Infrastructure construction — roads, bridges, water and wastewater systems, and public utilities — is the backbone of the built environment. These projects are typically publicly funded, subject to competitive bidding, and governed by strict technical specifications and materials testing requirements. Estimating infrastructure projects accurately requires knowledge of civil construction methods, materials, and the regulatory environment that governs public works.

What Makes Infrastructure Construction Different

Public Procurement and Competitive Bidding

Most infrastructure projects are publicly funded and subject to competitive bidding requirements. Bids are opened publicly, which means your number is visible to competitors. The low bidder typically wins, which puts a premium on estimating accuracy — bid too high and you lose the job; bid too low and you win a contract that costs you money.

Technical Specifications

Infrastructure projects are governed by detailed technical specifications published by state DOTs, AASHTO, FHWA, and other agencies. These specifications define the materials, construction methods, and testing requirements for every item of work. Estimating infrastructure projects requires knowledge of these specifications and their cost implications.

Materials Testing and Quality Control

Infrastructure construction requires extensive materials testing and quality control:

• Soil compaction testing — nuclear density testing or sand cone testing at specified intervals
• Concrete testing — cylinder breaks, slump tests, and air content tests for every pour
• Asphalt testing — density testing, core samples, and mix design verification
• Pipe testing — pressure testing and leakage testing for water and sewer mains

The cost of testing and quality control must be included in the estimate, either as a direct cost or as part of the general conditions.

Environmental Compliance

Infrastructure projects often involve environmental compliance requirements:

• Stormwater pollution prevention — SWPPP preparation and implementation
• Wetland mitigation — permits and mitigation for impacts to wetlands and waterways
• Hazardous materials — identification and remediation of contaminated soils or groundwater
• Archaeological monitoring — required on some projects in areas with cultural resources

Types of Infrastructure Projects

Roads and Highways

Road construction involves earthwork, drainage, base course, and pavement. Key cost items include:

• Earthwork — cut and fill volumes from the roadway cross-sections
• Drainage — culverts, storm sewer, and roadside ditches
• Base course — aggregate base by thickness and area
• Asphalt pavement — tons of asphalt by lift thickness and mix type
• Concrete pavement — cubic yards of concrete for rigid pavement sections
• Signing and striping — traffic signs, pavement markings, and guardrail

Bridges

Bridge construction involves specialized structural systems — concrete or steel superstructure, concrete substructure, and foundation systems. Key cost items include:

• Foundations — driven piles, drilled shafts, or spread footings
• Substructure — abutments and piers in cast-in-place concrete
• Superstructure — precast concrete beams, steel girders, or cast-in-place concrete deck
• Bridge deck — reinforced concrete deck with waterproofing and wearing surface
• Expansion joints and bearings — specialty items with significant material costs

Water and Wastewater

Water and wastewater infrastructure includes treatment plants, pump stations, and distribution and collection systems. Key cost items include:

• Pipe installation — water main and sewer pipe by material, size, and depth
• Structures — manholes, valve vaults, and pump stations
• Treatment equipment — process equipment for water and wastewater treatment
• Electrical and controls — SCADA systems and process controls

Key Cost Drivers in Infrastructure Estimating

Earthwork — Earthwork is often the largest cost item on infrastructure projects. Soil conditions, haul distances, and the cut/fill balance all affect earthwork costs significantly.

Pavement — Asphalt and concrete pavement costs are driven by material prices, which fluctuate with oil prices and cement costs. Current material pricing is essential for accurate pavement estimates.

Prevailing wage — Most public infrastructure projects are subject to prevailing wage requirements. The labor cost estimate must reflect the applicable prevailing wage rates for each trade.

Utilities — Existing underground utilities must be identified and protected or relocated. Utility conflicts are a common source of cost overruns on infrastructure projects.

Union Estimating provides infrastructure construction estimating services for general contractors and specialty subcontractors working on road, bridge, and utility projects, with 48–72 hour turnaround on most projects.