Memorandum 13-105 Sewer Manhole Repair

M E M O R A N D U M  13-105

TO:   Walt Wrede, City Manager
FROM:   Carey Meyer, Public Works Director
DATE:   July 16, 2013
SUBJECT:  Sewer Manhole Repair/Erosion Protection
   Construction Contract Award Recommendation 

Last winter, a sewer manhole near a creek became the source of serious inflow which caused the flooding of four homes and damaged the sewer treatment plant. The cause of this problem was the frost heaving of the upper manhole sections combined with high creek flows that eroded the bank, exposing the manhole to creek water. Cold early winter temperatures (with no snow cover) created deep frost penetration and unusually high frost heave potential in Homer last winter.  Warm temperatures, rain and snow melt created unusually high creek flows in late December. Public Works has developed a plan to repair the manhole and prevent this unusual circumstance from happening again.

The repair consists of exposing the manhole’s exterior, wrapping the exterior with a waterproof membrane, and providing a riprap slope between the creek and the manhole. This will minimize the potential for the manhole sections to frost jack (creating a smooth outer surface), making the manhole water-tight, and prevent future flood events to erode the bank and expose the manhole to creek flow.

This work is planned to be completed in August when creek flows are low. The culvert that was placed in the creek by Public Works crews to divert flows past the manhole during the event will be removed. A Corps of Engineer’s permit will be required to work in and adjacent to the creek. Public Works is in the process of competitively bidding this repair work (in accordance with the City’s Procurement Manual).

The City Council has previously authorized funds from the Sewer Reserve account for the repair of flood damage resulting from the event and for implementing mitigation measures (Ordinance 13-08) Fiscal Note: 256-379. If the cost of this work exceeds the previously authorized budget, additional City Council authorization will be acquired during the mid-year budget adjustment.

RECOMMENDATION:  The City Council pass a resolution awarding the Meadow-Wood Place Subdivision Sanitary Sewer Manhole Repair Project to the low bidder in the amount of the low bid and authorized the City Manager to execute the appropriate documents.

Fiscal Note:  256-379 (Sewer Reserve Fund)