Engineer recommends countywide tree clearing, mapping and targeted projects for drainage ditches

The Dallas County Board of Supervisors received a drainage reconnaissance report from AgriVia that documents the condition of roughly 14 open ditches across the county and recommends a program of tree removal, ongoing spraying, and digital mapping to reduce future maintenance costs and protect tile outlet structures.

The report, prepared for the Board acting as trustees of drainage districts, summarizes aerial field observations made in March 2026 and notes common problems including bank sloughing, erosion gullies, beaver dams, submerged tile outlets, and dense woody vegetation in many ditch reaches. AgriVia’s authors wrote that, in many locations, trees growing adjacent to outlet bulkheads and above tile mains have led to root intrusion and damage, increasing the risk and cost of future repairs.

AgriVia recommended a structured first phase of tree removal (to be bid by drainage district), followed by a recurring three‑year rotation of spraying and cutting to prevent regrowth. The report estimates the cost to prepare the digital mapping package at approximately $20,000 and recommends a separate $10,000 estimate to prepare a bid package for tree‑clearing work. AgriVia advised a public hearing is required only where district costs exceed $50,000 and indicated that preliminary review suggests only DD 10 might surpass that threshold.

The packet described construction considerations, including clearing and grubbing, seeding and bank stabilization practices, pollution and erosion control, and landowner notification and compensation mechanisms under Iowa statutes. The report stresses that the Board is obligated under Iowa Code Chapter 468.138 to maintain drainage district facilities in a reasonable state of repair.

AgriVia’s conclusion urged the Board to direct the engineer to proceed with GIS mapping and prepare bid packages to address backlogged tree‑related maintenance across affected districts. The Board placed the report into the record for Trustee consideration. No immediate district work authorization or bids were awarded at this meeting.