FEET

200

150

100

50

SL

-50

-100

-150

-200

-250

-300

-350

-400

-450

FEET

200

150

100

50

SL

-50

-100

-150

-200

-250

-300

-350

-400

-450

268

309

67

55

289290

189

178

GT-42 55

25

39

GT-191 155

121

GTB-88 155140

74

GT-147 96

GT-41 41

9

27

GT-181 38

7

23

GT-165 45

20

Totaldepth

not given

F-5 38

56

%

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GT133-18 42

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GT-5/16 49

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GT133-1 43

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J-3 50

100%

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17

GT-146 47

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GT-139 47

28

-400

D-14 30

Did

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reach

bedro

ck

GT-35 26

-52

5

Mount Ida

Mt Vernon Ave

Del RayFourMileRun

Beverley Park

Old Dominion Blvd

Monticello Park

Russell Road

Jefferson Park

Beverley Hills

Old TownNorth End

FOUR MILE RUN

MOUNT IDA

POTOMAC YARDS

EISENHOWER VALLEY

OLD TOWN

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NW C SEC’

BEVERLEY HILLS GEOLOGIC CROSS SECTION

by Anthony H. Fleming, 2015

City of Alexandria, Virginia Geologic Atlas of the City of Alexandria, Virginia and Vicinity – Plate 2C

1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

FEET

VERTICAL EXAGGERATION 20XSEE PLATE 5 FOR EXPLANATION OF MAP UNITS

EXPLANATION OF CROSS SECTION SYMBOLS:

WATER WELLWELL ID NUMBER AND SURFACE ELEVATION(SOURCE: J-JOHNSTON; D-DARTON; F-FROELICH)

WELL CASING

WATER LEVEL

WELL SCREEN

REPORTED BEDROCK LITHOLOGY

BOTTOM ELEVATION

% SAND IN 100-FT INTERVAL REPORTED BY FROELICH (1985)

BEDROCK SURFACE

BOREHOLE IN BEDROCK

sch

ist

147

J-60 250

195

70

% s

an

d1

0%

sa

nd

GEOTECHNICAL BORING SITES

127

GT-27 222

147

ID NUMBER AND HIGHEST SURFACE ELEVATION

APPROXIMATE LATERAL ANDVERTICAL EXTENT OF SITEALONG CROSS SECTION LINE

WATER LEVEL

BOTTOM ELEVATION OF DEEPEST BORING

GT133-15 42

2

17

NOTE: GEOTECHNICAL BORING SITE #133 CONSISTS OF 25 BORINGS DISTRIBUTED ALONG THE ROUTE OF A TWO MILE LONG TRUNK SEWER. ICONS SHOWN ON THE CROSS SECTION INDICATE THE LOCATIONS, IDENTITIES, DEPTHS, AND WATER LEVELS OF THE INDIVIDUAL BORINGS

119

210

132

WATER LEVELS REPORTED IN WELLS AND GEOTECHNICAL BORINGS

WATER LEVEL MEASURED IN WELL ORCASED GEOTECHNICAL BORING COMPLETEDIN THE CAMERON VALLEY SAND (LOWERAQUIFER OF THE POTOMAC FORMATION)

WATER LEVEL MEASURED IN 1976 FROM WELL COMPLETED IN CAMERON VALLEY SAND (JOHNSTON AND LARSON, 1977)

WATER LEVEL MEASURED IN WELL OR GEOTECHNICAL BORING COMPLETED INOTHER AQUIFERS. MAY REPRESENT A COMPOSITE OR AVERAGE WATER LEVEL AT GEOTECHNICAL SITES WITH MANY BORINGS

OTHER SYMBOLS

SURFACE EXPOSURE. SOME EXCAVATIONS COINCIDE WITH GEOTECHNICAL BORING SITES

GRAVELLY ZONES IN THE OLD TOWN TERRACE REPORTED IN GEOTECHNICAL BORINGS

ORGANIC ZONES REPORTED IN GEOTECHNICALBORINGS FROM THE POTOMAC FORMATION, QUATERNARY ALLUVIUM, AND OTHER SEDIMENTS.INCLUDES WOOD, PEAT, LIGNITE, LEAVES, DARKORGANIC SILT, AND OTHER ORGANIC MATERIAL

INTERSECTION WITH ANOTHER CROSS SECTION.CROSS SECTIONS ARE DISTINGUISHED BY NAMEAND COLOR-CODED SECTION LINES AND TITLES

SPECULATIVE POST-CRETACEOUS FAULT OR FLEXURE ASSOCIATED WITH THE ROCK CREEKSHEAR ZONE

47

g

ORG

MOUNT IDA

The cross sections are intended to be used together with the The large gravel-filled channel beneath Old Town is recognized in GEOLOGIC CROSS SECTION 2C– BEVERLEY HILLSother maps, particularly Plate 5, to illustrate the third dimension of a few geotechnical boring sites and appears in other cross Cross section 2C extends southeast from near the map units. Contacts between map units are approximately sections that traverse Old Town. the Old Town waterfront. The section traverses nearly the entire located; the abundance of control points (surface exposures, width of the Old Town terrace between Old Town and Del Ray, as wells, geotechnical boring sites) along the cross section provides By virtue of its orientation, the Beverley Hills cross section well as a large swath of the northeastern highlands. The view is a general indication of the reliability of contact locations. Map probably comes the closest of all the sections to paralleling the generally to the northeast along the section line, which locally units are depicted using the same colors, patterns, and labels as regional dip of the bedrock surface and the depositional axis of bends to take in the locations of nearby geotechnical boring sites, on Plate 5, and the explanation of map units on Plate 5 serves as the Potomac Formation. Heterogeneous sediments of the historical water wells, and significant natural areas (e.g., the legend. The section also depicts some bedrock units and a Chinquapin Hollow member make up the great bulk of the outcrop Monticello and Beverley Parks) where many outcrops are few gravelly zones in the Old Town terrace that are present only area of the formation in this section; however, the character of the present. These features, and other sites of cultural, historical, and in the subsurface, and thus do not appear on Plate 5. formation at depth, and the eastward continuity of the individual environmental interest. are indicated by labels and symbols along

The Beverley Hills section illustrates the general eastward units from their outcrop areas further to the west, are highly the cross section. The specific location of the cross section is thickening of the Old Town terrace, as well as local stratigraphic speculative, especially beneath Old Town, where only a handful indicated on Plate 1 by a dark green section line. details, as deduced from subsurface data and geomorphology. of old wells penetrate to such great depth.

City–which separates the relatively level and low-lying Old Town terrace from the elevated and strongly dissected uplands that Four Mile Run to comprise the northeastern quadrant of the City. Part of this scarp coincides with the magnetically defined trace of the Rock Creek Shear Zone, raising the question of whether its location may be partly tectonically influenced. The northward extension of a fault or flexure postulated on sections further south appears as the queried fault at the base of the scarp. The sharp increase in slope of the bedrock surface below Old Town could also be attributable to another fault, as discussed in chapter 8.

The dominant physiographic feature is the east-facing Mount Ida escarpment – one of the most imposing natural landmarks in the

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