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MEMOS TO D ESIGNERS 21-19 J ULY 1996

21-19 GUIDELINES FOR CLEARANCE TOCoNSTRUCTION OPERATIONsThe letter transmitting the General Plan to the Disttict shall include information concerning theworking space which will be required for use by the Contractor during construction. I f theavailable clearances to theworkappear inadequate toconduct the operation in a safe manner, laneclosure or other measures to provide the necessary space should be recommended.When recommendations are made for the diversion or halting of traffic, the letter shouldinclude specific information concerning the lane or lanes involved and the sequence ofoperations along with an estimate of the time each ctiversion or closure will be required.The District should be asked to comment on this information. This response will be helpfulin determining i f we have selected the proper structure type for the site.After approval of the General Plan by the DiStrict, the District project engineer should be keptinformed of any changes in the bridge design that would affect traffic handling. The Strucruresproject designer should review the traffic handling plan and verify it prior to PS&E.The followingare guidelines thatshouldbeusedindevelopingtheabove-mentioned information.

GeneralThe construction of structures across or adjacent to roadways which are open to trafficrequires that adequate spacebe provided between the work and traffic so that the construction operations can be performed without hazard to the traveling public and to the workers.Special traffic handling, such as intermittent or long-term lane closures, detours, staging towork, etc., may be required to provide the necessary space.During the General Plan development stage, the designer shall review the available informationto determine i f adequate space is available or i f special traffic handling may be necessary.In the transminalletter forwarding the General Plan, the designer should inform the Districti f there is a need for special traffic handling. For example, for a bridge with a bent to be builtin a&meterwidemedian, the designer should include a statement such as:

Memo convened to metric. 21- 19 GUIDELINES FOR CLEARANCE TO CONSTRUCTION OPERATIONS

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MEMOS TO DESIGNERS 21-19 JULY 1996

"Based on the assumption of (choose applicable type) spread footings/pile sup-ported footings/drilled shafts. the construction of the footings and columns in themedian will require a working space of approximately __ ....___ . _meterS between therraffic faces of the temporary railing for a period of _ weeks. Construction offalsework bents will require approximately m e ~ ' ! between the traffic faces_ofthe temporary railing for a period of approximately __ weeks. (The existingmedian is not wide enough to conduct the operations safely.) Laneclosuresor othermeans to provide the necessary clearance will be required unless special and moreexpensive construction methods are employed."

The intentof this notification is to provide the District with relevant data associated with thestructure type selected. and to initiate action so that adequateprovisions aremade in the earlystages of design and to avoid last minute changes.The following are some typica l situations.The dimensions specified are those which wouldbe required if conventional construction methods are used They may be reduced by the useof special and more expensive construction methods. Before making any reduction, allfactors must be carefully weighed. Various alternatives such as detouring traffic. narrowingtraffic lanes, etc., should be considered . Deviations should be discussed with Construction.

1. Construction ofFootings and Columnsin Existing Median

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0.75 mmt77 1----!\ ~ nJl.Oii\Iu u u

Shoulder X=Required Work Space Shoulder .Footing andColumn Construction

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MEMOS TO DESIGNERS 21-1 9 J ULY 1996

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MEMOS TO D ES IGNERS 21-19 JULY 1996

4. Fabricating and Erecting Precast Concrete Girdersor Structural Steel GirdersPrecast or structural steel girders over'33 m long or weighing overfl3 tOpne usually cannotbe transported on the highway in one piece. These girders are segmentally hauled to the joband joined at the site. However girders up to ,36 m length have been permitted with specialexpensive equipmenL and the length limitation does not apply where the gi rders (such as atan overhead)may be transported by rail. Structures Maintenance should be consulted whengirder lengths exceed;3$..Ourstandard special provisions prevent the casting, assemblingorstoring ofgirdersin the medianor within6m-of the edgeof the pavemenL Thedesignershall check with theDistrict to detennineif adequate space is available at the bridge site to assemble these girders.When erecting girders over traveled ways, traffic must always be stopped or detoured Theerection ofa memberweighing up to4$.tonnewill usually require thestopping of traffic no morethan 30 minuteS. However, heavier members , or lifting over' mhigh will usually take longer.

5. Erection and Removal of Falsework and FormsTraffic mu st be rerouted orstopped for 30 minute minimum intervals during theerection andremoval of falsework stringers over traffic openings. Strippingof deck soffit forms usuallyrequires lane closures under the immediate area of stripping. However when stripping overthe middle lanes, it is desirable to close one of the adjacent lanes so traffic is not routed onboth sides of the closed lane.

6, Sidehill Viaduct, Half-Width Construction,Special Retaining Walls, etc.These special designs are usually used when construction space is limited. The designershould point out operations that will require short or long-term closureof all or pan of theroadway to traffic.

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MEMOS TO DESIGNERS 21- 19 JULY 1996

7. WideningWhen forwarding the GeneralPlan to the District, the location of the temporary traffic barriershould be shown on the Plans and the District should be asked to comment on it. Locationof the barrier is a trade-off between giving the workers enough space versus giving trafficas much space as possible. The minimum distance between the cut line, where the existingdeck is to be removed, and the edge of the barrier : Q ' i f i l . ~ This distance may be increasedif traffic conditions permit.

, Distance to ~ Freeway or other control line~ -Intermittent LaneClosure Required min dearance

8. Bridge RemovalRefer to Memo to Designers 9-5 for a discussion ofthe various methods of bridge removal.The District should be advised as to which method we believe is appropriate and asked toconfirm this decision.

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.. MEMOS TO DESIGNERS 21-19 JULY 1996I ~ ' f ~ e t r i c9. ConclusionThere are many other si tuations where special traffic control is ~ s s a r y . The Construction

Office is always available for consultation. Although traffic control is the responsibility ofthe District, our timely input to the Districts is necessary so that a well developed trafficcontrol plan is included in the contract.The attached sketches show the space normally needed for some typical operations inthe median.

i-t" 1 r t f t v l ~. . / S h ~ n H. Post

JRM:jgf/jlwAttachments

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