Overview
~39% of Illinois cropland is underlain by drainage systems, making accurate drain tile estimation critical for AIMA compliance and zoning. During early project stages only existing drain tile data is available, making remediation scope difficult to predict. A data-driven tool was built using a historical cost database of known remediation quantities, proposed installation requirements, and impacted system percentages.
Methodology
- Scope inputs: Users enter drain tile quantities (LF) by pipe diameter from available existing data
- Historical cost database: Unit rates per LF derived from actual project data across a range of observed costs
- Risk-based tiers: Low (optimistic), Medium (most likely), High (conservative) — tailored to project stage and risk tolerance
- Direct costs: Scope quantities × historical unit rates by diameter
- Indirect costs: Fixed allowances for consulting, contingency, equipment transport, investigation & repair crew
Key Findings
- Estimates align closely with Vendor-1 bid ranges
- Higher than Vendor-2 bids — indicates potential conservatism
- Limited economies of scale for large quantities (>5,000 LF) on smaller diameter pipes
Limitations & Recommendations
- Limited differentiation across pipe material types (clay vs. HDPE)
- Missing cost data for non-standard diameters — approximations required
- Recommended: expand dataset with material-specific cost variations and interpolation logic for non-standard diameters
- Refine cost curves to better reflect economies of scale