Drainage engineer warns main tile near Slater may be failing; trustees order further investigation

Boone and Story County Drainage District trustees on July 15 directed an engineer to investigate an obstruction and the condition of the district's 36-inch main tile that outlets into Four-Mile Creek near the High Trestle Trail and runs under Highway 210 north of Slater.

Tyler Conley, a drainage engineer with Bolton & Menk, told trustees the tile is clay for most of its length but is corrugated metal under Highway 210. An initial inspection found clay and concrete debris inside the line, and crews encountered an immovable piece of debris directly under the highway centerline that prevented jetting and video inspection past that point to the development site north of the highway.

"It was running half full yesterday, so it is functioning and carrying a significant amount of water," Conley said, adding that holes had appeared on the surface above the tile north of the highway that were not present a week earlier, which raised concern the line may be failing.

Conley told the trustees any development over a district tile warrants investigation or relocation of the tile at the developer's expense. He recommended the trustees either authorize repair work on the main tile or require the landowner or developer to sign an agreement acknowledging the district is only liable for repairs to the district tile and not for damage to private property caused by necessary repairs or excavation.

Board members pressed Conley on coordination with the City of Slater and on the span of tile across the proposed development. Conley said he had not yet contacted Slater and recommended doing so before the district spends money on a replacement that the city might later replace with storm sewer. He said the tile crosses approximately 457 feet of the proposed development.

Lisa Heddens of Story County said she concurred that the district should not conduct repairs until staff has spoken with the City of Slater about the city's broader plans for the area. The trustees voted unanimously to direct Conley to further investigate the blockage under Highway 210, assess the tile under the proposed development, and begin conversations with the City of Slater.

Property owner Tanya Doyle told the trustees the 80 acres north of the proposed development are currently subject to a handshake agreement for future development but she does not expect activity there for five to seven years.

The trustees approved the meeting agenda earlier in the session and adjourned at 9:23 a.m.