grade separation alternative a feasibility analysis of the reconfiguration of genesee avenue at...

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