HomeMy WebLinkAboutSUB200500130 Assessment - Groundwater 2005-06-01 Tier 3 Groundwater Assessment
and
Groundwater Management Plan
Proposed family division of TMP 22-4B
Helios Path
Prepared for:
Mike Sadler
Jefferson Area Builders, Inc.
520 Greenfield Terrace, Suite 100
Charlottesville VA 22901
Draft submitted June 1, 2005
Nick H. Evans PhD CPG
Virginia Groundwater LLC
4609 Burnley Station Road
Barboursville, VA 22923
E �
REC1W
304 "13 20n
Key Findings
Hydrogeologic unit: Lynchburg Group (IV)
Groundwater availability zone: Class 3 (highest relative availability)
Hydrogeologic conditions favorable to proposed use? yes
Site within groundwater sensitivity zone? no
Groundwater flow pattern: east southeast, toward discharge into Preddy
Creek; shallow groundwater on site flows northeast and south to discharge into
unnamed drainage in center of parcel
Contamination threats on record: no open UST cases inside one mile buffer;
no open cases of toxic release
Additional contaminant threats observed in field reconnaissance? no
Impacts of proposed use on existing users: none anticipated
BMP recommendations: maintain undisturbed forest cover as much as possible
during development, particularly on steep slopes bordering intermittent stream in
the center of the parcel; implement runoff-neutral site plans insofar as
practicable.
Site Overview: The parcel (TMP 22-4B) is located in the northern part of
Albemarle county off Burnley Station Road, about a mile west of Burnley. The
setting is rural, existing land uses surrounding the parcel are residential. Lot
sizes in the immediate area are on the order of 2 to 5 acres, with larger parcels
abutting to the southeast (Figure 1).
The parcel encompasses the headwaters of an unnamed intermittent stream that
flows southeast into Preddy Creek. Preddy Creek is a tributary of the North Fork
Rivanna River.
Field reconnaissance was conducted on
111111.
• the property on May 17, 2005. The
northern portion of the property is
presently forested in mixed hardwoods,
with some open areas. The southern
portion is an open field (left), where three
of the four proposed new houses would
be sited. The fourth would be located
northwest of the open field, on land that is
presently wooded.
There is about 150 feet of relief on the parcel, with 15 to 45 percent slopes in the
northern portion, and gentler slopes in the open southern portion.
Hydrogeologic Assessment
Bedrock geology
The parcel straddles three mapped bedrock units within the ProterozoicZ-age
Lynchburg Group (Figure 2, Geologic Map of Virginia, 1993). The rock-types
contained in these units are metamorphosed
eirf
sedimentary rocks including metagraywacke, -. may: '. •► ' '".1+ :
graphite schist, sandstone, siltstone and slate. ;KV `.�¢ :'• - .
The contacts between the three mapped - " ` ,
bedrock units are gradational in nature over .'�� ° ; 'r,� iy � -.
several hundreds of feet.
Right: graphite schist exposed in fill from ` '
Drainfield test pit %/Pv- _. '15 =
Of the various rock types that occur within ' .� ^°' # `,~ '�
these units, graphite schist is the dominant
rock observed during field reconnaissance, amply exposed in each of several
exploratory test pits that had been previously dug in the process of drainfield
evaluation on the portion of the property where the proposed
Figure 1 : Location map, TMP 22-4B, Helios Path;
local surface water drainage areas mapped in blue.
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Figure 2: Mapped geologic contacts Zlm: Lynchburg Group metagraywacke
TMP 22-4B, Helios Path Zig: Lynchburg Group graphite schist
Zch: Charlottesville Formation sandstone,
(1993 Geologic Map of Virginia) siltstone and slate
v database water well
.+
4
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houses are sited. Within the schist are interlayers of ', 71,7' NS IQ
iron-rich sandstone that contain the mineral pyrite. ��ti
144
Right: sandstone layer in graphite schist contains •
;weathered remnants of pyrite crystals. °rs '• -�
#,
All three geologic units that cross the parcel are L I J r
included in the Lynchburg Group (IV) hydrogeologic _, �+ i r • • '1 •
unit, with Class 3 (highest) relative groundwater
( g )
availability, as defined in the Albemarle County Hydrogeologic Assessment
Summary Report of 2003.
Bedrock fracture density and water well productivity
The bedrock underlying this parcel does not contain primary intergranular
porosity through which groundwater might pass. Groundwater flow is confined to
bedrock fractures and fissures. No significant linear features, fracture traces or
structural features were identified on air photos or other maps in this study that
would be useful indicators of bedrock fracture orientation on this parcel.
In the absence of good bedrock exposures with which to directly observe
bedrock fractures, the yields of randomly-sited water wells can be used as a
proxy for fracture density. Table 1 (below) summarizes data from 226 wells
constructed in the Lynchburg Group within Albemarle County. The data indicate
that on average, ample water-bearing bedrock fractures exist in these rocks to
supply groundwater to drilled water wells.
Table 1: Database wells county-wide
within each represented geologic formation
Average total depth Average Average yield
Geologic formation (feet) casing (gallons per count
length (feet) minute)
Lynchburg Group, 197 47 15' 76
Charlottesville Formation (Zch)
Lynchburg Group 186 45 12 128
metagraywacke (Zlm)
Lynchburg Group 204 65 14 22
Graphite schist(ZIg)
In terms of the immediate vicinity of the parcel, there are 22 domestic water wells
in the Albemarle County database that are within 1000 feet of the property (Table
2, below). Some of the numbers suggest that this set of data contains duplicate
entries, but overall the reported yields are more than adequate for a domestic
well. It should be noted that dry holes are under-represented in the database.
The success of a water well still depends on whether or not the well intersects
water-bearing fractures, and "0" yield holes result if no fractures are encountered
at the drilling site chosen.
Table 2: wells within 1000 feet of TMP 22-4B
Total depth Casing length Yield "natural flow rate" Static water level
(feet) (feet) (gallons per minute) (gallons per minute) (feet)
122 50 0.0 7 0
165 45 0.0 20 0
165 71 6.0 0 0
165 64 30.0 0 0
205 65 30.0 0
205 65 30.0 0 0
206 55 10.0 10 30
215 42 15.0 0 42
215 42 15.0 0 42
225 34 0.0 5 0
225 84 5.0 0 0
225 165 5.0 0 0
225 135 4.0 0 0
265 4.0 0
265 107 4.0 0 0
305 82 5.0 0
305 82 5.0 0 0
305 2.0 0
305 117 2.0 0 0
325 146 3.0 0 0
405 128 4.0 0 0
405 I 14.0 10 133
Graphite schist bedrock presents challenges in water well construction. The rock
is relatively soft, and readily crumbles or collapses into an open well bore, even
at considerable depth where the rock is fresh. Wells drilled into this particular
rock commonly need to be cased to depths of 100 feet or more, and may then
need to have screen installed in order to prevent graphite powder from entering
the usable water column. There are also commonly groundwater chemistry
issues in wells constructed in this type of rock. The presence of the mineral
pyrite in water-bearing bedrock fractures can result in high levels of iron and
acidity in groundwater.
Soils and saprolite
Soils on the parcel are Watts channery silt loam (Figure 3), which are derived by
in situ weathering of graphite schist. Permeability of these soils is moderately
rapid; hazard of erosion is classified as severe.
Graphite is relatively stable in the weathering environment, and saprolite derived
by chemical weathering of the graphite schist bedrock is thin to non-existent.
Pieces of graphite schist bedrock occur within a few feet of the surface. Although
a thick prism of clay saprolite is not present in this type of geology, the upper 50
feet or more of bedrock schist is fragmented, and appears to be an effective
medium for storage of groundwater and transmission to deeper bedrock
fractures.
Due to the low natural fertility of these soils, the root zone is very shallow, and it
is difficult to establish stable vegetative cover on slopes that have been cleared.
On this parcel, groundwater recharge, as well as surface water quality
downstream, would be best served by preserving existing forest cover on the
slopes bordering the unnamed intermittent stream in the center.
Groundwater flow, recharge and discharge
The groundwater flow pattern on the property is estimated to mimic surface
topography, with local recharge at higher elevations along the ridge that borders
the western edge of the parcel, and discharge to the east into the unnamed
intermittent stream that bisects the parcel (spring, Figure 4).
- ' "..::vM f 4-7-,-,,,..'
a ti y��.
Right: spring at head of intermittent #,`4
stream on parcel; black, graphite-rich_, ' _ - r "`�'y
soils exposed in bank. .. ,; . ., - , w-
41i)(7 . "..-- ' ... . -
At deeper levels, groundwater flow is predicted to be generally southeast, with
discharge into Preddy Creek and the North Fork Rivanna River.
Figure 3: Soils mapping in the 93C--Watt channery silt loam, 7-15%slope
vicinity of Helios Path 93D--Watt channery silt loam, 15-25% slope
93E--Watt channery silt loam, 25-45% slope
1/ L.r ]` - r r ` r r
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Figure 4: Estimated local groundwater flow
paths (blue arrows) in the vicinity • spring
of TMP 22-4B
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Groundwater sensitivity and contaminant threats
The parcel is not within an area of recognized groundwater sensitivity according
to a County study or databases that were assembled during the 2003 Albemarle
County Hydrogeologic Assessment, Phase II (Figure 5). The property is about 2
miles from the closest known LAST or LUST case site, and about 3 miles from
the closest public water supply well.
Toxic releases on record
As of May 18, 2005, the US Environmental Protection Agency Toxic Release
Inventory contained no entries that are within one mile of the site an ne
beyond one mile that are considered a threat to groundwater re rge. Ott-, (/ka
The Virginia DEQ toxic release database does not show open cases that are
within one mile of the parcel, or beyond one mile, in areas considered a threat to
groundwater recharge affecting the site.
Underground storage tanks
The current Virginia DEQ registry of underground storage tanks does not show
registered tanks that are within one mile of the parcel, or beyond one mile, in
areas considered a threat to groundwater recharge affecting the site.
Residential drainfields
There are 26 or more residential drainfields on nearby properties within 1000 feet
of the parcel (Figure 6). However, few if any of these are up topographic
gradient from the probable well sites for the proposed houses. All but one are
on land that slopes away from the proposed development lots. There is little
likelihood of this parcel receiving contamination from a drainfield on a
neighboring parcel.
Potential for proposed use to affect existing users of groundwater
The proposed subdivision is for the most part within its own watershed; existing
users on adjoining parcels are either up gradient, or on the other side of
topographic divides from the proposed house sites. Existing forest cover has
been widely preserved in site design on adjoining parcels. The geology and soils
characteristics of the area, discussed above, are favorable to groundwater
development at the proposed density of 4 additional users on 20 acres.
The proposed use of groundwater is not predicted to interfere with existing users
on adjoining parcels or elsewhere. Groundwater availability is estimated to be
Figure 5: Locations of known LAST and LUST 0 LAST and LUST case sites,
case sites and public water supply 1000-foot buffer shown
wells in northern Albemarle county
• Public water supply wells,
1/2 mile buffer shown
141
imoik _ s
410 kill
11( 41,jv
/407-- 1)#111k
Pejk./ wry
•
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t4,141-- *Iek
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w+E
¶,p miles� i'les ,0
Figure 6: Locations of drainfields
in the vicinity of TMP 22-4B • inferred drainfield, location imprecise
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more than adequate to supply the needs of the 4 proposed additional houses
without affecting neighboring wells.
Reserve wellfield
The individual proposed parcels are large enough that it appears there would be
room on each to site a second or a third well to be sited, should that become
necessary.
Dedicated Monitoring well
This parcel is not in an area of intensive groundwater development at the present
time, and the proposed use is not predicted to stress groundwater resources off
site. It would seem this is not a priority site for a County dedicated monitoring
well.
Best Management Practices: recommendations
Steep slopes on this parcel and sever erosion hazard make it imperative that
existing forest cover be left undisturbed wherever possible. This is particularly
important on the steep slopes adjacent to the intermittent stream in the middle of
the parcel.
Prepared and submi d by Nicholas H. Evans, CPG # 2801 001041
May 28, 2005 11111;
DEPARTMENT OF PROFESSIONAL AND OCCUPATIONAL REGULATION
COMMONWEALTH OF VIRGINIA NUMBER
EXPIRES ON 3800 West Broad Street,Richmond,VA 23230
08-31-2005 Telephone:1(804)387-8500 2801 001041
J
BOARD FOR GEOLOGY
CERTIFIED AS A PROFESSIONAL GEOLOGIST
NICHOLAS H EVANS
4609 BURNLEY STATION ROAD ."W
BARBOURSVILLE, VA 22923
AMMrd W 111t1 OOOmen,USE ui[5 EXPRCICk oa use IY eel601e oA MSS ONES Louise P. Were, Director
Oux moce Mwr,O.uv rw c�uc PAOtaanicu ueoa 1,C coer a VS001A
0 50 100 200
SCALE IN FEET
Legal Reference:
D.B.762 Pg.710
I .S .= Iron Set
I .F .= Iron Found
U.P.= Utility Pole
Owners: John L Sadler C
Betty W. Sadler
2478 Milton Hills Dr.
Charlottesville, Va. 22902
Property Zoning: RA
The boundaries of the land
shown hereon is from a
current field run survey.
Utilities and easements other
than those shown may exist.
The contours shown were interpreted from the U .S .G .S . map,
however,
the drainfields shown are from a current field run
survey.
EN
l0 Co
.H
L CL
� �Y'
Building
Setbacks:
ON
Front
= 25'
000
LN
Side
= 15'
o •
Rear
= 25'
U Co
a) -
cc o
T.M.P. 22-39
Douglas E. Chandler; etux
0.8.823 Pg.507
0.8.816 Pg.283 (plat)
The properties shown hereon lie
in Flood Zone C and not in an
area designated as Zone A
MO Year Flood Hazard) .
Only 1 dwelling will be allowed
on Parcel "A".
Parcels "A" & residue each have
30,000 sq . ft . of contiguous
buildable area in slopes less
then 25%.
All parcels will be served
by private water and septic
systems.
The private road will provide
reasonable access by motor
vehicle as required by Sec.
14-514 of the Alb. Co. code.
The said road may not meet
the standards for acceptance
into the secondary system
of State Highways and will
not be maintained by V .D .O.T .
or the Co. of Albemarle.
This is a family division created
in accordance with Sec.14-208
and related provisions of the
Alb. Co. code. Ownership of
Parcel "A" shall not be trans-
fered to a person other than a
defined member of the immediate
family for a period of two years
from the date of recordation of
this plat except as authorized
by Sec.14-212 (A) of the Alb.
Co. code. If Parcel "A" is
conveyed back to the grantor
within this period it shall be re-
combined with the residue
shown.
PLT H O,c
o
O H
U D
Robert W. Coleman, Jr.
No. 2007
SUR���i
r
/ T.M.P. 22058
Ricky u Kathleen
OahlstOrm
O.3.1303 Pg.741
Iron Iron \
Fd. __Set_
Iron N�6 - r+-- S28DA0 itotal) _ Iron
Fd. utility 98 - _ Fd.
/ pole
r /r
r
r
�Parcel 4B
3.1504 Acres
/ --
utility residue
Pole �. -�-i-
` / \
/Parcel4B-1
P ___. / / 4.5473 Acres
rn�
Cl)
Parcel 4B-2
Z 4 n231 Acres
J
17 / \ spring
16 \ no \ \ S \C\ \ x \ \5 S00 \ •ti��
T.M.P. 22-10C
Harold T. Chapman, etux
0,51453 P9.304
O.8.404 P9.397 (Plat)
Iron
Set
Iron
Set
OWNERS APPROVAL
The family division of the land described
hereon is with the free consent and in
accordance with the desire of the under-
signed owners. Any reference to future
development is to be deemed as theorectical
only. All statements affixed to this plat are
true and correct to the best of my knowledge.
Owners: T.M.P. 22 - 4B
John L. Sadler
Betty W. Sadler
NOTARY PUBLIC
The foregoing instrument was
acknowledged before me this
day of
200_.
My commission expires,
,200
Lau Lll.
Date
APPROVED FOR RECORDATION
Director of Planning Date
�k Iron \
\ Fd.
14
��* \ �,�\ SO ~ ,� ` -,' \ \ -- creek --•� _ / ��'
O (3 ®V I ��Iron Set 25' Ano 0,o xA\ \ \ c
B)6 9, 12 ` from corner , O�e1 aSea \ \� \ \ Parcel 4B-4
1 Dr in rj 4.1252 Acres
9._08 10 \ IFie�ld \ s�o \ �2A \ \ \
I \ • D
T.M.P. 22-40
Marc T. Alderdice, etux
0.8.1941 P9.593
0.8.762 P9.708 (Plat)
.Metal
Shed SS
\ o. cc
ParcelAID —3
�-- 4.2634 Acres
�0 \ \\ \\ 540 20,
15 \°°^ �s 90 ; Pro ' ' \ \\ \\ \\\� \ b`� ��,•
\ e pose a��, n \ \ \ \ ^ \
Property Line Courses 1 - 18
along � Helios Path
1)
N48 '47 '30 "W
55.78 '
10)
N71 ' 12 '42 "W
36.49 '
2)
N47 °13'15"W
124.24'
11)
N79 °55'22"W
108.86'
3)
N42 °19'48"W
112.36'
12)
N72'19'35"W
115.28'
4)
N34 '08 '35 "W
58.09 '
13)
N65 °47 '03 "W
65.16 '
5)
N25 °39 '37 "W
57.69 '
14)
N54 '26 '52 "W
52.83 '
6)
N21 ' 19 '32 "W
55.66 '
15)
N47 ' 18 '36 "W
52.06 '
7)
N 15 ° 12 ' 14 "W
36 ,79 '
16)
N37 '45 '27 "W
48.82 '
8)
N33 '57 '06 "W
36.79 '
17)
N29 °27 '40 "W
101.63 '
9)
N52 °37 ' 15 "W
36.49 '
18)
N23 *41 '28 "W
72.52 '
\ \ s Proposed
5 \ °°h�� \Dwelling
0''s' 524—
\ \ Ap
4 \
\ — —Dr-a
516 — ` Field, —
\ l
ti
512.---
T.M.P. 22-44
Carlton W. Carr011, etux 2�
0.8.974 Pg.388 4
0.8.752 Pg.708 (Plat) \ \ \ \
s°0/1
\
a \�
T M.P. 34-50A
E16an01- M. Santic
D.8.987 0g.607
O.B.921 Pg.188 (Plat)
PLAT SHOWING
FAMILY DIVISION OF
T.M.P. 22 - 4B
LOCATED ON
HELIOS PATH
RIVANNA DISTRICT
ALBEMARLE COUNTY, VIRGINIA
JANUARY 28, 2005
04-424 FD