Sigma monitors manhole structural components and integrity



The Sigma Group has performed manhole integrity inspections of targeted sanitary, storm, and utility structures for the City of Milwaukee for 11 consecutive years. Averaging between 6,000 and 8,000 structures per year, these inspections involve visual evaluations, digital photo-documentation, and completion of discrete database inspection forms used to manage inspection reports. The information gathered by our field crews is analyzed and used by the City to prioritize system maintenance and rehabilitation as part of the street improvements program.

The purpose of the sanitary and storm structure inspections is to determine structural integrity and infiltration sources. Storm structure inspections include all storm manholes, catch basins and inlets.

Utilizing above-ground visual inspection techniques, our field crews analyze areas where infiltration is occurring, measure various structural components, and suggest structural and operational repairs. Inspection deliverables include photos and database inspection forms.

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The purpose of the utility manhole inspections is to determine structural integrity. This is accomplished primarily by confined space entry combined with above surface visual inspections. Our field crews measure and analyze various structural components and suggest structural repairs. Inspection deliverables include sketches of each structure layout including connecting utility conduits, photos, and database inspection forms.

2015 Manhole Statistics:

  • 4,500 sanitary sewer inspections
  • 2,000 storm sewer inspections
  • 1,500 utility structure inspections
  • 115 combined sanitary/storm sewer inspection on Milwaukee streetcar route

The combined sanitary and storm sewer inspections along the Milwaukee streetcar route included the evaluation of the integrity of the manhole structures as well as plan and profile view sketches containing the structure layout, lateral connections, and channel flow information.

Sigma has met an aggressive year round and as needed emergency basis inspection schedule.