East Mineral Avenue Storm Sewer Collapse

• Project typeStreets
• Project statusConstruction

Record-breaking rainfall in the spring and summer of 2023 stressed Littleton’s stormwater infrastructure, causing several aging corrugated metal culverts to collapse beneath city roadways. Crews are hard at work replacing failed metal culverts with larger reinforced concrete pipes, which will increase durability and resilience. City engineers are proactively examining other elements of Littleton’s stormwater infrastructure to prevent further issues. 

East Mineral Avenue Project Summary

• Corrugated metal pipe failure beneath East Mineral Avenue between South Pennsylvania Street and East Kettle Place. 
• Roadway depression first observed August 3. Hole in asphalt observed later that evening. 
• Further inspection showed approximately 1,000 linear feet of storm sewer in danger of failure and will be replaced with new reinforced concrete pipe. 

Detour Maps

• mineral-driving-detour-map.pdf(PDF, 889KB)
• mineral-pedestrian-detour-map.pdf(PDF, 876KB)

Current Updates 

• Full road closure of westbound Mineral from Dry Creek to E Kettle Ave will occur between 11/29-2/2.
• Lee Gulch Trail is closed from E Mineral Ave west to Littleton Adventist access. Detour maps are posted on site and detour signs have been placed along the trail.

Project Milestones

Weeks of January 1, 2024 and January 8, 2024

• Why is it so quiet out there - Flu season has hit hard.
• Freezing temperatures are unsafe working conditions. Work will continue after the artic freeze has lifted.
• Due to inclement weather the road open date has been extended out until February 2, 2024.

Week of December, 25 2023

• Due to inclement weather and utility crossing conflicts, the road open date has been extended out until January 19.

Week of December, 4 2023

• Work begins in the creek for the new outfall

Week of November, 27 2023

• WB road closure begins through end of year
• Site will be stabilized, surveyed and additional materials brought in for project construction

Week of November, 18 2023

• East bound E Mineral Ave complete and open to all EB traffic

Week of September, 11 2023

• The final outfall alignment has been determined, so pipe installation continued this week. 
• Rainy Thursday and Friday caused flooding in the work zone
• The tree near the pedestrian crossing had to be removed due to the proximity of the new pipe alignment. The tree was removed on Friday, making the pedestrian flashing beacon more visible.

Week of September, 4 2023

• West side of Lee Gulch was grubbed out to better see the outfall location and create a clear work environment – large trees will try to be preserved.
• Pothole for Denver Water Crossing.
• LPD to monitor the neighborhood to help with speeding concerns from neighbors.
• New outfall design is complete. Work on the excavation continues. 
• To avoid full road closure, C&L crews will complete the outfall re-alignment to the median. Once the project us fully complete on EB Mineral Ave, the eastbound lanes will be opened and westbound lanes will be closed, this will be approximately 3-4 weeks for completion of outfall and adjustment of waterline.  

Week of August, 28 2023

• Full road closure of Eastbound East Mineral Avenue was done 8/28/2023.
• Materials are brought in and excavation started
• Milling started northern 400 ft – milling machine collapsed into new sinkhole. Will need to open cut the remaining sections as the rest of the line is too unstable to carry a load. 
• Open cut showed tied into existing outfall is not going to work. The bottom of the existing outfall is corroded, and the inlet has no remaining bottom of structure - will need to be repaired now. Additionally, the 18” CMP that crosses Mineral has voids at bottom of pipe  – this will be fixed with the outfall realignment. 
• This outfall was identified to need replacement, but Staff was hopeful to delay until completion of other projects. The outfall is currently flowing upstream – Staff is correcting alignment with project will need to work on design. 

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