C0M731 1 285

illlilllllllllllllllillltl HAimHAl BUREAU OF STANDARDS REPORT

10 961

FIELD INVESTIGATION

OF THE

NATURAL GAS PIPELINE ACCIDENT AT

CANTERBURY WOODS, ANNANDALE, VIRGINIA

Report to

National Transportation Safety Board

Department of Transportation

Washington, D, C. 20591

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U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

REPRODUCED BY. N l| U S. Department of Commerce

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1. PUBLICATION OR REPORT NO." NBS Report 10-961

1 Recipient' s Accesstoo No- »: Hhkz 7. 3- ld3£S-_

4. TITLE AND SUBTITLE . ,

/

FIELD'' INVESTIGATION OF THE NATURAL GAS PIPELINE ACCIDENT

AT CANTERBURY WOODS, ANNANDALE , VIRGINIA

S. Publication Date

4- Petfcmtog Organization Code

7. AUTHOR! S) Robert W. Beausoliel, Clinton W. Phillips, and Jar.k F. . Snpl l

-8. Performing Organ itafloa

^6. Proiec t/Task." Work U it No.

' >

' A -r9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

1 1. Contract/Grant No,

12, Sponsoring Organization Name end Address National Transportation Safety Board

Washington, D. C.

13, Type of Report & Period Covered * >• Final' ri

"l4, Spon soring A&<b*grO<>de^. .

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' ATV*."

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15. SUPPLEMENTARY NOTES

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16. ABSTRACT (A 200-word or le^s factual summary of most significant information. If document includes a significant - . bibliography or literature survey, mention it here.) .5 *

. •

' On the morning of March '24, 1972, in Annandale, Virginia, two homes were destroyed

a third home^. damaged by gas explosions and fires resulting from a construction accident

that caused the gas main leak. The—National Transportation Safety Board is responsible

for investigating this accident and requited that the National Bureau of Standards assist

them with their investigation by conducting a field test at the accident site.iA A/.

.

The objective of the test was to determine how the natural gas entered the homes and

the paths the gas followed from the leak to the homes. The premise of the NBS test was

that if an air-tracer mixture could be detected at locations where natural gas was known

to. have escaped, then the original underground gas paths may still exist.""'- A detailed

test plan was developed to determine gas escape locations and paths ,>«-This plan included

a simulation of the underground gas movement, excavation of -.various utility trenches,

soil tests, and dismantling of the foundation wall -of "one of the destroyed homes. The

equipment used to introduce the -tracer—into Idle ground near the original leak consisted

of an air compressor, a tracer-source (harmless refrigerant R-12 )

,

air flow .measuring,

piping and control valves. '^Electronic catalytic leak detectors were used to detect fchs- tracer in homes and elsewhere on the test siteX , •

. The test results substantiated the basic test premise , and tracer was detected in the r basements of the two destroyed homes and the damaged home, but not in the undamaged hones.

rom the results, it... is concluded that gas traveled through rock rubble on the Site

used as backfill .in utility trenches containing the individual water and sewer lines to

the des troyed/damaged homes and entered the homes through leaks in their concrete block

foundations. Further study is recommended to develop means to prevent similar incidents

17. KEY WORDS (Alphabetical order, separated by semicolons)

Annandale ; field test; gas explosion; leak detection

in the future.

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•

NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

4624192

NBS REPORT

10 961

FIELD INVESTIGATION OF THE NATURAL GAS PIPELINE ACCIDENT

Robert W. Beausoliel, Clinton W. Phillips, and Jack E. Snell

National Transportation Safety Board

Department of T ransportation

Washington, D. C. 2059 1

Building Environment D ivision

Center for Building Technology

Institute for Building Technology

National Bureau of Standards

Washington, D. C. 20234

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

AT

CANTERBURY WOODS

ANNANDALE, VIRGINIA

Report to

Contents

Page

' Abstract iii

1. INTRODUCTION 1

2. BACKGROUND 4

3. DESCRIPTION OF THE TEST SETUP AND TEST PROCEDURE ...... 7

3.1. Overall Test Plan 7

3.2. Test Setup 8

3.2.1. Air Compressor . 11

3.2.2. Air-Tracer Detectors 11

3.2.3. Air Flow Measurement at Test Trenches 11

3.2.4. Pavement Deflection Measurement 11

3.3. Test Procedure 14

3.3.1. Test of Simulation 14

3.3.2. Leakage Patterns on Site 15

3.3.3. Tests in Utility Trenches 16

3.3.4. Examination of Foundation Wall 17

4. TEST RESULTS 20

4.1. Test of Simulation 20

4.2. Leakage Pattern on Site 21

4.3. Tests in Utility Trenches 25

4.4. Examination of Foundation Wall 30

5. DISCUSSION OF RESULTS 34

6. CONCLUSIONS. 36

7. APPENDICES 40

7.1. Names of Individuals Who Participated in the NBS Test

40 Program

7.2. List of Drawings Furnished by Fairfax County 46

7.3. Federal Highway Administration's Description of Soil

and Aggregate Materials at the Canterbury Woods Subdivision 4 '7

ii

Abstract

On the morning of March 24, 1972, in Annandale , Virginia

,

two homes were destroyed and a third home damaged by gas

explosions and fires resulting from a construction accident

that caused the gas main leak. The National Transportation

Safety Board was responsible for investigating this accident

and requested that the National Bureau of Standards assist

them with their investigation by conducting a field test at

the accident site.

The objective of the test was to determine how the

natural gas entered the homes and the paths the gas followed

from the leak to the homes. The premise of the NBS test was

that if an air-tracer mixture could be detected at locations

where natural gas was known to have escaped, then the original

underground gas paths may still exist. A detailed test plan

was developed to determine gas escape locations and paths.

This plan included a simulation of the underground gas movement, excavation of various utility trenches, soil tests, and

dismantling of the foundation wall of one of the destroyed

homes. The equipment used to introduce the tracer into the

ground near the original leak consisted of an air compressor

,

a tracer source (refrigerant R-12) , air flow measuring , piping

and control valves. Electronic catalytic leak detectors were

used to detect the tracer in homes and elsewhere on the test

site.

The test results substantiated the basic test premise,

and tracer was detected in the basements of the two destroyed

homes and the damaged home, but not in the undamaged homes.

From the results, it is concluded that gas traveled through

rock rubble on the site and used as backfill in utility

trenches containing the individual water and sewer lines to

the destroyed/damaged homes and entered the homes through

leaks in their concrete block foundations

.

Keywords: Annandale ; field test; gas explosion; leak detection.

1. INTRODUCTION

The National Bureau of Standards (NBS) was requested by the National

Transportation Safety Board (NTSB) to conduct a field investigation at

the site of the natural gas pipeline accident that occurred at the

Canterbury Woods Subdivision, Annandale, Virginia on March 24, 1972, as

part of their overall investigation of the accident. The objective of

the investigation was to determine how the natural gas entered the homes

and the path the gas followed from the leak to the homes. The basic

approach used to reach the objective was to simulate natural gas flow

underground by introducing a harmless mixture of air and refrigerant R-12

(tracer) in the vicinity of the underground gas leak and checking for the

tracer within homes and other locations.

The strategy for the NBS test plan was approved by the NTSB at

a meeting held at NBS on April 26, 1972. Representatives from the

Washington Gas Light Company and the American Gas Association were also

present at this meeting. NTSB made arrangements for NBS personnel to

inspect the accident site at Magdalene Court on March 28, 1972. At that

time arrangements were also made to confer with Washington Gas Light

Company officials in regard to the accident.

NTSB requested that NBS attend a public hearing concerning the

accident. The hearing was held all day on April 5th and 6th in Room 2008,

Federal Office Building No. 7, Washington, D. C. The hearing was called

by NTSB under the authority of Section 5 of the Transportation Act of

1966 and was conducted as part of the overall investigation of the

March 24th natural gas pipeline accident in Fairfax County, Virginia

involving a pipeline owned and operated by the Washington Gas Light Company.
The purpose of the investigation was to determine the cause or probable

cause of the accident, to report the facts, conditions, and circumstances

relating to the accident, and to assist NTSB in making recommendations

that would tend to prevent such accidents in the future.

NTSB made arrangements for NBS to meet with Fairfax County officials

on May 2, 1972. At that time, Mr. George H. Alexander, Director,

Fire/Rescue Services, Fairfax County was designated coordinator of NBS

field test activities because these activities related to county

functions. The county subsequently performed the following functions.

a. Delivered a Notice of NBS Field Test to residents of South

Magdalene Court, Annandale, Virginia where the NBS test was to

take place. This notice stated the purpose of the test, the

name of the Fairfax County Coordinator, the type of test results

expected, and that the test would be performed by using a

harmless air- tracer mixture introduced into the ground near

where the natural gas leak occurred. The notice stated that

NBS personnel might need to have access to the following homes

in order to perform the test. The complete notice is presented

in Appendix 7.1 of this report.

4907 South Magdalene Court

4908 South Magdalene Court

4909 South Magdalene Court

4910 South Magdalene Court

4911 South Magdalene Court

8601 Queen Elizabeth Boulevard.

b. Placed barricades around the NBS test equipment.

c. The County Plumbing Department flushed debris from the building

drains in the destroyed buildings so that NBS could test these

drains for indication of the tracer (refrigerant R-12)

.

2
d: Furnished what drawings were available showing sewer and water

main locations. Five drawings were furnished. They are listed

in Appendix 7.2.

e. Furnished REPORT OF ANALYSIS OF SOIL for the road sub-base.

f. The water authority furnished "as-built information" for

Canterbury Woods showing the water mains

g. The county furnished equipment and manpower as required to make

excavations during the NBS test.

The Washington Gas Light Company furnished a site drawing showing

their utility lines. The company furnished manpower to dig by hand as

required to assist in the installation of the NBS test setup over the

2-inch-diameter gas main on South Magdalene Court.

The Federal Highway Administration, Fairbanks Laboratory, Soils

Group took soil samples as required from South Magdalene Court.

The names of individuals who participated in this investigation are

listed in Appendix 7.1.

In view of the limited funding available to NTSB for conducting this

study and because of the interest of the Center for Building Technology

in it, a substantial portion of the support for this investigation was

provided by NBS to complement NTSB contract number CB 20169 dated 5/11/72.

3
2 . BACKGROUND

Unfortunately, certain of the events which took place on March 2b ,

1972 at South Magdalene Court, Canterbury Woods Subdivision, Annandale,

Virginia will never be known. However, the principal events relating to

the fatal pipeline accident as found by heating officials, are as follows:

a. At 7:55 a.m. , during the process of excavating for storm sewer

pipe replacement for Queen Elizabeth Boulevard, a contractor's

back hoe hooked a 2-inch, schedule 40, steel gas main serving

five houses on South Magdalene Court, as indicated in Figure 1.

b. Approximately 22 feet downstream from where the gas

line was hooked, a compression coupling in the 2-inch gas main

separated by 2 1/2 inches. The coupling was located 42 inches

below finished road grade.

c. Natural gas entered homes at 4907, 4909, and 4911 South Magdalene

Court, and subsequent explosions occurred before the gas was

shut off.

d. At about 8:55 a.m. an explosion occurred in the home at 4911.

A woman and child escaped without injury.

e. Shortly after the explosion at 4911, an apparently more severe

explosion occurred at 4909 killing two children, fatally

injuring their mother, and severely injuring a gas company

employee.

f. A third explosion, at 4907, occurred about the same time as the

explosion at 4909. This explosion occurred in the west basement

wall. No one was injured at 4907.

4
'tore

o

Figure 1. Accident Site.

5
g. The gas was turned off at about 9:52 a.m.

A video tape was made by the Fairfax County Fire and Rescue Service

during the time that they were fighting the fires. This tape shows gas

escaping from the following locations.

a. Expansion joint between driveway and carport concrete slabs at

4907.

b. Crack in the concrete gutter in front of the water meter box

at 4909.

c. Blacktop and concrete gutter interface located about three feet

north of the catch basin adjacent to 8601 at the corner of

South Magdalene Court and Queen Elizabeth Boulevard.

6
3. DESCRIPTION OF THE TEST SETUP AND TEST PROCEDURE

3.1. Overall Test Plan

The premise of the NBS test was that if the tracer could be detected

at locations where natural gas was known to have escaped, then the underground paths followed by the natural gas at the time of the accident may

still be intact. It is assumed that the tracer would follow the same

paths as the natural gas even though certain characteristics of the two

gases are different because pressure is the main driving potential. The

test plan developed to determine existing gas escape locations and paths

consisted of four basic phases sequenced as follows:

a. . Test of Simulation . The purpose of this phase, once the test setup had been installed and checked out, was to test the air-tracer injection strategy by determining whether this mixture could be detected at

points where natural gas was known to have escaped during the accident.

b. Leakage Patterns on Site . The purpose of the second phase was to

comb the site, particularly the basements, foundation walls, and grounds

of all the homes on the site to attempt to reconstruct the pattern of the

natural gas leakage that occurred downstream of the separated pipe

coupling during the accident.

c. Tests in Utility Trenches . The first purpose of the third phase

of the investigation was to pinpoint the paths followed by the natural gas

to the homes destroyed in the accident. The second purpose of this phase

was to obtain quantitative estimates of gas flow to these homes.

d. Examination of Foundation Wall . The purpose of the last phase

of the study was to attempt to determine the means by which natural gas

entered the basement of one of the homes (4911) destroyed in the accident.

7
3.2. Test Setup

Figure 2 shows the air-tracer test setup which consisted of the

following major pieces of equipment:

a. Air compressor connection.

b. A source of refrigerant, R-12 (tracer)

.

c. A needle valve for controlling air flow input.

d. An air flow measuring section.

e. Meters and manometers for measuring air pressure.

f. A vertical section of piping (injection piping) for introducing

air and refrigerant R-12 into the ground above the gas line.

g. A section designed to introduce a harmless smoke tracer.

In order to simulate the leak from the gas main beneath the road

surface, air under controllable pressure was fed to the gas main location

through a 2-inch steel pipe as shown in Figure 3. A hole, approximately

12 inches square, was dug in the street down to the bottom of the gas

main. The air-injection pipe was placed in this hole with the pipe outlet just above the gas main. A six-inch-deep layer of large crushed

stone (1 1/2 to 2 inches) was placed in the bottom of the hole around the

injection pipe and a 1/4-inch pipe used to transmit cavity pressure as

shown in Figure 2. Above these large stones a 2- inch-deep layer of 3/4-

inch maximum size crushed stone concrete aggregate was placed. A 10-inch

layer of damp, stone free clay, brought in from Maryland for this purpose,

was well-tamped in three layers over the concrete aggregate layer. The

hole was then filled to the bottom of the asphalt pavement with the clay

taken from the hole. The top of the hole was sealed with an asphalt cold

patch to slightly above the street surface. This hole was located

8
VENT

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ATMOSPHERE

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9

Figure

2.

Air-tracer

test

setup.
1/4" STEEL PIPE USED TO

SENSE AIR- REFRIGE RANT R-12

MIXTURE PRESSURE WITHIN

Figure 3. Air-tracer injector pipe installation

10
approximately six feet downstream from the natural gas leakage position

because the soil had been disturbed in the leakage area when the trench

was dug to repair the gas leak (see Fig. 1)

3.2.1.

Air Compressor

A diesel engine driven air compressor supplied air to the test setup

shown in Figure 2. This compressor supplied air at 100 psi pressure and

had a capacity of 600 cfm of free air.

3.2.2.

Air-Tracer Detectors

In addition to the test setup shown in Figure 2, an electronic

catalytic leak detector, as shown in Figure 4, was used to detect the

refrigerant R-12 tracer. This detector, which operates on 110V AC, was

powered from portable electric generators.

3.2.3.

Air Flow Measurement at Test Trenches

A quantitative air flow test was conducted in a test trench using

the test setup shown in Figure 5. The vacuum pump shown in this test

setup was powered by the generators mentioned above.

3.2.4.

Pavement Deflection Measurement

A precision level was used to monitor road surface deflection (lift)

during the first two phases of the test to permit air flow control to

insure against excessive road surface lift.

11
Figure

4.

The

electronic

catalytic

leak

detector
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Fiyure

5.

Test

setup

for

determining

air

flow

rate

in

the

test

trench

at

4909.
3.3. Test Procedure

The following is the test procedure used.

3.3.1. Test of Simulation

The first day of the test. May 16, 1972 was devoted to determining

how much air could be pumped into the ground and to validating on-site

the tracer detection technique. It was believed that a cavity pressure

equal to that of the gas main (22 psig) would rupture the asphalt road

surface; therefore, the elevation of the pavement was monitored at 31

reference points with a precision level while the cavity pressure was

slowly increased. The intent was to adjust the cavity pressure to

a value high enough to obtain a workable air flow without disturbing the

pavement. .

a. The injection piping and piping used to transmit pressure in

the rock fill cavity as shown in Figures 2 and 3 had been

installed by NBS and the Washington Gas Light Company personnel

prior to the first day of the test. On May 16, the test setup

was assembled to the injection piping.

b. The compressor rental company connected their air compressor

to the test setup connection as shown in Figure 2 and operated

the compressor as directed by NBS.

c. Air was allowed to enter the test setup by way of the 1/2-inchdiameter needle valve shown in Figure 2. This valve was used

to control cavity pressure. Cavity pressure was regulated

while observing for road deflection with the precision level.

d. Air flow was measured in the orifice meter section of the test

setup shown in Figure 2. It was hoped that adequate flow would

14
be established so that soil could be seen blowing up from the

ground as had been observed during the accident and at the

locations noted from the aforementioned videotape. These

positions are (1) the blacktop and concrete gutter interface

near the catch basin, (2) the driveway and carport concrete

slab expansion joint at 4907, and (3) the joint in the concrete

curb in front of the water meter box at 4909. See Figure 1.

e. The refrigerant R-12 was introduced into the injection piping

test setup as shown in Figure 2. The rate of R-12 injection

was measured by periodically monitoring the weight of the R-12

tank using a platform scale.

f. At the end of the test each day (at about 4:00 p.m.) the test

setup was disassembled and barricades were positioned around

the injection piping and air compressors.

3.3.2. Leakage Patterns on Site

The second day of the test. May 17, was devoted to determining if

R-12 tracer could be detected at the locations noted on the videotape.

The test procedure for this day consisted of the following:

a. The test setup was assembled to the injection piping, and the

compressor connected to the test setup.

b. Air and refrigerant R-12 (tracer) were introduced into the

injection system as explained for phase 1 above and the road

surface level was monitored with the precision level.

c. Electronic leak detectors were used to check for tracer escaping

from positions inside the test homes and selected site locations.

15
d. At the end of the day smoke tests were attempted using smoke

candles in the test setup as shown in Figure 2.

e. The phase 2 test was concluded at 4:00 p.m.

3.3.3. Tests in Utility Trenches

The third and fourth days of the test were used to determine how the

natural gas got from the leak position to the homes. The test procedure

for these two days was as follows:

a. The test setup was assembled as explained for phases 1 and 2.

b. On the third day, at NBS request, a Fairfax County Department of

Public Works employee used a backhoe to dig two test trenches

across utilities located in the front yard at 4909. The location of these trenches is shown in Figure 1. One trench was dug

for the gas line (two feet deep) and the second trench was dug

for the sewer and water lines (five feet deep) . Also, as shown

in Figure 1, a trench was dug (10 feet deep) across the combined

utilities (gas, water and sewer) in the front yard at 4911.

This trench was completed on the morning of the fourth day.

c. A check for tracer was made in these test trenches using an

electronic leak detector. An electric fan was used to ventilate

the trenches and prevent the tracer from accumulating so that

the exact positions of leakage could be noted.

d. A soil expert from the Federal Highway Administration took

samples of the soil in these trenches and at the tree belt in

front of 4908.

16
e. On the morning of the fourth day, approximate quantitative air

flow measurements were taken in the test trench containing the

water and sewer lines for 4909. The test procedure used was to

cover the trench, as shown in Figure 5, with a 2-mil sheet of

plastic which was sealed around the top of the trench with soil.

The face of the trench on the house side was covered with plastic.

The purpose of this test was to determine the quantity of air

pumped to the trench through the rock fill passages from the

injection setup. At the same time, a vacuum pump was used to

remove air from the trench to maintain atmospheric pressure in

the trench. The manometer shown in Figure 5 was used to observe

the pressure in the trench. A laboratory grade, bellows-type

gas meter (conventional residential gas flow meter) was used to

determine volume rate of air flow being drawn from the trench.

f. A Washington Gas Light Company employee drilled a network of

holes approximately one-inch diameter and two- feet deep throughout the right-of-way at South Magdalene Court. Also, holes were

drilled in the lawn and driveway in front of 4907. See Figure 6.

g. The tracer portion of the test was terminated at 4:00 p.m. on

the fourth day, May 19. The drilled holes in the right-of-way

were filled by the Washington Gas Light Company. The trenches

were filled by Fairfax County. The NBS test setup was disassembled.

3.3.4. Examination of Foundation Wall

On June 4, 1972 additional information and soil samples were obtained

from the site. The procedure involved the following:

17
(io

!

I

—30 60 90

O NO TRACER DETECTEO

-f-l - INCH DIAMETER X 6- INCH

DEEP HOLES -NO TRACER

DETECTED

Scole in feet

Figure 6. Network of drilled test holes.

18
a. A section of the front basement wall at 4911 containing the gas

and water lines was dismantled by removing one concrete block

at a time. The purposes of this work were to determine soil

condition at the outside face of the front wall, and to examine

the condition of the wall and the utility pipe seals

b. The soil expert from the Federal Highway Administration took

soil samples from the front yard at 4907 and from the wall area

at 4911.

19
4. TEST RESULTS

The following paragraphs describe the results of the various phases

of the test.

4.1. Test of Simulation

When air was first introduced into the test setup to check for air

leaks in the test setup and to obtain familiarity with the test procedure,

a cavity pressure of 6 psig was observed for about 30 seconds. At this

time a section of the road surface on the south side of the test setup

lifted appreciably, and the air was shut off. Maximum lift appeared to

have occurred in the center of a circular section of road surface estimated to have an area of approximately 6-foot diameter. Although elevation of the lift area was not monitored by use of the precision level, the

maximum lift was estimated visually to have been several inches. Perceptible lift appeared to have settled down over a period of about two

minutes after the air was shut off. Subsequent examination of the road

surface showed that the lift did not break up the surface. Thereafter

air and refrigerant R-12 tracer were introduced for about two hours into

the cavity at pressures starting at 0.5 inches W.G. (water gage) and

increasing gradually to about 51 inches W.G. (1.8 psig). This was done

to determine the on-site functioning of the electronic detector technique

and to observe the road lift at different pressures. At cavity pressure

of 1.8 psig the road lift was negligible. The maximum cavity pressure

during the time that the tracer detection technique was being checked

on the first day of the test was 0.8 psig. Based on subsequent measured

air- tracer flows at higher cavity pressures, the combined air-tracer flow

at 0.8 psig cavity pressure was about 11 cfm, including a measured flow

20
of 1.1 cfm of refrigerant tracer. At these relatively low injection

pressures and flow rates, positive traces were observed at curb cracks

adjacent to the injection point and at the patch surrounding the injection

tube, indicating that the air- tracer detection technique was functioning.

4.2. Leakage Pattern on Site

On May 17, an average measured air- tracer flow rate of 29.2 cfm

(including 3.6 cfm of refrigerant tracer) at an average cavity pressure

of 2.2 psig was maintained during the four-hour period when trace detection measurements were being made at many points on the site. The

measured road lift during this period also was negligible. Using the

electronic detector (see Fig. 4) tracer was detected at the following

locations

a. Blacktop and concrete gutter interface near the catch basin at

the corner of South Magdalene Court.

b. Driveway/carport concrete slab expansion joint at 4907.

c. Crack in the concrete gutter and curb in front of 4909 water

meter box. (See Fig. 7.)

d. At the front inside basement walls of 4907, 4909, 4911, where

the water lines enter.

e. Within concrete blocks at the front basement wall next to the

utility trench for water, sewer, and gas at 4911 and within the

same area for the utility trench serving water and sewer at 4909.

f. Within the rock rubble located below the carport and adjacent

to the fireplace foundation wall at 4907. (See Fig. 8.)

g. At the gas line where it penetrates the concrete block wall in

the basement of 4911.

21

Figure

8.

Rock

rubble

against

the

foundation

wall

at

4907.
h. In all water meter boxes located on South Magdalene Court.

i. In the gas curb box for 4911. (This curb box had been dug up

for repairs so this indication of tracer does not necessarily

mean natural gas was in the box at the time of the accident.)

j. At many positions along concrete gutter and curb, including

curb joints near several water boxes, and curb joints adjacent

to driveways at 4907 and 4911.

k. At the interface between the sanitary sewer manhole rim and

surrounding blacktop located in the South Magdalene Court

cul-de-sac.

l. In catch basins located at (a) Queen Elizabeth Boulevard in

front of 4907 South Magdalene Court, (b) Queen Elizabeth

Boulevard in front of 8526 (at the corner of North Magdalene

Court) , and (c) the north corner of South Magdalene Court and

Queen Elizabeth Boulevard.

Air tracer was not detected at the following locations:

a. Interior of homes at 4908 and 4910 South Magdalene Court and

the home at 8601 Queen Elizabeth Boulevard. The slab on grade

home at 8601 was not entered but was judged to be free of tracer

because a check for tracer at the front foundation wall, the

gas curb box, and the water meter box at 8601 did not reveal

tracer.

b. The gas curb box for 4908 and 4910. It was not possible to

check the gas curb box at 4907 since it had been removed by the

gas company when gas was shut off to 4907 after the accident.

24
c. Gas line at the point of basement entrance and gas curb box

at 4909.

d. Gas line at the point of basement entrance at 4907.

e. Water and gas valve boxes located in the right-of-way at the

intersection of North Magdalene Court and Queen Elizabeth Blvd.

f. The sanitary sewer in 4907, 4909, 4911, and street manholes.

At 4907 normal water seals were in all traps. At 4909 and 4911,

measurements were made in the open basement commode drain line.

The commodes had been removed and there were no water seals.

No tracer was detected either in or around the sanitary drain

lines

g. Two one-inch holes , six inches deep, drilled in cul-de-sac

surface. (See Fig. 6.)

h. Curb joints adjacent to driveways at 4908 and 4910.

Smoke was generated in the air-tracer injector system through the

special valve shown in Figure 2 to give visual indication of leakage

path. Although preliminary tests at NBS demonstrated that the smoke

would pass through wet sand, there was insufficient air flow on the site

for this test and no smoke traces were observed.

4.3. Tests in Utility Trenches

The test trenches in front of 4909 and 4911 contained much rock

rubble. See Figures 9 and 10. This rock rubble consisted of looselyplaced rock backfill. The Federal Highway Administration's report

containing results of rock-soil samples is attached as Appendix 7.3.

This report shows that the trench at 4909 containing the water and sewer

lines had fine soil to a depth of 0.4 of a foot, course angular rock

25
Figure

9.

Rock

rubble

in

the

water

and

sewer

service

trench

at

4909
Figure

10.

Rock

rubble

bed

for

water

and

sewer

services

at

4909
fragments loosely placed as backfill between 0.4 and 5.8 foot depths, and

at 6.8 foot depth a fine soil existed. In other words, the rock fill of

five inches or greater sieve-size was sandwiched between layers of fine

soil material in the 4909 water and sewer line trench. The water/sewer

lines were covered by about six inches of rock-free fill in this trench

but rested directly on rock fill. No tracer was detected in the immediate

vicinity of the water/sewer lines. The water line was beside and below

the sewer line.* (See Fig. 10.) Water line depth was 69 inches below grade

and sewer line depth was 63 inches. No tracer was detected in the gas

line trench at 4909. Appendix 7.3 shows that this trench contained a

mixture of fine soil and angular rock fragments. The gas line was bedded

in rock-free fill and covered with rock-free fill about eight inches deep.

The gas line depth was about 24 inches.

Throughout the digging process on May 18, tracer was detected in the

trench at 4911. Rocky fill was found in direct contact with water, sewer,

and gas lines. Appendix 7.3 shows that coarse angular rock fragments,

five inches or greater sieve size, were loosely placed around the water

line

.

During this day's testing, the air flow was increased to a maximum

of 49.3 cfm at a cavity pressure of 2.9 psig. No refrigerant tracer was

added because measurements during the excavation process could be made

from residual trace. No road lift was observed during the period.

^Federal Housing Authority Minimum Property Standards (FHA 300), November ‘ 1966, para. 1006-4. 5d, page 214, "(Water) service pipe may be laid in same trench with sewer pipe provided it is laid on a shelf of solid

earth at least 1 foot above the sewer pipe. Service trenches shall be

filled, with earth free of . . . rocks." !/• y

2 Ibid .

: :V

Y 28
On May 19 (the 4th day of the test) three principal tests were performed.

a. Refrigerant trace detection checks were made in the excavations

at 4909 and 4911 for verification of checks made on May 18 during

excavation.

b. A quantitative air- tracer flow measurement was made at the

sewer/water excavation at 4909.

c. Refrigerant trace detection checks were made in a series of

one-inch holes, 24-inches deep, drilled in the street and along

the front edge of the lawn at 4907.

During these tests, a maximum air-tracer flow rate of 65.5 cfm

free air rate (including 2.7 cfm of refrigerant) was obtained with a

maximum cavity pressure of 4.2 psig.

Positive refrigerant- tracer detection was made at the rock-fill

face of the sewer/water trench at 4909 and at the sewer/water/gas trench

at 4911. No tracer was detected in the gas line trench at 4909. Shoring

was needed in the trench at 4911 because of the depth (^10 feet) and

because the rock fill kept falling into the excavation.

In the quantitative air flow test at 4909, with the vacuum pump off,

air tracer entered the trench through the rock fill and caused the plastic

cover sheet to be forced up. With the vacuum pump operating at a measured

maximum capacity of 15.0 cfm, this capacity was not sufficient to cause

the plastic cover to collapse. A micromanometer indicated a varying

positive pressure of up to 0.02 inches W.G. (water gage) in the trench

with the pump running. To determine if a slight wind was affecting this

observation , the vacuum pump and the air supply to the street cavity

were turned off. The plastic cover sagged into the trench within one

29
minute. See Figure 11. The air supply was turned on and within ten

seconds the plastic cover began to rise and was taut within one minute.

See Figure 12.

This test indicates that the air-tracer flow into the trench was in

excess of 15 cfm. Also, this air flow test showed that the air-tracer

readily passed through voids in the rock rubble from the injection point

150 feet away to the front of the foundation wall at 4909. Air flow at

the injection point was 41 cfm and cavity pressure was 3.5 psig at the

time of this test.

The 2-foot-deep drilled holes in the Magdalene Court right-of-way

showed that tracer existed under most of the right-of-way surface at or

above a depth of two feet. Tracer was not detected in the drilled holes

in the portion of the cul-de-sac in front of the undamaged home at 4908,

as shown in Figure 6. Tracer was detected in most of the drilled holes

next to the sidewalk in the front lawn of 4907, and was detected in the

drilled hole in the concrete driveway ramp of 4907.

4.4. Examination of Foundation Wall

The dismantling/examination of the foundation wall at 4911 produced

the following observations:

a. Coarse rock fill existed against the front wall surface in the

utility trench. Analysis of rock-soil fill is contained in

Appendix 7.3.

b. The gas line and water line were laid on top of rock fill.

There was no evidence that either of these lines had been

bedded in soil.

30
Figure 11. Sagging plastic cover over 4909 test trench.
Figure

12.

Taut

plastic

cover

over

4909

test

trench.
c. The water line and gas line did not have good seals at the

penetrations in the concrete block. Both showed evidence of

having been sealed prior to the accident. It is likely that

the foundation wall was moved by the explosion-fire.

d. The street side of the concrete block foundation wall had

a protective coating to prevent water penetration.

e. One shortened (cut) concrete block located in the center of

the wall did not have a mortar seal between its cut/shortened

end and the adjacent block. Appendix 7.3 shows the analysis

of the soil samples taken from the front yard of 4907 at the

positions of the drilled holes shown in Figure 6. The gas

test holes referenced by number in Appendix 7.3 are these

holes numbered from left to right in the front of 4907.

Figure 6 shows that tracer was not detected in holes numbered

1, 2, 3, 4, and 10. All of these holes were located in the

lawn area except hole number 16 which was located in the

concrete 'ramp of the driveway. Soil samples were taken near

gas test hole 2, between gas test holes 10 and 11, and near

gas test hole 18. No tracer was detected in hole 10 and this

may be because of the red-brown dense clayey silt sampled

between holes 10 and 11.

33
5. DISCUSSION OF RESULTS

The repair work on 4907 prior to the NBS test reduced the usefulness

of tracer simulation results for this home because

a. The concrete carport slab had been completely broken up. The

expansion joint between this slab and the driveway slab was

considered an important simulation point where natural gas

was seen burning in the videotape.

b. During the process of repairing the house, a hole had been made

in the side of the house above the carport slab area which

exposed the entire void space under the first floor fireplace

where an explosion had occurred.

The basements of 4909 and 4911 had been cleaned of debris prior to

the tracer test. The equipment used to clean up the basement at 4909

appeared to have

a. Bent the gas line.

b. Made a hole approximately 4 feet by 2 feet in that portion of

the front foundation wall containing the water line penetration.

The equipment used to clean up the basement at 4911 appeared to

have

a. Punched several holes, judged to be about one foot long and

two inches wide, in the front foundation wall.

b. Caused cracks around water and gas line penetrations in the

front foundation wall.

34
For these reasons, the detection of tracer at water and gas lines

where they penetrate the walls of these homes does not necessarily indicate that the natural gas entered the homes by way of these penetrations.

Since the water line in 4907 did not appear to have been damaged, it is

judged that tracer detected at this line at its penetrative position on

the concrete block wall is good simulation of one possible natural gas

entrance into 4907.

The Fairfax County soil analysis sheets for Magdalene Court show

only sub-base soil condition (approximate depth 10 inches) and do not

show soil or fill condition beneath the sub-base. The drill hole pattern

showed that tracer existed generally under the entire right-of-way

surface at or above a depth of 2 feet. If a record of type of fill

materials used in each utility trench and the depth below the right-of-way

that these materials are located had been available, a better judgment

could be made concerning the probable distribution paths of tracer in

light of the tracer pattern recorded over the plan view of the right-ofway .

35
6. CONCLUSIONS

The following are concluded from the results of the field investigation .

a. The air-tracer traveled through soil and rock rubble located

in the utility trenches containing the individual water and

sewer lines for the destroyed homes at 4909 and 4911.

b. The investigation showed that tracer did not flow on the outside

of any particular pipe, per se, but rather, traveled through

soil and rock fill. It was not possible to determine precisely

how gas actually entered the houses through their foundations

from the rock-rubble-fill that was found in the utility trenches.

The water lines, gas lines, and concrete block walls had been

disturbed by the explosions, fires, and fire-fighting and

clean-up activities in the homes. Repair work carried out on

4907 prior to the tests further altered the test simulation in

this home. As a result it is surmised that the gas entered 4909

and 4911 through the front walls by way of piping penetrations

and/or through the mortar and asphalt coated concrete block construction. Because tracer was detected at the apparently undisturbed water line at its penetration in the front wall and at the

fireplace foundation wall under the carport of 4907, it is

assumed that gas entered this building in the same manner. Soil

tests and drilled hole tracer tests at 4907 indicated that

possibly more than one rock fill path exists between the injection area and the house.

36
c. The undamaged homes at 4908 and 4910 South Magdalene Court

and the home at 8601 Queen Elizabeth Boulevard did not

experience explosion or fire during the accident and did not

receive tracer during the air-tracer test.

d. Natural gas could flow again into or to the same homes if

another natural gas leak were to occur in the vicinity of

the leak of March 24 unless the rock rubble paths are

eliminated

e. In the tests conducted, it was not possible to duplicate enough

conditions to pinpoint the time required for natural gas to

travel from the leak to the homes at the time of the accident.

However, it was established, based on the following two facts,

that the gas could have traveled to the homes in less than

30 minutes. It was documented at the public hearing that the

odor of natural gas was detected by residents of 4909 and 4911

in their homes at about 8:30 a.m. on the day of the accident,

and air tracer traveled from the injection point to the front

wall of 4909 in less than 30 minutes during the tests on

May 17. Secondly, during the test, air tracer injection began

at 11:00 a.m. and tracer was detected inside the front wall

of 4909 in the vicinity of the water line at 11:31 a.m.

Further, because this wall position had not been monitored

before 11:31 a.m., the tracer could have arrived at the wall

in less than 30 minutes.

37
f. The quantitative air flow test at 4909 showing more than 15 cfm

of air tracer flowing from the point df break on the gas main

to the trench in front of the foundation wall with a source

(cavity) pressure of 3 1/2 psig indicates that gas flow at the

time of the break through this same path could easily have been

considerably in excess of that required (12 cfm) to form an

explosive mixture (5% by volume) in one half hour in an

unventilated volume of 7200 cubic feet, the approximate volume

of the 4909 basement, if the cavity or source pressure was

sufficiently high. The source pressure at the time of break

could possibly have approached 22 psig, far in excess of the

3.5 psig source pressure used in the quantitative air flow test.

The actual volume of the 4909 home is not known, nor is the

ventilation/infiltration rate existing at the time of the

explosion.

g. Although tracer was detected in the storm sewer, tracer was

not detected in the sanitary sewer. The storm and sanitary

sewers are not interconnected. It is concluded that natural

gas did not enter the sanitary sewer because tracer was not

detected in sanitary manholes servicing South Magdalene Court

or in sanitary sewer connections within the homes. If natural

gas had existed in the storm sewer at the time of the accident,

the gas in the storm $ewer could not have contributed to the

accident since the storm sewer does not extend up the Court.

38
Examination of drawing no. 4, as listed in Appendix 7.2, shows that

the home at 4907 is built on fill and also that the entire front yard of

this home is fill. It is concluded from test results that the tracer

must have traveled through this fill to the home. The rest of the houses

on the site, including the destroyed homes at 4909 and 4911, were built

on excavated land and not on fill. Except for the utility trenches,

little or no fill exists in the front yards of the destroyed homes. The

middle of the cul-de-sac area is about 14 feet lower than the original

land grading indicating that considerable material had been removed.

It may be that the removal of this material exposed bed rock since the

service trenches at 4909 showed the existence of solid rock. It appears

that some blasting must have taken place in order to form the trenches.

The rock rubble found as fill in the trenches at 4909 and 4911 was

probably produced by the blasting.

39
7. APPENDIX

7.1 -Names of Individuals Who Participated

in the NBS Test Program

Because concern for building systems in general is within the

scope of the mission of the NBS, Center for Building Technology, Building

Service Systems Section, and because of section participation on the

National Fuel Gas Code, ANSI Z223, Dr. Jack Snell, Chief, Building Service

Systems Section, requested that Robert W. Beausoliel, Mechanical Engineer

for the section, determine if anything could be learned from the Annandale

pipeline accident that might contribute to Z223 work. Discussion with

Mr. Barry M. Sweedler, Chief, Pipeline Safety Division, National Transportation Safety Board disclosed that NTSB was investigating the accident

but did not know how the natural gas entered the homes. Subsequently,

NTSB requested that NBS determine how the gas entered. In order to

assist with the investigation, Robert W. Beausoliel attended the public

hearing concerning the accident, visited the accident site, and developed

the test plan and test organization presented in this report.

On April 26, a meeting was held at NBS for concerned parties to

discuss and approve the basic test plan. The meeting was attended by

the following individuals:

Mr. Barry M. Sweedler, Chief, Pipeline Safety Division,

National Transportation Safety Board

Mr. Lance F. Heverly, Assistant Chief, Technical Division,

Office of Pipeline Safety

Mr. Paul R. Achenbach, Chief, Building Environment Division,

(462.00) NBS

Dr. Jack E. Snell, Chief, Building Service Systems Section

(462.03) , NBS

Mr. Frank J. Powell, Chief, Thermal Engineering Systems Section

(462.01)

, NBS

40
Mr. Clinton W. Phillips, Engineer, (462.01) NBS

Mr. Robert W. Beausoliel, Engineer, (462.03) NBS

Dr. Charles M. Hunt, Engineer (462.02) NBS

Mr. Keith H. Fellows, Assistant Superintendent, Transmission & Distribution Department, Washington Gas Light Company

Mr. Kenneth G. Behrens, Field Engineer, Transmission & Distribution

Department, Washington Gas Light Company

Mr. Richard G. Little, Junior Staff Engineer, American Gas

Association.

On May 2, a meeting was held at the Massey Building, Fairfax County

to brief the County officials concerned with the test and to outline the

assistance that NBS requested from the County in order to conduct the

tests. The following persons were present at the meeting.

Mr. Barry M. Sweedler, Chief, Pipeline Safety Division, NTSB

Capt. John Wahl, Fairfax County Police

Mr. George H. Alexander, Director, Fairfax County Fire/Rescue

Services

Mr. George H. Williams, Chief Plumbing Inspector, Fairfax County

Mr. Rudolf Schroeck, Assistant Chief Plumbing Inspector,

Fairfax County

Mr. Winford Atkins, Field Supervisor, Fairfax County Plumbing

Department

Mr. Jack Liedl, Director, Office of Capital Facilities, Department

of Public Works, Fairfax County

Mr. Joseph E. Sunday, Chief of Planning Programs, Program

Administration Division, Fairfax County

Mrs. Audrey Moore, Fairfax County Supervisor for the Annandale

District

Mr. Clinton W. Phillips, Engineer (462.01) NBS

Mr. Robert W. Beausoliel, Engineer (462.03) NBS

41
It was agreed during this meeting that Mr. George H. Alexander would

act as coordinator between the concerned Fairfax County functions and NBS.

Also, Mr. Alexander would make arrangements to notify the residents of

South Magdalene Court of the test. The written notice, which was subsequently prepared, read as follows:

NOTICE OF NATIONAL BUREAU OF STANDARDS FIELD TEST

FOR

THE NATIONAL TRANSPORTATION SAFETY BOARD

"The purpose of this notice is to provide you with detailed ‘information on the tests to be conducted by the National Bureau

of Standards (NBS) at South Magdalene Court, Annandale, Virginia

during the week of May 15, 1972.

Chief George H. Alexander, Director, Fire and Rescue Services,

Fairfax County, Virginia, has been designated coordinator of

this test for Fairfax County and for making arrangements with

the residents of South Magdalene Court to facilitate the work

of the NBS engineers.

As you may be aware, the National Transportation Safety Board

(NTSB) is responsible for investigating the gas explosion

which occurred at this location on March 24, 1972. NTSB has

requested that the NBS conduct a field test on the site to

determine (a) how the gas entered the homes, and (b) the path

or paths the gas followed from the leak to the homes. This test

may help us in improving the safety of such installation.

The test will be performed by introducing a harmless tracerair mixture into the ground at the position where the natural

fuel gas leak occurred. Hopefully, this harmless mixture will

be detected at various locations in the area by use of special

electronic indicators.

To do this, NBS personnel must have access to the following

homes (outside yards and basement areas primarily)

4907 South Magdalene Court

4908 South Magdalene Court

4909 South Magdalene Court

4910 South Magdalene Court

4911 South Magdalene Court

8601 Queen Elizabeth Boulevard.

42
"Residents may remain in their homes during the tests; however,

as an added precaution during the test, the Washington Gas Light

Company will turn off the gas supply to each of these houses and

will restore service in the evenings and at the end of the test.

The present schedule calls for preparations and test set up on

Monday, May 15, and the tracer air mixture tests on Tuesday and

Wednesday, May 16 and 17. Three large air compressors will be

required on these dates to inject the mixture into the ground.

The residents should be advised that these machines are quite

noisy.

You will be advised promptly if it becomes necessary to alter

this plan or schedule.

Again, thank you for your cooperation in this experiment.

Chief Alexander will be happy to provide any additional information you may require."

Mr. Liedl made arrangements for equipment and men to dig the test

trenches across the utility services at 4909 and 4911 and supplied drawings

showing sewer mains, plot plans, and grading at South Magdalene Court.

Mr. George H. Williams made arrangement for plumbing assistance as

required to locate and clean building drains and building sewers at

4909 and 4911.

Mr. John W. Peck, Engineer, Fairfax County Water Authority, supplied

drawings of the water service main for South Magdalene Court.

The injector pipe hole was hand dug by Washington Gas Light Company

(WGLC) employees under the supervision of Mr. Kenneth Behrens, WGLC

engineer. The one-inch-diameter by 24-inch deep test holes were drilled

in the South Magdalene Court right of way by WGLC employees. WGLC

supplied a drawing showing their distribution and service piping.

Mr. Jerome R. Blystone, Highway Research Engineer, Materials

Division, Federal Highway Administration, took soil samples at South

Magdalene Court.

43
Mr. John L. Stecklen, Representative, Washington Air Compressor

Rental Co. supplied the air compressor services during the NBS test.

The following NBS personnel participated during the test:

1. Dr. Jack Snell, 462.03, Chief of the Building Service Systems

Section, was responsible for overall test supervision.

2. Mr. Robert W. Beausoliel, Engineer, 462.03, was responsible for

overall test planning, test organization, supervision of activities during the test, reduction of test data, and the final report.

3. Mr. Clinton W. Phillips, Engineer, 462.01, was responsible for

development of the tracer techniques, air flow measurement in

the test trench at 4909, data reduction, and the final report.

4. Dr. Jim Shaver, Mr. Robert G. Mathey and Mr. Tom Reichard , engineers,

461.01, were responsible for injection tube bedding and road lift

monitoring.

5. Mr. Jim Melvin, engineer, 213.06, was responsible for air flow

measurement at the injection setup.

6. Mr. Raymond J. Mele, Visual Information Specialist, and Mr. Franklin

K. Mackley, Engineering Draftsman, 463.03, were responsible for

the photographs taken during the test.

7. The following technicians served to install and operate the test

equipment:

a. Mr. Julius T. Cohen, 462.03

b. Mr. John W. Grimes, 462.01

c. Mr. Lymus Payton, 461.01

d. Mr. Boyd L. Shoemaker, 462.01

8. The piping systems were fabricated and assembled by:

Mr. Joseph Clem, pipefitter, 126.07

Mr. Thomas S. Fisher, pipefitter, 126.03

The number shown after each name indicates NBS Division and Section.

That is:

44
OFFICE OF THE ASSOCIATE DIRECTOR FOR ADMINISTRATION (120.00)

126 Plant Division

03 Piping Shop

INSTITUTE FOR BASIC STANDARDS (200.00)

213 Mechanics Division

06 Fluid Meters Section

INSTITUTE FOR APPLIED TECHNOLOGY (400.00)

Center for Building Technology (460.00)

461 Structures, Materials & Life Safety Division

01 Structures Section

462 Building Environment Division

01 Thermal Engineering Systems Section

02 Building Service Systems Section

45
Appendix 7.2 - List of Drawings Furnished by Fairfax County

1. Plan and Profile, MAGDALENE COURT, Section 5, Canterbury Woods,

Falls Church Magisterial District, Fairfax County, Virginia.

Drawihg by Greenhorne, O' Mara, Dewberry and Nealon, Civil Engineers,

Land Surveyors, Arlington, Virginia. (Drawing Sheet 6 of 8) . This

drawing shows views of the sanitary and storm sewer system including

the water mains.

2. Plan and Profile drawing with the same title as in (1) above, and

sheet 6 of 8 also. The drawing was made by the same company.

3. Plan and profile QUEEN ELIZABETH DRIVE, 10F2, Section 5, Canterbury

Woods, Falls Church Magisterial District, Fairfax County, Virginia

(drawing sheet 3 of 8). Similar to drawing mentioned in (1) above.

The drawing was made by the same company.

4. DRAINAGE PLAN, Section 5, Canterbury Woods, Falls Church Magisterial

District, Fairfax County, Virginia (sheet 2 of 8) . This drawing

shows land contours before and after construction.

5. Drawing titled FAIRFAX shows the location of building lots by number

and street.

46
Appendix 7.3 - Federal Highway Administration's Description of

Soil and Aggregate Materials at the Canterbury Woods Subdivision

47
June 20, 197?

Description of Soil and Aggregate Materials at the

Canterbury Woods Subdivision

Fairfax County, Virginia

By Jerome R. Blystone, Highway Research Engineer

Materials Division, Federal Highway Administration

Profile of the waterpipe and sewage trench in front of Building 4909

0.0 to 0.4 ft. - Fine soil with some coarse angular fragments. (S. No. 47344)

0.4 to 5«8 ft. - Coarse angular rock fragments. Loosely placed as backfill

Had large continuous voids. Extremely porous. (S. No. 47340)

9.8 to 6.8 ft. - Fine soil with some coarse angular fragments. (S. No. 47343)

Profile of the gas line trench front of Northeast Corner of Building 4909

0.0 to 2.4 ft. - Mixture of fine soil and angular rock fragments (S. No. 4?34l)

Aggregate Material Around the Gas Pipe front of Building No. 4911

2.0 to 3»0 ft. - Mixture of coarse angular rock fragments and fine soil.

Was loosely placed and contained large continuous voids.

(S. No. 47342)

Back fill against side wall of 4907 Magdolene Court, and under parking slab

Coarse angular rock fragments with large voids. This material was not

sampled.

Backfill around water pipe in front of front wall of 4911 Magdalene Court

Coarse angular rock fragments loosely placed with large continuous voids.

(S. No. 47345)

48
Data from shallow drill holes

Hole No. Location Depth,

ft.

Description

of Material

1 Front of U908

Magdalene Court

0.0 to 2.0

(stopped by rocks)

Mixture of fine soil

and coarse angular

fragments of micaceous

schist (not sampled)

2 N. end of gas

line trench

4909 Magdalene

Court

0.0 to 1.5 Mixture of soil and

angular particles of

micaceous schist.

(S. No. 47346)

3 Near gas test

hole 18

0.0 to 0.6 Fine soil and coarse angular particles of

micaceous schist

(not sampled)

0.6 to 2.2 Fine soil - some coarse angular particles of

micaceous schist.

(S. No. 47347)

2.2 to 2.8 Coarse angular particles

of micaceous schist.

Some soil. (not sampled)

4 Between gas test

holes 10 and 11

0.0 to 0.7 Mixture of fine soil ana some coarse angular

particles. (not sampled)

0.7 to 4.0 Red brown clayey silt,

dense. (S. No. 47340)

5 Near gas test

hole 2 0.0 to 1.5 Mixture of fine soil and coarse angular rock fragm

(S. No. 47349)

49
FORM P R -? 0 ? IRE V. 8-65) U. S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINI STRATION

REPORT ON SAMPLES OF and_Soil _ Aggregate .Mixtures.

llATK

June 19, 19??

State Virgi nia

Date sampled

May 19 , 1972

Sampled ptiom

Project

-Gas Explosion .Site, . Canterbury_Woods—Subdi vision

Received May-19, 1 972.

Da^Ai j. j_ jl -LiJ water pj.pt: ana gas ±

Tested for use in Identification of materials

me. tnenenen

Submitted by J. R. Rlystone

IDENTIFICATION

B. P. R. Report No

Field No - - ySociuok xnu&radacuhtocL oc ati on

XSlKMXiOX )OX depth (below surface)

Soil description

-S.... 473.4.Q. .S. 4.73.41. S...47342. .S....42343

u

l.o* to U.o'

u. , 3L : 2,0\_.io 3.0'

;/—

I

—^^CLASSIFICATION TEST RESULTS

-7g —- — - -mo—

ii

Mechanical analysis: d,

Percentage passing— 3

62

IDO l

-34 9Z 54

1-inch sieve 23 ....80 .49- 100...

$4 -inch sieve 19 74 ..45 93..

%-\nrh sieve .14 63 38 97

4 sieve (4 7 mm.) 12 58 33 96

\T n 7 0 sieve (2.0 mm.) 10 .54 - - 29 . 9:

i Nn 40 sieve (0.42 mm.) 7 5.Q 23 88

fsln 00 sipve (0 2 fS mm.) —

No. 200 sieve (0.074mm.)- .. 5 33 l"6 58

Percentage smaller than

0 . 0 .3 0 mm : 4 .29 14 51

0.020 mm 3 18 10 lc

0.005 mm 2 10 5 20

0 002 mm 1 7 4 11

0 . 001 mm i 6 4 10

Liquid limit (LL) 32 . 32 30 38 Lie Plasticity index (PI) - . -5- 6 6 7 Pla

.

Classification 1 C!a$ Remarks; Front of house - 4909 Magda].ene Court. fej| 2/ Front of N. E. corner of house - 4909 Magdalene Court.

3/ Front of house - 4911 Magdalene Court.

* V/.QQ.dxoH.. J.-.-.Halst eadj. _ .Chief* . .Ma Divide

U *.r DMM.nr nE.Dn s 50 Per — .1
torm PR-202

•REV. 8.051 U, S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

REPORT ON SAMPLES OF .Soil and Sol 1 Aggregate Mixtur e

s

JMte

June 19, 1972

Stats Virginia

Date sampled

May 19 and ^une 7, 1972

Project

Gas_JExplosion Site, Canterbury Woods Subdivision

I RECEIVED

j May 19 and June 7, 1972

Sampled prom Backfill in water pipe and gas line t renches

Tested for use in Identification of materials

Submitted bt J. R. Blystone

IDENTIFICATION

JL P. R. Report No. . S 47344 3T4T345

Field No. — —

aoxisMXKixSMxasKaxLQ cation

.

. 1/.. ... t

T

£&H’»tf8iKKi>Cdep:h (below, surface)

.

Soil description

...Q,.QA..1q_.Q,4 , __.

i©0 :

Mechanical analysis: If" Percentage passing—

u

2-inch sieve A... 1%-inch sieve 1-inch sieve -

%-inch sieve %-inch sieve... No. 4 sieve (4.7 mm.)

No. 10 sieve (2.0 mm.).... No. 40 sieve (0.42 mm.) ... No. 60 sieve (0.25 mm.)... No. 200 sieve (0.074 mm.)

Percentage smaller than

0.050 mm

0.020 mm

0.005 mm

0.002 mm

Q^DOl.mm.

CLASSIFICATION T,IJST RESULTS

=^rti

-1GQ.

...97..

...96.. ...9k.

...9.?..

...6.8..

...6.1

51.

.4-5-

- 3-3-

.16..

. 1-4..

. 11.

1

4

27

17

. 1. ” a

6

"

. 1. 4

2

Liquid limit (LL)

Plasticity index (PI).

.3k..

....6.. .IQ.

..J..

Classification If-MARKs pyont of house - 4909 Magdalene Court.

2/ Sample from area immediately above water pipe - front wall of building

No. 4911. W.O.C.d.rQw _J ...Hals t cad , Chi e f . Mate r i c_]_s Division

Per

51
FORM PR-202

(REV. 6-08) U. S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

REPORT ON SAMPLES OF ..and Soil

.

e.. f:' i.x.t ur. e. s.

State VirginiaProj ect Gas Explosion Site, Canterbury Woods Subdivision

Daik sampled

June 7, 1972

Received June 7, 1972

Sampled from " ' ' Auger holes

Tested For use in Submitted dy Identification of materials J- R. Blystone

IDENTIFICATION

B. P R Report No. __ S 473L6 S...4.73.4.7. .... S.. .4.73.48 ....S..47349

Field No mm

vr* (vi Y/tovAcvsi nMfdv nh Location iZ Iz u 4/

Elevation or depth (below surface). 0.0’ to 2.0’ 0.5' to 2.0’ 0-7’ to 4.0’ 0.0’ to l.V

CLASSIFICATION TEST RESULTS

Mechanical analysis: -5 " Percentage passing— b 100

89

100

99..

1 i^-inrh sieve 89..

1 -inrh sieve _ .. 69 94

% -in rh sieve ...; 62 90 100 ICO

4s 77 .....98

.

91

No 4 sieve (4.7 mm.) 68 .... . 93 Qc; Nn If) sieve ( 2.0 mm.) .59 91 80

Nn. 40 sipve (0.42 mm.) 21 5.3.... 83 74

No. f!0 sieve (0 25 mm.) __

Nn. 200 sieve (0.074mm.). 16 3.8.... 74 52

Percentage smaller than

!l. 3.2. 68

0 020 mm .7. 21 55 83

0 005 mm .... 4 12 35 22

0 002 mm : I 9 24 in

2 9 20 14

10. 31 37 ) (

Plasticity index (PI) 5. 9 13 q

| Classification 1 Remarks: ±J North end of gas line trench, L909 Magdalene Court

2/ Near gas test hole l8

3/ Between test holes 10 and 11

4/ Near gas test hole 2

1 iQCOMu.nr o<i tifi.Dce 52
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