Most municipal manhole registries are a quiet mess: the same structure entered three times under three IDs, half the records missing coordinates, inspection photos scattered across email and SD cards, and condition grades that mean different things depending on who typed them. That mess has a real cost — crews drive to the wrong location, capital dollars chase the wrong repairs, and an auditor asking for a structure's history gets a shrug. The fix isn't another inspection campaign; it's a disciplined cleanup of the data you already own. This guide walks through deduplicating records, adding GPS, attaching photos, standardizing NASSCO MACP grades, and ranking structural repairs by real risk — all inside OxMaint's asset and inspection management tools. To see it run against your own registry, book a demo.
Wastewater & Sewer / Asset Management & GIS
Manhole Inspection Data Cleanup Guide for Municipalities
Turn a duplicated, location-less manhole registry into a clean, GPS-tagged, photo-backed asset record that drives repair priorities and survives an audit.
1-5
NASSCO MACP condition grade scale, excellent to immediate
6
Manhole components MACP grades from cover to channel
2
Inspection levels: rapid screening and full defect coding
5%
Minimum of surveys NASSCO suggests checking for QC
Why manhole data goes bad
Bad data is rarely one big mistake — it's dozens of small ones across years of crews, contractors, and spreadsheets. Naming the failure modes is the first step to fixing them.
Duplicate records
The same structure logged under multiple IDs by different crews, inflating counts and splitting its history.
Missing GPS
Records with a street name but no coordinates, so the asset can't be mapped or routed to.
Unattached photos
Inspection images sitting on phones and drives instead of linked to the structure they document.
Inconsistent IDs
No naming convention, so the same manhole appears as MH-12, 0012, and Cover-12 across systems.
Map vs ground mismatch
Old as-built maps that don't match what crews actually find in the field.
Orphaned structures
Buried or undocumented manholes found in the field that were never added as assets.
Read the MACP condition grade scale
Clean grades make repair priorities defensible. NASSCO MACP rates each defect on a five-point scale, scored separately for structural and operation-and-maintenance issues, so a sound cover and a cracked wall in the same structure get their own grades.
1
MinorCosmetic deterioration; note and monitor, no action needed.
2
SlightEarly wear; track over time for progression.
3
ModerateDefect needs planned maintenance within the cycle.
4
SignificantSerious deterioration; schedule near-term repair.
5
ImmediateStructural or safety failure; act now.
Those grades roll up into a Quick Rating, an Overall Manhole Rating, and a Manhole Rating Index — letting asset managers sort thousands of structures at a glance instead of reading every defect log.
Turn a messy registry into a clean asset record
OxMaint dedupes, geo-tags, and grades your manhole data in one place — so every structure has one record, one location, and one history.
The five-step cleanup pipeline
Work the data in order. Each step depends on the one before it, and skipping ahead just bakes the errors in deeper.
1
DeduplicateMatch records by location, ID, and attributes, then merge duplicates into one master structure — preserving every inspection in its history.
2
GeolocateAdd field-collected GPS coordinates, reconcile map-versus-ground mismatches, and register any buried structures crews uncover as new assets.
3
Attach photosLink inspection images to each structure — at minimum an area shot, a cover-and-frame close-up, and a top-down view with the cover removed.
4
Standardize gradesApply consistent MACP coding so structural and O&M grades mean the same thing across every crew and contractor.
5
Prioritize repairsRank structures by condition grade and consequence of failure to point capital dollars at the assets that matter most.
What a clean manhole record holds
A complete record makes every downstream decision easier. These are the fields worth enforcing on every structure in the registry.
| Field | Why it matters |
|---|
| Unique manhole ID | Prevents duplicates and links the structure to its pipe segments |
| GPS coordinates | Lets crews find it and corrects map-versus-ground errors |
| Material & depth | Drives rehab method and confined-space safety planning |
| Structural & O&M grades | Separates condition issues from maintenance issues |
| Quick Rating | Sorts thousands of structures by worst-case severity |
| Inspection photos & video | Provides defensible, auditable evidence of condition |
| Last inspection date | Schedules the next screening and tracks deterioration |
Prioritize structural repairs by risk
Condition grade alone doesn't set priority — a Grade 5 under a hospital outranks a Grade 5 in an open field. Combine severity with consequence of failure to rank the work.
| Priority | Condition | Consequence | Action |
|---|
| P1 Critical | Grade 5 | High-impact location | Immediate repair |
| P2 High | Grade 4 | Trunk or critical line | Schedule near-term |
| P3 Medium | Grade 3 | Standard segment | Plan within cycle |
| P4 Low | Grade 1-2 | Low impact | Monitor & re-inspect |
Scoring risk as likelihood times consequence keeps the program objective — and gives finance a defensible reason behind every line in the capital plan.
Expert Review
"The single biggest waste I see in collection-system budgets isn't bad pipe — it's good money spent on the wrong manhole because the data was dirty. A registry full of duplicates and blank coordinates can't tell you what to fix first, so it defaults to whoever complained loudest. Cleaning the data changes that overnight: dedupe it, drop a GPS pin on every structure, attach the photos, and grade it the same way every time. Suddenly the worst structures rise to the top on their own, and the capital plan defends itself in front of council."
Reviewed by a municipal sewer asset-management consultant, 19+ years in NASSCO-based condition assessment and GIS.
See your registry cleaned and ranked
Walk through a live cleanup on your own manhole data — duplicates merged, GPS added, photos linked, and repairs ranked by risk in one view.
Frequently asked questions
Why is our manhole data full of duplicates?
Duplicates pile up when different crews and contractors log the same structure under different IDs with no shared naming convention. Matching on location and attributes lets you merge them without losing history. OxMaint dedupes while preserving every inspection —
book a demo.
How do we add GPS to existing manhole records?
Collect coordinates in the field during inspection and write them back to each record, reconciling any gap between old as-built maps and what crews actually find. Buried structures get added as new assets. See field GPS capture in
OxMaint.
What is the MACP 1-5 grade scale?
NASSCO MACP grades each defect from 1 (minor, cosmetic) to 5 (immediate structural or safety failure), scoring structural and O&M issues separately. The grade applies to a defect, not the whole structure. Standardize grading across crews in
a quick demo.
Which photos should each manhole record have?
At minimum an area shot, a close-up of the cover and frame, and a top-down view with the cover removed; Level 2 inspections attach a photo to each coded defect. Link them all to the asset so nothing is lost.
OxMaint stores them on the record.
How do we prioritize structural repairs?
Combine the condition grade with consequence of failure — a high grade in a high-impact location ranks first. Scoring likelihood times consequence keeps the order objective and defensible. Build the ranking automatically in
a demo.
What fields belong in a clean manhole record?
A unique ID, GPS coordinates, material and depth, structural and O&M grades, Quick Rating, photos or video, and the last inspection date. Enforcing these turns a list into an asset registry. Set required fields in
OxMaint.
How does clean data help with compliance?
MACP-coded, photo-backed records satisfy CMOM and audit expectations and give regulators a defensible condition history on demand. Dirty data can itself become a finding. Keep an audit-ready registry in
OxMaint — book a demo.
How often should manholes be re-inspected?
Re-inspection cadence follows condition and risk — high-grade or high-consequence structures get checked more often, while sound ones run on a longer rotation. A clean last-inspection date makes scheduling automatic. Track it in
OxMaint.
How does OxMaint clean up manhole data?
OxMaint merges duplicates, adds GPS, links photos, standardizes MACP grades, and ranks repairs by risk — turning a scattered registry into one clean, mappable asset record. Try it on your own data with a
free trial.
Clean the data, fix the right manholes
Stop letting a messy registry pick your repairs. Dedupe, geo-tag, photo-link, and rank every structure in one system — and build a capital plan that defends itself.
