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© 2017 USACE & City of Arvada, all rights reserved.
Study developed by the U.S. Army Corps of Engineers, the Urban Drainage and Flood Control District, the City of Arvada and other participating agencies
PRESENTATION STARTS AT 6:30 P.M.
SECTION 205 FLOOD RISK MANAGEMENT FEASIBILITY STUDY FOR THE RALSTON CREEK WATERSHED
SECTION 205 FLOOD RISK MANAGEMENT FEASIBILITY STUDY FOR THE RALSTON CREEK WATERSHED
WELCOMEPreliminary Alternatives Informational Meeting
This study is authorized under Section 205 of the Flood Control Act of 1948, as amended, which allows the U.S. Army Corps of Engineers to assess the feasibility of and construct projects that reduce flooding-related damages
About the Flood Risk
Management Feasibility Study
About f looding problems and Preliminary Alternatives
to manage flood risks along Ralston CreekLearn More Provide Your Input
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History of flooding in Arvada
Infrastructure and safety risks
Study OverviewWHY ARE WE CONDUCTING THIS STUDY?
Examine the feasibility and environmental effects of implementing flood risk management
solutions along Ralston Creek in the City of Arvada
WHAT WILL THIS STUDY DO?
WHAT IS SECTION 205?
Authorizes the Corps to construct projects to reduce flooding-related damages
STUDY DURATION:
Fall 2016 – Summer 2018
The City of Arvada submitted a letter of
request to USACE for a study in May 2009
STUDY SPONSORS:
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Study Process & Schedule
FALL
2016
WINTER
2016
SPRING
2017
SUMMER
2017
FALL
2017
WINTER
2017
SPRING
2018
SUMMER
2018
FALL
2018
WINTER
2018
Compare Plans
Draft Report
Select Recommended Plan
Finalize Feasibility Report and Environmental Assessment
Public Comment on Draft Report
Public Comment on Alternative Plans
P Public Comment on Existing Conditions
P Identify Existing and Future Conditions
WE ARE
HERE
* Based on anticipated project schedule, dates are subject to change.
This study began in fall 2016 and is expected to last through summer 2018
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P Formulate Alternative Plans
STUDY LOCATION
The study area includes 3.5 miles of Ralston Creek from Beech Street downstream to the confluence with Van Bibber Creek just west of Garrison Street.
STUDY DETAILSThis study will seek to develop feasible flood risk management solutions by evaluating existing and future flood risk, economic costs and benefits, as well as environmental impacts.
Study Location & Details
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Flooding in Ralston Creek
1985 1990 1995 2000 2005 2010 2015
July 22, 1991*
* Listed as significant per Ralston Creek Flood Warning Plan (2009)
The following are documented flood events on Ralston Creek:
July 20, 1986
May 18, 1995 & June 4, 1995*
August 4, 1997*
August 4, 1999*
September 11-13, 2013
July 10, 2009*
June 8, 2004* & June 27, 2004*
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Damage to two water supply reservoirs
Turbid water caused problems at water treatment plants
Roadway overtopping
Damages to residential properties
Breaching of canal embankments
September 2013 Flood
SIGNIFICANT DAMAGES INCLUDED:
A
B
A: Ward Road at Ralston Creek
B: Ralston Creek near Memorial Park
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More than 70% of the expected annual damages occur between the Arvada Tennis Center and Brooks Drive
Flood Damage Risks to Property
Flood Damage
Category
Within 500-Year Floodplain Expected Annual
DamagesStructure Count Value
Residential (Homes) 688 $122,960,000 $2,858,400
Commercial (Businesses) 3 $590,000 $1,720,00
Other Associated Damage
Categories (e.g. vehicles,
emergency response, etc.)
N/A N/A $596,570,00
Totals 691 $123,550,000 $3,456.70
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IDENTIFY ALTERNATIVES THAT REDUCE FLOOD RISK
A potential project could lead to updated, FEMA-approved
floodplain maps and possibly reduce flood insurance requirements
in the 100-year floodplain.
Study Objectives
IDENTIFY ALTERNATIVES TO IMPROVE PUBLIC SAFETY
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Determined existing and future flood risk
Held a public scoping meeting on May 9, 2017 to gather your input
Held an Alternative Formulation workshop with the City on May 10 and 11, 2017
Identified three Structural Alternatives and one Nonstructural Alternative to reduce the
flood risk
Process & Measures
THE FOLLOWING HAS BEEN CONDUCTED TO DEVELOP THE STUDY:
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Reduces average annual damages 31% (37% from Arvada Tennis Center to Brooks Drive)
Alternative 1INITIAL PROJECT COSTS $16.3 MILLION
42 acre (520-acre-ft of storage) detention basin
Removal of grade control structure
Limited channel modifications for detention basin inlet and outlet
Vegetation thinning from Simms St. to Brooks Drive
No real estate acquisitions are anticipated
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Reduces average annual damages 53% (70% from Arvada Tennis Center to Brooks Drive)
Alternative 2INITIAL PROJECT COSTS $14 MILLION
Bridge removals W. 68th Ave. / W. 61st Ave.
New bridges at Ward Road and Rensselaer Drive
Modified channel walls from Arvada Tennis Center to Brooks Drive
Modified channel includes vegetation removal
Vegetation thinning from Beech St. to Arvada Tennis Center
Potential for select real estate acquisitions as yet to be determined
A B
A: Existing channel condition
B: After implementation channel condition11
Reduces average annual damages 49% (65% from Arvada Tennis Center to Brooks Drive)
Alternative 3INITIAL PROJECT COSTS $17.4 MILLION
12-foot-tall by 12-foot-wide box culvert under Johnson Way
Limited channel modifications for box culvert inlet and outlet
Vegetation thinning from Beech St. to Brooks Drive
Potential for select real estate acquisitions as yet to be determined
High flow box culvert typical cross section
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Understand importance of existing conditions
Portions of creek are narrow and flooding occurs at a 10-year event
Balance between the following:
Reducing flood risk
Minimizing impacts to private property
Minimizing impacts to trees
Vegetation Thinning and RemovalWHY CONSIDER IT?
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WHAT ARE THE OPTIONS?
Larger channel could be constructed
Higher cost and real estate acquisitions
May not be economically justifiable
Nonstructural AlternativesWET FLOODPROOFING DRY FLOODPROOFING HOME ELEVATION BUY-OUTS OR RELOCATION
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Structures impacted by flooding were reviewed to determine potential for nonstructural measures
Some structures are economically justified for nonstructural measures
No substantial grouping of structures
Without a substantial grouping, a stand-alone nonstructural alternative is not justified
Nonstructural measures will be considered in combination with the structural alternatives considered
Improving channel and overbank capacity of Ralston Creek
Creating riparian and wetland habitat areas
Improving recreation and transportation networks through recreational trails
upstream and downstream of the study area
Opportunities
ALTERNATIVE DEVELOPMENT OPPORTUNITIES:
Increasing local awareness
Gathering input from citizens, local, state and federal entities to aid in the
identification and implementation of flood risk reduction solutions
PUBLIC INVOLVEMENT OPPORTUNITIES:
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We want your input throughout the study process. You can provide feedback by filling
out a questionnaire today or by going online, printing it out, and mailing it back.
Public Involvement
Feedback on Preliminary Alternatives
Flooding problems, impacts, or damages in the study area
Potential outcomes of the study you’d like to see avoided
Your suggested improvements to recreational trails and networks in the study area
PROVIDE YOUR FEEDBACK ON THE FOLLOWING:
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Go to the project webpage to learn more at:
nwo.usace.army.mil/Missions/Civil-Works/Planning/Planning-Projects/ArvadaCO
How Can You Help?
LEARN MORE ONLINE
Rebecca Podkowka, ATTN: CENWO-PM-AC, 1616 Capitol Avenue, Omaha, NE 68102
MAIL US ANY COMMENTS OR QUESTIONS
EMAIL US ANY COMMENTS OR QUESTIONS
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© 2017 USACE & City of Arvada, all rights reserved.
THANK YOU FOR ATTENDING
