-----Original Message-----
From: Harold Cunliffe [mailto:hcunliffe@pacificgroupinc.com]
Sent: Tuesday, May 07, 2002 9:20 PM
To: Walda Lavroff; Clair Muller; Gordon Certain; Howard Shook; Lucy Smethurst; Mary Norwood; Nancy Jones
Subject: Report
Dear All:
Attached is a report (my first) concerning the Nancy Creek Tunnel. Council Member Howard Shook has looked at it and asked me to pass it onto you. Please tell me if you wish to be removed from my list or if there are others that may wish to be added. I do not usually send messages such as this by attachment but it is thought that someone may wish to include it in a newsletter and thus, it can be easily edited. Also, my system has been recently checked for viruses and it is clean.
I have not delved into specific issues such as “Will the Tunnel run under my house?” The answers to questions such as these can best be determined by visiting my house and looking at plans (or you could also visit City Hall!). Please e-mail such requests and we will set a time. If you have questions that you believe would be of general interest, please e-mail them to me and I will answer next report.
Thanks:
Harold Cunliffe
Nancy Creek Sanitary Sewer Tunnel
Report as of May 7, 2002
A few months ago, the Council of the City of Atlanta passed an Ordinance establishing the Technical Advisory Committee for the Nancy Creek Sanitary Sewer Tunnel project. The Committee consists of nine members I was fortunate enough to be appointed by Council Member Howard Shook from District 7. Later, NPU - B endorsed my appointment. The Committee's mission is to ensure that the Tunnel is constructed in a timely and cost-effective manner but the Mayor's office and Council Member Shook have emphasized that it is equally important to make sure that this project receives full public scrutiny. In a series of articles to follow, I will attempt to explain my perception of what is happening. These reports are not sanctioned by the Advisory Committee nor are they sanctioned by the City so I may err with some aspects but you can be assured that at least, I will not be parroting the "Party Line".
As background, the City is obligated by Consent Order to perform several items of remedial work in order to meet terms of compliance with the Clean Water Act. One critical step is to eliminate the sanitary sewer overflows into our creeks that occur on an all-to-regular basis. Two years ago, a citizen's group was established under the leadership of Mary Norwood (now Council Member Norwood). That group sought to provide a long term solution that would bring minimum disturbance to our neighborhoods and the environment. From this, the concept of a large diameter, deep tunnel evolved.
Subsequent engineering studies were undertaken and it became apparent to the designers that for a relatively small marginal cost, the tunnel could be enlarged to provide storage upstream of the receiving wastewater treatment plant - the R. M. Clayton facility located near Bolton Road and Moore's Mill Road. Storage is an important component of the plan because it "shaves" off the peaks experienced by wet weather flows and allows the R. M. Clayton plant to operate at a rate that is steadier.
In very simplistic terms, the Nancy Creek Tunnel project can be described as a sixteen foot diameter hole that will be bored horizontally approximately 44,000 feet from the R. M. Clayton plant in a northeasterly direction terminating on Johnson's Ferry Road near Nancy Creek. The Tunnel will start off at a depth of about 150 feet and will have a uniform grade of 0.1%. As the ground above rises and falls, the Tunnel depth will be as little as 125 feet deep and as much as 325 feet deep. Three access shafts will be deployed, the first at the R. M. Clayton plant, the second at Roswell Road across from Pike's Nursery and the final one at the termination point on Johnson's Ferry Road. In addition, a number of intake points will connect to the existing system. The current thought is that the contractor will employ two tunnel boring machines. One will start at the R. M. Clayton plant and the other, at Roswell Road. Two machines are necessary to meet the time constraints stipulated in the Consent Order. The project completion date can be no later than August 23, 2005 leaving 1100 days from start to finish. The estimated construction cost is 150 million dollars. The City is currently negotiating cost sharing with Dekalb and Fulton Counties based on their use of the Tunnel. Bonds have been issued and the project has current funding of 162 million dollars.
The Advisory Committee and various interested parties have posed a number of questions that I will try to answer below.
Q: Will the City obtain easements on properties under which the Tunnel passes?
A: Yes, the City will negotiate the purchase of easements or use its power of eminent domain. The Council will adopt a policy for compensation and all affected property owners will be contacted in advance of construction beneath your property.
Q: Will the Tunnel affect the ground water table, wells or water levels in Nancy Creek?
A: No. First, 75% of the Tunnel will be bored through solid rock. Fissures will be pre-grouted 300 feet ahead of the tunnel boring machine and in areas of fragmented rock. The circumference of the Tunnel will be lined with a one foot layer of reinforced concrete where conditions dictate.
Q: Will sewage leak out of the tunnel?
A: No, for the same reasons above.
Q: Will the Tunnel smell?
A: Yes, the sewage in the Tunnel will smell to the same extent that it currently does in the collector system. During wet weather events, the Tunnel will fill, thus expelling the gases within. To mitigate this situation, air treatment filters will be installed at the access shafts and at the intake locations. Overall, the smell will be drastically reduced from that which we are accustomed.
Q: How will the excavated material be dealt with?
A: The excavated rock will be conveyed from the tunnel boring machine back through the Tunnel to the access shafts. From here it will be lifted to the surface and loaded into trucks. The trucks will then haul it to one of many rock processing plants located in the metropolitan area. The total volume of material will be 415,000 cubic yards. If the job takes 1100 days and if the rock is removed from only two shafts, this will require an average of 19 dump trucks to leave each site every day. The contactor will work 24 hour days so the truck traffic could be as little as one per hour but also could be two per hour if they are constrained to daylight hours.
Q: Will sewage continue to spill into our streams and creeks?
A: Notwithstanding small local blockages that may cause an overflow, the vast majority of spills will now be captured in the Tunnel. The trunk collectors will continue to operate during normal flows and they will be fitted with overflow diverters that will direct the sewage into intake shafts that are connected to the Tunnel.
Q: Can't something else be done?
A: Yes, several options are available. We could store peak flows in an above-ground pond. This pond would be approximately 8 acres and would be 25 feet deep. For most of the time, it would be a 25 foot deep depression strewn with sewage debris. More significantly, it would have to be located somewhere along Nancy Creek, i.e. Buckhead. This idea has already been rejected.
We could also increase the treatment capacity of the R. M. Clayton plant. This option has also been considered. The problem is that the size of the plant would have to be tripled to accommodate relatively infrequent wet weather events and that is not an efficient use of resources. Further, the City would be required to apply for a new point-discharge permit from the EPD and construct the new facility. We would not likely meet the Consent Decree mandated time constraints.
Q: Since Inflow and Infiltration due to storm water triples the amount of sewage entering the system, why don't we just fix the leaks?
A: This is part of the program and it is underway. Perhaps you have already noticed City crews working in your neighborhood. Counter-intuitively, fixing leaks contributes to higher flow during dry weather conditions because now the sewage will not leak out into creeks, streams and the groundwater. Our consultants have told us that 3.3 X peaks are not unusual for cities of our age and size. It appears that, at best, we may reduce Inflow and Infiltration down to 2.5 X.
Q: Are we spending too much money by making the Tunnel so big? Is the Tunnel too small to accommodate future growth, etc.?
A: These two questions have dominated the discussions at the Advisory Committee meetings. In my opinion, we don't know the answer with certainty. We do know that we need a solution now and we hope that the solution will last until 2050 or 2100. The model assumes that Buckhead will double in size but since we don't know what existing flows are (because we aren't capturing them all), we don't know what to double. We also don't know the long-term capacity of the R. M. Clayton plant. It could easily be much higher with upgrades but it could also be lowered with a tightening of discharge regulations. Bigger plant capacity means higher discharges. That translates to less required storage and a smaller Tunnel. Unfortunately, the converse also applies. The model assumes that Inflow and Infiltration rates will remain at 3.3 X but that could be high or low and depends on our great-grandchildren's political and environmental resolve. It also assumes water usage rates per person remaining constant - again something that lies in our great-grandchildren's hands.
My best guess is that this is a good 20 - 25 year solution. Beyond that we will probably have to look at a combination of networking plants across the metro area, more storage tunnels in this and/or other basins, higher discharge permits at the plants combined with higher standards and water use restrictions.
