HomeMy WebLinkAboutR_MEF_SW_Ramp_200224_v4
Bruce S. MacVeigh, P.E.
Civil Engineer/Small Site Geotechnical
14245 59th Ave. S.
Tukwila, WA 98168
Cell Ph: 206-571-8794
February 24, 2020
Subject: Maximum Extent Feasible (MEF) Evaluation - ADA Ramp
Reconstruction, Southwest Corner of Cedar Avenue S. and S. 4th Street,
Renton, WA
Project Description.
A new single family residence is being constructed on the southwest corner of
the intersection of Cedar Avenue S. and S. 4th Street. A requirement of the
residential permit is to upgrade adjacent right-of-way where feasible.
The sidewalk fronting the property along S. 4th Street will be replaced in kind
due to the poor condition of the walkway.
The existing ADA ramps on that corner and to the north across S. 4th Street are
to be reconstructed to the maximum extent feasible to current WSDOT
standards.
This evaluation discusses the design for the reconstruction of the ADA ramp on
the southwest corner of the intersection.
Highway Parameters.
Design Matrix - Asphalt roadway with concrete curb, gutter and sidewalk
Road Classification - Neighborhood arterial or collector
Funding Source - Private
Posted/Design Speed - 25 mph
Average Daily Traffic - 500 trips per day (estimate)
Truck Percent - 2 percent (estimate)
Access Management Classification - None
Existing Pedestrian Facilities.
The concrete walkway on Cedar Avenue S. has a total width of 6.5 feet,
including curb width. There is no planting strip. The walkway on S. 4th Street
is 5 feet wide, with a 4.5 foot planting strip and 6” width curb.
REVISION
Received: 02/26/2020 / aalexander
BUILDING DIVISION
PR19000003
B19000388
V4
REVISION Received: 01/13/2021 / aalexander
BUILDING DIVISION
PR19000030
B19000388
V6
APPROVEDBUILDING DIVISION
THIS SET OF APPROVED PLANS MUST BE ON THE JOB AT ALLTIMES DURING CONSTRUCTION. THIS BUILDING IS NOT TO BEOCCUPIED UNTIL AFTER FINAL INSPECTION BY THE RENTONBUILDING DIVISION AND RECEIPT OF CERTIFICATE OFOCCUPANCY.APPROVAL SHALL NOT BE CONSTRUED AS THE AUTHORITY TOVIOLATE OR CANCEL ANY PROVISIONS OF CODES, ORDINANCES,OR OTHER REGULATIONS ENFORCED BY THIS CITY.DATE: 07/15/2021
The street slope of Cedar Avenue S. is downward to the north with a slope of
about 9.9 percent.
The street slope of S. 4 th Street is downward to the west at about 16.1 percent.
The related walks have the same slope.
The existing ADA ramp is older and consists of a standard trapezoid ramp with
minimal landing due to limited width of walkway to right-of-way line. The
landing is 6” above street flow line elevation. It has the impressed grid pattern
on the ramp surface. It is centrally oriented on the corner. It was constructed to
an older standard, but shows good workmanship for difficult slope conditions. It
is in good condition.
Pedestrian Design Standards.
Per Curb Ramps, WSDOT, DM Section 1510.09.
Running Ramp Slope = 1/12 max.
Side Ramp Slope = 1/48 max.
Walk Side Slope = 1.5 to 2 percent
Side Slopes = 1/10 max.
Landing Dimensions = 36” x 36” min.
Proposal.
To replace the entire ramp and landing area, and to extend walkway transitions
to the north and west 15 feet to match existing walkway slopes. The
reconstruction would lower to the maximum extent feasible the entire ramp and
landing area to flow line depth, with ramp slopes reduced to 0 to 2 percent
where possible.
The west transition run of walk will have slightly reduced down slope due to the
lowering of the ramp and landing area. The south transition run will have a
slightly increased up slope due to the lowering of the ramp and landing area.
Note that both of the runs of walkway will still be in excess of current design
criteria of 1/12 (of 8.33 percent)
A current standard 18” wide warning strip will be provided on the ramp prior to
the curb line.
Since the ramp and landing area are in a continuing down slope run of the
walks from the two streets as they round the corner, the landing cannot meet
the desired 1.5 to 2 percent slopes but, with best fitting, will still have portions
exceeding the desired design slopes.
Justification.
The combined ramp and landing will more or less meet available design
standards in horizontal dimensions, and will have surface slopes more closely
meeting design standards. As noted, the ramp face follows the curb flow line
around the corner at a continuous down slope (typically down at 12 percent).
For this reason, while the ramp and landing area is significantly improved, it
cannot meet full design standards.
The transition runs cannot meet the 1/12 maximum slope standard due to the
slopes of the existing streets and their related walkways. The slope in the west
transition run will still be a slight improvement over the existing walkway slope
in that section.
The only true solution is to regrade the streets of the entire hillside
neighborhood. That is obviously not feasible.
Submitted:
Submitted concurrently with this evaluation are construction plans showing the
proposed ADA ramp and landing reconstruction.
Bruce S. MacVeigh, P.E.
Civil Engineer
joenguyenrentonadarampjustificationnwramp01/1830