INTRODUCTION
& GENERAL INFORMATION
The applicable
sheets of the 2000 edition Typical Sections and Related Details are
to be used in the preparation of contract plans. Changes and/or exceptions
to these details are to be approved by Engineering Division or District
Director of Engineering.
A
numbering sequence has been assigned to the various items in the legends
to retain consistency throughout and to avoid duplication. Blank spaces
have been provided for certain items such as widths, thicknesses, rates of
application, aggregate items and classes, etc.
DITCHES
It
is the Design Policy of the Division to divert water from the pavement.
The desirable ditch in slope should be 4:1 or flatter with the ditch
bottom 6 lower than the subgrade.
When
the proper ditch requirements cannot be met the alternative to using a
ditch section is a non-ditch section with proper drainage of the subbase.
These typicals may be modified to accommodate a non-ditch section. If a
non-ditch section is provided the contract documents are to be accompanied
by an explanation of the factors involved, such as traffic volume,
right-of-way requirements, and cost differences.
EMBANKMENTS
Fill
slopes are to be 2:1 or flatter for adequate soil stability. Where the
height of the fill is 10 or less, it is desirable to flatten the slopes
to 4:1 or flatter if possible. When a 1 1/2:1 fill slope is required the
embankment must be constructed of rock (select embankment or rock borrow
excavation). Sliver fills require benching to provide stability and to
allow compacting by equipment. Fill benching (Sheets 36-39) should be
considered from the first feasibility study to the final plans as it can
be a substantial cost item.
SHOULDER WIDTHS
Shoulder
widths on certain typical sections, where indicated, are to be designated
as maximum and minimum. In some cases, the two dimensions are equal
because of non-varying widths. The designer shall measure the shoulder
widths and specify the maximum and minimum to ensure proper quantity
calculations and to assure that the full width is stabilized by the
addition of stone. The existing and available shoulder widths are to be
preserved. On projects where
shoulder widths are predominantly less than two feet, the shoulders should
be paved and edge striping is to be placed at the previous pavement edge.
SHOULDERS AND DITCHES
In extreme erosion areas, ditches may
require rock borrow excavation as shown in Sheet #30 Correcting Deep
Ditches. Correcting of ditch depth is in the interest of safety, but
flowline of ditches should be maintained to provide a minimum 6 of
freeboard for effective road drainage.
SHOULDER
RECONSTRUCTION
Appropriate
shoulder reconstruction details shall be included with the resurfacing
typical section in the contract plans. Shoulders can become too steep by
successive resurfacing, erosion, or ditch cleaning operations and should
be restored to an appropriate slope. Repairs may require rock borrow
excavation or gabions to prevent stream or right-of-way encroachment.
Shoulders are to be restored with stone or pavement to a height equal to
the finished roadway.
DRIVEWAY AND SIDE ROAD
TREATMENT
The
intent of this detail is to assure, during resurfacing operations, proper
treatment of driveways and side roads to maintain safe vehicle operation
on the main road. On paved driveways and side roads, a minimum amount of
HMA is usually necessary to avoid an elevation difference (drop-off) at
the pavement edge. The intent
is not to pave every unpaved approach.
It
is the designer's responsibility to recognize existing and potential
problem approaches they are to be listed in the table provided and
included in the contract documents. If more space is required, additional
tables shall be provided. All
problem approaches shall be documented with proper justification in the
project file.
Underdrain
or fabric drain is to be installed where approaches have caused pavement
distress by trapping water.
BASE FAILURE REPAIR
Identify
in the contract documents, all areas of base failure that are to be
repaired.
HMA SKID RESISTANT
PAVEMENT
All
Hot-Mix Asphalt wearing course must be a skid-resistant mix in accordance
with DD-644. If a project has severe curvature, high wet accident data, or
high frictional demand, skid-resistant pavement may be required and should
be documented in the project file.
WINTER GRADE PATCHING
REMOVAL
The
designer should determine the extent and condition of any winter grade
patching material that is to be resurfaced in a particular project. Any
such material, which would be detrimental to the new surface, is to be
removed and replaced with Hot-Mix Asphalt. If any removal is necessary the
plans shall indicate an approximate quantity and method for pavement
repair.
ADJUSTING MANHOLES,
INLET GRATES, AND VALVE BOXES
Many
objects, such as manholes, gas and water valves, etc; must be adjusted for
a smooth riding surface. When utility companies own such items the
Designer will coordinate with the District Utilities Supervisor to
determine all intended work and the required amount of adjustments. If
certain utilities are not capable of the adjustments prior to the start of
the work it shall be included in the contract. If it is determined by the
District Utilities Supervisor that the work is to be reimbursed by the
affected utility company the Designer shall prepare a separate engineers
estimate for each utility company and include them with the normal
engineer's estimate when the P.S. & E. package is submitted to the
Program Administration Division.
MATERIALS
Testing
of materials may be waived on minimum usage items. The designer should
make this determination on a project by project basis and so note on the
appropriate plan sheets or in a general note.
GUARDRAIL
The
class of guardrail to be installed on a particular project shall be as
specified by the current Design Directive, DD-662. When the top of the
guardrail is less than 24 or greater than 30 above the finished
grade, the guardrail shall be removed and reset to the correct height, as
per standard details, in conjunction with adjacent work.
GUARDRAIL INSTALLATION
ON HEADWALLS, PARAPETS, BOXES CULVERTS, AND BRIDGES
Many
bridge parapets have intermediate vertical faces that can catch vehicles
and cause damage. It is the policy of the Division to remove or isolate
these hazards. The intent is to avoid guardrail installations where a lack
of connection to the structure allows vehicles to deflect the rail and hit
the concrete. The purpose of these details is to provide safe methods of
guardrail installation where existing headwalls and/or parapets present a
hazard to vehicles. However, there are certain physical limitations that
may require such structures to remain. Before guardrail is added to a
structure a comparison should be made to determine the feasibility of
removing the obstruction and extending the culvert rather than installing
guardrail. In many cases it is safer to install guardrail along the length
of the parapet to minimize vehicle contact.
These
details, which are to be inserted into the contract document, include a
table that should be used to specify locations, lengths, class of
guardrail and quantities of various appropriate end treatments, unless
such information is shown in full-size plans for the projects.
The
details should be applicable in the majority of situations where existing
headwalls and bridge parapets are to remain. Certain bridges will require
special consideration and design. Modifications of these details may be
made for a project only after approval by the Engineering Division.
GUARDRAIL PLACEMENT AT
INTERSECTIONS
Details
for guardrail placement at intersections are to be included in the plans
to ensure well define end points for guardrail and guardrail end
terminals. The designer is to add information such as the A, B, and C
dimensions, the end treatment (TET, FET, CST, or buffer end), and the
approximate milepost (or station) of the intersection in the spaces
provided. Some intersections will require more than one detail sheet where
guardrail is to be installed in more than one quadrant.
The
following is a list of considerations in specifying guardrail:
1.
TETs, FETs, and CST's are the end treatments are the most
commonly used.
2.
Errant vehicles normally leave the roadway at an angle of 8 or
less.
3.
The departure must also be considered for the traffic movement in
the opposite direction on the other side of the highway, but the near side
would normally be more critical.
4.
It is desirable to extend the guardrail around the intersecting
roadway radius to move the end away from the mainline traffic.
5.
The ending point of the guardrail must be established considering
the departure, the significance of roadside hazard adjacent to the roadway
and the available right‑of‑way.
6.
If the guardrail end is within the angle of departure, a FET, TET,
or CST is required.
7.
If the guardrail can be extended around the radius to outside the
departure angle, the need for an end treatment for the intersecting must
be considered. If the guardrail can be extended around the radius enough
to develop strength for the guardrail adjacent to the mainline, a buffer
end is adequate.
8.
Additional data may be found in Design Directive 662.
MODIFIED
CUT SLOPE TERMINAL
This
detail should only be used on 3-R type projects where a cut slope terminal
is desired but the cost of drainage through the cut slope area is
uneconomical. If the existing ditch is more than 18 below the required
grade for a CST the ditchline will need adjusted.
MODIFIED
CONCRETE END POST
This
detail is to be used on NHS 3R-type projects to upgrade existing bridge
end posts to a shape which will accept the Thrie Beam Guardrail Bridge
Transition and Connection as per Standard Detail GR9.
The
designer should determine if non-NHS end posts should be upgraded based
upon the specific location with emphasis on the likelihood of impact,
traffic data, etc.
TRAFFIC CONTROL PLAN
The
traffic control plan (applicable sheet 25 or 26) can be used on most
resurfacing, widening, and stabilization projects. If the project contains
work beyond the scope of the resurfacing traffic control plan the designer
shall develop a more appropriate, detailed traffic control plan.
Additional
signs or devices needed are to be listed on the table in the traffic
control plan and the unit values for the additional signs are to be
obtained from Section 636 of the Specifications.
The
manual Traffic Control for Street and Highway Construction and
Maintenance Operations is to be used for additional methods of
traffic control and promotion of safety through the work area.
INSTALLATION OF
HAZARD PANELS
Hazard
panels are to be installed within the clear zone of the project when it is
not feasible to remove or isolate the hazards with guardrail. Hazard
panels are to be installed at headwalls, box culverts and bridge parapets
protected by guardrail whenever the bridge shoulder widths are 8 feet or
less.
The
designer is to designate locations of the panels and delineators in the
table on the appropriate detail sheets.
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