HomeMy WebLinkAboutLake Line 101 PP SupplementalStormwater 101
Bellevue Utilities Lake Washington Lake Line Management Plan Project
Lake Line 101
Informational Briefing to Medina City Council
Angela Chung, PE, Senior Project Manager,
Engineering Division
Bellevue Utilities Department
May 9th, 2022
Purpose
Inform City of Medina Council of Bellevue Utilities Lake Line Management Plan Project and Respond to Questions
Agenda
A Lake Line History
Lake Washington Lake Line Challenges
Potential Lake Line Replacement Options
Lake Washington Lake Line Management Plan & Anticipated Schedule
A Lake Line History
Many species lived in Lake Washington.
In the 1900s wastewater was being directly discharged into the lake… and development increased
In 1940s – 50s, the nutrients in the lake caused unpleasant blooms of noxious blue-green algae
…and cleanup begins
1950’s: Clean-up of Nutrient-rich water begins
1950’s- 1960’s: Lake Line Sewer Mains are installed in Lake Washington
After the 60s, the Lake Lines were transferred to the City of Bellevue
By 1975 Lake regained clarity. Present day it is clean enough to swim and recreate and healthier for our returning salmon to spawn.
Lake Line
Bellevue’s Lake Washington Lake Lines
Yarrow Point
Hunts Point
Medina
Bellevue
Beaux Arts
King County
Lake Washington Lake Lines in City of Bellevue Service Area
Jurisdiction
Approx. Length (Miles)
% of total Lk Wa Lake Lines
Yarrow Point
1.5
10%
Hunts Point
2.0
14%
Medina
4.5
31%
Bellevue
5.7
39%
Beaux Arts
0.3
2%
Unincorporated King County
0.6
4%
TOTAL
14.6
100%
Note: City of Renton has 1 tax parcel being served by the Bellevue Lake Line
Problem Statement
The Lake Washington Lake Line infrastructure is aging and portions may present potential service level, financial, and environmental risks.
Photos from 2007 Lake Line Cleaning Project
Project Goal
Understand, identify, and prioritize the Lake Washington Lake Lines and key operational, financial and capital investment strategies to phase future repair, replacement and operations of the Lake Lines in a Sewer Lake Line Management Plan.
Existing System Knowledge
Approximately 65 years old
Missing or inaccurate as-built records
Sags in the system
Nightly to Weekly flushing done by O&M
Risk of Failure: Need more information
2016 Condition Assessment
Potential Options for Lake Line Replacement
Options Within the Lake
Pipe Bursting
Options On Shore
Options Upland
Gravity Sewer Line via Trenchless Technology
Gravity Sewer Line via Open Cut Construction
Grinder Pumps
Cured-in-Place Pipe (CIPP)
Significant Challenges
Real Property
Technical challenges
Environmentally sensitive
Impacts to waterfront property owners
No single “fix-all” solution
Public Outreach: Affects multiple communities in multiple jurisdictions
Working with Property Owners
Street </a:t>
Privately Owned Side Sewer (from building to easement)
Example cross section
Technical Challenges
Environmentally Sensitive
Communities and Public Outreach
Yarrow Point
Hunts Point
Medina
Bellevue
Beaux Arts
Unincorporated King County
Public Involvement Plan – Engagement Platforms
Lake Washington Lake Line Management Plan and Schedule
Lake Washington Lake Line Management Plan Components
This plan will include:
Community involvement
Environmental Policy Act (SEPA) & Environmental Impact Statement (EIS)
Decisions based on financial, environmental, and social risks and benefits analysis
This plan will help determine:
Operational strategies and capital improvement projects.
Construction Phasing & Timing
Financial Strategy
Anticipated Project Schedule
Questions?
END
Medina
N
Yarrow Point
N
Hunts Point
N
Bellevue
N
Beaux Arts
N
Unincorporated King County
N