MACP Inspection Scoring: A Practical Field Guide for Public Works Teams

If your municipality manages a collection system with manholes — and virtually every municipality does — you need a systematic, defensible way to assess their condition and prioritize rehabilitation spending. NASSCO’s Manhole Assessment and Certification Program (MACP) is the industry standard for doing exactly that.

This guide breaks down MACP scoring in plain language, explains what each grade level means in practical terms, and shows you how to turn inspection data into an actionable rehabilitation program. It’s written for field crews, public works supervisors, and asset managers who need to understand MACP without wading through the full technical manual.

What Is MACP and Why Does It Matter?

MACP is a standardized protocol developed by the National Association of Sewer Service Companies (NASSCO) for assessing the condition of manholes. It’s the manhole equivalent of the Pipeline Assessment and Certification Program (PACP) used for sewer pipes — in fact, the two systems are designed to work together as part of an integrated collection system asset management approach.

MACP matters because it provides a common language. When a MACP-certified inspector grades a manhole as a Grade 4, every engineer, contractor, and regulator who understands MACP knows exactly what structural conditions that score implies. This consistency enables better planning, better procurement, and — critically — better regulatory documentation in the event of a sanitary sewer overflow (SSO) event.

Many state environmental agencies now require MACP-documented inspections as part of SSO elimination programs, consent decrees, or capacity, management, operations, and maintenance (CMOM) programs. Even if your state hasn’t mandated it yet, building MACP data now creates the asset management foundation you’ll need when they do.

The MACP Rating Scale

Grade 1 — Light Condition

Surface deposits, minor cracks (less than 1/4 inch wide), light deterioration of mortar joints, or minor infiltration. The manhole is structurally sound. Normal preventive maintenance and monitoring is appropriate.

Grade 2 — Minor Condition

Multiple minor defects, more significant crack widths (1/4 to 1/2 inch), moderate infiltration, evidence of root intrusion at joints, or beginning stages of H2S-driven surface deterioration. Monitoring and preventive rehabilitation (coating application) are appropriate within 3–5 years.

Grade 3 — Moderate Condition

Cracks wider than 1/2 inch, significant infiltration, missing mortar, exposed aggregate from H2S corrosion, damaged or deteriorated frame/cover connection, or structural distortion. Rehabilitation is warranted within 1–3 years. This grade is the decision point for protective coating vs. structural relining.

Grade 4 — Severe Condition

Loss of section (concrete wall thickness measurably reduced), large open cracks or separated joints, significant structural distortion, collapse of partial sections, or active infiltration at multiple points. Rehabilitation or replacement is required within 12 months. Emergency inspection by a licensed engineer is recommended.

Grade 5 — Critical Condition

Imminent risk of collapse or failure. Void behind the manhole wall, partial collapse, complete loss of structural integrity in sections, or severe distortion that prevents normal access. This manhole is a public safety risk. Emergency action is required immediately. Bypass operations should be considered.

Key Defect Categories in MACP

MACP scoring encompasses more than just the barrel condition. Inspectors evaluate each of these components:

• Frame and cover — condition, fit, material type, and any evidence of unauthorized access or vehicle damage
• Cone/corbel section — cracking, settlement, displacement, or separation from the barrel
• Barrel sections — the primary structural element; assessed for cracking, corrosion, infiltration, offset joints, and section loss
• Bench and invert — condition of the flow channel, evidence of grease accumulation, structural integrity of the bench
• Pipe connections — condition of incoming/outgoing pipe connections, drop connections, evidence of offset or shear
• Steps/rungs — presence, condition, and compliance with current OSHA requirements
• Surface condition — evidence of H2S attack, coatings condition (if previously lined), biological growth

Field Tips for Accurate MACP Scoring

Preparation Before Entry

Proper atmospheric testing is non-negotiable before any MACP inspection. Continuously monitor for H2S, CO, LEL/methane, and oxygen deficiency throughout the inspection. Review any available historical data, previous inspection reports, or as-built drawings before entering — context matters for accurate scoring.

Documentation Standards

Photograph every defect, not just the worst ones. Establish a consistent camera position for barrel shots (typically from the top looking down) so future inspections can make valid comparisons. Record depth and orientation of all defects. Use the exact MACP defect codes — improvised descriptions make database analysis impossible.

Probing and Testing

Don’t just look — probe. A screwdriver or pick handle dragged across the barrel surface quickly reveals the difference between sound concrete and H2S-converted gypsum. The dull thud of firm concrete versus the soft crumbling of gypsum tells you more than visual inspection alone in low-light conditions.

Infiltration Measurement

Wherever possible, quantify infiltration rather than just noting its presence. Even a rough estimate (e.g., “minor seep,” “continuous flow approximately 0.5 GPM”) is far more useful for prioritization and specification than a simple Y/N notation.

From Inspection Data to Capital Planning

The real value of MACP isn’t the grade — it’s what you do with the data. A properly built MACP database lets you:

• Rank your entire system by condition grade and generate a priority queue automatically
• Filter by high-risk characteristics (H2S environment, traffic loading, depth, diameter) to identify manholes that warrant expedited attention even at lower grade levels
• Model your rehabilitation backlog and project future condition grades to identify the “do nothing” cost trajectory
• Demonstrate regulatory compliance with your SSO program, consent decree, or CMOM program requirements
• Develop defensible capital budget requests with clear prioritization rationale

Most modern collection system management software (InfoAsset, CityWorks, Cartegraph, and others) support MACP data import and analysis. If you’re working in spreadsheets, our Resources page has a free MACP tracking template you can download.

Getting Your Team MACP-Certified

NASSCO offers MACP certification training through their online and in-person course offerings. The certification involves classroom instruction, field training, and a written examination. Certified inspectors must maintain CE credits to keep their certification current.

Manhole Recovery’s own training webinars complement NASSCO certification with practical application guidance and case study examples. Check our Events page for the next MACP-focused webinar, and join the community to connect with other certified inspectors in your region.