Officials of the Hamilton County Water and Wastewater Treatment Authority (WWTA) said growth will be curbed in the Ooltewah area if a controversial new sewage treatment plant is not built.
The WWTA also said a variety of treatment options are planned to cut down on odors from the plant that is projected for Mahan Gap Road.
The rezoning case goes before the Planning Commission on Nov. 12. The final decision is by the County Commission in December.
Here are questions posed by the staff of the Regional Planning Agency and answers from the WWTA:
Staff Review of Zoning for Case 2018-206 questions:
1. Why this site was chosen, or why this site is better suited for the treatment plant and the overall system than the other sites?
This site was chosen because it allows for gravity flow from the potential 20,000 +/- acre future service area and it is in close proximity to the existing 7,500 +/- acre existing service area. The existing service area has 11 pump stations. The chosen site will allow service to the area with fewer pump stations, which will reduce costs substantially as pump stations are expensive to build and to maintain. The chosen site did not have any environmental or archaeological concerns.
Based on the preliminary evaluation, the other sites have the potential for environmental concerns, archaeological concerns, and topography that would necessitate addition pumping stations to accomplish the goal of servicing the existing and future areas.
2. What type of TDEC Permit is the facility, is it a Type I, II, or III permit?
The permit will be a National Pollutant Discharge Elimination System (NPDES) permit and require at least one TDEC-certified Grade 4 Wastewater Treatment Plant Operator to be in responsible charge of the site at all times. The plant will be designed as a Reliability Class I Facility which is the highest class of reliability in Tennessee for a wastewater facility.
3. Describe the components of the odor control system and typical best management practices and how these will be incorporated into the site? We understand from your response that the plant has not been designed; we just need additional information that clarifies or describes how the potential technologies such as carbon filter beds are expected to perform relative to odor management based on industry practice.
Odor control will be accomplished via physical, chemical, and biological methods. There is not a “one size fits all” for odor control. Odor treatment is generally characterized as whether the odors are treated in the “Vapor-Phase” and “Liquid-Phase” processes. The following are likely methods but the final methods will be a combination of the results of the waste characterization prior to the plant design, the treated water effluent limits established by TDEC, and the actual plant layout.
The following are considered Vapor-Phase methods which are known to be very effective at minimizing or eliminating odors:
A) The treatment facilities will be physically enclosed when possible to eliminate fugitive odors.
B) Carbon Adsorption, Biofiltration, and/or Wet Air Scrubbing facilities will be either individually located at specific high odor potential components of the treatment works or centrally located with individual air-stream conveyances.
Liquid-Phase methods will also be employed as necessary at certain pumping facilities upstream of the Plant to reduce incoming odors. The most likely process will be the injection of Calcium Nitrate into the raw wastewater at a pump station or incoming gravity line at a location to be determined.
4. Describe the conservation area and proposed walking trails on the site?
The conservation area will generally be to the eastern portion of the property from Turtle Lane up to Mahan Gap. The specific location of walking trails has not been determined.
5. Why is the new plant needed? Describe some specific challenges of the system without the new treatment plant, past overflows, etc?
The WWTA is at the current contractual wastewater flow limit with both the City of Collegedale and the City of Chattanooga. Significant upgrades to the Chattanooga infrastructure will be necessary to accommodate the future projected flow from the Ooltewah and Collegedale service areas that currently enter the Chattanooga Regional System at the same location. The construction of the new plant and subsequent reroute of new and existing flows will provide capacity for WWTA as well as improve capacity downstream in the Regional System.
6. What is the impact on Hamilton County if the new plant is not constructed, particularly as it is related to TDEC compliance?
In order to maintain compliance with the Clean Water Act as enforced by TDEC and EPA, Ooltewah growth will have to be limited so that the sewer system capacity will be sufficient to avoid overflows and other non-compliance issues. The growth that does occur will have to be serviced via septic tank or decentralized treatment systems.
7. Quantify the current capacity limits, projected growth in new demand, and the current capacity design of the plant?
The Ooltewah area is currently connected to the Collegedale system and is limited to 2.97 Million Gallons Per Day (MGD). In 2020, most of the Ooltewah system will be connected directly to the Chattanooga Regional System with a limit of 3.29 MGD. The projected need is between 6 and 8 MGD depending on the strength of the local and national economy. The plant will be designed for 10 MGD.
8. Is the permit needed for the entire site, particularly for the southern portion of the site adjacent to Heron Bay Subdivision?
There will be no Plant construction in the southern portion of the property near the Heron Bay Subdivision.