GEOLOGICAL SURVEY CIRCULAR 747

Environmental Geology, 

Allegheny County and Vicinity, 

Pennsylvania Description of a 

Program and its Results

Prepared in cooperation with The 

Appalachian Regional Commission
Environmental Geology, 

Allegheny County and Vicinity, 

Pennsylvania Description of a 

Program and its Results

By Reginald P. Briggs

GEOLOGICAL SURVEY CIRCULAR 747

Prepared in cooperation with The 

Appalachian Regional Commission

Summary description of geologic 

and hydrologic studies

1977
United States Department of the Interior

CECIL D. ANDRUS, Secretary

Geological Survey

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Briggs, Reginald Peter, 1929-

Environmental geology, Allegheny County and vicinity, Pennsylvania

(Geological Survey circular; 747)

Supt. of Docs, no.: I 19.4/2:747

1. Landslides-Pennsylvania-AHegheny Co. 2. Subsidences (Earth movements)--

Pennsylvania-Allegheny Co. 3. Land use-Pennsylvania--AHegheny Co.

I. Appalachian Regional Commission. II. Title. III. Series: United States.

Geological Survey. Circular; 747. 

QE75.C5 no. 747 [QE599.U5] 557.3 08s [551.3 5] 76-608388

Free on application to Branch of Distribution, U.S. Geological Survey 

1200 South Eads Street, Arlington, Va. 22202
CONTENTS

Page

Abstract _____________________________________________ 1

The setting _________________________________________________________ 2

Purpose and scope of this report ______________.________________ _ 4

List of final reports _________________.________________________ 4

Open-file reports _____________________________________________________________ 5

Aerial photographs _ ___ ___ _______________________________________ 5

The U.S. Geological Survey-Appalachian Regional Commission interagency agreement _ 5 

Other participants in The Appalachian Regional Commission's land-use and physical resource analysis program _________________________________________________________________ 8

Acknowledgments _______________________________________________________________ 8

Limits of applications of USGS-LUPRA reports ___._______________________________ 9

Designed product audiences ______________.______________________ 9

Base maps ____________________________________________ 9

Geologic studies ______'____________._____________________ 10

Earth-disturbance inventory and analysis of susceptibility to landsliding ______ _ 10

Methodology _________________._______________________ 10

Reports ___________________________.____________________________________ 11

Applications of reports __________________________________________________ 13

Maps showing underground coal-mining activity that can relate to surface subsidence, Allegheny, Washington, and Westermoreland Counties, Pa _._________________ _ 13

Methodology ____________________________________________ 13

Reports r ^ _ ____ _ __________________-_______________J _________________________ __ 13

Application of maps _____________ _______________________ 15

Integration of results of the geologic studies with existing data and summary of geologic and hydrogeologic results _________________________________________ 15

Methodology ______________._______________________ 15

Reports _____________________________________________________________ 16

Applications of reports ________________________ ____________________________ 19

Hydrogeologic studies ________________.______ __________________ 20

Reconnaissance appraisal of the role of shallow ground water in mining and slope-stability problems, 

incuding problems associated with periods of intense precipitation such as accompanied tropical

storm "Agnes" in June 1972, Allegheny County, Pa ___________________________ 20

Methodology _____________________._____________________________ 20

Reports __..________________._______________________ 20

Applications of reports ____________________________________ 21

Summary of results and findings _____________._______________________ 21

Landsliding _____________________._______________________ 21

Flooding _____________________._________________________ 23

Mine subsidence ________________,_________________________ 23

Other processes and problems ___________._______________________ 24

Evaluation of methodologies ____________._______________________*_ 24

Earth-disturbance inventory ______,_____.__________________________ 24

Maps showing underground coal-mining activity that can relate to surface subsidence _________ 25

Integration of results of the geologic studies ____._________________________ 25

Reconnaissance appraisal of the role of shallow ground water in mining and slope-stability problems._ 25

ILLUSTRATIONS

Page

FIGURE 1. County-outline map of Pennsylvania locating Allegheny, Washington, and Westmoreland

Counties _____________________________________ 2

2. Area urbanized, 1970, Allegheny County, Pa _____________________________ .3

» 

III
Page

FIGURE 3. Index to TMs-minute quadrangle maps, Allegheny County, Pa 6

4. Map of parts of Pennsylvania, West Virginia, Maryland, and adjacent States showing areas

covered by topographic, slope, and land-use work elements 7

5. Map of susceptibility to landsliding in Allegheny County, Pa ___ 12

6. Map of Allegheny, Washington, and Westmoreland Counties, Pa., showing Pittsburgh coal

bed mining activity and mine-subsidence incidents ___ ____ _______ _ __ 14

7. Map of Allegheny, Washington, and Westmoreland Counties, Pa., showing Upper Freeport

coal bed mining activity and mine-subsidence incidents __ _ _ 15

8. Map of Allegheny, Washington, and Westmoreland Counties, Pa., showing areas correlating

with recorded subsidence incidents ______________________ 16

9. Map of flood-prone areas, Allegheny County, Pa _.__________________________ 17

10. Map of underground coal mining in Allegheny County, Pa _________________ 18

11. Map of Allegheny County showing areas that can be affected by flooding, landsliding, and

undermining _______________________________________________ 19

TABLE

Page

TABLE 1. Potential applications of products _______ _ ____ ___ _ _ __ 22

IV
Environmental Geology,

Allegheny County and Vicinity, PennsylvaniaDescription of a Program and its Results

By REGINALD P. BR1GGS

ABSTRACT

Past land-use practices, including mining, in Allegheny County, Pa., have resulted in three principal environmental problems, exclusive of air and water contamination. They are flooding, landsliding, and subsidence over underground mines. In 1973, information 

was most complete relative to flooding and least complete relative to landsliding.

Accordingly, in July 1973, the U.S. Geological Survey (USGS) and The Appalachian Regional Commission 

(ARC) entered into an agreement by which the USGS 

undertook studies chiefly aimed at increasing knowledge 

of landsliding and mine subsidence relative to land 

use, but having other ramifications as well, as part of 

a larger ARC "Land-use and physical-resource analysis" 

(LUPRA) program. The chief geographic focus was 

Allegheny County, but adjacent areas were included in 

some investigations.

Resulting products, exclusive of this report, are:

1. Forty-three provisional maps of landslide distribution and susceptibility and of land modified by man 

in Allegheny County, 1:24,000 scale, 7%-minute 

quadrangle format, released to open files.

2. Four USGS Miscellaneous Field Studies (MF) maps 

of Allegheny County showing (a) bedrock, MF685A; (b) susceptibility to landsliding, MF-685B; 

(c) coal-mining features, MF-685C; and (d) 

zones that can be affected by flooding, landsliding 

and undermining, MF-685D; all at the scale of 

1:50,000.

3. Two MF maps showing coal-mining activity and related information and sites of recorded mine-subsidence events, and one MF map classifying land 

surface by relative potentiality of mine subsidence, 

in Allegheny, Washington, and Westmoreland 

Counties, Pa., at a scale of 1:125,000 MF-693A 

through MF-693C.

4. A companion report to the Allegheny County map 

of susceptibility to landsliding USGS Circular 

728.

5. Five MF maps, largely in chart form, describing interaction of the shallow ground-water regime with 

mining-related problems, landsliding, heavy storm 

precipitation, and other features and processes,

largely in Allegheny County MF-641A through 

MF-641E.

Map products are directly applicable to general 

classification of land for susceptibility to landsliding and 

mine subsidence and, to a lesser extent, flooding and 

engineering characteristics. The hydrogeologic charts 

enable greater understanding of environmental effects of 

ground water. All products are guides to expected conditions, but none are substitutes for detailed investigations of specific sites by competent technical personnel 

on the ground.

Specific results and findings are:

1. Knowledge of susceptibility to landsliding in Allegheny County now is adequate for application to 

countywide land-use planning.

2. About 110 mi2 (285 kma), or 15 percent, of the 

county has some significant degree of susceptibility 

to landsliding.

3. Although a general classification of land in Allegheny, Washington, and Westmoreland Counties 

relative to mine-subsidence incidents was prepared, 

data are wholly inadequate for even moderately 

precise prediction of subsidence events over previously mined-out areas; the accumulation of adequate data might not repay the effort in terms of 

damage prevention.

4. Commonwealth-of-Pennsylvania regulations have 

been very successful in limiting mine-subsidence 

damage over areas mined after 1966.

5. Undermining and consequent subsidence may have 

affected the ground-water regime more widely 

than heretofore believed.

Except for the earth-disturbance inventory that resulted in the maps of susceptibility to landsliding and 

man-modified land, methods used in the studies largely 

were conventional. The inventory and ensuing analysis 

combined aerial photographic interpretation with field 

work and incorporation of existing data. The method 

worked very well for the purposes of defining 'distribution of landslides and areas having different susceptibilities to landsliding. However, if susceptibility to landr 

sliding alone had been the goal, this could have been 

determined adequately by using photographs at smaller 

scales and appreciably less expenditure of effort per 

unit of ground area.
THE SETTING

Allegheny County (fig. 1), centered around 

Pittsburgh, Pa., has become over the last two 

centuries one of the important industrial centers of the United States, largely because of 

an original abundance of environmental resources : rivers and streams for transportation 

and water supply, timber for construction material, fuel and charcoal for the early iron 

furnaces, iron ore and limestone for the iron 

and steel industry, coal for fuel and coking, 

oil and gas, and others. These resources 

strongly counterbalanced the unfavorable configuration of the land surface, which is characterized by streams flowing in narrow steepsided valleys at levels commonly 300 feet and 

locally more than 600 feet below intervening 

ridges, each ridge about the same height as 

its neighbor. In the early days of development, 

accessible flat-lying land therefore was limited 

to narrow flood plains, and these soon largely 

were preempted by industry for access to water 

power, water supply, and water transportation,

and by railroads for access to industry and because of grade requirements. Residential and, to 

some extent, commercial development thus was 

forced to occupy adjacent slopes. This restricted condition prevailed until about 1900, 

but thereafter, development also spread along 

ridge crests, largely because of the trolley and 

the automobile which made the uplands generally and economically accessible.

Allegheny County today (1975) retains the 

impress of this topographically controlled development, for the majority of the county's 

1,600,000 people still live and work in congested 

valleys or on their slopes. Ridge-top areas, 

however, also are widely developed, largely for 

low-density residential uses, particularly in the 

east and south. By U.S. Bureau of Census definition, about 430 mi2 (1,114 km2 ) (60 percent) 

of the county's 728 mi2 (1,886 km2 ) were considered urbanized in 1970 (fig. 2).

Of the original resources, rivers and streams 

remain, although modified extensively by locks, 

dams, and other works and affected by urban

50 i

100 MILES 

I

50 100 150 KILOMETERS

FIGURE 1. County-outline map of Pennsylvania: Allegheny County is shown in gray, Washington County is indicated by horizontal lines, and Westmoreland County by vertical lines.
80°00'

10 20 MILES

u 10 20 30 KILOMETERS X.__-^*

FIGURE 2.-Area urbanized in 1970, Allegheny County, Pa. Adapted from U.S. Department of Commerce,'

Bureau of Census.

and industrial contamination. Timber as an 

economic resource has disappeared from the 

county, although the lumber industry remains 

active elsewhere in western Pennsylvania. 

Local iron ore long has been supplanted in the 

area's iron and steel industry chiefly by ore 

from the Lake Superior region, and most limestone now is brought in by river barges. Coal 

has been mined out in much of the county, 

mostly underground but also by surface mining, 

although significant coal production still can be 

expected for some years, and coal in adjacent 

areas probably will be sufficient for power and 

industrial needs for many decades. Western 

Pennsylvania was the birthplace of the oil and 

gas industry, but production has not met local 

requirements for many years.

The legacies of two centuries of development 

are many. On the positive side is a varied, vital 

society, relatively stable in population, having 

established institutions and a broad economic 

base. Negative aspects include environmental 

problems. The consensus of the scientific and 

technical community of the region is that the 

principal problems of the physical envire:nment, exclusive of urban and industrial contamination of air and water, are flooding, landsliding, and "mine subsidence," that is, surface 

subsidence due to underground mining. Other 

problems are mine-water discharge, effects of 

surface coal mining, foundation conditions, 

water supply, waste disposal, shortages of construction aggregates and other resources, and
redistribution of earth materials during development.

PURPOSE AND SCOPE OF THIS REPORT

In planning the present series of studies, 

two basic questions, therefore, were raised. 

What areas of geologic and hydrologic knowledge were most needed to address the principal 

problems perceived? Which of these areas of 

deficient knowledge could be improved in a relatively short time, considering available manpower and support?

In early 1973, answers to the first question 

were: knowledge of flooding and areas susceptible to flooding was generally well advanced, due chiefly to work by the U.S. Army 

Corps of Engineers, the National Weather 

Service, and existing USGS hydrologic programs; knowledge of susceptibility to countywide landsliding was wholly inadequate for application to improved land-use planning; knowledge applicable to amelioration of the problem 

of surface subsidence over underground coal 

mines was fairly complete in some aspects and 

in others lacking or inadequate.

In response to the second question, it was 

decided to concentrate on landsliding, and to 

conduct the studies so that they applied to other 

problems as well.

This report describes and summarizes results of the studies, now complete, and their 

geologic and hydrogeologic products that are 

elements of the larger USGS contribution to 

a broad Appalachian Regional Commission 

(ARC) "Land use and physical resource analysis" (LUPRA) program; product applications 

are also discussed. USGS reports described 

herein contribute to ongoing USGS research 

on environmental problems of the greater Pittsburgh region, an area that includes Allegheny 

County and five adjacent counties.

The principal geographic focus of the USGSLUPRA studies was Allegheny County, but 

three map products also include Washington 

and Westmoreland Counties (fig. 1), and results of other studies in Allegheny County also 

have broader application.

LIST OF FINAL REPORTS

The prime results of this effort have been 

published separately; the reader should treat 

these geologic and hydrogeologic products as

appendices to this report. Maps are symbolized 

in black and white, allowing users to emphasize distinctions important to their purposes 

by adding colors. When ordering reports, references must be made to USGS series and number, for example, Miscellaneous Field Studies 

Map MF-641B. They may be acquired at the 

indicated prices from:

Branch of Distribution 

U.S. Geological Survey 

1200 South Eads Street 

Arlington, Virginia 22202

Summary of the hydrogeologic regime as related to environmental characteristics, Allegheny County, Pennsylvania, by Seymour 

Subitzky. 1975. USGS Misc. Field Studies 

Map MF-641A. $0.75

Hydrogeologic framework and generalized shallow ground-water circulation system, Allegheny County, Pennsylvania, by Seymour 

Subitzky. 1975. USGS Misc. Field Studies 

Map MF-641B. $1.50.

Mining and related problems of the shallow 

hydrogeologic regime, Allegheny County,

, Pennsylvania, by Seymour Subitzky. 1975. 

USGS Misc. Field Studies Map MF-641C. 

$0.75

Heavy storm precipitation and related mass 

movement, Allegheny County, Pennsylvania, 

by Seymour Subitzky. 1975. USGS Misc. 

Field Studies Map MF-641D. $0.75

Some aspects of water quality as affected by 

land use in McLaughlin Run and Painters 

Run basins, Allegheny County, Pennsylvania, 

by Seymour Subitzky. 1975. USGS Misc. 

Field Studies Map MF-641E. $0.75

Maps of rock types in bedrock of Allegheny 

County, Pennsylvania, by W. R. Kohl and 

R. P. Briggs, 1975. 1:50,000 scale. USGS 

Misc. Field Studies Map MF-685A. $1.50

Map of susceptibility to landsliding, Allegheny 

County, Pennsylvania, by J. S. Pomeroy and 

W. E. Davies. 1975. 1:50,000 scale. USGS 

Misc. Field Studies Map MF-685B. $1.50

Map of coal-mining features, Allegheny 

County, Pennsylvania, by W. 'E. Davies, J. S. 

Pomeroy, and W. R. Kohl. 1976. 1:50,000 

scale. USGS Misc. Field Studies Map MF685C. $1.50

Map of zones where land use can be affected 

by landsliding, flooding, and undermining, 

Allegheny County, Pennsylvania, by R. P.
Briggs, and W. R. Kohl. 1975. 1:50,000 scale. 

USGS Misc. Field Studies Map MF-685D. 

$1.50

Map showing depth to the Pittsburgh coal be,d, 

mining activity and related surface subsidence, Allegheny, Washington, and Westmoreland Counties, Pennsylvania, by K. 0. 

Bushnell. 1975. 1:125,000 scale. USGS Misc. 

Field Studies Map MF-693A. $0.75

Maps showing depths to the Upper Freeport 

coal bed, mining activity, and related surface 

subsidence, and the Redstone coal bed mines, 

Allegheny, Washington, and Westmoreland 

Counties, Pennsylvania, by K.O. Bushnell and 

J. R. Peak. 1975. 1:125,000 scale. USGS 

Misc. Field Studies Map MF-693B. $0.75

Map showing areas that correlate with subsidence events due to underground mining of 

the Pittsburgh and Upper Freeport coal beds, 

Allegheny, Washington, and Westmoreland 

Counties, Pennsylvania, by K. 0. Bushnell. 

1975. 1:125,000 scale. USGS Misc. Field 

Studies Map MF-693C. $0.75

Landsliding in Allegheny County, Pennsylvania, by R. P. Briggs, W. E. Davies, and 

J. S. Pomeroy. 1975. USGS Circular 728. 

Free on application.

Environmental geology, Allegheny County and 

vicinity, Pennsylvania description of a program and its results by R. P. Briggs. 1977. 

USGS Circular 747 (the present report). 

Free on application.

OPEN-FILE REPORTS

In addition to published reports, 43 maps of 

landslide susceptibility and man-modified land 

have been released in open file. Although data 

from these maps are included in published 

maps MF-685B and MF-685C, the open-file 

maps constitute sources of somewhat more complete and detailed information chiefly owing to 

their larger scale, 1:24,000 (1 in. = 2,000 ft; 

1 cm = 240 m) as opposed to 1:50,000 (1 in.= 

4,170 ft; 1 cm = 500 m), the scale of the final 

Allegheny County maps.

The open-file maps are available for public 

inspection and copies may be purchased at cost 

of reproduction from:

Department of Works

County of Allegheny

County Office Building, 5th floor

Forbes Avenue and Ross St.

Pittsburgh, Pennsylvania

In addition, the open-file maps may be inspected at:

U.S. Geological Survey Library

National Center

12201 Sunrise Valley Drive

Reston, Virginia 22092 

The open-file landslide-susceptibility maps 

and land-modified-by-man maps include all of 

Allegheny County and immediately adjacent 

parts of neighboring counties. They were prepared on the 71/^-minute-quadrangle format 

and are listed below alphabetically by quadrangle. The columns on the right list the openfile serial numbers for maps of the subjects. 

Authorship is shown by initials: William E. 

Davies WED; John S. Pomeroy JSP. Locations are shown on the index to 71^-minute 

quadrangles (fig. 3).

AERIAL PHOTOGRAPHS

Aerial photographs were found to be of significant value in the earth-disturbance inventory. As an example of their resolution, outdoor tennis and basketball courts are readily 

identified and differentiated by their line patterns. Details concerning the photography obtained specifically for the inventory are: 

Project number (series) : GS-VDGY. 

Exposures and dates: 988 exposures made 

on April 14, 1973; 31 exposures made 

on May 6, 1973; 79 exposures made on 

December 3, 1973; total number of exposures required for stereoscopic coverage of Allegheny County and immediate 

vicinity 1,098.

Flight height above mean ground level: 

6,000 ft (1,830 m). Nominal scale of 

contact prints: 1:12,000 (1 in. = 1,000 

ft;lcm = 120m).

Film: Panchromatic black and white 

Information on acquiring series GS-VDGY 

photography is available from:

National Cartographic Information Center 

U.S. Geological Survey 

National Center 

Reston, Virginia 22092

THE U.S. GEOLOGICAL SURVEYAPPALACHIAN REGIONAL COMMISSION 

INTERAGENCY AGREEMENT

The USGS participation in the ARC-LUPRA 

program is based on an interagency agreement
FIGURE 3. Index to 7%-minuts quadrangle maps, Allegheny County, Pa.

Open-file numbers

7^-minute 

quadrangles

Landslide 

susceptibility 

map

Landmodifiedby-man

map

Aliquippa (part of) JSP __ 74-120

(both subjects on one map)

Ambridge JSP ________ 74-76 74-74 

Baden (part of) JSP ______ 74-121

(both subjects on one map)

Braddock WED _________ 74-273 74-285

Bridgeville (part of) WED __ 74-274 74-286

Canonsburg (part of) WED __ 74-275 74-287

Clinton (part of) JSP ____ 74-234

(both subjects on one map)

Curtisville (part of) WED __ 74-276 74-288

Donora (part of) WED ___ 74-277 74-289

Emsworth JSP _________ 74-75 74-73

Freeport (part of) WED __ 74-278 74-290

Glassport WED ________ 74-279 74-291

Glenshaw JSP _________ 74-118 74-119

Mars (part of) JSP ______ 74-114 74-115

McKeesport WED ______ 74-280 74-292

Monongahela (part of) WED- 74-281 74-293

Murrysville (part of) WED __ 74-282 74-294 

New Kensington East

(part of) WED ______ 74-283 74-265

New Kensington West WED _ 74-284 74-296

Oakdale JSP __________ 74-232 74-233

Pittsburgh East JSP _____ 74-229 74-231

Pittsburgh West-^JSP ____ 74-228 74-230

Valencia (part of) JSP ___ 74-116 74-117

(ARC contract No. 74-81) dated July 13,1973, 

aimed chiefly at improving management of

land resources in Allegheny County but also 

applicable to other areas in Pennsylvania and, 

to a lesser extent, West Virginia and Maryland. 

Work agreed upon was grouped into four discrete classes, as follows.

1. Geologic studies:

(a) Earth-disturbance inventory and ananlysis of susceptibility to landsliding Allegheny County, Pa.

(b) Maps shtfwing underground coalmining Activity that can relate to 

surface,, subsidence, Allegheny, 

Washiiigion, and Westmoreland 

Count&a^Pa.

(c) IntegratieW^ of results of the geologic 

studies ^ith existing data and 

summajSof geologic and hydrogeologie-'results (this report).

2. Hydrogeologic studies:

(a) Reconnaissance appraisal of the role 

of shallow groundwater in mining 

and slope-stability problems in 

Allegheny County, Pa., including 

problems associated with periods 

of intense precipitation such as accompanied tropical storm "Agnes" 

in June 1972.

3. Topographic studies:

(a) Topographic map of the Monongahela River basin, Pennsylvania, 

West Virginia, and Maryland (fig. 

4) ; 6 sheets, scale, 1:250,000.

(b) Satellite-image mosaic of the Monongahela River basin, Pennsylvania, 

West Virginia, and Maryland (fig. 

4); 1 sheet, scale, 1:250,000.

(c) Slope maps.

(i) Monongahela River basin, 

Pennsylvania, West Virginia, and Maryland (fig. 

4) ; 24 maps, 4 maps of 

each of 6 sheets necessary 

to cover the basin showing 

different slope zones, 

steeper and gentler than 

(1)8 percent, (2) 15 percent, (3) 25 percent, and 

(4) 361/2 percent [20 degrees], scale, 1:250,000. 

(ii) Allegheny County, Pa., 4- 

zone (gentler than 8 percent, 8 to 16 percent, 16
80°

Smtthport

MC KEAN j POTTER

- k '

50 100 150 MILES

0 50

I

100 150 200 KILOMETERS

FIGURE 4. Map of parts of Pennsylvania, West Virginia, Maryland, and adjacent States showing areas covered by ARC-LUPRA topographic, slope, and land-use work elements. The Monongahela River Basin is shown 

by northwest-southeast diagonal lines; the Greater Pittsburgh region by northeast-southwest diagonal lines; 

Allegheny County is outlined within Greater Pittsburgh region; Lycoming County is shown by horizontal lines.

to 25 percent, steeper than 

25 percent) slope maps of 

the 23 7i/^-minute quadrangles that include Allegheny County (figs. 3 and 

4), scale, 1:24,000.

(iii) Lycoming County, Pa. (fig. 

4); 2 sheet 5-zone (gentler than 8 percent, 8-12 

percent, 12-20 percent, 

20-36^ percent [20 degrees], and steeper than
36y2 percent) slope map, 

scale, 1:50,000. 

4. Land-use studies:

(a) Land-use maps

(i) Greater Pittsburgh region, 

Pennsylvania (fig. 4) ; 26 

black-and-white open-file 

sheets, scale, 1:50,000; and 

one all-inclusive multicolor 

sheet, scale, 1:125,000. 

(ii) Lycoming County, Pa. (fig. 

4) ; two multicolor sheets, 

scale, 1:50,000.

(b) Land-use-change map, 1969-73, Allegheny County, Pa. (fig. 4) ; four 

black-and-white open-file sheets, 

scale, 1:50,000.

Detailed description and discussion of topographic and land-use maps are beyond the 

scope of this report. Further information on 

these products is available from:

National Cartographic Information Center 

U.S. Geological Survey 

Reston, Virginia 22092 

and

The Appalachian Regional Commission 

1666 Connecticut Avenue, N.W. 

Washington, D.C. 20235

OTHER PARTICIPANTS IN THE

APPALACHIAN REGIONAL COMMISSION'S

LAND-USE AND PHYSICAL-RESOURCE

ANALYSIS PROGRAM

Department of Planning and Development, 

County of Allegheny (ACDPD). Contributions of the ACDPD include: Analysis of previous landslide history, experience, and costs; 

analysis of previous governmental action in 

controlling development of areas susceptible to 

landsliding and other physical hazards; analysis of existing ordinances and preparation of 

model land-use-control ordinances; education 

of the public concerning landsliding and other 

hazards; and encouragement of adoption of 

land-use-control ordinances by local jurisdictions.

Center for the Study of Environmental 

Policy, the Pennsylvania State University 

(PSEP). Until recently there has been available little systematized information on the 

perceptions of needs for geological data on the 

part of planners and decision makers in southwestern Pennsylvania. The PSEP work was 

designed to supply such information by a program of extensive interviews and mailed questionnaires, coupled with computer analysis of 

responses. The results are applicable to the 

ACDPD-LUPRA program as well as to the 

problem of effective dissemination of environmental information by the USGS and others. 

Study results were reported in detail to the 

ARC and have been briefed in a summary report titled: The Use of Geological Information 

in the Greater Pittsburgh Area (by Peter 

Wissel, Robert O'Connor, and Beverly Cigler, 

CSEP, PSU, January 1976, 23 p.)

LUPRA program management. David A. 

Maneval and Hugh B. Montgomery are coordinating the LUPRA program for the ARC. 

They have redelegated general oversight of the 

program to an advisory panel established for 

the purpose by the ARC and composed of residents of Allegheny County and vicinity. Jonathan A. Green, private consultant, Chairman; 

H. Alan Speak, Southwestern Pennsylvania Regional Planning Commission; Suzanne M. 

Broughton, Allegheny County League of 

Women Voters; Bambridge E. Peterson, Allegheny County Council of Governments; Harry 

A. Barnett, Allegheny County Conservation 

District; Harry F. Ferguson, U.S. Army Corps 

of Engineers; and David W. Craig, Attorney.

ACDPD and PSEP investigators reported directly to the ARC; information on their results may be obtained on application to the 

ARC. USGS, ACDPD, and PSEP personnel 

conferred periodically with the LUPRA advisory panel for advice and exchange of information.

ACKNOWLEDGMENTS

USGS-LUPRA efforts in this series of 

studies profited from advice and other assistance kindly given by many persons, notably 

William C. Morrison and others of ACDPD; 

Beverly Ann Cigler and Peter A. Wissel of 

PSEP; Donald R. Williams of the Pittsburgh 

Subdistrict Office, Water Resources Division, 

USGS; Samuel E. Cortis and Thomas B. Alexander of the Division of Mine Subsidence 

Regulation, Pennsylvania Department of Environmental Resources; William W. Beck, Jr. 

of A. W. Martin Associates, King-of-Prussia, 

Pa.; and members of the LUPRA advisory

8
panel. Most importantly, without the support 

and encouragement by Hugh B. Montgomery 

of the ARC during- planning and formulation 

stages, the studies would not have been possible.

LIMITS OF APPLICATION OF USGSLUPRA REPORTS

In following sections of this report, methods 

used to prepare reports are described and potential applications are discussed.

Reports contain three kinds of information:

(1) Maps generally applicable to classification 

of land relative to processes and problems, (2) 

tables and diagrams for better understanding 

of processes and for enhancement of map information, and (3) explanatory texts. Hydrogeologic reports here largely are tables and 

diagrams, containing map and text information. One g-eologic report, in addition to the 

present report, is in book form, but all others 

are maps, some accompanied by appreciable 

marginal information in texts, tables, diagrams, or subsidiary maps.

Maps are divided into separate zones or areas 

by lines and symbols, and map explanations 

and accompanying- marginal information describe attributes of these areas. The maps are 

intended as tools for planning-, at levels defined 

by the scales of the maps. Appreciable variation can be found within outlined areas, and 

boundaries between areas largely are gradational over tens and, locally, hundreds of feet. 

The information given for a particular symbolized area thus is a general statement of 

expected conditions and must not be taken as 

rigidly applicable to all localities within that 

symbolized area. The maps call attention to potential problems or likely attributes, but they 

must not be used as substitutes for detailed investigations of specific sites by competent technical personnel.

DESIGNED PRODUCT AUDIENCES

The USGS-LUPRA reports were designed 

chiefly for two potential user groups: (1) Persons concerned with problems of the environment but not having extensive technical training or background, such as interested private 

citizens and most of those responsible for making decisions affecting the public welfare and

(2) a technical audience, principally engineers

and engineering- geologists and hydrologists 

but including other technically-oriented persons, such as some planners, contractors, and 

developers. In the discussion of potential report applications, the orientation of reports 

toward the first group is described as "nontechnical" that toward the second group as 

"technical." However, there is a broad and not 

well-defined overlap between technical and nontechnical reports and groups, so a nontechnical 

person can likely get understandable information from a report that is chiefly technical. On 

the other hand, a technical reader may find a 

nontechnical report very useful. Some of the 

reports are expected to appeal to wider audiences, such as scientists, for background for more 

detailed work on specific aspects of the physical environment, and high-school and college 

educators.

BASE MAPS

Base maps provide a frame of reference that 

enables readers to locate data points and other 

localities on the ground by reference to common, readily recognizable features such as 

roads, streams, and hills.

The base maps used during investigations 

and for the provisional products of the earthdisturbance inventory were USGS quadrangle 

topographic maps of the T^-minute series at 

a scale of 1:24,000 (1 in. = 2,000 ft; 1 cm = 240 

m). They are identified in figure 3.

The base map for final Allegheny County reports was prepared by reducing- topographic 

maps of the TV^-minute series from a scale of 

1:24,000 to 1:50,000, followed by preparation 

of a controlled mosaic. Scale 1:50,000 (1 in.= 

4,170 ft; 1 cm = 500 m) was selected to conform with the scale of the new county-base-map 

series of the Pennsylvania Bureau of Topographic and Geologic Survey.

The base map for the three mining-related 

reports that include Allegheny, Washington, 

and Westmoreland Counties was adapted from 

the USGS Greater Pittsburgh region topographic map at 1:125,000 (1 in. = 2 mi; 1 cm = 

1,250 m or 1.25 km). This also is the regional 

scale used by the Southwestern Pennsylvania 

Regional Planning Commission.

A variety of map scales and base materials 

were used in reports of the hydrogeologic 

studies.
GEOLOGIC STUDIES

EARTH-DISTURBANCE INVENTORY AND 

ANALYSIS OF SUSCEPTIBILITY TO LANDSLIDING

METHODOLOGY

An earth-disturbance inventory presents, in 

map form, surface features of the earth that 

differ from or contrast with an interpretive 

view of the expression that the ground surface 

would have if only continuous and gradual 

geologic processes, such as stream erosion and 

sedimentation, were acting upon it. An earthdisturbance inventory thus includes three general categories of features:

1. Those disturbances that chiefly involve 

earth materials in their natural setting 

and that may or may not have been 

caused or influenced by human activity 

in Allegheny County chiefly landslide deposits from natural or man-modified 

slopes but also including features such as 

the surface expression of subsidence in 

areas that have been undermined.

2. Features that are the inadvertent effects of 

natural processes on earth materials that 

have been moved by man in Allegheny 

County chiefly landslides from fills and 

embankments but also including such features as the expression of excessive erosion of rearranged earth materials and 

resulting sedimentation.

3. Earth features that are the intended or unavoidable results of human activity examples : highway cuts and embankments, 

surface mines, mine dumps, slag heaps. 

This category approximates "disturbed 

ground" or "disturbed land" in common 

usage.

The inventory had two main steps: (1) interpretation of aerial photographs; (2) verification of findings in the field, largely by traversing the dense road network of the area, 

using off-the-road traverses as needed. Analysis of susceptibility to landsliding proceeded 

concurrently and involved the correlation of 

landslide distribution, as revealed by the inventory, with available geologic, geomorphic, and 

soil survey data.

The use of aerial photographs for mapping 

of surface features resulting from human 

activities is as old as aerial photography, but 

systematic interpretation of the phenomena of 

landsliding from aerial photography is relatively new. It was used extensively by USGS 

personnel during the San Francisco Bay region studies (SFBRS) in California and locally 

elsewhere.

The SFBRS landslide maps were made using 

existing aerial photographs, some older than 

10 years at the time of the studies and all 

taken for different purposes at a variety of 

nominal contract-print scales, rarely much 

larger than 1:24,000 (1 in. = 2,000 ft; 1 cm= 

240 m). Time available for field verification, or 

"ground truth," was minimal or, in some areas, 

lacking. Although this work was remarkably 

successful and the results were well received 

by potential users in the region, those who did 

the SFBRS mapping advised that better results 

could be obtained by using larger scale photography and by including an allowance of time 

for verification on the ground (Tor H. Nilsen, 

oral commun., 1972). This advice was accepted 

in planning the Allegheny County inventory. 

Moreover, the SFBRS photographic interpretation concentrated on landslides exclusively, but 

the scope of the Allegheny County inventory 

included man's surface effects, which are changing constantly. To show this, aerial photography as current as possible was planned.

Aerial photographs of Allegheny County 

were taken for the specific purpose of the 

study, largely in April, 1973, because photographs without the dense summer foliage were 

necessary. The nominal scale of contact prints 

of the photography is 1:12,000 (1 in. = 1,000 

ft;l cm=120 m); they are black and white.

Aerial-photographic interpretation by the investigators, W. E. Davies and J. S. Pomeroy, 

was completed by June 1974. Field verification 

was accomplished during sporadic one- or twoweek visits to Allegheny County. Investigations averaged about 3 weeks of interpretation 

and 1 week of field verification for each complete 71/£-minute quadrangle (about 57 mi2 ; 

148 km2 ), or 1 man-month per quadrangle.

Allegheny County includes about 728 mi2 

(1,886 km2 ) and is equivalent in area to about 

13 71/£-minute quadrangle maps. However, because county and quadrangle map boundaries 

do not coincide, 23 separate quadrangle maps 

are required for countywide coverage (fig. 4), 

and these quadrangles also cover appreciable 

parts of adjacent counties. Because of this 

overlap and because aerial-photographic coverage extended short distances beyond the Alle10
gheny County boundary, interpretation and 

verification was carried into small parts of the 

adjacent counties, with the result that a total 

of about 850 mi2 (2,200 km2 ) was inventoried.

REPORTS

Provisional maps are titled landslide-susceptibility and land-modified-by-man maps. 

They include all or almost all the area of 10 

quadrangles (only 4 completely within Allegheny County) and parts of 13 quadrangles. 

Separate landslide-susceptibility and landmodified-by-man maps were prepared for each 

of 20 full or partial quadrangles; both landslide-susceptibility and land-modified-by-man 

information were combined on 3 partial quadrangles. In total, there thus are 43 separate 

maps, each at the scale of 1:24,000; they are 

listed earlier in this report.

The open-file maps of landslide susceptibility 

show the following by map symbols and lines:

Recent landslides. Dominantly earth slumps 

and earth flows that are recorded historically or are characterized by fresh scars.

Debris slides. Landslides primarily of rock, 

soil, and vegetation debris in steep narrow 

valleys.

Prehistoric landslide deposits. Dominantly 

earth slumps and earth flows characterized 

by hummocky topography and slump 

benches.

Slopes with conspicuous soil creep. Clayey 

soils, generally less than 5 ft (1.5 m) thick, 

commonly underlain by weathered shale 

and characterized by shallow, slow, but distinct, downslope movement.

Outcrop areas of thick "red beds" and associated rocks. Weathered rock and related soil commonly result in soil creep and 

landsliding.

Relatively stable ground.

Steel slopes susceptible to rock fall. Natural and cut slopes and cliffs, 15 to more 

than 150 ft high, (4.6 m to 46 m) mainly 

thick-bedded sandstone and limestone, 

having layers 1 to more than 10 ft (0.3 m 

to 3 m) thick, that are highly fractured 

and locally undercut by weathering of interbedded subordinate flaggy sandy shale 

and silty and clayey shale;

Manmade fill. Heterogeneous soil and rock 

material.

Land modified-by-man maps show:

Surface (strip) mines, reclaimed and unreclaimed. Primarily coal but includes some 

developed for sandstone and limestone.

Areas in which surface patterns are indicative of mine subsidence.

Areas of active, controlled, and extinguished 

mine and coal bed fires. Generally confined to vicinity of outcrop of coal bed.

Refuse banks. Primarily coal waste, most 

burned to ash and clinkers (red dog).

Quarries and pits.

Slag dumps.

Urban development. Modification, primarily after 1969, includes removal of vegetation, removal and redistribution of topsoil, 

some excavation of bedrock, and placement of impervious streets and parking 

lots.

Predevelopment modification. Ultimate land 

use not identified during investigation.

Land modified for transportation. Modifications, primarily after 1969, include extensive deep excavations, redistribution of 

topsoil; and local removal of structures.

Earth and rock fill. Primarily at industrial, 

commercial, educational, and housing sites 

and along transportation routes.

Nearly vertical cuts and cliffs. Primarily 

cuts along highways and adjacent to commercial and industrial sites, highwalls in 

surface mines, and some natural cliffs.

Water impoundments. Primarily farm 

ponds, reservoirs, and settling basins.

Information and insights resulting from the 

earth-disturbance inventory and analysis of 

susceptibility to landsliding contributed directly to four final reports of the USGSLUPRA program. Two are described below; 

the other two, maps of mining features and 

zones that can be affected by landsliding, flooding, and undermining, are described in the later 

section concerning integration of results of the, 

geologic studies. This separation, though.somewhat artificial, has a logic because the latter 

maps also contain appreciable information that 

did not result from the inventory and analysis.

Map of susceptibility to landsliding, Allegheny County, Pennsylvania, by John S. Pomeroy and William E. Davies, 1975. U.S. Geological Survey Miscellaneous Field Studies Map 

MF-685B. Scale, 1:50,000. Essentially all features shown on the provisional landslide sus11
ceptibility maps were transferred to the Allegheny County base map, within limitations 

imposed by scale, except that features outside 

the county boundaries were not transferred. 

Shown on this black-and-white map as highly 

sensitive to disturbance by man are areas 

mapped as recent landslides, prehistoric landslides, and slopes having three categories of 

susceptibility to landsliding. Also shown are 

steep slopes prone to rockfall and manmade

fills that may be subject to failure. More than 

2,000 recent and prehistoric landslide areas 

were mapped; slopes that may be susceptible to 

significant landsliding underlie about 110 mi2 

(285 km2 ) or 15 percent of the county. Marginal sketches illustrate types of landslides and 

conditions typical of the area. A small-scale 

geologic map, columnar section, and explanatory text are included. Figure 5 is a reduced, 

simplified version of this map.

80°

40"30'

FIGURE 5. Generalized map -of susceptibility to landsliding in Allegheny County, Pa. Areas with some degree of 

susceptibility are shown by dotted pattern; area with variable susceptibility lies inside dashed and toothed 

line; areas with little susceptibility are unpatterned. Dashed lines show channels of Ohio, Allegheny, and 

Monongahela Rivers.

12
Landsliding in Allegheny County, Pennsylvania, by Reginald P. Briggs, William E. 

Davies, and John S. Pomeroy. 1975. U.S. Geological Survey Circular 728. Owing to the 

limited space for marginal information on the 

map of susceptibility to landsliding (MF685B), much information applicable to that 

map was assembled into this companion report. 

A small amount of information is repeated so 

that the reader will find the report useful if 

he does not at the same time have the map for 

reference. The report contains nontechnical advice to buyer, builder, and homeowner; describes actions to be avoided on susceptible 

slopes; describes geologic setting, geologic factors affecting susceptibility to landsliding, and 

selected landslide localities; and includes a 

glossary, photographs, and other illustrations.

APPLICATIONS OF REPORTS

The l:24,000-scale provisional landslide-susceptibility maps and the resulting 1:50,000- 

scale map of susceptibility to landsliding (MF685B) are directly applicable to the general 

classification of land on both nontechnical an4 

technical levels. Nontechnical users can see 

which parts of the county are likely to be susceptible to landsliding by coloring as one group 

the map units bracketed as "highly sensitive to 

disturbance by man," whereas technical users 

can interpret the map-unit descriptions to find 

general degrees of susceptibility for their purposes. Because susceptibility to landsliding is a 

function of instability of materials on slopes, 

these maps also have direct bearing on foundation and earthworking conditions. The 1:50,000 

scale map is more applicable to countywide 

planning owing to the format, and it has explanatory information that is oriented particularly toward the nontechnical reader. On the 

other hand, there is a slight loss of detail and 

content due to the reduced scale.

The companion report on landsliding (Circular 728) largely is intended for nontechnical 

users, but technical users may find that the 

discussions of geologic factors and setting are 

useful summaries and that the brief case histories of the selected landslide localities are 

helpful relative to other sites in the area.

The open-file maps of land-modified-by-man 

are basically nontechnical in nature, depicting 

changes in the land surface, and thus are directly applicable to land-use classification, including surface mining and earthworking activity. Abandoned surface mines are also 

important sites for current and potential disposal of solid waste, and slag dumps and coalmine-irefuse piles are current and potential 

sources of construction aggregates.

MAPS SHOWING UNDERGROUND COAL-MINING

ACTIVITY THAT CAN RELATE TO SURFACE

SUBSIDENCE, ALLEGHENY, WASHINGTON, AND

WESTMORELAND COUNTIES, PENNSYLVANIA

METHODOLOGY

The first two of the three black-and-white 

maps (MF-693A and MF-693B) described below were compiled largely by conventional 

methods from existing map information, but 

the second required appreciable effort in the 

search for data, and both required development of new information on overburden thickness by comparing topography and geologic 

structure. In addition, the principal investigator, Kent Bushnell, was able to expand the 

content of the maps to include appreciable data 

on subsidence events through cooperation of 

William W. Beck, Jr. (A. W. Martin Associates, King-of-Prussia, Pa.) who had collected 

this information in the course of work on another project sponsored by the ARC. The third 

map (MF-693C) resulted from comparison of 

the first two and from consideration of geologic 

and mining factors. Tables accompanying the 

maps were prepared in part by comparing the 

incidence of subsidence events to housing-density information.

REPORTS

Although the USGS-ARC reports were intended to treat only parts of Washington and 

Westmoreland Counties, it was possible to expand the geographic focus to include these entire counties (fig. 1). The reports are:

Map showing depth to the Pittsburgh coal 

bed, mining activity and related surface subsidence, Allegheny, Washington, and Westmoreland Counties, Pennsylvania, by Kent 

Bushnell. 1975. U.S. Geological Survey Miscellaneous Field Studies Map MF-693A. 

Scale 1:125,000. The map shows the extent of 

the coal bed and subdivides it on the basis of 

three periods of completed and potential mining (mined out before April 27, 1966; mined 

out between April 27, 1966 and June 30, 1974; 

potentially mineable after June 30, 1974) and

13
three categories of overburden thickness 0 to 

200 ft (0 to 61 m); 200 to 500 ft (61 to 152 

m); greater than 500 ft (152 m). Locations of 

recorded damaging subsidence events are 

shown, and a table relates these locations to 

mining periods and thickness of overburden. 

Factors bearing on mining-induced surface 

subsidence and the incidence of subsidence are 

discussed in the accompanying text. To give 

the reader a view of the area potentially subject to subsidence from Pittsburgh coal-bed 

mining, the part of the three counties undermined for the Pittsburgh coal bed prior to June 

30, 1974, is shown in reduced form in figure 6. 

Map showing depth to the Upper Freeport 

coal bed, mining activity and related surface 

subsidence, and the Bedstone coal bed mines, 

Allegheny, Washington, and Westmoreland 

Counties, Pennsylvania, by Kent Bushnell and 

John R. Peak, 1975. U.S. Geological Survey 

Miscellaneous Field Studies Map MF-693B. 

Scale 1:125,000. This map shows and discusses 

the same subjects relative to the Upper Freeport coal bed as does the above map relative

to the Pittsburgh coal bed. In addition, it 

shows the locations of some mines in the less 

important Redstone coal bed. Figure 7 shows 

at a reduced scale the extent of Upper FVeeport undermining as of June 30, 1974.

Map showing areas that correlate with subsidence events due to underground mining of 

the Pittsburgh and Upper Freeport coal beds, 

Allegheny, Washington, and Westmoreland 

Counties, Pennsylvania, by Kent Bushnell. 

1975. U.S. Geological Survey Miscellaneous 

Field Studies Map MF-693C. Scale 1:125,000. 

The three-dimensional map data of the above 

two maps (MF-693A and MF-693B) were 

analyzed and combined to yield this two-dimensional classification of the land surface. 

Four basic categories include: (1) areas that 

correlate with high numbers; (2) moderate 

numbers; (3) minor numbers of damaging 

subsidence events due to present or potential 

undermining; (4) areas in which there is no 

foreseesable subsidence hazard from underground mining of the Pittsburgh and Upper 

Freeport coal beds. Figure 8 is a simplified re40°30V

40°

30 MILES

40 KILOMETERS

FIGURE 6. Generalized map of Allegheny, Washington, and Westmoreland Counties, Pa., showing the Pittsburgh 

coal bed mined out before June 30, 1974 (dotted pattern), the Pittsburgh coal bed probably mineable after 

June 30, 1974 (horizontal lines), the recorded damaging surface-subsidence incidents over mined-out areas of 

the Pittsburgh coal bed (marked by X), and areas where the Pittsburgh coal bed is absent (no pattern), i

14
\

\

\

40' 30 MILES

L^/*" 0 10 20 30 40 KILOMETERS

FIGURE 7. Generalized map of Allegheny, Washington, and Westermoreland Counties, Pa., showing the Upper 

Freeport coal bed mined out before June 30, 1974 (dotted pattern), the Upper Freeport coal bed probably 

mineable after June 30, 1974 (horizontal lines), the recorded damaging surface-subsidence incidents over 

mined-out areas of the Upper Freeport coal bed (marked by X), and areas where the Upper Freeport coal bed 

is absent (no pattern).

duction of this map in which areas correlating 

with high and moderate numbers of events are 

combined.

APPLICATION OF MAPS

The abundant information on the first two 

maps largely will be meaningful only to the 

technical audience. The overburden-thickness 

information is applicable to the mine-subsidence problem, but thickness of overburden also 

bears directly on the potential for surface mining and thus also on resource considerations. 

Areas mined out and potentially mineable underground areas are factors in subsidence and 

resource potential, and undermining is a factor 

in ground-water supply and mine-water discharge.

The third map is a nontechnical report that 

is directly applicable to regional planning relative to the potential for damaging surface subsidence, one aspect of foundation conditions. 

From it also can be read the extent of undermining through 1966.

INTEGRATION OF RESULTS OF THE GEOLOGIC 

STUDIES WITH EXISTING DATA AND SUMMARY 

OF GEOLOGIC AND HYDROGEOLOGIC RESULTS

METHODOLOGY

The first map described below (MF-685C) 

is taken largely from the 1:24,000 scale provisional maps of land-modified-by-man, by reduction to scale 1:50,000 and compilation on 

the Allegheny County base map. Although most 

of the provisional maps contain information 

beyond the borders of Allegheny County, compilation on the county base map was restricted 

to Allegheny County only. Moreover, it was 

decided to transfer to the county base map only 

coal-mining and other mineral industry features. This decision was based largely on the 

fact that the other features on the maps of 

land-modified-by-man are related chiefly to development from 1969 to 1973. These maps, 

.though differently derived and at different 

scales, approximate those of the USGSLUPRA Allegheny County land-use-change 

map prepared by the USGS, description of

15
40°30: , - 

30 40 KILOMETERS

FIGURE 8. Map of Allegheny, Washington, and Westmor eland Counties, Pa., showing generalized areas correlating 

with numbers of recorded damaging surface-subsidence incidents over mined-out areas, extrapolated to include 

areas of future coal mining. High and moderate numbers are indicated by ab and dotted pattern; minor 

numbers by c and horizontal lines; no correlation by d (unpatterned).

which is beyond the scope of this report. The 

resulting map of coal-mining features was 

completed by adapting map areas shown as 

undermined on the Pittsburgh coal bed (MF693A) and Upper Freeport coal bed (MF693B) maps described above.

The second map described below (MF-685D) 

was prepared by generalizing the map of susceptibility to landsliding (MF-685B) and the 

map of coal-mining features and combining the 

generalizations with a compilation and reduction of flood-prone area maps. Figure 9 shows 

the general limits of flood-prone areas in Allegheny County. The map of rock types in bedrock (MF-685A) is a combination of interpretations from soil-survey work and information 

chiefly from published geological and engineering reports.

Most compilation for integrated maps was 

by William R. Kohl; the present writer largely 

was responsible for the preparation of texts 

and tables and for the assembly of maps, texts, 

and tables for publication.

Illustrations accompanying this report summarizing the geologic and hydrologic studies 

were reduced by photomechanical transfer 

from the appreciably larger originals. The reductions were then simplified and generalized 

as page-size maps.

REPORTS

Map of coal-mining features, Allegheny 

County, Pennsylvania, by William E. Davies, 

John S. Pomeroy, and William R. Kohl. 1975. 

U.S. Geological Survey- Miscellaneous Field 

Studies Map MF-685C. Scale, 1:50,000. Three 

categories of information are shown: (1) extent of mined and mineable coal in the Pittsburgh and Upper Freeport coal beds; (2) surface features related to underground mining; 

and (3) features resulting from surface mining and other activity. Included in the second 

category are mine entries, mined-out areas, 

mine and coal-bed fire areas, refuse banks, and 

areas of probable past surface subsidence identified through aerial-photogrjaphic interpreta16
r

FIGURE 9. Generalized map of flood-prone areas (shown in black) Allegheny County, Pa.

tion. In the third category are surface (strip) 

mine areas, surface-mine high walls, and slag 

dumps. Underground mining has taken place 

under about 250 mi2 (648 km2 ) or 35 percent 

of the county (fig. 10). Surface mining has 

disturbed about 30 mi2 (78 km2 ), or less than 

5 percent of the county. The coal beds are related tcrthe geologic setting by the accompanying [ small-scale geologic map and columnar 

section; a brief text supplies additional information.

Map of zones where land use can be affected 

by landsliding, flooding, and undermining,

Allegheny County, Pennsylvania, by Reginald 

P. Briggs and William R. Kohl 1975. U.S. 

Geological Survey Miscellaneous Field Studies 

Map MF-685D. Scale, 1:50,000. This map 

provides a general land classification relative 

to the three named processes. Areas are numbered from slashed zero (0) to 3 depending on 

how many of the processes can affect a given 

locality. Letter suffixes identify which of the 

processes are of concern. The accompanying 

text compares effects of the processes, suggests 

how the map can be used, and lists sources of 

more detailed information. Figure 11 is a reduced and simplified version of the map.

17
are shown by horizonta

show approximate

Ohio, AUegheny, and Monongahela

0/ rocfc ^pes in bedrock of Allegheny 

bounty, Pennsylvania, by William R. Kohl and 

Reginald P. Briggs. 1975. U.S. Geological Survey Miscellaneous Field Studies Map MF685A --Scale, 1:50,000. Five map units show 

the distribution of different assemblages of 

rock types in bedrock. Surficial deposits are 

shown only where relatively large areas of bedrock are concealed. A small-scale geologic map 

and columnar section relate bedrock types to

««

beds Pr°bably mineable after June 30, 1974 

""patterned. Shortened' lines 

lines ««ow channels of

conventional stratigraphy. One table describes 

the general engineering characteristics that 

may be found in bedrock units, and a second 

more detailed table presents characteristics of 

specific rock types. The text briefly describes 

the general geology and the principal categories of problems in environmental geology. 

Examples illustrate the use of map and tables 

in conjunction. A glossary is included.

18
r

40°30'

FIGURE 11. Generalized map of Allegheny County showing areas that can be affected by one or more processes of 

flooding, landsliding, and undermining. Areas which can be affected by all three processes are indicated by 3 

and black pattern; affected by two processes by 2 and horizontal lines; affected by one process by 1 and 

dotted pattern; unlikely to be affected by 0 and no pattern.

Environmental geology, Allegheny County 

and vicinity, Pennsylvania description of a 

program and its results by Reginald P. Briggs. 

1977. U.S. Geological Survey Circular 747. 

This report.

APPLICATIONS OF REPORTS

The map of coal-mining features (MF-685C) 

has both technical and nontechnical applications. As examples of the former, surface 

mines are sites of current and potential storage of solid waste, and construction aggregates

can be mined from coal-mine-refuse piles and 

slag dumps. In addition, the distribution of 

surface mines and areas undermined provides 

a view not only of areas currently affected by 

coal mining but also of areas that may be 

mined in the future. This view is important in 

both mineral-resource and environmental-problem considerations. Nontechnical users may 

find the map valuable for general land classification, provisional home-site selection, and 

recreation.

19
A general nontechnical land classification is 

provided by the map combining information on 

landsliding, flooding and undermining (MF685D). The chief application is tentative identification of potential problems for the selection of sites for residential, public, commercial, 

industrial, and transportation purposes, but the 

information also may be applied to existing 

structures and other features.

The map of rock types in bedrock (MF685A) is largely technical in content, but instructions are provided that will allow the nontechnical user to make provisional identifications of some engineering characteristics of 

bedrock, such as facility of excavation, stability of cut slopes, and foundation strengths. 

Specific rock-type characteristics, though 

largely from published sources, previously 

have not been assembled in one publication. The 

technical user may find this summary applicable 

to planning a variety of works.

The present report summarizes the studies 

and their reports and presents a general view 

of the principal factors that may limit land 

use for some purposes. It classifies the reports 

by potential applications, and with its smallscale illustrations provides a regional overview 

of environmental factors.

HYDROGEOLOGIC STUDIES

RECONNAISSANCE APPRAISAL OF THE ROLE OF 

SHALLOW GROUND WATER IN MINING AND

SLOPE-STABILITY PROBLEMS, INCLUDING 

PROBLEMS ASSOCIATED WITH PERIODS OF

INTENSE PRECIPITATION SUCH AS

ACCOMPANIED TROPICAL STORM "AGNES" IN

JUNE 1972, ALLEGHENY COUNTY, PENNSYLVANIA

METHODOLOGY

Ground water in rocks and soils above the 

levels of stream channels in adjacent valleys 

generally is considered shallow for present 

purposes. For example, in an area where topographic relief (the vertical distance from valley bottoms to adjacent ridge crests) is about 

300 ft (91 m), the zone of shallow ground 

water is about 300 ft (91 m) thick beneath 

ridge crests, thinner beneath slopes, and very 

thin beneath valley bottoms. In Allegheny 

County, the shallow ground-water regime has 

been believed to be interrelated significantly 

with landsliding and mining, but the validity 

of this belief has not been systematically tested 

until the present study. The aim of the reconnaissance appraisal was to systematize and

enhance knowledge of the shallow groundwater regime. There were no known precedents 

so the methodology used by the principal in>- 

vestigator, Seymour Subitzky, was innovative. 

The steps followed were:

1. A thorough search of the geologic, hydrologic, and engineering literature for data 

and theory relevant to the Allegheny 

County setting, and analysis of the results of the search.

2. A widespread series of interviews with 

technical personnel in a variety of employments, fo»r the purpose of gleaning 

applicable unpublished data and unwritten insights.

3. Field investigations viable within the 

framework of available time and support.

4. Synthesis of results into reports.

Steps 2 and 3 continued simultaneously, and 

there were no firm time lines to other steps 

because obscurely published applicable material was found occasionally and analysis of 

some factors became possible only with synthesis relative to others. Step 2 was particularly time consuming, but produced valuable information.

REPORTS

The result of the reconnaissance appraisal is 

a series of five reports in chart form.

Summary of the hydrogeologic regime as related to environmental characteristics, Allegheny County, Pennsylvania, by Seymour Subitzky. U.S. Geological Survey Miscellaneous 

Field Studies Map MF-6UA. The chief feature 

of this report is a table in which geologic units 

underlying the county at shallow depths are 

classified according to lithologic, structural, 

and hydrologic characteristics, mass-movement 

characteristics on natural and cut slopes, and 

response to heavy storm precipitation. The 

table is supported by a brief text.

Hydrogeologic framework and generalized 

shallow ground-water circulation system, Allegheny County, Pennsylvania, by Seymour Subitzky. U.S. Geological Survey Miscellaneous 

Field Studies Map MF-641B. In this report, 

the regional framework is illustrated by a 

county map showing axes of folds and by cross 

sections perpendicular to fold axes. Probable 

paths of groundwater circulation are shown in

20
larger scale cross sections selected as characteristic of the hydrogeologic setting. A third 

level of detail is added by a large-scale block 

diagram illustrating water circulation through 

rock fractures and along bedding planes. The 

accompanying text coordinates the illustration 

and adds other information.

Mining and related problems of the shallow 

hydrogeologic regime, Allegheny County, Pennsylvania, by Seymour Subitzky. U.S. Geological 

Survey Miscellaneous Field Studies Map MF641C. Local case histories of the interaction 

of underground coal mining and the groundwater regime are illustrated. Included are actual patterns of rock features over mined-out 

areas, traced from photographs of outcrops; an 

example of the effect of mining on water supply from shallow wells; a verified case of decline of ground-water level due to undermining; 

and an amplifying text.

Heavy storm precipitation and related mass 

movement, Allegheny County, Pennsylvania, 

by Seymour Subitzky. U.S. Geological Survey 

Miscellaneous Field Studies Map MF-641D. 

The tracks of extratropical storms in the Ohio 

River basin between 1871 and 1972 are illustrated and are related to precipitation recorded at Pittsburgh. Landslides caused by 

tropical storm "Agnes" (June 1972), as determined by ACDPD, are located on a map at 

scale of 1:125,000 (1 in. = 2 mi; 1 cm=1,250 

m ). The text and a table expand on the relationship between precipitation and. landsliding.

Some aspects of water quality as affected by 

land use in McLaughlin Run and Painters Run 

basins, Allegheny County, Pennsylvania, by 

Seymour Subitzky. U.S. Geological Survey Miscellaneous Field Studies Map MF-641E. 

These small basins, totaling about 12 mi 2 (31 

km2 ) in area, in many respects are typical of 

the setting of the parts of Pittsburgh's urban 

fringe that are closely underlain by mined-out 

coal beds. Two series of water-quality measurements were made, one during a period of low 

base flow and one during a period of high base 

flow, and the results are tabulated, shown by 

symbols on maps, and discussed in the accompanying text.

APPLICATIONS OF REPORTS

The summary of the hydrogeologic regime 

(MF-641A) supplies the basic background for 

the succeeding four reports, although in large

part they can be used independently. The orientation of the summary largely is toward a 

technical audience. The two sheets of the hydrogeologic framework chart (MF-641B) provide technical and nontechnical readers with 

insight into the ways that shallow groundwater moves, and resulting applications to aspects of mine-water discharge and water 

supply both under natural conditions and as 

affected by fracturing related to mine subsidence. Further application is to the interplay 

of solid waste and ground-water circulation. 

The mining-and-related-problems chart (MF641C) is oriented somewhat more toward the 

technical reader than is the hydrogeologic 

framework chart, and it focuses more closely 

on the effects of mine subsidence. The information in the fourth chart (MF-641D) largely is 

technical, but the nontechnical reader also will 

find the relation between heavy storm precipitation and landsliding of interest. Experience 

from tropical storm "Agnes" should prompt advance planning to ameliorate unstable conditions and thus reduce landsliding under future 

similar rainfall conditions. The technical report 

on the McLaughlin Run and Painters Run basins (MF-641E) enhances knowledge of the 

effects of undermining and urbanization on 

water quality. Recognition that similarly complex effects may apply in similar basins can be 

beneficial in water-supply planning and related 

efforts.

SUMMARY OF RESULTS AND FINDINGS

In table 1, potential applications of reports 

of the USGS-LUPRA geologic and hydrogeologic studies are summarized. Reports are 

identified by series (MF or Circular), numbers, 

and abbreviated titles.

LANDSLIDING

The open-file landslide-susceptibility maps at 

scale 1:24,000 and the Allegheny County map 

of susceptibility to landsliding (MF-685B) at 

scale 1:50,000 constitute a knowledge of distribution of landslides and susceptibility to 

landsliding that heretofore did not exist, and 

the map of zones (MF-685D) contains a nontechnical generalization of this information. 

The many landslides that resulted from tropical storm "Agnes" (MF-641D) demonstrate 

the marginal stability of many slopes. The re-' 

port on landsliding in Allegheny County (Cir21
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cular 728), the Allegheny County rock-type 

map (MF-685A), and the hydrogeologic summary and framework charts (MF-641A and 

MF-641B) provide insight into factors that 

influence landsliding.

In summary, knowledge of susceptibility to 

landsliding now is wholly adequate for general 

planning in Allegheny County, and past and 

future detailed studies of specific slopes and 

landslide events now can be included in this 

countywide frame of reference. About 110 mi2 

(285 km2 ) or 15 percent of Allegheny County 

has some significant susceptibility to landsliding.

FLOODING

Little USGS-LUPRA effort was directed at 

flooding by rivers and streams, due to the generally well-advanced work on the subject by 

previous workers, and the fact that needed 

studies of dynamic hydrologic processes were 

not so amendable to short-term attention as 

were the studies carried out.

However, the chart concerning heavy storm 

precipitation (MF-641D) deals with a floodrelated incident and provides a compilation of 

flood history related to extratropical storms, 

and the 1:50,000-scale Allegheny County map 

of zones (MF-685D) combines information 

about distribution of flood-prone areas with 

information about landsliding and undermining.

MINE SUBSIDENCE

The problem of mine subsidence was addressed specifically. The map of Pittsburgh 

coalbed features in Allegheny, Washington, 

and Westmorland Counties (MF-693A) and 

the similar map of Upper Freeport coalbed 

features and Redstone coalbed mines (MF693B) are basic data contributions; these were 

synthesized to produce the map of areas that 

correlate with subsidence events (MF-693C) 

which classifies land relative to the potential 

threat of subsidence, at the regional scale of 

1:125,000.

Areas identified as undermined in Allegheny 

County were adapted to the coal-mining features map (MF-685C) at scale 1:50,000 and 

were recombined with other information to 

yield the nontechnical map of zones (MF685D) at the same scale. The hydrologic chart 

on mining and related problems (MF-641C)

deals with the effects of undermining and subsidence on the shallow ground-water regime, 

and the McLaughlin Run and Painters Run 

basin chart (MF-641E) reflects this relationship in a local case historyIn the course of the Allegheny County earthdisturbance inventory an experiment was attempted to define subsided areas by aerialphotographic interpretation. The results were 

promising, although the method needs refinement.

Specific findings relative to undermining and 

subsidence are:

1. The record of subsidence events doubtless 

is very incomplete (MF-693A, MF693B).

2. Legislation by the Commonwealth of Pennsylvania in 1966 enabled the development 

of regulations and the necessary administrative machinery to reduce the minesubsidence hazard from post-1966 bituminous coal mining (MF-693C) to a minimum.

3. Damaging mine subsidence now is chiefly, 

but not exclusively, a threat over areas 

undermined many years ago which have 

relatively thin less than 200 ft (61 m) 

 overburden (MF-693C).

4. Compared with flooding and landsliding, incidents of subsidence damage owing to 

undermining are infrequent and least expensive to the overall community. However, they probably are most damaging 

and expensive to the average individual 

involved in one of the relatively rare 

events (MF-685D).

5. Undermining and consequent subsidence 

have fractured overlying rocks widely 

and affected the shallow ground-water 

regime to an extent probably greater 

than heretofore believed (MF-641C).

6. A large effort would be required to allpw 

even a moderately precise prediction of 

damaging subsidence events in undermined areas of the bituminous coal fields, 

and considering the relatively low level 

of subsidence losses, such an effort might 

not repay its costs. Possible lines of investigation are:

1 (a) Expanding the record of subsidence 

events by research into historical 

records and coal-mining and en23
gineering records. Newspaper files 

have been searched with minimal 

results.

(b) Further refining knowledge of 

subsided areas by architectural 

studies, refined remote-sensing 

techniques, and fracture and geomorphic analysis.

(c) Seismic and other geophysical research over mined-out areas.

OTHER PROCESSES AND PROBLEMS

As indicated in preceding sections and summarized in table 1, USGS-LUPRA studies 

also apply to other environmental processes and 

problems, mainly the syntheses of existing information, such as the summary of hydrogeologic regime (MF-641 A), the maps of coal 

beds in Allegheny, Washington, and Westmoreland Counties (MF-693A and MF-693B), and 

the Allegheny County rock-type map (MF685A) ; the studies also resulted in new information and insights, such as the provisional 

maps of land modified by man, and the hydrogeologic charts on mining and related problems (MF-641 C) and the McLaughlin Run and 

Painters Run basins (MF-641E). The more 

significant of these ancillary contributions relate to mine-water discharge, surface mining, 

foundation conditions, water supply, and landuse classification.

EVALUATION OF METHODOLOGIES

EARTH-DISTURBANCE INVENTORY

A distinction must be drawn between an inventory of landslides, which results in a map 

showing distribution of active landslides or 

landslide deposits, and an investigation of susceptibility to landsliding, which results ins, a 

classification of land by degrees of susceptibility. The provisional landslide-susceptibility 

maps, and the Allegheny County map of susceptibility to landsliding (MF-685B) include 

both types of information, whereas the map in 

the hydrogeologic chart on heavy storm precipitation and related mass movement (MF-641D) 

is a synoptic landslide-inventory map; figure 5 

of this report is a small-scale map of susceptibility to landsliding, and the Allegheny County 

map of zones (MF-685D) is a map of areas 

susceptible to landsliding as well as to flooding 

and potential mine subsidence.

In the Allegheny County work many small 

significant active landslides were not discernable on the aerial photographs, despite their 

relatively large scale and excellent resolution. 

However, these small landslides were readily 

identifiable on the ground, so field verification 

was a necessity for a reasonably complete inventory of landslides.

On the other hand, experience gained in the 

Allegheny County terrane suggests that aerialphotographic interpretation and integration of 

the results with geologic, soils, and other data, 

that is, laboratory and office work alone, would 

have yielded an adequate map of susceptibility 

to landsliding, assuming only that investigators 

had a reconnaissance familiarity with the terrane as seen from the ground.

Extrapolating the Allegheny County experience in landslide studies to elsewhere in the 

Appalachian Plateau, the following general 

conclusions can be drawn:

1. If landslide inventories are required, the 

Allegheny County methodology probably 

is directly applicable. The aerial-photographic scale is appropriate, as is the allowance of time for interpretation and 

field verification, about one man month 

for the area included in each T^-minute 

quadrangle. The basic data on geology, 

soils, and other features can be reasonably 

sparse and still result in a good inventory, 

for the inventory method basically is objective rather than interpretive. Investigators' would gain necessary ground 

familiarity during the field verification 

stage of an inventory.

2. If maps of susceptibility to landsliding only 

are required, the general Allegheny County methodology is applicable in that the 

basic method included aerial-photographic interpretation and integration of results with other information. Aerialphotographic scale need not be so large; 

1:24,000 scale or somewhat smaller would 

suffice provided photographic quality is 

good and photographic flights are during 

leafless seasons. Field verification could 

be minimal, providing investigators had a 

reasonable familiarity with the area and 

an adequate framework of geologic and 

other information. In summary, if goodquality aerial photography at an inter24
mediate scale, an adequate basic-data 

framework, and investigators generally 

familiar with the setting can be brought 

together, adequate maps of susceptibility 

to landsliding in the Appalachian Plateaus probably can be prepared quite 

rapidly.

The part of the earth-disturbance inventory 

that resulted in the provisional maps of manmodified land and was extrapolated in part to 

the coal-mining features map (MF-685C), was 

done simultaneously with the landslide parts of 

the investigation and probably accounted for 

less than one-fourth the total effort on the 

earth-disturbance inventory. Similar, though 

somewhat less detailed, work can be done over 

large areas using small-scale aerial photography, as has been demonstrated in the course of 

land-use mapping in the Greater Pittsburgh 

region and many other areas. It probably is uneconomic to use large-scale aerial photographs 

for making maps of man-modified land only. 

However, when coupled with a complete earthdisturbance inventory, such as was done in Allegheny County, large-scale aerial photographs 

can yie!4 land-modified-by-man maps as a useful byproduct with economy of effort.

MAPS SHOWING UNDERGROUND COAL-MINING

ACTIVITY THAT CAN RELATE TO SURFACE

SUBSIDENCE

Principal methods used in compiling information for these three county maps are those common to many regional geologic studies. Chief 

innovations were the adaptation of statistical 

data on mine-subsidence events to the maps of 

Pittsburgh coal-bed and Upper Freeport coalbed features (MF-693A and MF-693B, respectively), and the combination of these maps to 

produce the map of areas that correlate with 

subsidence events (MF-693C). Evaluation of 

the innovations must await distribution and the 

response of potential users to the reports.

INTEGRATION OF RESULTS OF THE GEOLOGIC 

STUDIES

The chief methods used to achieve the coalmining features map (MF-685C) were evaluated above, and these methods were followed 

by conventional reduction and transfer of information and development of texts and illustrations. The Allegheny County map of zones 

(MF-685D) was prepared conventionally by 

simplifying landslide-susceptibility and undermined-area map data and combining the results with other data. Interpretation of soilsurvey information and comparison with existing geological information resulted in the Allegheny County rock-type map (MF-685A). This 

method was quite successful in enhancing 

geologic knowledge in an area of complexly 

interlayered sedimentary rock; the methodology also should be applicable to other areas 

of similar geological character where modern 

soil surveys have been completed.

RECONNAISSANCE APPRAISAL OF THE ROLE OF

SHALLOW GROUND WATER IN MINING AND

SLOPE-STABILITY PROBLEMS

Briefly stated, the method included gathering 

information, identifying inadequacies of information, attempting to rectify these inadequacies within the time available, and synthesizing 

the information. The method worked well in 

Allegheny County largely because Pittsburgh 

and its vicinity includes a large technical and 

scientific community from which information 

and insights could be drawn. Lacking such information, the same methodology in the same 

time frame probably would have proved less 

productive elsewhere in the predominantly 

rural Appalachian Plateaus. Thus, the methodology probably is not directly extrapolatable, 

but the contributions to understanding contained in the hydrogeologic charts (MF-641A 

through MF-641E) are themselves capable of 

wider application. An innovation is the chartlike format of the products, but its evaluation 

must await user response.

25