1.4 BMP C105 - Stabilized Construction Entrance and Exit
Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by vehicles or equipment by constructing a stabilized pad of quarry spalls at entrances and exits to construction sites.
Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site.
Construction vehicle ingress and egress shall be limited to one route. Additional routes may be allowed for very large projects or linear projects.
For residential construction provide stabilized construction entrances/exits for each residence. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking based upon lot size and configuration. See Figure 3 - 1: Stabilized Construction Entrance.
1.4.3 Design and Installation Specifications
The stabilized construction entrance shall be:
A minimum of 15' wide; and a minimum of 100' feet long.
The length of the entrance may be reduced to the maximum practicable size when the size or configuration of the site does not allow the full lengths.
Construct stabilized construction entrance with a pad that is:
A minimum 12" thick pad of 4" to 8" quarry spalls, or
A minimum 4" course of asphalt treated base, or
A minimum 12" thick pad of permeable ballast meeting the requirements of WSDOT's Standard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(2).
For single-family residence construction, the concrete pad may be clean 1 ½" minimum aggregate placed at least 8" thick.
Manufactured alternatives to construction entrance may be used provided they ensure no track-out.
Do not use crushed concrete, cement or asphalt rubble for the stabilized construction entrance.
Place a separation geotextile under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet WSDOT Standard Specification 9-33.2(1) Table 3 - Geotextile for Separation or Soil Stabilization or the following standards:
Grab Tensile Strength (ASTM D4751) – 200 psi min.
Grab Tensile Elongation (ASTM D4632) – 30% max.
Mullen Burst Strength (ASTM D3786-80a) – 400 psi min.
AOS (ASTM D4751) – 20 to 45 (U.S. standard sieve size)
Consider early installation of the first lift of asphalt or extra concrete in areas that will be paved; this can be used as a stabilized entrance.
Install fencing (see BMP C103 - High Visibility Fence) as necessary to restrict traffic to the construction entrance.
Whenever possible, construct the entrance on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance
If possible, install the stabilized construction entrance on the uphill side of the site so that stormwater will not pond near the stabilized construction entrance.
Construction entrance should avoid crossing existing sidewalks if possible. If a construction entrance must cross a sidewalk, the sidewalk must be covered and protected from sediment leaving the site.
Add quarry spalls or additional permeable ballast if the pad is no longer in accordance with the specifications.
If the entrance is not preventing sediment from being tracked onto pavement, alternative measures to keep the streets free of sediment shall be used. This may include replacement of the stabilized construction entrance, street sweeping, an increase in the dimensions of the entrance, or the installation of a wheel wash.
No tracking of sediment onto the roadway is allowed. If sediment is tracked onto the road, immediately clean the road thoroughly by shoveling or pickup sweeping. Transport sediment to a controlled sediment disposal area.
Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches.
Keep streets clean at ALL times. Clean tracked sediment immediately.
Street washing of sediment to the stormwater system is not allowed.
If sediment is discharged to the stormwater system it is the responsibility of the applicant to clean the downstream system.
Immediately remove any materials that are loosened from the pad and end up on the roadway.
Install fencing if vehicles are entering or exiting the site at points other than the construction entrance(s).
Upon project completion and site stabilization, permanently stabilize all construction accesses intended as permanent access for maintenance.
Figure 3 - 1: Stabilized Construction Entrance