92. Evolution of Seawall Construction Methods in Boston Harbor MA

8/2/2019 92. Evolution of Seawall Construction Methods in Boston Harbor MA

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Proc. lnstn Civ.

Engrs Structs &

Bldgs, 1995, 110,Aug., 239-249

Evolution of seawall constructionmethods in Boston Harbor,

Structural and

Building BoardStructural PanelPaper10539

. S. Rosen and D. B. Vine

Written discussion

closes 7 October 995Seawall onstructionmethodsn Boston,Massachusetts, USA, evolved as materialssuch as cut stone, concrete and steelbecame available, as the understanding of

geotechnical principles grew, and as thegrowth of trade required more substantialcoastal structures. As a significant

number of 19th century stone seawalls arestill in use in the Boston region, tech-

niques for evaluating and repairing sur-viving historic structures, as opposed to

replacing them, are important during theongoing revitalization of the harbour.

~~

P. S. Rosen,

Department of

Geology,Northeastern

University, Boston,

Massachusetts,

USA

out of fines; the shifting of stonesor the oss ofchink stones.Woodcomponents ecay,whilestonesmay crack or spall as a result of fires or .

intensewave action.Historic walls are oftenunderdesigned y modernstandards n terms oflateral forcesand stonesize.A commonproblem s foundation ailure, caused y the.underminingof the footing or exposure fwooden oundations,which leads o marine

borer activity or rot. In addition, many other-wise soundseawallscan be affectedby chang-ing uses,which alter load or draft

requirements.5. As plans often do not exist for older sea-

walls, historical research, valuationof the his-torical significance,and detailec!.nspectionsand surveysare necessaryo both plan the res-toration and define he constraintson theproject alternatives.

6. Frequentlyusedmethods or main-tenance f walls includepointing of the stonejoints. Fabric barriers can be placedon thelandwardside of a wall by excavatonof the fillto prevent he washoutof the fines and sink-holes.Also, the fill behind he wall can bereplacedwith standardor ligqtweight concreteto add m!lss, o relieve oad and to increasebondingwith the stone.Thesemethodsdo notaffect the outward appearance f the wall. If thelandwardside of the wall cannotbe altered,stonecan be placedon the seaward ide oincrease assivepressures nd o reduce he

exposed eight.7. The seawallsof New Englandhave

evolvedconsiderably ince he colonial period,350yearsago (Fig. 1). Contributing actors

include he development f maritime trade anddeeper raft ships, and the advancement f con-struction methods, quipmentand materials.The development f seawalls s intertwined his-torically with the development f wharves,orstructures ying alongsidenavigablewaters urthe purposeof unloadingvessels.

8. Documentation f early seawallconstruc-tion by plans or recordsof proceduress rare inthe USA. Bray and Tatham ndicate eferencesto early British designers f seawallprojects nmany parts of the country and overseas.!Similar parallels with Americancolonial engi-neershavenot beendocumented. ray2 ndi-cated n his discussionon the restorationofcolonial wharves n Salem,Massachusetts,Itbecame vident hat wharfs as such werecon-

IntroductionThe earliestseawalls n the Boston egion wereof crib construction.Cobbcribs had an openframeworkand could eadily be loated ntoposition and sunk with rock from local sources.As fill material became carcerowing toongoingwharfing and andfilling activities,solid cribs were usedwhich were illed with alarge variety of materials, ncluding soil andrefuse.Thesewooden tructuresunderwentcontinual epair as a result of the rapid decayof woodcaused y marineborers.

2. Stone eawallsdate rom as early as 1784in the region,althoughconstructionwas diffi-cult. Methods o efficiently cut, or hew, helocal graniteswere not widely useduntil about1830.Some arly stoneseawallsusedwoodplatforms as foundations,which sunk n themud as weight was added.

3. With cut stone,a vertical wall with fewerwoodsupportswas possible. n the 1800s, heimportance f the characteristics f the fill

materialbehind he wall in reducing ateralforcesand promotingdrainagewas recognized.After the mid 1800s, toneseawallswere ypi-cally supportedby woodpile foundations.While concretewas developedn the mid 1800s,the harsh environmental onditions n Bostonmay have esulted n the common racticeofconstructinga seawallof concrete, nd of con-tinuing to face he structure n stone. n the20thcentury,concretewas usedpredominantlyfor shallow seawalls,while steel sheetpilingwasused or deeper tructures.

4. Many stoneseawallsdating from beforethe 20th century are still in use n the BostonHarbor egion. Rehabilitation s often necessaryowing to a variety of factors: sinkholes and-ward of the walls; voids caused y the washing

D. B. Vine,

Nucci VineAssociates,Newburyport,Massachusetts,USA

239



ROSENAND VINE

Fig. 1. BostonHarbor and other

locations

sidered too commonplace to merit descriptionby historians of the time, while the builderswere for the most part not given to writing '. A

similar conclusion was reached by

Table 1. Maximum observed water levels in Boston Harbor,

Massachusetts 11

Date Name

7 Feb. 1978

16 Apr. 1851

26 Dec. 1909

1 Feb. 1987

12 Dec. 1992

30 Oct. 1991

25 Jan. 1979

29 Dec. 1959

27 Dec. 1839

15 Dec. 1839

19 Feb. 1972

24 Feb. 1723

26 Mar. 1830

26 May 1967

21 Apr. 1940

29 Dec. 1853

4 Dec. 1786

20 Jan. 1961

30 Nov. 1944

4 Mar. 1931

3 Dec. 1854

3 Nov. 1861

Blizzard of 78

Minots light storm

Christmas gale

Christmas nor'easter

Halloween nor'easter

Triple hurricanes

Triple hurricanes

Heintzelman-Muego,3 . The small amount of

data available is scattered throughout theUnited States in the form of field notes, sitefiles, project reports and some photographs, all

of which are located in usually little known

labs, offices of contracting ag~ncies, he private

files of local historians or a few historicalsocieties, museums and libraries '.

9. Another factor in the development of sea-walls is the evolution of the accompanying

engineering sciences. Modern soil mechanics isgenerally considered to date back to the 1920s

with the works of Karl Terzaghi. However,much earlier work by Rankine4 and Coulombs

developed the initial basis for the theories on

lateral earth pressure. This work was supple-mented by the work of Poncelet,6 Rebhann,7

and Meem.8By the late 1800s, several pub-lications on harbour and dock construction

included empirical methods to size and designseawalls. Colson9 discussed the theory that theearth pressure can be determined by the weight

of the angle mass above the angle of one-halfthe angle of repose. Experiments demonstrated

that this theory yielded a factor of safety ofabout two.

10. Seawalls were built as a response o eco-

nomic expansion of the region. However, sea-

walls were often reconstructed as a result ofperiodic damage by storms. A study of thehistory of seawalls in the Boston region has

revealed that rebuilding often falls i~to pat-terns that coincide with major storms that

affected the region. While hurricanes (tropicalcyclones) and nor'easters (extra tropicalcyclones) are the dominant storms on the eastcoast of the USA, nor'easters have historically

had the greatest impacts on coastal floodingand impacts on coastal structures in the Massa-

chusetts Bay/Boston region. The south-facingcoasts of New England have been mostimpactedby hurricanes.0 Table III shows the

maximumhistoric water evels n Boston,which wereprobably ollowed by periodsofmaj~r seawall epair. The decade f the 1990ssproving to be oneof severe torms.The Hal-

loweennor'easterof 1991, he Decembernor'easter f 1992, nd the Decembernor'easters f 1993haveall caused ignificantdamageo Bostonareaseawalls.

Colonial seawalls11. Colonial seawall construction was

centred around the needs of the maritimeindustry. Until about the mid 1700s, maximumship draft requirements generally were in theorder of 10-15 ft (3.3-4.5 m) thus allowing

berthing facilities to be of relatively simple,forgiving construction. As the tide range in the

Boston region is about 10 ft (3 m), early sea-

walls were, in most cases, ocated just abovemean low water. Vessels would enter berths athigh tide and rest on the bottom at low tide.

December gale

* Mean tide height in Boston is 4,58 ft (1'37 m) above mean low water.

NGVD references National Geodetic Vertical Datum of 1929, which is the current

standard for vertical datum; it approximates mean sea evel.

t Approximate value based on historical account.



SEAWALL

CONSTRUCTION INBOSTON HARBOR

Fig. 2. Example of acolonial cobb wharf

crib constructed of

notched, trunnelledlogs (based on

Douglass Wharf, New

London, Connecticut3)

12. Construction f waterfront facilitiesweregen~rallyundertakenby merchant radersor by cooperative own efforts. The Revolution-ary War was a great stimulus to commerce ndtrade,as the colonistswere orced o expandand werenow allowed o establishnew trade

routesand markets.Later development entredaround he railroad industry which had theability to subsidizemuch arger facilities, andto provide a mode or transporting seawallmaterials o the site.

13. An early exampleof the efforts made ocreateand expandwaterfront facilities is LongWharf n New Haven,Connecticut.n 1644, ixyearsafter the town was ounded,every malebetweenhe agesof 16and 60 was asked oprovide our days work on the constructionof awharf. It was completedn 1663,and wasenlarged n stagesover the next century. By

1774, lottery was established o raise unds topay or furtherenlargementf thewharf.2

14. Early colonial seawallsusedbothtimber and stone.The abundance f timber,however,made t the first choice or colonialwalls. Early walls madeuseof joinery that wasindicative of Europeanmethods. ron nails werenot economicalo useuntil about 1840.Tree-nails, or trunnels,often madeof hickory, wereused n joinery for early seawalls.Stonewasreadily available n New Englandas roundedglacial cobblesand boulderscommonly oundalong he shoreline.

15. The most successful olid wharfstruc-

ture of early colonial imes was the crib wharf.This type of structure ypically utilized atimber crib formedby laying timber membersin alternating rows of' headers'and. stretchers. The useof the crib for construc-

tion of seawalls s very ancient.An exampleofa crib in London hat dates rom the secondcenturyhas a similar style of constructionasan 18th century crib excavated t the Charles-town Navy Yard, Boston.3 This structure was

of solid crib construction,built with squared,hewn imbers of white pine. Trunnels were hemainmethodof fastening he imbers. Cobbor

crib seawallswereused hroughout he 19tncenturyand nto the 20th century. As older cribstructureswereoften buried during landfillingand wharf expansion, xamples f thesestruc-tures may still be preserved.

16. The bottom of the crib had a floor whichservedas a platform for the fill. This type ofconstructionwas deal or the idal conditionsof NewEnglandwherecolonial builders couldfloat the cribs to the proper ocation and sinkthemwith cobblesor ballast. Sometimes,heflooring formedonly a partial platform, so thatthe ballast serves o anchor he crib fromlater:almovement. lso, the crib floor was

occasionally uilt up several ogs up from hebottom,which allowed he crib to sink into thebottomwhen ballasted. 3

17. The earliest crib wharf was the' cobbwharf'. By meansof simple construction ech-niques,horizontal ogs werenotched ogetherand oined with trunnels o form cribs. A gapexistedbetween )ternating ows of timber(Fig. 2), such hat finer fill material wouldquickly be washedout. A wharf of cobbcon-struction was built at the cornerof North andBlackstoneStreetson BostonNeckaround1676. t was built of alternating rows of roughtimber and illed with logs and cobblesorballast.3

18. Another exampleof this type of struc-

ture is the solid cr4bwharf. This systemusedaseriesof interconnected ells which weremoreclosely itted together,preventing iner fillmaterial, such as mud or sandysilt, fromwashingout of the timber framework.

19. The transition from cobb o solid cribframeworks n the Boston egion s probablyrelated o the availability of fill material.Theopencobbstructure requiredcoarsermaterialthan would notwashuut, suchas cobblestones,from which its name s probably derived.Suchcoarsematerial was available,nitially alongthe erodingglacial shorelinesof the Boston

region.However,other materialswereused ofiU cobbs, ncluding ballast rock discardedby,

.tradevessels, rush, ree stumpsand dredgedharbour deposits.The solid crib frameworkdidnot haveopertingsand ould be filled with awider variety of material.

20. As seawalland wharf.building inBostonwas typically related o ongoing and,fillingatt,ivities, fill material was soon n gre.atdemand.Once ocalsourceswereexhausted,twas derivedliirgely jromthe excavationofnearbydrumlins. As demand ontinued,a wider

'" ,variety of material was used~s fill. Boring logsfrom subsequently landfilledwaterfront areas

reveal that fill material typically containsbricks,asphalt, wood, cinders, ash, coal,ceramics, glass and le~ther, along with soil. An

241



ROSEN AND VINE

analysisat one ocation 200StateStreet)showed hat the fill material ncluded7% wood,8% coal, 19%cjnders,8% brick, 3% ceramic,3% glass and 3% leather.14

21. On Long Wharf, New Haven,Connecti-cut, in the late 18th century,eachproprietor

who eased paceon the wharf was responsiblefor keeping heir section n goodstructural con-dition.12Historical recordsshow hat largeamountsof fill were outinely purchased ndplacedon the wharf, so that repairing washoutsand slumping appear o havebeena normalaspectof wharf maintenance.

22. Early seawalls n the Boston egionunderwentcontinual repair. Such actors assusceptibility of wood o marineborers, arityof cut stone,and continualwashoutof fillmaterialwere dealt with by continual illingand acing of structures.Marine borersappear

to havebeenmoreabundant n harbours ncolonial imes,owing to their intolerance opresent-day ollution levels.S As late as the

early 20th century, Greenel6 ited the need oreplaceportions of timber structuresevery12-15 yearsowing to marineborers.

23. Oneexampleof the repair of a cobbstructure beyondongoing illing and replace-mentof timbers was the facing of Derby Wharf,Salem,Massachusetts ith stoneat a timebeforequarry stone-cuttingwas developed. hewharf was built between1762and 1771as atimber crib. It was acedwith stone n 1784and1800.The stone acing containssplit boulders

and beach ock. Small 7 described he processbasedon observationsmadeduring reconstruc-tion of the wharf in 1938: These bouldersweresplit by fire, or by wetting down woodenpegsor wedges nserted nto crevicesof the naturalrock. . . For the foundationsof the walls, largerafts weremadeof hewn imbers. . . fastenedtogetherwith crosspiecesof oak-pins' (Fig. 3).The rafts would be loated nto position,alignedwith guide piles, and weighteddownwith rock. As constructioncontinuedslowly,the entire structure would settle nto the mud.By the time the wall was up to grade, he settle-

ment should haveceased.Hydrostaticpressure

against he wall sometimes aused he founda-tion raft to shift, or dislocate, esulting n anirregular rubble-pile hat prevented he closeberthing of ships. n thesecases, he DerbyWharf was apparently epairedby meansofextendingwoodenpile-supported latforms

over he damaged reas o allow efficient wharfoperations.

24. Recent rchaeologicalnvestigationsatDerbyWharf indicate hat the oldestbulkheadsectionswere not constructed f the standardcrib type construction. nstead, he face of thebulkheadwas constructed f horizontal imbersattached o seawardalignmentpiles with trun-nels.The bulkheadderived ts horizontal resist-ance rom timber tiebacksnotched ntoopenings etween orizontal acemembers tvarying heights and varying spacingswhichaverage ft (1 m) on centre. t is believed hat

this earlier type of structure required esssophisticated onstructionoperationsand couldbe undertakenby a smaller, essskilled workcrewduring periodswhenwharf activity waslow.

25. Three ypes of early stonecontainmentwall were dentified by Weinrauband Frank. S

The earliest,and hat requiring the east stone-work skill, consistedof a containmentwall ofundressed tonewhich sloped andward. t wasstabilizedwith wooden ap ogs, piles and, pos-sibly, transverse endersand iebacks or sta-bility (typeC,Fig.4).BrayandTathan

indicate hat failures of walls of this type were

by: 'overturning following destructionof theties by marineborersor by decay,by bulging,sliding, or combinationof these'.

26. The ability to set (and retain) roundedstones o the desiredheights imited this typeof construction n colonial years.The difficultyin splitting and transporting cut stone o a sitemadeother methods,which could utilize themoreabundant ound stones,moreattractive.

27. The abundance f marinewood-borersin colonialwaters,along with the ocal abun-danceof rock, probably explainswhy timberwall construction n New Englandwas not par-

ticularly widespread.Oneexampleof a colonial

Fig. 3. Cross-section

of a stone wall on asunken raft (left) and

a Platform built overa dislocated wall

(right) (Such stone

walls were built toface or repair early

cobb wharves 17)



SEAWALL

CONSTRUCTION INBOSTONHARBOR

timber seawall s CentralWharf, Salem,Massa-chusetts.The original seawall,constructedbefore1780,was of cobbconstruction.Foraddedstrength and stability, the wall was notbuilt straight but with jogs every 30-40 ft(9-12 m). Thesewerecoveredwith planking to

form a uniform wharf decksurface.After 1805,the timber wall was refaced o eliminate hejogs. Piles were driven approximately5 ft(1.5m) on centre,with horizontal imber planksfastened rom behind.There s believed o be astone ooting, at least 3 coursesdeepandslightly wider than the timbers,placedbelowthe bulkhead.13 he wall was backfilled withcobbles,which would haveminimized helateral oading on the wall.

Fig. 4. Three types of stone wharf: type A is constructed of dressedor

semi-dressedPlain stone.. type B is constructed of dressed or semi-dressed

stone with oak cap and fender piles.. type C is constructed of undressed

stone with cap and piles using transverse enders and bolted oak/spruce

drifts for stability 18

Fig. 5. Nineteenth century seawall constructed of semi-dressedstone withoak fender piles (tyPe B),' Central Wharf, Hingham Harbor, Massachusetts

Nineteenth century seawalls28. The prominence f the USA as a trading

nation grew n the 19th century. Long-distancetrade,particularly with the Far East, and anincreased olumeof trade with Europe ed tothe useof larger ships with deeper raft. Wharffacilities in cities wereundergoingcontinuousupgradingand expansion o attract and toaccommodatehese arger vessels.The mostobviousdirection of growth was the extensionof solid-fill wharves nto deeperwater. Thisoften took placeby building woodenpiersseawardof the existing wharf, and then extend-ing the solid.fill seawardwhen he projectprovedsuccessful.9 Examplesof this type of

growth are the' Long Wharves' of Boston,Mas-

sachusetts, nd NewHaven,Connecticut.29. By the early 1800s, tonewharveswere

being built throughoutNew England.Theyweremost ikely constructedof beachorcobblestone nd not quarry-cut stone.Wharvesof quarry-cut stonewerenot common efore1830.Up to that time, stoneusedeven n build-ing constructionappears o havebeenworkedprimarily from rock which lay on the surfaceofthe ground.Quarrieshad not yet beenopenedin the local granites,as tools that would workthe rock effectively had not beendevised. n1803, methodof splitting large stone hatmadeuseof iron wedgeswas devised,whichled to the openingof quarries n Quincy,Massa-chusetts.However, he useof stone rom thesequarriesdid not flourish until the GraniteRailway was built in 1826, acilitating transferof the stone. 7

30. With the useof dressed r semi-dressedstone,a vertical wall and ewer imber supportswerepossible.There were wo general ypes offitted stonewharf in the 19th century.The firstwas built of rough quarriedstone aid up inrandompatterns and chinkedwith smallerstones.This could ncludeusing a caplogandfenderpiles (Fig. 4, type B; Fig. 5), or semi-

dressed lain stone Fig. 4, type A; Fig. 6). Thesecond ype was built with larger quarriedstoneblocks dressed nd aid up dry in a

Fig. 6. Face view of 19th century seawall constructed of semi-dressed

plain stone (type A); Barnes Wharf, Hingham Harbor, Massachusetts

243



RO~ENAND VINE

brokenstoneand oyster shells adjacent o thewall.

33. The substrate n BostonHarbor shighly variable, consistingof extensiveglacio-marineclay deposits,glacial tills and alluvialsands.Thesenatural conditions,along with the

extensive andfilling in the area,have esultedin most of the stonestructuresafter the mid1800s eing supportedon wood pile founda-tions. Many of thesestructuresare on frictionpiles which are prone o settlement.A survey ofBoston'sCommonwealth ier No.6 indicatedthatover2 ft (0.6m)of pile settlementadoccured inceconstruction n 1911.A measureused o preventsoil underminingand exposureof the piles was o constructa short timberbulkheadcut-off wall within several eet of thetoe.Fig. 9 showsa pile-supported eawall nEast Bostonwith a timber cut-off wall whichwas constructed uring the 1860s. he plan of1909 llustrates the nstallation of a replace-mentbulkheadand the backfilling of the repairwith concrete.

34. Several echnological dvances llowedthe constructionof morepermanent nd stableshoresde structures.The adventof the steamengine ed to the developmentn circa 1.825 fthe steampile-driver. Along with iron, that was

becomingncreasinglyavailable,and, ater,steelspikes, imber piling became moreattractive alternative.After about 1840,wrought-iron ie rods came nto common se.With the ability to drive woodenpilings effi-

ciently, a different methodof woodseawallcon-struction became revalent.This involveddriving closely-spacedertical piles, sheathingthe nterior with heavyplanking, and back-filling. This methodof constructionwaspopular n New York Harbor by 1840.The sametype of structure was attributed to Bpston,with. moreattention. . . by the builders o the dura-

bility of the work .19This addedattention odurability may havebeena necessity n anenvironmentwith greater mpactsarising fromice;greater idal ranges,and exposureo north-eaststorms.

Fig. 7. Nineteenth

century seawall

constructed withquarried stone blocksdressed and laid up ina common running

bond; HinghamHarbor,Massachusetts at the

Rotary

common unning bond Fig. 7). Many of the sea.walls remaining n Boston,Salem,Hingham,Allerton and Cohasset arborsconsistof thesetypes rom the 1800s. he quality of stone,alignmentpatterns and quarry-face haracter-istics are generally ndicative of the ageof thewall.

31. By the mid 19th century,muchof thewaterfront development entredaroundcom-mercewhich was supportedby the ntermodalrailroad industry. Unlike the earlier ship-building industry of New England, he railroadindustry provided a readily availableway oftransportingcut stoneby rail to the waterfront.

The adventof rail transportation s responsiblefor the many cut granite seawallsobservedthroughoutNew Englandharbours.

32. The importanceof using quality fill,adjacent o a seawallappears o havebeen ec-ognized n the mid 1800s.Records f 18thcenturyseawalls arely reference toneor char-acteristicsof fill. Plans rom the ate 1800sspecify stoneor riprap adjacent o seawalls oreduce ateral forcesand to provide drainage.Fig. 8 showsplans or a portion of Long Wharf,Boston,n 1869, onsisting f a timber- --

supported ut granite seawallbackfilled with

-::r~W'

~J1

Fig. 8. Plan for a

Pile-supported graniteseawall with stone

and oyster shell

specified as backfill;Long Wharf, Boston,1869

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COMMON;EARTH .-,co'

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OYSTER SHELLS ~;. i;' 1/ fJ':)'t



SEAWALL

CONSTRUCTION INBOSTON HARBOR

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35. A major factor that affected he con-struction of seawalls n the 1800swas heinvention of Portland Cement y JosephAspdinin 1824.This invention resulted n an imme-diate cost advantage ver timber or stonewalls.Formsof concrete ad beenusedsinceRoman

times.With the fall of Rome, he art of buildingwith concretewas dimin~shed ntil the 19th

century.36. Aspdin's patentedPortland Cementwas

successfullyutilized in the constructionof thefirst ThamesTunnel n 1828.From the 1830sthrough to about 1880, oncrete echnologyhadnot developedo a level where t consistentlyprovided a durable structure n the salt/tidalenvironment.For many yearsafter its intro-duction,seawallsand bridge piers continued obe facedwith granite or other masonry,although he backingwas of concrete.

37. The severeenvironmental onditionsofNew Englandmay also be responsible or theextensivenumberof granite (insteadof con-creteor steel)seawallstructures ound n theregion. his s substantiatedy Greene:The

fact that the climate n Boston s severeand thetidal range s unusually arge and that therehad beenmany ailures of concretebetweenhigh and ow water may havehad considerableinfluence n the choiceof granite nsteadofconcrete.16Many of the 19th century seawallsthroughoutNew Englandharbours hat appearto be granite may haveconcrete acking.Fig. 10showsa cross-section f a seawall acedwith

dressed-granite, ith concrete nterior, fromGallops sland, BostonHarbor,built in 1870.

38. The forerunnerof steelsheet-pilebulk-headswas the useof cast ron. The cost of castiron and difficulty of installation apparentlylimited its use n the USA. A seawallwas builtin Englandby Rennie n 1804and repaired n1834with cast ron sheetpiling.Seventy earslater (1904), he cast ron was observed o be ngoodcondition except n the tidal zonewherethe ron was described s' graphitic'.2O

39. As concrete echnologyprogressednthe 1800s, o did steel echnology.With the

.,.,I!

~-;..,~.": ":

. :1'

Wf'

invention of the Bessemer rocess by HenryBessemern Englandand William Kelly in theUSA, working independently f eachother) nabout 1847.Steelsheetpile walls providedameansof constructionwhere he wider gravitywalls could not be used.By the turn of the 20th

century,steelsheetpiling was recognized shaving a clear advantage n cost, n having essvolume, n simplicity, easeand speedof con-struction.13While most of. hese echnologiescontinued nto the 20th century, he useof con-crete or seawallsof shallow depth and of steelfor seawallsof deeperdepthsbecamemore

prominent.

Fig. 9. Plan or aPile-supported eawallwith a timber cutoffwall,.East Boston,circa 1860

Repair of seawall structures40. The rehabilitation of colonialseawalls

has continuedsince heir initial construction,whenbuilders began o recognize he difficulty

Fig. 10. Cross-sectionof seawall on Gallops

Island, BostonHarbor, constructed

in 1870 of concretewith facing of dressed

granite

245



ROSENAND VINE

in dealingwith the extreme idal and stormconditionsof New England.

41. The repair of historic seawalls equiresa thoroughunderstandingof the constructionand condition of the structure. The conditionsresulting from the evolution of the seawall

structure o its presentcondition are varied andoften difficult to ascertain. t is critical toderive as much background nformation as pos-sible about he structure. Although assump-tions are necessaryn qualifying conditions,they are secondary o first-hand field documen-tation. Since he majority of surviving historicseawallsare stone, he following discussion sfocused n their rehabilitation.

and dry rot in timber members.Walls with con-creteelements an experience urfacespallingand deteriorationof concrete omponents wingto the expansionby salt water corrosionof thereinforcing rod. Mortared oints deterioratebyfreeze-thaw nd water pressures.Concreten

older NewEnglandseawallshas been dentifiedto be experiencing hemicalalkali-silica reac-tions which causeexpansion f the concreteand severe trength deterioration.

45. The loss of foundationsoil coverbyscouringor anothercoastalprocess an be amajor problem o stoneor masonrywalls. Withpile-supported oundations, his conditioncanexpose imber piles to biological and environ-mentalattack which can result in rapidmaterial oss.The underminingof footingswithout pile support can createunbalancedbearing hat results n the eaningor bulging ofthe structure.These educed tructuresareprone o severedamage y stormsor extremetidal conditions.

46. A seawallmay require epair if the useof the site has changed.ncreasedoad or draftrequirementsor historic seawallstructuresmay cause ailure of the structure.

Investigations47. The history of the constructionof a his-

toric seawallshouldbe performedearly in theprogramme s t always ncreaseshe efficiencyof the field investigations.For many projects,historic tidelandsdocumentations requiredas

the Commonwealth f Massachusettsetains aninterest n intertidal and subtidal areas.Forharbour sites with a complexhistory, a plan ofthe structural history and sequence an become

Common conditions requiring repair42. A common roblemwith historic sea-

walls is that of sinkholesadjacent o walls thathavebeencaused y the migration of finesthrough voids. Large voids often exist as aresult of movement long he oints or the ossof the smaller stonesused n interlocking thelarger stonecourses.

43. The structural integrity of seawallscanbe affectedby poor details, small sizestone,difficult environmental iting and mproperaccounting or hydrostatic orcesand idal lag.Suchdeficiencies re prone o the ravelling anddislodging of stoneby constantcoastalpro-cesses,ncluding scour, ce, wind, wavesandcurrents Fig. 11).Gradualdeterioration saccelerated y stormsand extreme idal condi-

tions.44. Material deterioration n granite sea-

walls can nclude he cracking of stoneas aresult of wave action or fire, and borer attack

Fig. 11. Dislodgedstonewith washout

behind he seawallatMoon sland,BostonHarbor



SEAWALLCONSTRUCTION IN

BOSTONHARBOR

include physical characteristics, orizontalandvertical alignment,notation of any evidence fpast repairs, oint conditions,material deterio-ration and any other conditions hat couldaffect the overall stability. Gooddocumentationwith photographsand/or videos s important.

50. Geotechnicalnvestigationsare aprimary part of any seawall epair or rehabili-tation programme. est pits, borings andprobescan provide nformation on the wall con-figuration, bearing soils and backfill qualitynecessaryor the structural analyses.Waterconditions, ncluding drainagecharacteristicsand idal lag, should be defined,as they aremajor factors n the analysis.Quite often,unless here s a clear understanding f soilparameters nd past constructionprocedures,tis uncertainwhy the structure s still standing.

51. Structural and geotechnical nalysesofhistoric structurescan result in modern-daylow factors of safety for stability, sliding andoverturning. Owing to the nherentvariablesencounteredn historic seawalls, t is essentialthat rehabilitation designutilizes modernfactors of safety.Seismic odesand require-

a useful tool. Fig. 12 llustrates the icencehistory for the East BostonPiers 3-5 since1866.Sources f information nclude ecordsfrom regulatory agencies Stateand US ArmyCorpsof Engineers), egistry of deeds, istori-cal and archeologicalecords,annual municipal

reports,and nformation derived rom adjacentor similar structures.

48. The historical significanceof the struc-ture and any restrictions hat could be placedon rehabilitation, suchas restoration equire-ments,aesthetics r archeologicalssuescan bemajor factors n the eventualchoiceof anapproach.Often,altering the wetlandsseawardof the wall is not possibleowing to environ-mental egulations.Logical engineering olu-tions must be modified o conform o theseenvironmentaland historic requirements. hesefactors should be determined arly in the pro-

gramme.49. A visual and actical inspectionof thestructure s essential.Frequently, he alignmentor uniformity of historic seawallsare not con-sistent owing to poor constructioncontrol orundocumentedepairs. The nspectionshould

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NUMBERING SYSn:M OF PIERS AND DOCXS HAVE CHANGED OVER PAST 100 YEARS. DASHED LINE INDICATI.5 LIMm OF THEN PIERS1-1 PER LIC. 3" (1/11/1111). SUBSEQUENT NUMBERS REFERENCE NUMBERING AT THE TIME OF UCENSE. LICENSED WORK NOT

SHOWN ABSORBED BY LATER LICENSES.LIC.1'6' (1/I3/01) PERMITTED CONSTRUCTION OF PILE PLATFORM (SHOWN) " ENLARGEMENT OF THEN PIER 1 (ABSORBED IN CUNARDPIER LIC. 33IS).LIC. :S31 (II/IJ/OI) PER~IITn:D RE~IOVAL OF THEN PIER 3 AND CONSTRUCTION OF A NEW STRUcruRE CONNECTING TO THEN PIER.. LIC.1S31 ALSO PER.'"TTED REHABILITATION WORK ON THE ADJACENT PIER I.LIC. 1111 (112110") FOR PIER 3 RECONSTRUCTION SHOWED ORIGINAL PIERS 6" 1 COMBINED AS SHOIVN. NO LICENSE FOR COMBINING

WORK FOUNDLIC. 33IS (IO/II/OI) PER~IITTED CONSTRUCTION OF PRESENT PIER 3 ALIGNMENT SHOWN (THEN KNOWN AS CUNARD PIER). WORK

ABSORBED PILE STRUCTURES BUILT UNDER PRIOR UC. 3'1 (WAREHOUSE II/IJ/I111). S1S (EXTENDED DOCK 3 3/1/1111). AND I..6'.ALSO PER~IfTTED RE~IOVAL OF PILE STRUCTURES BUILT UNDER LIC. S91 (WIDEN PIER I 3/I/IIII) " I'3S (REHAB. PIER I).

LIC. JJ6S (61'/09) PER~IITTED CONSTRUCTION OF PRESENT PIER.. (THEN KNOWN AS LEYLAND PIER) ALIGNMENT SHOWN. (ABSORBINGPILE STRUcruRES BUILT UNDER LIC. SI6 (WHARF SECTION PIER S II/IO/IIII) & 1111' AND FOR REMOVAL OF STRUCTURES BUILTUNDER LIC. NOS. 110S (REPAIR PIER NO. . '/11/11") AND ISJI. LIC. JJ6S ALSO PERMnTED DREDGING ON THE EAST AND WEST SIDE

OF THE NEw STRUcruRE TO EL -3S (MLW).LIC. 33" (I/S/O') PERMITTED CONSTRUCTION OF THE PILE SUPPORTED TRESTLE STRUCTURE SHOWN AND FOR DREDGING OF THEN

DOCKS' AND S.LIC. )43' (6/IJ/I!)) PERMITn:D CONSTRUCTION OF PRESENT PIER S AT SITE OF THEN PIERS 6" 1 AND TO DREDGE DOCK S TO EL -3S.

LIC. ~61 (6/11/.6) PERMITn:D FILLING OF THE PILE STRUcruRE BUILT UNDER LIC. 33" AND FOR PLACING RIPRAP nLL ALONG THE

THEN EXISTING FACE OF THE STRUcruRE.

Fig. 12. Licencehistory Plan of EastBoston Piers 3-5since1866

247



ROSENAND VINE

ments, although not always well-defined forwaterfront structures, must be accounted for indesign. The effect of new drainage systems andmodifications !o tidal current patterns must be

considered. Design solutions must be evaluatedfor longevity, cost, constructability, aesthetics

and safety, and must be tolerant of the manyunknowns.

Repair techniques52. Thereare many proven epair tech-

niques or seawallstructures.Longevity ofrepair s generallya function of price and aes-thetics.Attention to details n design,contrac-tor experience nd commitment, nd theengineer'snsistence n proper nstallation, arecomponentsor an effective epair.

53. In the following paragraphs, eneraldescriptionsof typical repair methodsare

gIven.

54. Stonealignment mprovement. Almostall stoneor masonryseawalls equire someperiodic esetting or pointing stone. n seawallrepair, the ssueof dry or mortared oints andthe placement f weepholesmust be resolved.Most early New Englandstoneseawallswerenot originally mortaredand ypically do nothavesafety actors consistentwith modernstandards.Surface oint mortaring or anattempt o drive small stones nto the ointstypically cannotprovide asting repair onaccountof the extremeenvironmental orcesand reeze-thaw onditionsof New England.Morepositive methods or increasingwall sta-bility includegrouting, shotcreting,dowelling,and stitching or stapling stone ogetherwithsteel ods. njection grouting seawallmain-tenance nd rehabilitation can be effective nsealing oints, but is expensive nd highlydependent n quality control. The stability ofthe wall must be analysed or changed ydro-static conditions f mortaring s adopted.

material can be variable, contaminated, ndexpensiveo disposeoffsite.

56. Fabric repairs can be performed obelow he baseof the wall, or as a cost-cuttingmeasure, s a shallow repair within 3-4 ft(0,9-1,2 m) of the top of wall. The deeper he

repair and the moreattention paid to qualitycontractor nstallation, the more ong-lastingand effective he repair will be. This type ofrepair will not increase he capacityof the wall,unless ighter backfill is used.

57. Placement f standardconcrete,ight-weightconcrete r fill. A method o increasethe stability of a wall and to maintain he aes-thetic appearances to install concrete illbehind he wall. This increaseshe massof thewall and providessomebonding o stone.Anewdrainagesystemwill be required o relievepotential ncreased ydrostatic pressureswhichcould result from thesealteredconditions.Avariation to this technique s providing light-weight concrete r soil fill. Lightweight backfillwill relieve back and oads, hus increasingsta-bility. Lightweight concrete ill is availablewith unit weights n the rangeof 24-115Ib/ft3(1150-5520Pa).A non-restoration ariation isto provide a new concrete tructure seawardofthe wall, possibly using the wall as a backform. Granitestonecan be embeddedn theface,similar to the 19th century concrete-backedgranite walls.

58. Foundation mprovementechniques.The repair of undermined ile-supported oun-dationscan nclude epair to the piles, placingmaterial n front of the piles, and filling voidswith tremieconcrete.Portionsof piles withinsufficient diametermust be replacedorstrengthened. ile repairs whereadditional areais requiredwould nvolve removalof the dete-riorated pile section, nstallation of a pile jackor post, and backfilling the adjacentvoid withconcrete.

59. Wherepiles hare sufficient diameterorat locationsof foundationunderminingwhereno piles exist, filling the void with concretes

the most practical repair. Methods o containthe areaadjacent o the void include he place-ment of stone, imber, concrete-filled agsorthe creationof a form for tremie concrete ack-fill. Often a timber or stone evetmentor ascourmat are provided o inhibit deteriorationof the form. This repair s consistentwith theshallow imber bulkheads ound at the toe ofmany historic seawalls (Fig. 8).~

55. Fabric barriers. The most commonproblem ound n historic seawalls s sinkholes

adjacent o the wall resulting from movementof the fine soil material hrough oints or voidsin the structure. The most simple repair for thiscondition s to place ilter fabric barriers adja-cent o the wall to inhibit soil movement.Geo-technical nvestigations o define he wallcompositionand sectionand est pits to evalu-ate he wall's ability to be excavated re criticalfor such epairs. Unless he fabric is laidcloselyagainst he wall, this methodmay havelimited effectiveness, s sinkholesadjacent othe cap stonesmay continue o develop.Specialattentionshould be provided n the contractdocumentso ensure hat the contractorpro-

vides horough nstallation of oneor morefabric barriers. Plansmust thoroughly detailwall protrusionsand end conditions.Excavated

60. Wall height reductionmethods.Another echniquequite often usedwhen heoverall stability and conditionof the structurerequiremajor rehabilitation s seaward illingto reduce he height of wall and o increase hepassivepressures. his technique s often hemost cost-effective olution which allows



SEAWALL

CONSTRUCTION INBOSTONHARBOR

minimumdisturbance o the back and area.Negative actors nclude estrictions due owetlandsprotection equirements,oss of aes-thetic quality,decreased raft and possibleincreasedwave runup.

61. Major rehabilitation. With changedusageor need or additional draft, majorrehabilitation programmesmay be required.Typically, the foundationmust be strengthenedusing sheetpiling, njectedpiles, embeddedanchors,or other underpinningmethods.Quiteoften, he historical significanceof a structuremust be evaluated,as a complete bandoning fthe structure may be the more ogical solution.

Conclusions62. A remarkable number of historic stone

seawalls in the Boston region have survived to

the present time because hey performed theirfunction and required little maintenance. Withthe revitalization of the city's waterfront andthe growth of the region, the future of these

walls is coming into question. In many cases,

proper engineering solutions can maintainthese walls to allow them to be integrated into

new waterfront land-uses.

References

1. BRAYR. N. and TATHAMP. F. B. Old waterfront

walls: management, maintenance and rehabili-

tation.Chapman & Hall, London, 1992.2. BRAYO. Restoring historic wharf at Salem, Mas-

sachusetts. Civil Engineering, Feb. 1940, 105-

107.

3. HEINTZELMAN-MuEGOA. Construction material

and design of nineteenth century and earlier

wharves: an urban archaeological concern. Paper

presented at the Society for Historical Archae-

ology and Council for Underwater Archaeology,

Jan., 1983, Denver, Colorado, 1983.

4. RANKINEW. J. M. On the stability of loose earth.

Phil. Trans. Roy. Soc.,London, 1857, 147, Part 1,

9-27.

5. COUWMB . A. Essai sur une Application des

Regles des Maximis et Minimis a quelque Prob-

lemes de Statique Relatifs a I' Architecture (Anattempt to apply the rules of maxima and minima

to several problems of stability related to

architecture). Mem. Acad. Roy. des Sciences,

Paris, 1776, 3, 38.

6. PONCELET. Mem sur la stabilite des revetements

et de leurs Foundations. Mem. de l'officier du

genie, 1840, 13.

7. REBHANN . Theorie des Erddruckes und der Fut-

termauern. Vienna, 1871.

8. MEEM . C. The bracing of trenches and tunnels,with practical formulas for earth pressures. Am.

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sions 24-100.

9. COLSON. Notes on docks and dock construction.

Longmans, Green & Co., London, 1894.

10. US ARMYCORPS FENGINEERs.assachusetts

coastal study. US Army Corps of Engineers, New

England Division, 1978, Sept.11. US ARMYCORPS FENGINEERS.lood damage

reduction: Saugus River and Tributaries. Draft

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uncovering the untold past. The Log of MysticSeaport, 1986,37, No.4, 124-135.

13. WILSONM. A. and MORANG. P. /fistoric structure

report. Central Wharf, Salem Maritime National

Historic Site, Massachusetts: Denver Service

Center, Branch of Historic Preservation, US

National Park Service, Denver, Colorado, 1980.

14. FEDERAL HIGHWAY ADMINIsTRAnoN. Draft supple-

mental environmental impact statement. Central

Artery/Third Harbor Tunnel Project, 1982,

FHW A-MA.EIS.82.02.DS2, Part II.

15. BOYLE . J. Marine wood-borers in Boston Harbor.

Report submitted to Massport Authority Engin-

eering Department. Edgerton Research Labor-atory, New England Aquarium, Boston, 1986.

16. GREENE. Wharves and piers.. their design, con-

struction, and equipment. McGraw-HilI, New

York,1917.17. SMALLE. W. Wharf building of a century and

more ago. Popular Study Series, History No.9, US

National Park Service, Washington, D. C., 1941.

18. WEINRAUB . C. L. and FRANKS. Industrial, com-

mercial and maritime introduction to New

Bedford, Massachusetts 1760-1900. G. W. Blunt

White Library, Mystic Seaport Museum, Mystic,

Connecticut, 1975, unpublished manuscript.19. HODGSON. W. Shore protection and harbor

development work on the New England coast.

Am. Soc. Civ. Engrs, Trans., 1923, 86.

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92. Evolution of Seawall Construction Methods in Boston Harbor MA

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