Countywide Sanitary Sewer Evaluation Services

Background

Woolpert has been working with Gwinnett County on their sanitary sewer collection system since 2005. Woolpert has developed the County’s long-term monitoring plan and has been using temporary flow monitoring studies to advance this plan. These temporary studies have included selecting locations and installing the meters, performing monthly maintenance, and data acquisition and processing.

Challenge

The main challenge is to identify, prioritize, and implement a find-and-fix program to reduce infiltration and inflow (I/I) in the County’s system, which includes over 2,140 miles of pipeline ranging from 8 to 72 inches in diameter and contains 197 pump stations and 8 water reclamation facilities.

Solution

For the past 18 years, Woolpert has provided flow monitoring, smoke testing, dye flooding, CCTV inspections, manhole inspections, data review, report preparation services, and technical advisement. Between 2014 and 2015, these activities included smoke testing over 1.5 million feet of sanitary sewer and the inspection of over 6,000 manholes.

In both 2016 and 2021, Woolpert was awarded back-to-back 5-year contracts that involve the CCTV and cleaning of 750,000 linear feet per year and the inspection of 5,700 manholes each year. Additionally, in June 2020, Woolpert began providing the field maintenance and data analysis for 130 flow meters.

Projects completed include the following:

• Big Haynes Basin – 27 flow meters, 6 rain gauges, 4 groundwater gauges, 2 stream gauges, 2,563 manhole inspections and GPS surveys, and 521,504 linear feet of smoke testing.
• No Business Basin – 7 flow meters, 2 rain gauges, 2 groundwater gauges, and 2 stream gauges.
• Beaver Ruin – 3,152 GPS manhole surveys and 899,558 linear feet of smoke testing.
• Ezzard Basin – 2 flow meters, 2 rain gauges, 522 manhole inspections and GPS surveys, and 109,818 linear feet of smoke testing.
• Ivy Basin – 5 flow meters, 2 rain gauges, 2,127 manhole inspections, and 2,228 GPS manhole surveys.
• Suwanee Basin – 1,192 manhole inspections and 1,766 GPS manhole surveys.
• Countywide Flow Study I/I – Installation of over 100 flow meters for data collection to calibrate the hydraulic model.
• Long-term Flow Monitoring Meter Network – Operation and maintenance services on the long-term meter network, including over 100 ISCO 2150 flow meters for a six-year period.
• Data Review and Field Inspections – Utilized the County’s GIS data as a background layer on the field pentop computers while performing all of the SSES activities
• Report Preparation – Converted database into a GBA master series compatible format for the County’s CMMS.

Outcome

At the conclusion of the monitoring periods, Woolpert prepared reports to document the project findings. The reports utilized the correlations to calculate the I/I induced peaking factor in each sub-basin, the total I/I in gallons per day (gpd) contributed by each sub-basin, the gpd per inch-diameter-mile contributed by each basin and sub-basin, and other parameters, as required, that provided insight to the operation of the sewer system. The reports used the peaking factors, gpd, and gpd per inch-diameter-mile to develop basin and sub-basin priorities for the County’s follow-on I/I reduction program. Woolpert also converted the database into a GBA master series compatible format for delivery into the County’s computerized maintenance management system (CMMS).

Woolpert is currently under another ongoing contract with Gwinnett County for Sewer and Stormwater Assessment work that began in January 2016. This new contract continues work that was enacted under the previous agreements discussed in this description.

Benefits

Identifying and removing I/I from the system offers many benefits, including reduced sanitary sewer overflow occurrences and reduced capital improvement costs to upgrade/increase the sanitary sewer system (pipe, connections, pump stations, and wastewater treatment plants).