CHAPTER 5 SHOULDERS TABLE OF CONTENTS. 5.1 General Shoulder Maintenance Schedule Shoulder Categories and Maintenance...

Transcription

1 CHAPTER 5 SHOULDERS TABLE OF CONTENTS 5.1 General Shoulder Maintenance Schedule Shoulder Categories and Maintenance Earth Shoulders Stabilized Shoulders Paved Shoulders Combination Shoulders Entrances to Driveways and Side Roads Mailbox Approaches and Roadside Rest Areas Environmental Concerns i

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3 5.1 GENERAL The term "shoulder" refers to the graded area or surface adjacent and parallel to the traveled way, whose purpose is to give lateral support to the road surface and to be used by traffic in emergency situations. Shoulders should be stable enough to support normal traffic loading, and their surfaces should be adequately sloped to provide for the quick removal of surface water from the roadway into the drainage system. Shoulder drop-offs can present a hazard to the motoring public. Drop-offs greater than two inches, whether created by maintenance operations or routine edge deterioration, should be scheduled and addressed as resources permit. Signing and or delineation may be required in the event repairs can not be completed in the short term. See Publication 408 section (j) for guidance in this area. Shoulder maintenance can be performed throughout the year but the most desirable times are when sufficient moisture is present to provide maximum compaction and densities. This phase of highway maintenance is of major importance, because the failure of a pavement often starts at the joint between the roadway and shoulder. Shoulder maintenance also includes the areas just outside the normal shoulder, but not beyond the legal right-of-way limits such as approaches to the roadway at side roads on the state system, turnouts for school bus stops, and graded surfaces adjacent to rural mailboxes. At entrances to private drives and places of business, the Department will not be responsible for the maintenance of theses areas within the normal shoulder width. Maintenance in these cases shall be by the owner (Ref. 5.8). 5.2 SHOULDER MAINTENANCE SCHEDULE The Department Maintenance Manager should plan the routine maintenance of shoulders in accordance with a detailed seasonal schedule. The following is a list of items which may require completion during each season of the year. It is meant as a guide in the development of the county seasonal work plans. SPRING: 1. Field inspection of shoulders by county maintenance personnel to determine the amount and type of maintenance work required and the priority of that work. 2. Conduct inventory of concrete shoulder patching and joints that will need to be sealed in the fall. 3. Patching of bituminous paved shoulders. 4. Grading, rolling and the application of dust palliatives to earth or stabilized shoulders to attain proper grade and slope, and to remove false, or secondary, ditches or gutters. 5. Cutting high shoulders and refilling scoured areas to ensure proper drainage, and to provide for the safety of the motoring public, with priority given to routes on scheduled surface treatment programs. 6. Posting of low and/or soft shoulder areas on medium and heavily traveled roads, in the interest of traffic safety. SUMMER: 1. Continue cutting high earth shoulders. 2. Continue routine grading and rolling of sod, earth or aggregate shoulders and replacing of lost shoulder material where needed. 3. Rebuilding and stabilizing shoulders with aggregate where possible. 4. Surface treatment when needed on stabilized, paved and combination shoulders. 5. Removing all false ditches along shoulders. 6. Mowing of sod shoulders. 7. Raising low spots on paved shoulders. 8. Making permanent repairs to the surface and/or base on paved shoulders. 9. Resurfacing paved shoulders. 10. Continue applying dust palliatives. 11. Continue routine inspection of all shoulders. 12. Patch concrete shoulders. 13. Upgrade shoulders where necessary. FALL: 1. Continue cutting high earth shoulders. 2. Continue routine grading and rolling of all earth shoulders. 5-1

4 3. Replace shoulder material to assure proper cross-section of shoulder. 4. Stabilize spots that show signs of erosion and instability. 5. Completion of improvements and major repairs. 6. Sealing all cracks and the joint adjacent to rigid pavement. Care shall be taken as to not cover edge of pave/fog line with sealant. 7. Continue routine inspection of all shoulders. 8. Seal joints on concrete shoulders. WINTER: 1. Grading and adding of material to all shoulders that have become excessively rutted, when weather and soil conditions permit. 2. Patching potholes in paved shoulders. 3. Continue routine inspection of all shoulders, paying particular attention to ice conditions caused by improper shoulder grade and/or encroachments onto PennDOT right-of-way. 5.3 SHOULDER CATEGORIES AND MAINTENANCE The several types of shoulder surfaces may be broadly grouped into the following four general classifications: 1. Earth shoulders. 2. Stabilized shoulders. 3. Paved shoulders. 4. Combination shoulders. The proper maintenance procedures are different for the various types of shoulder surface. These procedures will be explained in the following sections. A brief description of each type will be given first. 5.4 EARTH SHOULDERS Most earth shoulders are capable of supporting vegetation; this covering normally will be established by natural growth without artificial seeding. Granular material may be added to the native soil to give increased stability to the surface. The amount of granular material added must not be enough to interfere with the natural drainage runoff. An earth shoulder should have a minimum slope of 3/4 inch per foot and maximum slope of 1 1/2 inches per foot of width. It is required that a belt truck (or equivalent) be used in front of the grader to place suitable material into drop off areas and compacted prior to the completion of the grading/cutting of the shoulder. Earth shoulders are not practical on heavily traveled roads. However, on local service roads and rural roads, an earth shoulder provides a relatively stable surface and will resist erosion. Where earth shoulders are used on a road, certain portions should be upgraded by the addition of aggregate. Some of these locations are at roadside turnouts, mailboxes, entrances to driveways, the insides of some curves, and intersections. When an improperly constructed drive entrance or approach causes a drainage or any other undesirable condition, the owner should be contacted and advised of his/her responsibility to correct the condition. An earth shoulder should be maintained with a minimum cross slope of 3/4 inch per foot. A flatter slope will not assure rapid runoff of surface water. Maintenance of earth shoulders consists of the following operations: 1. Mowing. 2. Repair of ruts, holes, and low spots to the graded contour. 3. Cutting or grading high areas to return to proper cross slope. 4. Providing stabilized areas at roadside rest locations, mailbox turnouts, and at all other critical locations. Earth shoulders should be mowed as required, but a minimum of twice a year late spring and mid-fall to keep vegetation sufficiently low for safety. The Foreman responsible for the mowing of earth shoulders should coordinate the operation of picking up litter along the roadside before the mowing operation. This will reduce the chance of the mower hitting an object, causing damage to employees and/or equipment and private property. Damage to an earth shoulder in the form of ruts caused by traffic or erosion should be repaired by scarifying, adding select material if needed and compacting to conform to proper shoulder cross slope. Holes and other low spots in a shoulder should be repaired in a similar manner. Ch. Updated 4/ Update #2

5 If ruts continue to occur on the inside portion of an earth shoulder, the original soil adjacent to the roadway should be removed to a average depth of 6 to 8 inches, the full width of the rut, usually 2 to 3 feet. The trench should then be backfilled with a mixture of granular material and soil. For extreme or persistent rutting, the addition of bituminous material to the affected area should be considered. Upon completion of the compaction of the added material, the new portion of the shoulder should be flush with both the adjacent roadway and the remaining portion of the shoulder. The surface of an earth shoulder has a tendency to become too high as a result of the growth of vegetation, the collection of anti-skid and foreign material and the action of frost. It is sometimes possible to remove the effects of frost heave by compacting with a three (3) wheeled roller when weather conditions permit. When rolling will not depress a high shoulder sufficiently, it is necessary to regrade or "cut" the shoulder. Shoulders should not be unnecessarily cut. If proper precautions are taken, this work can be done by graders without serious or permanent damage to the root structure of the sod present. The remaining root system will soon cause the sod to regrow. Grading should be followed up by rolling, except in extremely wet or muddy areas. Graded aggregate or similar stabilizing material may be added at certain times of the year where necessary to prevent rutting of turnouts for roadside rest areas, scenic overlooks, and mailboxes, taking care not to raise the shoulder or flatten the shoulder slope. During the winter and extended periods of bad weather, these locations may require special attention. 5.5 STABILIZED SHOULDERS A stabilized shoulder usually consists of coarse, graded aggregate spread on or incorporated into the existing natural soil. If the aggregate is spread in a separate layer, it is usually laid on a prepared subgrade. Typical aggregates that are suitable for stabilizing are limestone, slag, gravel, or reclaimed asphalt (RAP). When RAP material is used the requirements of the General Permit WMGR090R018 apply. (Material will be obtained from a permitted stockpile and documentation kept of the quantity shipped). Chemical and bituminous materials may be used to stabilize granular materials. When RAP materials are used, compaction and sealing are required by the general permit. Reclaimed Asphalt Pavement (RAP) is the product of hot or warm mixed asphalt pavement that may include surface treatments which are milled. Clean RAP is such material that is free of subbase, dirt, soil, or other contaminates. Milling travel lanes for overlays should always yield clean RAP. Contaminated RAP is milled asphalt pavement mixed with materials such as subbase or soil. Milled shoulder material, widening or base repairs may include contaminated RAP if the milling extends beyond the depth or width of the asphalt pavement. Do not co-mingle clean RAP and contaminated milled bituminous material. Clean or uncontaminated RAP is to be used exclusively for paving roadways or shoulders. This work includes widening, shoulder upgrades, cold recycling and full depth reclamation. The use of clean RAP for shoulder back up and fill activities is specifically prohibited. Only contaminated RAP is to be used for shoulder back up, and/or stabilization where the Department gains benefit from the asphalt properties in the material. In some cases, stabilization may be obtained simply by the progressive addition of granular material. In other cases it may be necessary to add some graded aggregate and binder and use mechanical mixing equipment. The degree of stability of the shoulder depends on the soil/aggregate mixture used. The addition of a well-graded granular surfacing material to a natural earth shoulder will provide stability and produce a good all-weather shoulder. After the first application of aggregate, it may be necessary to make spot replacements of this material from time to time. Stabilized shoulders should be constructed and maintained with minimum slope of 3/4 inch per foot of width and a maximum slope of 1 1/2 inches per foot of width. Care should be taken to see that this slope is maintained because shoulders with too little slope will tend to retain water. This water/moisture will soak through the shoulder material and tend to create soft spots. If it is noted during an inspection after a rain that a section of shoulder is holding water, that section should be marked and corrective action taken as soon as is practical. During a heavy rainfall, surface water 5-3 Update #2 Ch. Updated 4/15

6 will run across an unpaved shoulder with a slope that exceeds 1 1/2 inches per foot with enough speed to cause erosion. Occasional grading and rolling of a stabilized shoulder is required to keep the inside edge of the shoulder at the same level as the outside edge of the pavement and also to move and redistribute loose material to fill ruts. Stabilized shoulders are kept smooth and at the approximate correct crosssection by routine grading and periodic replacement of worn or lost material, the shoulders should be reshaped periodically in order to remove the buildup of anti-skid and foreign material. Maintenance of stabilized shoulders includes the following: 1. Cutting 2. Grading 3. Replacement of material 4. Reshaping 5. Rolling 6. Control of erosion 7. Application of dust palliative The most important purpose of routine grading is to prevent the formation of ruts at the edge of the roadway pavement. When such ruts are allowed to form and remain, the edge of the pavement is easily damaged because of the loss of lateral support. Also, during periods of wet weather, ruts/holes will hold water, causing the subgrade and base under the roadway to become saturated, thus producing surface failures. Also important is the prevention of low shoulders which reduce the amount of lateral support provided at the edge of the pavement and could also be a safety factor. Frequent grading of stabilized shoulders will be required where the shoulder material has poor binding quality, where traffic is relatively heavy, and where a narrow roadway carries a large volume of truck traffic. For routine procedure of the grading and cutting operations, see the foreman's manual. Another reason for building up a shoulder is the necessity of raising the shoulder when the roadway is resurfaced. To improve an existing stabilized shoulder for this reason, the old surface should be scarified with material added to it, and finally the graded surface should be properly compacted. If granular material is added to shoulders during a period of dry weather the moisture content must still be at the proper level to achieve optimum compaction. Water or chlorides should be added to the shoulder material before the final grading and compacting. This treatment of chlorides is also good for providing added stabilization where the shoulder material tends to lose fines quickly. Chlorides can be mixed into the aggregate before placing. If ruts continually recur in an area on the inside of a curve, it may be cost effective to pave the affected area. This is one of the most effective ways of reducing maintenance of the shoulder and the edge of pavement. Such pavement should be a minimum of five inches deep and one to two feet wide consisting of a base course and wearing surface. The tendency of surface water to erode shoulder material is most severe on steep grades where water flows along the shoulder rapidly and at the low point on a long sag vertical curve where a large amount of water must flow across the shoulder. In order that there will not be excessive erosion of a stabilized shoulder on a steep grade, a uniform cross slope of the proper amount must be maintained for the entire width of the shoulder. The surface water will then be able to run off the shoulder at a suitable velocity along the entire length of the shoulder. If a false ditch or gutter is allowed to form along the outer edge of a shoulder or if a rut is allowed to develop between the pavement and the shoulder, a large amount of water will be concentrated on a small portion of the width of the shoulder until it exerts enough force to break through a weak spot. Such action has been known to wash away a long portion of a shoulder during a single storm. This is especially true where a secondary ditch along guiderail sections prevents the even flow of water over the embankment. A special effort must be made to provide a uniform shoulder grade along all guiderail sections performing side-dozing operations to remove the ridge of anti-skid and foreign materials. Stabilized shoulders that continue to erode after other normal maintenance methods have been tried should be paved as a last resort. 5-4

7 5.6 PAVED SHOULDERS As the term implies, a paved shoulder is one having a special wearing course. This course may be composed of portland cement concrete, bituminous concrete, penetration macadam, or bituminous surface treatment. The slope of a shoulder of portland cement should be 1/2 inch per foot of width. For bituminous concrete, penetration macadam, or a bituminous surface treatment, the minimum slope should be 3/4 inch per foot of width and the maximum slope should be 1 1/2 inches per foot of width. Maintenance of a paved shoulder is similar in many ways to that of a roadway of the same surface type, although the degree of importance is different. Paved shoulders have been provided on many secondary roads where the volume of traffic is heavy and through urban areas where shoulders are needed to permit vehicles to park and to enter or leave driveways. Also, along such high-speed highways as those of the interstate system, shoulders are paved for improved safety and ease of day to day routine maintenance. The methods of maintaining paved shoulders correspond to those set forth in this manual for surfaces of similar types. The maintenance of paved shoulders includes the following operations: 1. Patching with plant mix bituminous material (hot) 2. Surface treatment 3. Repair of base failures 4. Skin patching 5. Sealing cracks and/or joints When paved shoulders are patched with bituminous material, care should be taken to see that the surface of the patch is even with the surrounding surface. The material used for patching a paved shoulder should be the same as the material of the existing shoulder. The correct procedure to be used in patching a paved surface of a certain type is described in detail by performance standards and also standard concrete patching procedures. When the bituminous surface on a paved shoulder becomes lean or dry, or oxidizes, the surface should be sealed or surface-treated with liquid bituminous material. The bituminous material will be covered with crushed stone, slag or crushed gravel. This treatment can also be employed to raise a paved shoulder that has had minor settlement. Where the settlement of the shoulder is so great that all the material required to raise it cannot be applied by the method just described in a single surface treatment, a bituminous concrete mixture should be applied using appropriate methods and procedures. The performance standards provide additional information in regard to the preparation, class of bituminous materials and aggregates used in surface treatment, and the proper procedure for applying the materials. When shoulders are repaired by surface treatment the finished surface must be flush with the edge of pavement and should slightly overlap the pavement edge. When the failure of a paved shoulder is due to the failure of the base, the repair procedure outlined in the appropriate performance standard should be followed. In general, repairs of this type include the following operations: 1. Scarifying 2. Removing and replacing unstable material 3. Reshaping the base material 4. Compacting material to obtain correct grade and slope When the failures are caused by water trapped in the subgrade, the use of french drains or underdrains is required. The use of subsurface drainage is covered in detail in the drainage structures section of this manual. Skin patching should be used under the following conditions: in areas where there is insufficient bituminous material or dryness (oxidation), on bituminous surfaces where raveling or spalling is evident, or on limited areas where there is map or alligator cracking. The importance of skin patching cannot be emphasized enough because of its ability to revitalize a shoulder surface and prolong its life at an economical cost. Cracks and/or joints in portland cement concrete and bituminous concrete will be sealed as 5-5

8 prescribed for each in the respective performance standard. The weakest point in a paved shoulder and the place where most failures start, is the joint between the roadway pavement and the paved shoulder. "Pumping" often develops when joints are not kept sealed and water is allowed to enter. Special attention should be given to the maintenance and sealing of this joint. During winter months, the freeze-thaw cycle has a tendency to break the joint. 5.7 COMBINATION SHOULDERS In a combination shoulder the surface for a width of 3 to 4 feet adjacent to the pavement is of a higher type than that of the remainder of the shoulder width. Such a shoulder is usually provided on the median side of a dual highway where the amount of traffic does not justify full width stabilization or paving. Without the better surfacing next to the pavement there would be continued rutting and drop-off of the shoulder along the edges of the pavement. A combination shoulder may be constructed by placing a stabilized or paved strip along the inside pavement edge of an earth shoulder, or by placing a paved strip along the pavement edge of a stabilized shoulder. The maintenance of combination shoulders is identical to that for shoulder constructed of similar materials. The nature of maintenance on a portion of shoulder used for an entrance to a driveway or that alongside a mailbox does not differ greatly for normal shoulder maintenance. However, the extent of the repair and maintenance operations may be quite different. 5.8 ENTRANCES TO DRIVEWAYS AND SIDE ROADS Whenever a public road intersects a paved highway, the approach to the side road should be stabilized or paved by the Department to the limits of the right-of-way of the through highway. Whether stabilization or paving is required will depend on the amount of traffic using the side road. At each approach, the normal shoulder width should be maintained by maintenance forces in the performance of regular routine shoulder main - tenance operations. At entrances to private drives and places of business, the Department "will not be responsible for the maintenance of these areas" within the normal shoulder width. Maintenance in these cases shall be by the owner. The presence of even one improperly constructed entrance along a highway makes it difficult to provide maintenance of the shoulder. Moreover, poor or improper drainage at the entrance often is a direct cause of failure of the road surface, and an improperly constructed entrance sometimes creates a hazard to the traveling public by directing surface water/ice onto the highway pavement. When an improperly constructed drive entrance or approach causes drainage or any other undesirable condition, the owner and District Permit Office should be contacted and advised of his/her responsibility to correct the condition. 5.9 MAILBOX APPROACHES AND ROADSIDE REST AREAS It is necessary at these locations to stabilize shoulders with suitable material and to provide regular maintenance. Proper shoulder slope must be maintained for the full width of the shoulder to insure adequate drainage. The slope should be as previously indicated for a particular shoulder type discussed in this manual ENVIRONMENTAL CONCERNS Environmental concerns such as wetlands, erosion control, and waterway pollution are to be addressed in the disposal of all excavated and waste materials and in all other actions related to this activity. All environmental policies, either by PennDOT, D.E.P. or others in effect at the time are to be adhered to by maintenance forces. PennDOT Publication 464 should be reviewed for BMP s (Best Management Practices), both installation and maintenance of erosion control devices related to shoulder cutting as well as other earth disturbance activities. Under SEM Program objective 433/434 Establish/Maintain SEM Program objectives and targets waste reduction and resource conservation matters apply, along with water quality control matters. 5-6