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Grade Separation Alternative
A Feasibility Analysis of the Reconfiguration of Genesee Avenue at Governor Drive
By: Daniel Aruta, P.E.
Topics for Discussion:• What is a Grade Separation?
• Construction Impacts
• Traffic Analysis
• Environmental Impacts
PART 1: What is a Grade Separation?• A facility which provides a physical vertical separation between two
roadways crossing each other to alleviate traffic congestion and promote safety
• One roadway passes over another crossing roadway, and both roadways do not meet
• The upper roadway crosses over the lower roadway via a bridge
• Similar to a diamond interchange on a freeway
• A Grade Separation is not a tunnel!
University Avenue in Park Slope
Sample of a Grade SeparationDiamond Interchange of Interstate 15 at El Cajon Blvd in San Diego
Interstate-15
El Cajon Blvd
Off
Ram
p
5 Basic Elements of a Grade SeparationInterstate 15 at El Cajon Blvd in San Diego
Retaining Wall
Bridge
RetainingWall
DepressedRoadway
Ramp
5 Basic Elements of a Grade SeparationInterstate 15 at El Cajon Blvd in San Diego
BridgeRetaining
Wall
RetainingWall
DepressedRoadway
Ramp
Genesee Ave Grade Separation at Governor Dr• Bridge on Governor Dr passes over Genesee Ave below• 2 Lanes on Genesee Ave are depressed to pass under the bridge• 4 Ramps• Inside Retaining Walls (4 each)• Outside Retaining Walls (minimum of 4 each)• Total Length from end to end = 1,787 ft.
Plan View
No
rth
Bridge
Inside Retaining Wall
Outside Retaining Wall
Depressed Roadway
Begin Walls Begin Walls
Ramp
Vertical Separation• Governor Dr above Genesee Ave• 2 inside lanes of Genesee Ave below Governor Dr• A bridge over a depressed roadway
Vertical Profile View
GovernorDrive
Genesee
Avenue
Depressed Roadway
Vertical Scale is Exaggerated!
Begin Grade Separation End Grade Separation
Existing Roadway
Section Through Bridge
• Length of Bridge (Span) = > 50 ft.• Width of Bridge = ± 110 ft.
Section where Genesee Ave passes under the bridge at Governor Dr
Section View
Section Through Retaining Walls
Section View
Section of Genesee Ave north and south of Governor Dr (beyond bridge)
Lengths of Retaining Walls
• South of Governor Dr: 731 ft. long, max height greater than16.5 ft.
• North of Governor Dr: 936 ft. long, max height greater than16.5 ft.
Inside Retaining Walls:
Plan View
731’ 936’
No
rth
Part 2: Construction Impacts• Utility Relocation
• Constructing the Bridge
• Constructing the Retaining Walls
• Road Closures
• Environmental Impacts
• Project Duration
Utility Relocation• Two 16” Water Mains• 8” Sewer• Electrical Duct Bank• Gas Line• Phone Cables
N
Water
Wate
r
Sewer
Elect
Gas
Phone
Phone
Genesee Ave
Go
vern
or
Dr
Constructing the Bridge• Drive Sheet Piling into the Ground
Section View
Sheet Piling
Constructing the Bridge• Drive Sheet Piling into the Ground
• Excavate Pit for the Bridge
Section View
Constructing the Bridge• Drive Sheet Piling into the Ground
• Excavate Pit for the Bridge
• Construct the Bridge
Section View
Constructing the Retaining Walls• Drive Sheet Piling into the Ground
• Excavate Channel
• Construct Inside Retaining Walls and Depressed Roadway
• Construct Outside Retaining Walls for Sideslopes and Outside Roadways
Section View
Extent of Sheet Piling in Genesee Ave
Plan View
No
rth
Sheet Piling
Depressed Roadway
For Depressed Roadway: Approx. 1,100 ft. each side of depressed roadFor Outer Retaining Walls: Lengths will vary
Environmental Impacts to Consider During Construction
• Noise
• Vibration
• Air Quality
• Truck Trips
• Contaminated Soils
• Backup Bells on Construction Equipment
• Driving Sheet Piling
• Diesel Exhaust from Construction Equipment
• Thousands of Truck Trips
• Soils Mitigation from 4 Gas Stations – Project Delay
Impact
Example
Project Duration• Utility Relocation = 6± months
• Mitigation of Contaminated Soils = ?
• Construction of Grade Separation = 2± years
• Total Project Duration = 2.5+ years
Road Closures during Construction
• Genesee Ave from Radcliff La to south of University City HS
• Intersection of Governor Dr and Genesee Ave
Plan View
1,800 ft.
No
rth
• Disruption to Vehicular and Pedestrian Traffic• Loss of Access to Schools and Businesses• Economic Hardship on Local Businesses• Huge Detriment to the Community
North/South Access during Construction• No Bridge on Regents Rd
• 1,800 ft. of Genesee Ave closed
• Intersection of Governor Dr and Genesee Ave closed
Police, Fire andParamedic Serviceto University City
will be severelychallenged
during construction
Alternate Routes during Construction• Interstate 5 Freeway
• Interstate 805 Freeway
• State Route 52
Detour!
Part 3: Traffic Analysis – Post Construction• Existing Traffic Movements at Intersection of Genesee & Governor
• Proposed Traffic Movements at Intersection of Genesee & Governor
• Level of Service and Lane Reductions at Split Points
• Elimination of Bus Stops
Existing N-S Traffic Lanes at Intersection• 2 Southbound Through Lanes• 2 Left Turns – SB Genesee to EB Governor• 1 Southbound Right Turn• 2 Northbound Through Lanes• 1 Left Turn – NB Genesee to WB Governor• 1 Northbound Right Turn
Existing Intersection
Proposed N-S Traffic Lanes at Intersection• 1 Southbound Combined Through/Right Turn Lane• 1 Left Turn – SB Genesee to EB Governor• 1 Northbound Combined Through/Right Turn Lane• 1 Left Turn – NB Genesee to WB Governor
Grade Separation
UC Golden Says:
…and…
Do The Math:
NB: 78% of 33,000 = 25,740 ADTSB: 70% of 33,000 = 23,100 ADT
Street Classification and Level of Service (LOS)• Level of Service “E” = 10,000 ADT for 1 Lane• NB Traffic: 25,740 ADT > 10,000 ADT• SB Traffic: 23,100 ADT > 10,000 ADT
NB: 2.57 x Failure Volume
SB: 2.31 x Failure Volume
Lane Reduction at Split PointDecision: Do I take the underpass or do I take the ramp to Governor Dr?
Split Point
1 T
hro
ug
h L
ane
Ram
p to Governor D
r“Governor Dr ”
As most cars from two lanes vie for position into one lane, this will effectively create a “lane reduction” at the split point and traffic will backup!
UC Golden:
3 Bus Stops on Genesee Ave are Eliminated
Post Construction
Part 4: Environmental Impacts – Post Const.• Noise
• Neighborhood Character
• Tree Removal
Noise• Sound acoustics are accentuated off retaining walls
• Increase in traffic volumes over time due to urban growth will increase ambient noise levels
Neighborhood Character• University City is a residential community
• Only small retail except for commercial district on Greenwich Dr
• UC is not a major traffic generator like Golden Triangle
• Grade Separation will “urbanizes” the character of the neighborhood
Should future University City appear like this?
Tree Removal• 88 Conifer Trees
• 22 Eucalyptus Trees
• 5 Sycamore Trees
• 3 Others
118 trees will be removed
The End