HomeMy WebLinkAboutMINUTES - 08041987 - 2.6 TO. BOARD OF SUPERVISORS ;gym°®O6
FROM; Contra
ra
Harvey E. Bragdon
Director, Community Development Dept. Costa
DATE: County August 4, 1987 LJ�JIJI R)I
SUBJECT;
Westbound Lane Interim Project on State Route 4 over Willow Pass
SPECIFIC REQUEST(S) OR RECOMMENDATION(S) a BACKGROUND AND JUSTIFICATION
REPORT
On July 14 , the Board requested a report on the capacity provided by
the interim capacity improvement to State Route 4 over Willow Pass,
and the affect of future housing activity on this capacity
improvement.
The interim project involves construction of a third westbound lane
on State Route 4 from the Willow Pass Road interchange in West
Pittsburg, to the Willow Pass Road interchange in Concord. Caltrans
has measured the capacity of the existing westbound lanes at 4 , 000
vehicles per hour, or 2, 000 vehicles per hour per lane. The added
capacity of the interim project will increase westbound freeway
capacity to about 6,000 vehicles per hour, or 50 percent.
Traffic counts indicate that the freeway is operating lat capacity
during the morning peak period. Existing demand exceeds capacity
which is why traffic backs up to the Railroad Avenue overcrossing.
As the objective of the interim project is to prevent further
deterioration of traffic conditions on State Route 4 until the
ultimate project to lower and widen the freeway can be implemented,
the project will provide additional capacity to serve another 4,000
vehicle trips during the two-hour morning commute period (2 ,000
vehicles per hour) . This figure assumes that some commuters will
continue to use alternate routes over Willow Pass (e.g. Port Chicago
Highway, Evora Road, or Bailey Road) , to avoid the congestion on
State Route 4 , and that traffic will increase on other roads leaving
Eastern Contra Costa County.
The new housing that could be served by the interim project depends
not only on the number of houses constructed, but also the number of
employed residents per household, the number of such residents that
will work on the west side of Willow Pass, which westbound road these
dp8 :Capacity.t07
Orig. Dept. - CDD, TPD
X
CONTINUED ON ATTACHMENT; _ YES SIGNATURE'
- RECOMMENDATION OF COUNTY ADMINISTRATOR RECO TION F BO RD COMMITTEE
- APPROVE OTHER
SIGNATURE(S):
ACTION OF BOARD ON _ August 4. 1987 APPROVED AS RECOMMENDED X OTHER
ACCEPTED report from Director of Community Development on Westbound Lane Interim
Project on Highway 4 over Willow Pass.
VOTE OF SUPERVISORS
1 HEREBY CERTIFY THAT THIS IS A TRUE
X UNANIMOUS (ABSENT ) AND CORRECT COPY OF AN ACTION TAKEN
AYES: NOES: AND ENTERED ON THE MINUTES OF THE BOARD
ABSENT; ABSTAIN: OF SUPERVISORS ON THE DATE SHOWN.
CC: Public Works ATTESTED
Community Development Director PHIL BACHELOR. CLER'K OF THE BOARD OF
County Administrator SUPERVISORS AND COUNTY ADMINISTRATOR
M382/7-83BY DEPUTY
residents will take, and their rate of carpooling. Staff developed
an equation to estimate the number of dwelling units required to send
4, 000 vehicles west on State Route 4 over Willow Pass during the
morning commute period. This equation and the assumptions behind the
equation are described in Exhibit A.
With construction of the interim project, approximately 12,000 new
housing units could be occupied before traffic congestion on State
Route 4 would again reach current levels. The Community Development
Department has developed housing projections in Eastern Contra Costa
County for the 1987 to 1992 period which can be used to indicate how
long it would be before the additional capacity is used. These
detailed projections are as follows: .
Area Units/Year 5 Year Total
Antioch 850 4,250
Pittsburg 400 2,000
Brentwood 250 1, 250
Unincorporated areas 645 3 , 225
- West Pittsburg 100 500
- Oakley 400 2 ,000
- Discovery Bay 115 575
- Other areas 30 150
A housing construction rate of 2 , 245 units per year is projected for
Eastern Contra Costa County. Using January 1, 1987 as a starting
point, and assuming it would take one year for a dwelling unit to be
constructed and occupied, the capacity of the interim project would
be fully utilized by the first half of 1992.
dp8 :Capacity.t07
Orig. Dept. - CDD, TPD
CC: Public Works
Attachment - Exhibit A
EXHIBIT A
CALCULATIONS FOR NEW HOUSING SERVED BY THE INTERIM PROJECT
Equation: A = ( B x C ) / ( D x E x F )
A = number of dwelling units
B = capacity of the interim project (4, 000 vehicles) .
The capacity of the interim project is given at 4,000 vehicles.
C = average vehicle occupancy (1.09 persons per vehicle) .
The average vehicle occupancy assumption is based on the number of
people driving alone to work. A recent telephone survey by Tri Delta
Transit found that 90 percent of the residents in their service area
who work in other parts of the County or Southern Alameda County drive
alone. The drive alone rate would be slightly lower if work locations
in San Francisco and Oakland are included. The 1980 Census indicates
the 90 percent drive alone rate should be adjusted to 86 percent if
the San Francisco and Oakland work locations are included. Therefore,
assuming an 86 percent drive alone rate and an average carpool size of
2.5 persons, the estimated average vehicle occupancy would be 1. 09
persons per vehicle.
D = number of employed residents per household (1.28 emp. res./ h.h. ) .
The Association of Bay Area Governments in Projections 85 anticipates
that there will be an average of 1. 28 employed residents per household
in Eastern Contra Costa by 1990.
E = percent of employed residents working outside East County (60
percent) .
A recent study by Tri Delta Transit estimates that the percent of
Eastern Contra Costa County residents employed outside the area would
increase from 56 percent in 1980 to 63 percent in the year 2000. For
this analysis, it will be assumed that 60 percent of the residents
will be employed outside Eastern Contra Costa County.
F = percent of employed residents working outside East County and using
SR 4 over Willow Pass (47 percent) .
A review of available traffic count data indicates that westbound
travel on State Route 4 over Willow Pass accounts for approximately 47
percent of the morning peak hour travel leaving Eastern Contra Costa
County.
Incorporating these assumptions into the equations results in the
following calculation:
A = ( 4000 x 1. 09 ) / (1. 28 x .60 x .47 ) = 12 , 077 dwelling units