CITY COUNTY DRAIN FLOOD MITIGATION PROJECT OUTLINE 1 What - PowerPoint PPT Presentation

CITY COUNTY DRAIN FLOOD MITIGATION PROJECT

OUTLINE 1 What Happened in 2018? 2 Overview of the Project 3 Challenges 4 Solutions 5 Construction Photos 2

Project Area Downtown Billings City County Drain CCD Project Area South Billings King Avenue Boulevard Interchange Interchange 3

What Happened in 2018?  Significant Runoff in the Yellowstone River − Prolonged flows greater than 40,000 cfs (2-Year) − Erosion along the North Bank of the River  Intense Rainstorm Occurring in Billings − Significant flows down City County Drain 4

2019 Conditions 2018 Conditions 5

Abrupt Change in Backwater Conditions City County Drain 2123.52 2133.28 Island Provides Bank Provides 2131.02 2-Year Protection 10-Year Protection 7.5’ 2.3’ 6

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Challenges 1 Schedule – Provide Protection By Spring 2019 2 Conflicting Objectives A Prevent Backwater from Yellowstone River B Maintain Capacity in CCD for Storm Runoff 9

Alternative #1 Reconstruct New Drainage Ditch NOT SELECTED Right of Way Costs • Schedule • Grey Eagle Ditch • Crossing 10

Alternative #2 New RCB Storm Drain NOT SELECTED Cost • Schedule • Limited Room • 11

Recommended Solution Inlet Structure Flood Control Gate 12

Accelerate Schedule Construction Manager / General Contractor Contract (CMGC)  Typical Design-Bid-Build Contract would not have met the schedule  City of Billings requested proposals from Construction Contractors − COP Construction was selected  Benefits − COP Construction provided Value Engineering recommendations for 30% Design − Early procurement of pipe allowed construction to begin before final design was completed − Contractor paid T&M plus an agreed-upon markup, with a maximum guaranteed price. − Allowed for efficient processing of minor field changes. 13

Construction  All permits were in hand for February 2019 Start − 2 nd Coldest February in Billings History − 29.4” of Snow (3 rd Snowiest February in Billings)  Construction − 4,250 LF 48” RCP Pipeline − Started 3-4-2019 and finished 4-15-2019 − Crest Gate Installed on 7-16-2019 (temporary sheet piling for water control) − Project Completed on 8-15-2019 14

48-inch RCP Pipeline

Yellowstone Outlet Structure

Pipeline Inlet Structure

Fish Bypass

Flood Control Crest Gate

Gate Automation

Gate Automation – Typical Position Yellowstone River WSEL Baseflow in CCD Through 48-inch Pipe

Gate Automation – Runoff From CCD Gate Lays Down Providing additional flow capacity for stormwater runoff Yellowstone River WSEL Baseflow

Gate Automation – Return to Typical Position Yellowstone River WSEL Baseflow in CCD Through 48-inch Pipe

Frozen Ground & Compaction 24

Groundwater 25

Backwater from Yellowstone River 26

City County Drain Stormwater Flows 27

Project is Completed  Protected Upstream Residence from 2019 Runoff Condition  Project came within the $2.85 million budget  Gate Automation Provided Limited Work for the City Maintenance Staff 28

Questions? 29