TheWall JournalTM12The International Journal of Transportation—Related Environmental Issues

Killer Tornado Slams Into Virginia SoundwallA Report on page 6

Editor’s CornerLetters to the EditorCover StoryCaltrans’ Eledronic NoiseControl TestCaltrans’ ENC Test ResultsFFIWA Model Update - Part 111

New JerseyNoiseWalls * PolicyFlorida DOT Notes— —

TRB Al F04Committee ColumnWetlands Replacement- Project Report

Minnesota Wood Wall ProjectAcousticAceof the MonthNot Just Another Letter to the EditorTRB Al F04 Summer Meeting 1994Index of AdvertisersReaderRegistration and Subscriptions

March/Apri1994

32-foot high SOL onl-~ mpated b~winds01 1 3-157 mph i Itorn~-~es.The only damage sustained ~as a slight hi ~ot the steel post designated by the arrow in tie photo above.

Also In This Issue:

JS

610

I’

1516

1$

1’1

U

13

141$16

We all have empathy for the victimsof this disaster, and much was writtenin the newspapers and reported on tele-vision of their personal grief and loss ofproperty. That is the province of thenews media, and they performed athorough and sensitive coverage of thewidespread disaster.

However, the province of The WallJournal is principally the reporting ofhighway traffic noise abatement, andthose activities and methods whichmake it possible. Arguably, the use ofa soundwall is the most efficient andgenerally the most widely-used.

Therefore, this piece will now turninto a story of one particular soundwalland how it fared when it was batteredby one of nature’s most destructive anderratic energy outbursts — the tornado.

We begin with a report written byGary Figallo of The Reinforced EarthCompany (manufacturer of the noisebarrier involved) to the Virginia Depart-ment of Transportation in Richmond.,to the attention of Cary B. Adkins,Chairman, Sound Barrier Review Com-mittee, which follows:

January21, 1994

Gentlemen:The afternoon of August 6, 1993

brought several tornadoes to the Colo-nial Heights, Petersburg and Hopewellareas. One of the tornadoes crashedthrough the Wal-Mart store in ColonialHeights, wrecked the historical sectionof Petersburg, and destroyed trees andproperty in the Hopewell area.

That tornado struck our No. 4DURISOL sound barrier in Hopewell.One W10 ~ 54 galvanized steel postwas bent. No damage occurred to theDURISOL panels.

The tornado, estimated by theNational Weather Service to be a cate-gory F-2 on the Fujita scale with gustwind velocities between 113 and 1 57miles per hour, passed across 1-295 anddirectly through the DURISOL soundbarrier, which is 32 feet exposed heightabove ground at that point.

The Durisol wall is comprised of steelposts mounted in drilled concrete cais-sons. Posts and caissons are spacedtwelve feet on centers. The caissonsand steel posts are designed for an 80mph wind velocity in accordance withthe requirements of the AASHTOGuide Specification for the StructuralDesign of Sound Barriers.

Durisol panels have a composite sec-tion, comprised of two layers of Durisolmaterial with a 1 3/4”-thick reinforcedconcrete core. They are designed usingactual panel bending tests for proof oflateral load capacity.

The estimated wind velocities (113-157 mph) are consistent with the dam-age observed for a category F-2 tor-nado. The observed tornado damagein the immediate vicinity of the wallwas snapped-off trees and roof dam-age. A tree with a measured circumfer-ence of 65 inches (24 inch diameter)was snapped off at an elevation of fivefeet above the ground, at a distance of21 feet from the residential (leeward)side of the wall. The National WeatherService also estimates that the tornadowas an F-2 category tornado as itpassed across 1-295 at the wall site.

The DURISOL wall has beeninspected by members of the Virginia

DOT Sound Barrier Committee. Nodamage to the panels is apparent, andthe deflection of the wall is not notice-able from vehicles traveling along I-295, nor from the residential housenear the wall. The Virginia Departmentof Transportation decided that norepair or corrective action to the wall isnecessary. The Reinforced Earth Com-pany engineers have also inspected thewall and confirm that no damage to thepanels occurred, and that the wallsafely withstood the force of the tor-nado.

The material which accompanies thisletter was compiled to document theincident which caused the deflection ofthe wall.

Very truly yours,Gary S. FigalloDurisol Product ManagerThe Reinforced Earth Company

Following are excerpts from the offi-cial report of the National Oceanic andAtmospheric Administration, NationalWeather Service, Weather ForecastOffice:

August6, 1993 Southeast VirginiaTornado Outbreak

By Barbara McNaught, Warning Coordi-nation Meteorologist, NWS Washington,D.C. Forecast Office, and

Laurd Cook, Meteorologist-in-Charge,NWS Norfolk Weather Office, and

Central Wills, Officer-in-Charge, NWSRichmond Weather Office.

“Tornadoes are not considered a com-mon event in Virginia and many of theCommonwealth’s people will tell youthat they do not even consider torna-does a threat. August 6, 1993 brokethat myth and shocked many with thereality of destruction that tornadoesbring. Prior to 1993, Virginia averagedsix tornadoes a year. Records keptsince 1950 showed 263 total tornadoesreported in the state, 21 fatalities, and192 injuries. There have been 56 fatal-ities since 1916. The most active yearfor tornadoes was 1975 with 22, andthe most active day was October 13,1983 with 10 tornadoes.

These statistics should help place incontext the August 6, 1993 outbreak.

“Tornado Kills Three Near Petersburg,Va.DepartmentStoreCollapses;100 Injured”

So read the headline in The Wash-ington Post on Saturday, August 7,1993. The accompanying story byStaff Writers D’Vera Cohn and DonaldP. Baker opened as follows:

liA large tornado tore through a tn-city area about20 miles south of Rich-mond yesterday afternoon, killing atleast three people when a suburbanWal-Mart collapsed and injuring morethan 100.

The storm smashed into a shoppingmall in Colonial Heights, leveledmuch of downtown Petersburg’s his-toric district and blasted the roofs offapartment complexes in Hopewell.Interstate 95 was littered with over-turned tractor-trailer trucks as a seriesof storm-related accidents causedmiles-long traffic backups.

Virginia Gov. L. Douglas Wildercalled out the National Guard to helplocal authorities overwhelmed by thestorm, toured the stricken area byheli-copter and promised to seek federaldisaster aid to help repair damage esti-mated at tens ofmillions of dollars.’~’

6 The Wall Journal — March/April 1994

Many records were broken. Eighteentornadoes occurred on that day, smash-ing the old record of ten. This broughtthe total record for the year to 25,breaking the old record of 22 only eightmonths into the year. The Petersburgtornado was rated an F-4 on the FujitaDamage Scale (see Table 1) with esti-mated winds peaking near 210 mph.This is the strongest recorded tornadoin Virginia since 1950. It was thecostliest tornado, with an estimated 47million dollars in damages. The totalestimated damage from the outbreakwas 52.5 million dollars. Twenty-oneVirginia jurisdictions were affected bytornado impacts”.

EL Following is a recap ofparts of theNWS report describing the paths oftwo of the tornadoes, their estimated

~stnen~ths.and the damage caused:

Tornado 1. First touchdown of theday occurred near the town of Ken-bridge at 12:43 pm. Roofs were blownoff a briquet plant and a furniture com-pany. The tornado began as an F-U onthe Fujita scale with a path width of100 yards. Estimated damage was$300,000.

In Nottoway County, the tornadostrengthened to an F-i as it leveled abarn, trees and outbuildings near thewest edge of Fort Pickett reservation.The tornado width was 100 yards. Esti-mated damage: #1 00,000

The tornado crossed Route 643 nearthe northeast corner of Fort Pickett andcontinued to the town of Ford. By thispoint, it had strengthened to an F-2.The second level of a house wassheared off, windows on the first levelwere blasted out, and a wooden shed,telephone pole and large trees wereleveled. The tornado tracked northeastto near the Chesterfield County line. Itlifted near Route 611 and 623. Aver-age width was 150-1 75 yards. Totaldamage was $320,500.

About 5 miles to the northeast inChesterfield County, the tornadotouched down again with damagealong Routes 628, 534 and 692 forabout 3.5 miles. The damage is ratedF-U. Total path length through the fourcounties was about 38 miles. Totaldamage is estimated at $720,500.

Total life of the tornado on the groundwas about 40 minutes.

Tornado 2. The most devastating tor-nado of the day touched down in thecity of Petersburg at approximately1:30 pm. The tornado grew rapidly insize and strength as it moved two milesnortheast into the commercial historicdistrict of Petersburg, known as OldTowne. Here, damage showed a pathwidth of 250 yards. Much of this dam-age was of an F-2 magnitude, however,within this path were smaller pathsabout 30 yards wide of more concen-trated F-4 damage (winds estimatednear 210 mph). Because of this pattern,the tornado has been designated an F-4multi-vortex tornado. The vortex of alarge tornado can sometimes breakdown into smaller tornadoes whichrotate around a central core. This is

called a multi-vortex tornado.Amazingly, no one was killed in

Petersburg, although 58 buildings werebadly damaged or destroyed. F-4 tor-nado winds were determined based onthe construction, design and damage tothese buildings.

From Old Towne, the tornado movedacross to the historic black neighbor-hood of Pocohontas Island at about1:35 pm. Here it destroyed or heavilydamaged 47 of the 57 homes on theisland, most of which were woodframe, and demolished a 200 year old

with a path width of 250 yards. Totaldamage to Petersburg and PocohontasIsland was estimated at 15 million dol-lars, but there were no deaths.

From Pocohontas Island, the tornadocrossed the river entering ColonialHeights and crossing 1-95 to the South-park shopping area (amazingly, novehicles were struck on this normallyvery busy interstate highway).Here, itwent on to damage several large storesincluding a K-Mart, a strip mall (South-gate Square) and then the Wal-Mart.The tornado had narrowed to about200 yards by this point (as described byeyewitnesses) and was weakening, butit still retained its multi-vortex charac-teristics when it struck the Wal-Mart.

The tornado was as wide as the Wal-Mart was long. It moved across thelength of the store. A small vortexwithin the length of the tornado struckthe front of the store, slicing a 20-yardwide path through the cinder blockwall and the store roof (this was from avector direction of 230 degrees con-verging into the main path of the tor-nado). The vortex gives the storm a rat-ing at the lower end of an F-3 withwinds up to 1 75 mph. Damage outsidethe small vortex was F-2.

Three people were killed near thestore front and another 1 98 injured. Inthe parking lot between the Wal-Martand Southgate Square, 500 cars were

(continued next page)

Fig. 1 — Fujita Scale(F-Scale)on Tornado Winds and Damage

E Number Winds (mph) Damage

0 40-72 Light damage. Tree branches snapped;(Very Weak) rotten trees down; TV antennas and

- ~nsdam~g~ —~

1 72-112 Moderate damage. Roofs peeled off;(Weak) windows broken; trees snapped;

trailers moved or overturned2 113-157 Considerable damage. Roofs torn off;

(Strong) weak structures and trailers demolished;trees uprooted~cars blown off road

3 158-206 Roofs and some walls torn off well-(Severe) constructed houses; some rural buildings

— demolished~cars lifted and tumI~ed4 207-260 Houses leveled leaving piles of debris;

(Devastating) cars thrown some distance5 261-318 Well-built houses lifted clear off foundation

(Incredible) and carried a considerable distance anddisintegrated

church. Damage was rated as an F-3

The Wall Journal — March/April 1994 7

(Tornado, frompage7)

removed, all with windows blown outand many completely totalled havingbeen tossed about and flipped over. Ofthe 185 people brought to area hospi-tals, only 23 had to be admitted (this isa typical percentage for disasters).Total damage in Colonial Heights wasestimated at 29.5 million dollars.

From the Wal-Mart, the tornadocrossed the Appomattox River again,this time entering Prince GeorgeCounty. About a mile from the Wal-Mart at about 1:40 pm, it struck TarmacVirginia, Inc., a sand and gravel pitcompany. The second floor of the cin-der block building collapsed, killingone man who was crushed between thecinder blocks and a large electricalpanel that fell. Cars, trucks and largeconveyor belts were overturned. Thetornado path width was 125 yards. Itwas a strong F-2 with winds estimatednear 1 50 mph. Damage at the Tarmacsite was estimated at $750,000.

The tornado then crossed 1-295, dam-aging a tall sound barrier wall andheaded for the independent city ofHopewell. (Ed. Note: The “sound bar-rier” is shown in the cover photo andphotos on this page). Here it slicedthrough the northern section. Thehardest hit was the Riverside ParkApartment Complex where it took offseveral roofs. The tornado destroyedtwo homes, caused major damage to13, and minor damage to 49. It struckHopewell around 1:45 pm. The tor-nado was rated an F-i with a width of75 to lOU yards. Damages were esti-mated at 2.2 million dollars. Eight peo-ple were injured.

The tornado weakened to an F-U as itcrossed Route 10 near the bridge andmoved out over the confluence of theAppomattox and James Rivers. It dissi-pated before entering Charles County.Total path length through three inde-pendent cities and one county wasabout 12 miles. Total damages wereestimated at 47.5 million dollars. Totallife time of the tornado on the groundwas 15 to 20 minutes.

Ed. Note: The National Weather Ser-

vice report continues:

“This was not the deadliest tornado

outbreak for Virginia. That occurredMay 2, 1929 when five tornadoeskilled 21 people and injured 70. In1929, it was a relatively unpopulatedstate and there may have been moretornadoes that day which went unre-ported. By comparison, the August 6tornadoes killed four and injured 259people. The tornado that struck Peters-burg injured as many people as all thetornadoes combined for the past 40years in Virginia. While not the dead-

liest, it was the worst tornado as far astotal citizens in the commonwealthaffected. We can thank the rapidresponse of emergency services andmedical personnel for saving lives andminimizing the potential death tollfrom this disaster.

After the Petersburg tornado, somepeople talked about how unusual itwas for a tornado to strike that area ofVirginia. While it was an unusualevent, it was nota first. Petersburg was

1 ~ ~~~. .:~ ~ ~~~~ ~~~!!:~.~~~~••r~~ ~~~~ ~~ ~:.••• ~~~~~~~~~

: ~~ -~ T~ FeeTI~otmcjwaT*

~~~~~~~ ~~~~~~.~ ~ •.•~:.•. ~~.~ ~:~ ~ ~~~ ~~~~~~~ir~~~~~.~~~ ~~~~~~~~~~~:~~~~ ~~ ~~,~~~ ~ ~ ~~ ~~ ~

Close up of snapped tree the break 0( ( ut red live t�E~tahove the grounrl level at that point. 1he’tornado path is In m righ to left 1 the photoJ he nterstitc’ 275 is approximately 60 feet away on the

other side ol the walL

8 The Wall Journal — March/April 1994

struck by an F-2 tornado on June 21,1970 and an F-3 tornado on May 8,1984. While no deaths or injuriesoccurred, there was significant dam-age. Nearby counties such as Chester-field, Dinwiddie, Prince George andCharles City have recorded nine, four,four and five tornadoes respectivelysince 1950. Chesterfield has been oneof the hotter tornado spots in Virginia’shistory. R

(Ed. Note: Following is further generalinformation on tornadoes, as excerptedfrom “Recommendations for WindDesign Parameters,” prepared for anoise barrier manufacturer by Technol-ogy Frontiers of Bethesda, MD, andco-authored by Dr. Michael P. Gaus ofTechnology Frontiers and Dr. KishorMehta of Texas Tech University).

TornadoesOn the average, 800-1UUU tornadoes

occur each year in the contiguousUnited States. Tornadoes are short-lived, randomly occurring, localizedstorms. It has not been possible to

place instrumentation inside the stormto measure intensity of the storm andassociated wind speeds. Damage andphotogrammetric analyses have beenused to estimate wind speeds; how-ever, detailed analysis of this nature isfeasible only in isolated cases.

The most commonly used method forassessing the intensity of a tornado isthe F-scale (Fujita, 1971). This methodassigns a numerical value of F-scale toeach tornado, based on the appearanceof damage. Since the assignments of F-scale are accomplished often bylaypersons, they are not expected to beprecise.

Dr. Fujita has designated a windspeed range to each F-scale damage. Itshould be noted that the designation ofwind speeds to F-scale are not basedon engineering analysis, but are basedon good subjective judgment. Hence,accuracy of wind speed estimates usingF-scale rating are not expected to behigh.

Notwithstanding the inaccuracies inassignments of F-scale, wind speedestimates based on F-scale rating is the

only method available that considersalmost all the reported tornadoes.From a statistical point of view, it isessential that a large sample of torna-does be considered to determine thetornado hazard probability at a givenlocation.

A review of F-scale rating data of alltornadoes that occurred in a 63-yearperiod reveals interesting results. Thereview shows that almost 86 percent oftornadoes are assigned to the scale of F-2 or smaller. The maximum designatedwind speed for F-2 is 157 mph. Thus,according to these data, 86 percent oftornadoes contained gust wind speedsof 157 mph or less (Dr. Fujita used gustwind speeds in designating ranges foreach F-scale), ~

(Ed. Note: This is the most detailed andthorough investigation of high windspeeds impacting a tall noise barrierthat we have seen. It demonstrates thedifference between gust winds andpre-vailing winds and speaks well for prop-erly designed barrier systems). ~

NoisDo your work faster and moreaccurately with RTA’s proven acousti-cal software.

Environmental Noise Model(ENM) is world-class. Now, the newWINDOWSversion is even more so.

Individually defined noise sources,ground effects, topography, wind andtemperature gradients, and barriers areall input on spreadsheets. Predictionsinclude contour maps and rankordering of noise sources.

Also available are dB box for fastcomputing in acoustics, including STC,TL and IIC. And dBray for model-ing acoustical paths in rooms. Alloperate on IBM compatibles.

Be time- and value-conscious.

Call today.

SCANTEK INC.916 Gist Avenue

5ilver spring, MD 20910Tel: (301) 495-7738 . FAX -7739

With more than 50 years of proven performance in the manufac-ture of products for building construction and highway trafficnoise abatement, DURISOL has been established as a worldleader of quality construction systems at competitive prices. Ourclients are serviced from manufacturing plants in the 14 countrieslisted at right.

I Licensing OpportunityManufacturing licenses are available in selected geographiclocations. We cooperate in materials research, processtechnologies, product and application development, designand engineering, and international marketing and sales.

Phone, fax or write for full details.World Headquarters

DURISOL INTERNATIONAL CORP~95 Frid Street, Hamilton, Ontario L8P 4M3, Canada

Tel. 905-521-0999 • Fax 416-521-8658

The Wall Journal — March/April 1994 9