Municipal Urban Forestry Tree Inventory Specification

Why this matters

A municipal tree inventory is a public-works contract: a municipality (or a utility, a transportation authority, or a state agency) pays a contractor to systematically catalog every public tree on right-of-way, in parks, or on a designated jurisdiction. The deliverable is a geo-referenced database and a written report that the urban forester uses to plan budgets, manage canopy, schedule maintenance, prioritize hazard removals, and apply for federal grants (USDA Forest Service Urban and Community Forestry program, Inflation Reduction Act Section 22002 funding, FEMA hazard-mitigation grants). The contract sits in the contractor's commercial book of business and is usually procured by competitive sealed bid or RFP. This article frames the technical specification a contractor needs to bid the work.

Scope of an inventory contract

A typical municipal tree inventory specifies:

• Geographic scope: every tree on right-of-way (street tree program), every tree in designated parks, every tree on municipal property, or some defined combination.
• Inventory attributes per tree: location (GPS, often sub-meter), species (genus, species, cultivar where known), diameter at breast height (DBH), height estimate, crown spread, condition rating, defect catalog, recommended maintenance action, priority.
• Data format: typically Esri shapefile or geodatabase, with the attribute schema defined in the RFP. Some municipalities specify TreeKeeper, Cartegraph, or ArborPro as the delivery platform.
• Deliverable schedule: phased delivery on large inventories, with field data due at quarterly intervals and the final report due at contract end.
• QA/QC requirement: typically 5 to 10 percent of inventoried trees are re-inspected by the municipality or a third-party QA contractor; defect rate above 5 percent triggers a rework clause.

Crew composition and credentials

Bid the work with a crew structure the RFP usually requires:

• Project arborist: ISA Certified Arborist, ISA Municipal Specialist credential preferred, ISA TRAQ qualification for hazard scoring.
• Field crew: each crew has one ISA Certified Arborist as the lead; tagger and data-entry technicians work under direct lead supervision. The credential-to-data-collected ratio is the QA control the municipality enforces.
• Subcontracted GIS or data manager: if the contractor lacks in-house GIS, subcontract to a firm that knows the target deliverable platform (Esri or the named municipal system).

Field protocol

Standard field protocol for a street-tree inventory:

• One-block sweep with a two-person crew: lead arborist calls the tree (species, DBH, condition); tagger records on a ruggedized tablet with the GPS receiver paired by Bluetooth. Sub-meter GPS receivers (Trimble Catalyst, Eos Arrow, or equivalent) are the inventory standard; phone GPS is not accurate enough.
• DBH measured at 4.5 feet above grade with a diameter tape (forester's d-tape), not estimated.
• Condition rating uses the ISA Tree Risk Assessment categories: good, fair, poor, dead.
• Recommended action coded from a fixed list: prune (priority 1, 2, 3), remove, treat (insect/disease), monitor, stump grind, plant (vacant site).
• Photo of every tree with a defect rating below "good," uploaded to the GIS record.

Standard schema

The municipal inventory schema typically includes:

• Unique tree ID (auto-generated, sequential within the project).
• Latitude / longitude (decimal degrees, WGS 84 or the municipality's projected coordinate system).
• Address (geocoded from the tree point to the nearest parcel).
• Species code (USDA PLANTS code, e.g., ACSA1 for Acer saccharum sugar maple).
• DBH (inches, single trunk; multi-trunk recorded as multiple DBH values).
• Height (feet, estimated to nearest 5 feet).
• Crown spread (feet, estimated).
• Condition rating.
• Defect codes (cavity, crack, deadwood percentage, included bark, root flare defect, lean change, mushroom fruiting body).
• Risk rating per ANSI A300 Part 9.
• Recommended action.
• Priority (1 immediate, 2 within 12 months, 3 within 5 years, 4 monitor).
• Inspector ID and date.

Bid pricing structure

Municipal tree inventory bids are typically structured as a fixed unit price per tree inventoried, with a separate mobilization line item and a separate report-writing line item. Bid the unit price knowing the per-tree time (typically 4 to 8 minutes per tree on a productive block, longer in parks with sparse trees and longer access distances).

Unit pricing covers field labor, GPS equipment, tablet, tagging supplies, and data upload. The mobilization line item covers crew travel and project setup. The report-writing line item covers the written summary, canopy analysis, and recommendations document.

Bond requirements vary; municipal inventory contracts often require a bid bond at 5 to 10 percent of bid value and a performance bond at 100 percent of contract value once awarded. Surety capacity is the constraint for new entrants; build a surety relationship before bidding.

Reporting and outcomes

The written deliverable typically includes canopy cover analysis (current canopy by neighborhood, gap analysis vs. municipal canopy goal), species diversity analysis (the Santamour 10-20-30 rule: no more than 10 percent of one species, 20 percent of one genus, 30 percent of one family), age class distribution, maintenance demand forecast (priority 1 immediate, priority 2 within 12 months, priority 3 within 5 years), and recommended annual maintenance budget.

References

• ANSI A300 Part 9 Tree Risk Assessment.
• USDA Forest Service Urban and Community Forestry Program, technical reports.
• ISA Best Management Practices, Tree Inventories, current edition.
• Santamour FS Jr., Trees for Urban Planting, Diversity, Uniformity, and Common Sense (Proceedings of the 7th Conference of the Metropolitan Tree Improvement Alliance).