.5 million spent to ready the plant for its February 1940 startup, $10 million was spent on plant construction with the balance going to complete the network of huge interceptor sewers through which a combined stream of storm and sanitary wastewater flows to the plant from communities throughout metro Detroit. (DWSD.2)
Today, the cost of upgrading and/or increasing the capacity of a waste water treatment plant requires a large amount of capital which most communities simply do not have.
Retention Basin:
A CSO Retention Basin temporarily stores wastewater flow that exceeds system capacity. The basin’s contents are released to the Wastewater Treatment Plant only after overall system flow has subsided and the plant is once again able to accept it. During its brief stay in a CSO basin, wastewater is screened and treated with a strong disinfectant.
The Decanting feature incorporated into the Department’s basins comes into play on those occasions when basin capacity is exceeded by successive storm flows. A portion of the basin’s contents are released into the river, but only after the wastewater has been subjected to prolonged settling, screening and adequate disinfection procedures. (DWSD.3)
Several of these retention basins are already in operation in and around the City of Detroit; however, again due to severely high costs in due to special construction techniques, this option is not as cost effective. One retention basin was originally projected to cost approximately 94 million dollars but the end cost was 168.7 million dollars.
CONCLUSIONS AND RECCOMENDATIONS:
Based on the research conducted and our extensive knowledge of the area, we believe that a self-sinking, circular, several staged, reinforced concrete caisson is the most technically, financially, and environmentally efficient method of storing and treating excess combined sewer overflow for this particular area. Several of these self sinking caissons have been constructed in the nearby city of Dearborn with moderate success.
Several problems could plague the construction phase of the caisson as encountered in Dearborn. The history of Zug Island is that of basically an industrial waste land used by steel manufactures for over 100 years. So one could hardly predict what kinds of obstacles could be encountered during the sinking phase. It is these obstacles which could be encountered that can possibly damage the caisson and/or present some other setbacks. Some of the previously encountered problems were:
Groundwater –
Boulders –
Differing Site Conditions (DSC) –
Inaccurate Geotechnical Data –
Poorly Controlled Sinking of the Caisson –
Tilt and Roundness Out of Tolerance –
Corrections made to the above mentioned circumstances:
Dewatering Wells
Mechanical Excavation of Boulders
Thorough Geotechnical Data (History and Present)
Proper Sinking Plan Submitted for Review
Constantly Surveying the Caisson
With the mentioned corrections and checks, as well as with care and proper oversight, the construction of the caisson should be relatively straight forward and completed without any major obstacles.
REFERENCES: