HomeMy WebLinkAboutWPO201300032 Correspondence 2021-12-02STEVENSON CONSULTING, INC.
GEOTECHNICAL INVESTIGATION & EVALUATION
Cascadia Detention Pond
Albemarle County, Virginia
Prepared for
Charlie Hurt
CEVA Contractors
P. O. Box 82147
Charlottesville, Virginia 22906
Stevenson Consulting Job No. 7-1916A
August 28, 2021
TABLE OF CONTENTS
1.0
PURPOSE AND SCOPE OF SERVICE...........................................................................................1
2.0
PROJECT AND SITE DESCRIPTION..............................................................................................1
2.1
Site Location and Conditions........................................................................................................1
2.2
Project Description........................................................................................................................1
3.0
FIELD EXPLORATION.....................................................................................................................2
4.0
SUBSURFACE CONDITIONS......................................................................................................:...2
4.1
Site Geology..................................................................................................................................2
4.2
Subsurface Conditions.......................................................:..........................................................2
4.2.1
Soils Encountered.....................................................................................................................2
4.2.2
Groundwater..............................................................................................................................3
5.0
DESIGN RECOMMENDATIONS......................................................................................................3
5.1
General....................................................................................................................:..:..................3
6.0
LIMITATIONS .....................••-----......................................................................................................8
APPENDICES
A. Figures: Site Vicinity Map
Boring Location Plan
B. Soil Boring Logs
C. Permeability Test
Cascadia Detention Pond l Project Number 7-1916A
Albemarle County, Virginia Geotechnic•al Investigation and Evaluation
1.0 PURPOSE AND SCOPE OF SERVICE
The purpose of the subsurface exploration and geotechnical engineering evaluation was to explore
the subsurface conditions in the existing pond embankment at Pond 2 within the Cascadia
development. If the project characteristics that are expected to exist based on documentation by
others differ from those discussed within our report, or if different subsurface conditions are
encountered during any other exploration, please contact our office immediately so that we may
reassess our recommendations.
Stevenson's scope of services included the following:
• Completion of three 10.5 to 18.5-foot-deep geotechnical test borings,
• Performance of a generalized geotechnical engineering evaluation with respect to the
existing dam, laboratory testing including standard compaction AASHTO T-99 and
permeability and
Preparation of this geotechnical report by professional engineers.
2.0 PROJECT AND SITE DESCRIPTION
2.1 Project Description
Stevenson understands that a stormwater detention dam was constructed with no quality control
testing during construction. Albemarle County Engineering Department requested confirmation of
embankment construction including compaction, suitable embankment material, cut-off trench and
other relative information. Our study was to determine the type of soil used for the construction of
the dam and the relative compaction of the soil based on three soil test borings and various
laboratory tests
The above project description and criteria form the basis of our evaluation and the
recommendations presented in this report.
notify us.
2.2 Site Location and Conditions
If any of these criteria are found to be different, please
The site is located within the Cascadia Subdivision in Charlottesville, Virginia, to the east of Stony
Point Road, to the north of Cascadia Drive, to the west of the residential lots along Marietta Drive,
and to the south of the Broadus Memorial Baptist Church entrance road.The pond was identified as
Pond 2 and borings were performed along the western embankment which is mainly covered with
grass with some sparce trees along the western edge.
Cascadia Detention Pond 2 Project Number 7-1976A
Albemarle Countv, Virginia CeotcehnicalInvestigation and Evaluation
3.0 FIELD EXPLORATION
To determine the general subsurface conditions at the site, three (3) Standard Penetration Test
(SPT) borings were drilled on July 21,2021. Borings, identified as B-1, B-2, and B-3 were drilled to
depths of 18.5 feet, 13.5 feet, and 10.5 feet, respectively, below the top of the dam. Test boring
locations were located and staked by Shimp Engineering team.
Drilling services were performed by Ayers and Ayers from Midlothian using a truck mounted CME-
45 drilling rig. Standard Penetration Testing was performed in the test borings as per ASTM D
1586, Standard Test Method for Penetration Test and Split -Barrel Sampling of Soils. The test
borings were advanced using hollow -stem auger procedures to the planned depths stated above.
Samples were obtained in the test borings by driving a 1-3/8-inch I.D. split spoon sampler in
accordance with ASTM D 1586. The sampler was first seated to penetrate any loose cuttings and
then driven an additional 18 inches with a 140-pound hammer free falling 30 inches. The numberof
hammer blows required to drive the sampler the latter 12 inches in the case of an 18-inch drive was
designated the penetration resistance or N-value. The N-value can be used as a qualitative index
of the relative density of non -cohesive or granular soils. In a more approximate way, the N-value
can be used as an index for the consistency of cohesive or plastic soils. Soil samples were
returned to Stevenson Consulting's laboratory for visual classification by our personnel and limited
laboratory testing. Logs of the test borings are included in Appendix B. Soil samples collected
during the field exploration program will be stored at Stevenson's office for a period of sixty (60)
days. After 60 days, the samples will be discarded unless prior notification is provided to us in
writing.
4.0 SUBSURFACE CONDITIONS
4.1 Site Geology
Geologically the site is underlain by the Catoctin formation. The Catoctin Formation is composed
primarily of metabasalt, commonly referred to as greenstone due to the rock's greenish tint. When
the original basalt was metamorphosed, igneous minerals Blue Ridge cross section in central
Virginia, note the Catoctin Formation is exposed in both a western and eastern belt. Pyroxene,
plagioclase, and olivine were converted to new minerals (chlorite, actinolite, and epidote), which
give the rock a gray -green color. The Catoctin Formation also contains discontinuous layers of
metasedimentary rock (including phyllite, quartzite, and even marble), as well as volcanic breccia
and metarhyolite.
4.2 Subsurface Conditions
The subsurface conditions encountered at the test boring locations are consistent with the site
geology and are shown on the logs in Appendix B. The strata interface locations recorded on the
boring logs should be considered approximate, as actual transitions between strata are generally
2
Cascadia Detention Pond 3 Project Number 7-1916A
Albemarle County, Virginia Geotechnical Investigation and Evaluation
gradual. Although individual test borings depict the subsurface conditions at the specific locations
on the dates shown, they are not necessarily indicative of subsurface conditions at other locations
or at other times. Data from the specific test borings are shown on the boring logs in Appendix B.
4.2.1 Soils Encountered
Surficial Soil was encountered in the borings to approximate depths of 17.5 feet in boring B-1, 12.5
feet in boring B-2 and 8.5 feet in boring B-3 below the existing ground surface. Surficial Soil
consists of fill material that classifies as a red clayey silt, (CH). SPT N-values for the fine-grained
soils range from 6 to 41 bpf indicating these soils are medium stiff to hard.
Natural residual soils of the Catoctin formation were encountered beneath the Surficial Soil. These
residual soils consisted of silty SAND (SM). The SPT N-values for the coarse -grained soils ranged
from 39 to 50/3" bpf, indicating these soils are dense to very dense.
4.2.2 Groundwater
Groundwater was not observed in any of our borings. Cave-in depths were observed at depths
ranging from 8 toll 0 feet below existing grades.
5.0 General Findings
5.1 General
The following evaluation is determined from the results of our borings and laboratory test results.
The soils used in the construction of the dam, in our opinion, are suitable for this type of
construction. Laboratory testing indicates that the soils in the dam are classified as a CH soil, which
is a clay with a high plasticity, which is ideal for dam construction. Permeability testing indicates a
value of 1.4EE10-7, which is also ideal for dam construction. SPT N-values in the fill of the dam
also indicate that the compaction of the material ranges from good to excellent. Also, our borings
indicate that the cut-off trench was excavated to proper material prior to the placement of fill.
In conclusion, it is our opinion that the construction of the dam is consistent with proper engineering
recommendations and should perform adequately.
6.0 LIMITATIONS
This report was prepared for the exclusive use of CEVA Contractors or their agent, for the specific
application to the existing stormwater detention dam for Pond 2 in Cascadia subdivision in
Albemarle County, Virginia, in accordance with generally accepted soil and foundation engineering
3
Cascadia Detention Pond
Albemarle County, Virginia
Project Number 7-1916A
Geotechnical Investigation and Evaluation
practices. No otherwarranty, express or implied, is made. Our conclusions and recommendations
are based on design information located in plans provided to our firm by CEVA Contractors.
Regardless of the thoroughness of a subsurface exploration, there is the possibility that conditions
in other areas will differ from those at the boring locations, that conditions are not as anticipated by
the designers, or that the construction process has altered the soils conditions. Therefore, our
experienced geotechnical engineers should evaluate any further construction to verify that the
conditions anticipated in the design actually exist. Otherwise, we assume no responsibility for
construction compliance with the design concepts, specifications, or recommendations.
ll
Stevenson Consulting, Inc.
SUBSURFACE PROFILE LOG
BORING NUMBER: B-1
PROJECTCLIEN
Cascadia Detention Pond
PROJECT NUMBER
7-1916A
CEVA Contractors
DATE
July 21, 2021
KATTON
LOCATIAlbemarle
Count VA
County,
ELEVATION
Sipe Plan
E\CAVATiON METHOD
Truck Mounted Drill Rig
LOGGER
EB
DEPTH TO WATER:
Nia
WHEN CHECKED;
CAVING:
10'
EL:
Depth'
(fll
SPT:
USCS:
DESCRiPTiON:
N/a
0.25
10-11-18
N/a
1.00
N/a
2.00
9-22-19
N/a
3.00
N/a
4.00
8-9-12
N/a
5.00
N/a
6.00
N/a
7.00
4-5-9
Red clay, CH Fill
N/a
7.50
N/a
8.00
N/a
9.00
7-7-9
N/a
10.00
/a
1 I.00
/a
P
11'00
/a
13.00
8-5-4
N/a
14.00
N/a
15.00
4-4-7
N/a
16.00
N/a
17.00
Brown silty sand, SM Residual
N/a
18.00
50/3"
Boring Terminated at 18.5 Feet
N/a
19.00
N/a
20.00
N/a
21.00
N/a
22.00
N/a
23.00
N/a
24.00
N/a
25.00
N/a
26.00
N/a
27.00
N/a
28.00
N/a
29.00
N/a
30.00
NOTES:
2116E Berkmar Drive Charlottesville, Virginia 434-244-0011
Stevenson Consulting, Inc,
SUBSURFACE PROFILE LOG
BORING NUMBER: B-2
ROJECT
Cascadia Detention Pond
PROJECTNUM13ER
7.1916A
CLIENT
CEVA Contractors
DATE
July 21, 2021
LocnnoN
Albemarle Count' VA
County,
ELEVATION
$i[e Plan
EXCAVATION METHOD
Truck Mounted Drill Rig
LOGGER
EB
DFPTI I TO WATER:
N/a
WHEN CHECKED:
CAVING:
9;
EL:
Depth:
(t)
SPT:
USCS:
DESCRIPTION:
N/a
0.25
8-12-12
N/a
1.00
N!a
2.00
5-6-10
N/a
3.00
N/a
4.00
5-5-5
N/a
5.00
N/a
6.00
N/a
7.00
4-4-5
Red clay, CH Fill
N/a
7.50
N/a
8.00
N/a
9.00
3-3-3
N/a
10.00
N/a
11.00
N/a
12.00
Brown silty sand, SM Residual
N/a
13.00
5-6-39
Boring Terminated at 18.5 Feet
N/a
14.00
N/a
15.00
N/a
16.00
N/a
17.00
N/a
18.00
N/a
19.00
N/a
20.00
N/a
21.00
N/a
22.00
N/a
23.00
N/a
24.00
N/a
25.00
N/a
26.00
N/a
27.00
N/a
28.00
N/a
29.00
N/a
30.00
NOTES:
2116E Berkmar Drive Charlottesville, Virginia 434-244-0011
`Stevenson Consulting, Inc.
SUBSURFACE PROFILE LOG
BORING NUMBER: B-3
PROJECT
Cascadia Detention Pond
PROJECT NUMBER
7-1916A
CLIENT
CEVA Contractors
DATE
July 21, 2021
I-OCATION
Albemarle County, VA
ELEVATON
Si[e Plan
E.XCAVATTON METHOD
Truck Mounted Drill Rig
LOGGER
EB
DEPTH TO WATER:
N/a
WHEN CHECKED:
CAVFNG
g,
EL:
Depth.
(ft)
SPT:
USCS:
DESCRIPTION:
N/a
0.25
10-13-19
11
N/a
1.00
N/a
2.00
12-11-12
N/a
3.00
N/a
4.00
6-10-12
N/a
5.00
N/a
6.00
N/a
7.00
9-5-13
Red clay, CH Fill
N/a
7.50
N/a
8.00
N/a
9.00
9-13-26
Brown silty sand, SM Residual
N/a
10.00
Boring Terminated at 10.5 Feet
N/a
11.00
N/a
12.00
N/a
13.00
N/a
14.00
N/a
15.00
N/a
16.00
N/a
17.00
N/a
18.00
N/a
19.00
N/a
20.00
N/a
21.00
N/a
22.00
N/a
23.00
N/a
24.00
N/a
25.00
N/a
26.00
N/a
27.00
N/a
28.00
N/a
29.00
N/a
30.00
NOTES:
2116B Berkmar Drive Charlottesville, Virginia 434-244-0011
Project Name:
CascadiaDetention Pond
Project Number:
7 1916A
Report Date:
07/22/21 Date Received:
Lab Number:
E7 Sampled by: EB
Proctor Method:
AASHTO T99 A Tested by: EB
Description:
Red Brown Clayey SILT w/ Gravel
Material Source:
Proctor 1
115
110
105
MI
85
Moisture Density Curves
20 25 30 35 40
Moisture Content, %
2120 Berkmar Drive, Unit D
Charlottesville, Virginia 22901
434-244-0011
PROCTOR MAX. DRY DENSITY
94.7
PROCTOR OPT. MOISTURE, %
30.0
MATERIAL PASSING SIEVE
#4
% MATERIAL RETAINED
32.5
Gs, RETAINED MATERIAL
2.7
CORRECTED MDD, PCF 110.4
CORRECTED OMC, . 20.9
SIEVE
SIZE
(in./#)
PERCENT
PASSING
BY WT.
2.5 in
100.0
2 in
100.0
1.5 in
100.0
1 in
98.1
3/4 in
91.7
3/8 in
77.8
#4
67.5
#10
40.9
#20
40.9
#40
-13.7
#60
-32.0
#100
-51.4
#200
-58.5
Zero Air -Voids Curve for SG=2.70
SG value determined by estimate
SAMPLE
NUMBER
SAMPLE
DEPTH
(ft.)
SAMPLE
TYPE
USCS
CLASS.
AASHTO
CLASS.
NATURAL
MOISTURE
%
ATTERSERG LIMITS
LL PL PI
E7
2
0
N/A
1 A-1
21.1
42 37 1 5
Test Procedures: Natural Moisture Content, ASTM D2216 Atterberg Limits, ASTM D4318 (Single Point)
Sample Gradation, ASTM D422 USCS Classification, ASTM D2487
AASHTO Classification, AASHTO M145
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VSMP AMENDMENT PLAN FOR
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ROUDABUSH, GALE & ASSOCIATES, INC.
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Bob Cantrell
Order
CEVA Contractors Inc.
10997
195 Riverbend Drive
i3s
Charlottesville , VA 22911
PO
p.(434)906-1761
Projected Receipt
f. n/a
Thu 7/29/21
e. rwcbuild@ntelos.net
estimated
WETLAND PLANTS INC.
Terms: Payment due 48 hours before plants shipped
Ceratophplkun demersum
Coontail 6 inch cutting
1,566 51.09
$1,706.94
Juncus ejjusus
Soft Rush 5" deep x 1.6" wide plug
1,567 $1.09
$1,708.03
Schoenoplectus tabernaemontani
Softstem Bulrush 5" deep x 1.6" wide plug
1,567 $1.09
$1,708.03
# items 4,700
total for above items
$5,123.00
Free Shipping! (one shipment
per order, please!)
50.00
The prices above have been reduced in
the expectation that at least 3000 plants will be ordered and
a single delivery is acceptable to you,
the customer. There will be additional charge if the total
total
55,123.00
plants per delivery drops below 3000.
812 Drummonds Point Rd Edenton, NC 27932 p: 252.482.5707 f. 252.482.4987 team@wetlandplantsine.com
Wetland Plants Inc
812 Dntmmonds Point Rd Edenton, NC 27932 252,482.5707 team(wlwetlandplantsinc.com
Projected Receipt 7.29.2021 CEVA Contractors Inc. Bob Cantrell
Order 10997 total plants this order 4,700
4,700
Ceratophyllum demersum Coontail 1566 6 inch cutting sub for Waterweed
Juncus eJfusus Soft Rush 1567 5" deep x 1.6" wide plug sub for Cattail
Schoenoplectus tabernaemontani Softstem Bulrush 1567 5" deep x 1.6" wide plug
generated 7/23/2021 2:38:53 PM