The Economics of Renewal

Trenchless Rehabilitation vs. Open Cut

The "Fix it First" Mandate

For decades, the standard response to a failing sewer asset was simple: Dig it up and replace it.

However, as municipal budgets tighten and the "Infrastructure Gap" widens, the math behind Open Cut replacement no longer adds up for the vast majority of assets. With the average cost of full excavation often exceeding $15,000 - $25,000 per manhole (factoring in restoration and traffic control), reliance on replacement is financially unsustainable.

In this analysis, we evaluate the economic argument for Trenchless Rehabilitation, factoring in not just direct bid prices, but the Social Costs and Risk Profiles that truly drive Capital Improvement Plans (CIP).

1. Direct Cost Comparison: The 50% Rule

When analyzing hard costs (CapEx), trenchless rehabilitation consistently demonstrates a 40% to 60% savings over excavation.

The Scenario:

Consider a standard 48-inch diameter brick manhole, 10 feet deep, located under a paved collector road.

Option A: Open Cut Replacement

Requires heavy mobilization, trench shoring (OSHA compliance), dewatering, removal of the old structure, setting a new precast base/risers, backfilling, and—most expensively—asphalt repaving.

Estimated Cost: $12,000 - $20,000+

Option B: Structural Lining (CIPM/Epoxy)

Requires a box truck and a 3-man crew. High-pressure water blast (5,000 psi), cementitious build-back, and a corrosion-resistant liner.

Estimated Cost: $3,500 - $6,500

The ROI: By choosing rehabilitation, a municipality can effectively renew 2.5 to 3 assets for the price of replacing one.

2. The "Iceberg" Effect: Social & Restoration Costs

Experienced engineers know that the bid price is rarely the final price. Open Cut projects carry massive "hidden" costs that trenchless methods eliminate.

Pavement Degradation: Cutting a trench into a road reduces the pavement’s service life by approximately 40% in the affected area, regardless of patch quality. This accelerates future repaving schedules (OpEx).
Traffic Control & Business Impact: Closing a lane for 3 days incurs significant traffic control costs and generates complaints from local businesses. Trenchless rehab typically requires a 4-6 hour window, often completed outside peak hours.
Carbon Footprint: Excavation involves heavy diesel machinery and dump trucks hauling spoil. Rehabilitation is a localized chemical process with a carbon footprint up to 90% lower.

4. The Decision Matrix: When to Dig?

We are not suggesting that replacement is obsolete. It is a necessary tool, but it should be the option of last resort.

Use Trenchless Rehabilitation When:

The structure is circular and capable of acting as a formwork.
The primary defect is Corrosion (H2S) or Infiltration (I&I).
The asset is located in a high-traffic zone or under expensive hardscape.

Use Open Cut Replacement When:

Total Structural Collapse: The manhole has shifted so severely that it cannot be re-rounded or lined.
Capacity Upgrades: You need to upsize the pipe connections or the manhole diameter itself.
Alignment Issues: The manhole is located in a position that impedes future development or utility routing.

3. The Risk Profile: Controlling the Unknown

From a project management perspective, risk mitigation is as valuable as cost savings.

Excavation Risks (Uncontrolled Variables):

Utility Strikes: Hitting a gas line or fiber optic cable is the single largest liability in sewer construction.
Soil Conditions: Unforeseen running sands or high water tables can blow up a budget via change orders.
Trench Safety: Deep excavations introduce life-safety risks (collapse) that require strict oversight.

Rehabilitation Risks (Controlled Environment):

The work is contained entirely within the existing footprint.
No interaction with adjacent utilities.
Predictable schedule and fixed pricing.