How Boston's City Archives Ended Up With Thousands of Duplicate Property Photos — and What It's Costing Taxpayers

Boston's property assessment database contains more than 40,000 duplicate or near-duplicate images tied to parcel records across the city — a problem that accumulated quietly over roughly 15 years of inconsistent scanning practices and now requires a structured remediation effort estimated to run well into 2027. The City Assessor's Office confirmed the scope of the problem in internal planning documents circulated this spring, though officials have not yet published a final cost figure for the cleanup.

The timing matters. Mayor Michelle Wu's administration has pushed hard on housing production in Dorchester and Jamaica Plain, and both neighborhoods sit at the center of the backlog. Assessors need clean, verified parcel photo records to support accurate valuations — and accurate valuations underpin everything from property tax bills to the City's capital planning assumptions. Duplicate images create ambiguity about which photograph is current, which matters enormously when a triple-decker on Blue Hill Avenue gets subdivided or a warehouse near the Forest Hills MBTA station converts to residential use.

How the Duplication Problem Built Up

The root cause is straightforward: Boston contracted field photography work to at least three different vendors between roughly 2008 and 2023, and none of those contracts included a mandatory deduplication standard before images were ingested into the Assessing Department's database. When a vendor re-photographed a parcel — sometimes because a prior image was blurry, sometimes because a property had been flagged for an appeal — the old image stayed in the system alongside the new one. Multiply that across fiscal year cycles and the accumulation becomes structural rather than incidental.

The City of Boston processes roughly 175,000 taxable parcels. Even a duplication rate of 20 to 25 percent across actively photographed properties represents a significant data-integrity problem. The Assessing Department, housed on City Hall Plaza, uses a platform integrated with the statewide CAMA — Computer Assisted Mass Appraisal — system maintained under Massachusetts Department of Revenue guidelines. State guidance requires municipalities to maintain a triennial re-inspection cycle, which means field photos are continuously added, compounding the problem if deduplication protocols aren't baked into intake.

Efforts to address this began in earnest in late 2024, when the City's Department of Innovation and Technology — based on Cambridge Street — flagged the image redundancy issue during a broader audit of municipal data infrastructure. That audit was itself a product of a $3.2 million digital modernization contract the Wu administration awarded in fiscal year 2024 to overhaul several legacy city systems. The property photo database was not originally a priority target, but auditors found it impossible to ignore once the duplication counts became clear.

What Remediation Looks Like in Practice

The current plan, as outlined in public budget materials, involves a combination of automated hash-matching software — which flags images that are pixel-identical or nearly so — and manual review for cases where two photos of the same parcel show different physical conditions. The manual review is the expensive part. Staff hours at the Assessing Department, combined with a vendor contract for the automated layer, put the remediation in a cost range that city budget analysts have described in planning documents as comparable to a mid-sized technology upgrade project, though no final appropriation has been voted.

Practically speaking, residents in Jamaica Plain and Dorchester who have filed abatement applications in the past 18 months may want to confirm with the Assessing Department — reachable through the City's 311 system — that the parcel photo attached to their property record reflects its current state. The abatement process runs on a strict calendar: applications for fiscal year 2027 assessments must generally be filed by February 1, 2027. Property owners whose records carry stale or mismatched images could face complications if their appeal relies on photographic evidence of a property's condition.

The Assessing Department has said it expects the automated deduplication phase to wrap up by the end of calendar year 2026, with manual review extending into the first quarter of 2027. Whether the cleaned database will be publicly searchable through the City's existing Assessing Online portal is still under discussion.