Wastewater Solutions in Fort Oglethorpe, Georgia

Wastewater Case Study - Fort Oglethorpe, Georgia

Customer Overview

The City of Fort Oglethorpe, Georgia, owns and operates a sewer collection system transporting wastewater from homes and businesses to Chattanooga’s Moccasin Bend Wastewater Treatment Plant (WWTP). Chattanooga’s WWTP operates under a consent decree with the EPA and the State of Tennessee, imposing specific requirements that flow down to Fort Oglethorpe through their sewer contract. These include detecting and eliminating inflow and infiltration (I&I) and adhering to volume restrictions, which limit growth planning capacity. The city needed a proactive, targeted approach to address system deficiencies while accommodating growth.

This project exemplifies how a targeted approach utilizing diverse technologies can improve system performance, reduce costs, and enhance infrastructure resiliency. The City’s efforts set the stage for efficient resource allocation, better growth management, and long-term operational success.

Name:

Wastewater Solutions in Fort Oglethorpe, Georgia

Location:

Southeast Region

Market:

Municipalities

Solution:

Wastewater Service Lifecycle

Services:

Acoustic Inspection Manhole Inspection I&I Micro Detection

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Challenge

The City’s gravity sewer collection system faced significant challenges due to Rain Derived Inflow and Infiltration (RDII), particularly in the Lynnwood and Black Branch sub-basins. A flow metering study in March 2020 and a sewer system analysis in June 2021 identified these areas as primary contributors of RDII. However, further investigation was necessary to pinpoint specific wet weather flow sources and create a prioritized, cost-effective rehabilitation plan. The City's goal was to improve hydraulic conditions, eliminate RDII, enhance structural integrity, and manage growth within permit constraints while avoiding fines from Chattanooga’s WWTP.

SOLUTION

To address these challenges, a comprehensive investigation and condition assessment were conducted for the Lynnwood and Black Branch sub-basins. A “system triage” approach was use d, incorporating multiple technologies:

SL-RAT Acoustic Pipe Inspection: 238,214 linear feet of sewer pipe were acoustically inspected to evaluate blockages and obstructions.
Micro Detection Sensors: 238,214 linear feet of sewer pipe were monitored using 187 level-based sensors deployed every 1,200 feet to detect inflow and infiltration sources.
Manhole Inspection: 1,168 manholes received a NASSCO Level 2 inspection to assess structural condition and I&I contributions.
Area Velocity Flow Monitoring: Monitored key areas within the Micro Detection Area.

IMPLEMENTATION

The investigation revealed specific areas requiring immediate attention:

Pipe Condition: 16,000 linear feet (7%) of inspected pipe received a BLOCKED or POOR rating based on SL-RAT technology.
Manhole Condition: 115 of the 1,168 inspected manholes (12%) were ranked as severe, indicating significant rehabilitation needs.
Inflow and Infiltration Contributions: 51,200 linear feet (24%) of inspected pipe were identified as contributing significantly to I&I.

Recommendations implemented included:

CCTV Inspection: Targeted inspection of segments with BLOCKED or POOR SL-RAT scores.
Manhole Rehabilitation: Rehabilitated 306 manholes, including 115 severe-ranked manholes and 191 additional manholes identified through broader inspection.
Smoke Testing: Conducted smoke testing on 85,147 linear feet of pipe to further identify inflow sources.

RESULTS

The project’s proactive, data-driven approach yielded significant improvements:

Since 2021, nearly 1.5 million gallons per day (MGD) of flow have been eliminated from the Fort Oglethorpe system.
A 9% year-over-year reduction in I&I gallons treated resulted in $214,000 in annual savings.