HomeMy WebLinkAboutHydrogeologic Assess 001063007Ac peCtconsutting
IN-DEPTH PERSPECTIVE
May 14, 2003
Mr. Anthony Pellecchia
WPA
911 Western Avenue, Suite 380
Seattle, Washington 98104
Re: Porter Lane Property Well
Hydrogeologic Assessment
Project No. 021067-003-01
JEFF£RSON COUNTY
~D.[P.T. OF CO.~.MUt~iTY OEVELOPM[NT.j
Dear Anthony:
This letter-report presents a hydrogeologic assessment pertaining to local ground water
conditions near your property located at 513 Porter Lane, Port Townsend, Washington. It is
our understanding that a drinking water supply well located on your property.is within a
1,000-foot radius of a High Risk Seawater Intrusion Protection Zone (SIPZ), as classified by
Jefferson County. Jefferson County Department of Community Development has required that
a hydrogeologic assessment be submitted as part of your building permit application process
since your well is within the High Risk SIPZ. This letter-report is intended to meet the
requirement of a hydrogeologic assessment per the Jefferson County Unified Building Code
Section 3 - Land Use Districts, Section 3.6.5 Critical Aquifer Recharge Areas; (9) Well
Drilling, Land Division, and Building Permits in Seawater Intrusion Protection Zones, iv, C 3.
High Risk SIPZ Mandatory Actions.
In preparing this hydrogeologic assessment, we have reviewed the following material to base
our findings and conclusions:
· Water Well Reports on file with the Washington Department of Ecology (Ecology).
· On-site well yield test data..
· On-site well water quality data. .
· Jefferson County Unified Building Code.
· Property Location Maps, Topography Maps.
· Jefferson County Coastal Seawater Intrusion Policy and Ordinance.
· Map of Seawater Intrusion Protection' Zones, Eastern Jefferson County.
· Ecology report on the' Geology, water resources, and seawater intrusion assessment of
Marrowstone Island, Jefferson County, Washington.
· WRIA 17 report on Groundwater Quality Data Summary for Water Resources Inventory
Area 17.
Mr. Anthony Pellecchia - WPA
May 14, 2003
Project No. 020167-003-01
Project Description
The project is located on the north end of the Quimper Peninsula, approximately 4 to ~ miles
west of downtown Port Townsend, Washington (Attachment 1). The Pellecchia Property
(Parcel Number 001063007) is located at 513 Porter Lane and is a high-bani( rectangular lot of
approximately 6 acres which abuts the Straitof Juan. De Fuca to the north. The.southern end of.
the Pellecchia Property borders the McLaughlin Property (Parcel Number 001063003).
Attachment 2 is a parcel map that shows- the layout of the Pellccchia Property to the
McLaughlin Property. Review of the United States Geological Survey 1:24000 Port Townsend
South topographic map indicates that both the PellecChia and McLaughlin property are at an
approximate elevation of 160 feet.
A water supply well loCated on the McLaughlin Property has had a chloride reading greater
than 200 parts per million (ppm). A water quality data report obtained from Jefferson County
for a water sample collected on November 2, 2000 from the McLaughlin well indicates a
chloride level of 326 ppm (Attachment 3). As a result of the elevated chloride reading, a High
Risk SIPZ surrounding the McLaughlin well has been established by Jefferson County. A
High Risk SIPZ extends in a 1,000-foot radius from any individual well that exhibits a chloride
reading of 200 ppm or greater. The McLaughlin well is the only well on the northern portion
of the Quimper Peninsula that is classified as a High Risk SIPZ, which indicates a very
localized condition.
The Pellecchia Property water supply well was installed on November 8, 2001 (prior to Mr.
Pellecchia's purchase of property) and is located near the western property boundary over 400
feet from the shoreline. The well is approximately situated between 835 to 840 feet from the
McLaughlin well (Attachment 4). As a result, the Pellecchia well lies within the High Risk
SIPZ and requires the development of a hydrogeologic assessment as per the mandatory
actions identified in the Jefferson County Unified Development Code.
· Hydrogeologic ASsessment
Well Log Information
Wate~ Well Reports on file with Ecology were obtained and reviewed for both the Pellecchia
well and the McLaughlin well. The Pellecchia well and McLaughlin well were originally
recorded with Ecology as Kalalin Degroot and John Cahill, as the respective well owners at the
time of well completion. Copies of the well logs are presented as Attachment 5. A summary
of Well completion data contained in the well logs is presented in Table 1. The well logs
indicate that the Pellecchia well is completed in a shallow water-bearing sand horizon
(aquifer), which was encountered between 154 feet and 159 feet below ground surface and is 5
feet thick. The McLaughlin well is screened between a depth of 251 and 256 feet below
ground surface in a deep water-bearing Sand horizon, which is about 97 feet deeper than the
Pellecchia well. A thick sequence of clay encountered at the McLaughlin well between 135
feet and 247 feet appears to develop a confined aquifer condition at this well location. The
confined aquifer condition is further supported by the fact that the static ground water surface
is at a higher elevation than the top of the water-bearing sand horizon. A cross section
completed between the McLaughlin well and the Pellecchia well projected out to 'sea level is
presented as Attachment 6. The cross section indicates that the Pellecchia well and the
McLaughlin well are completed in distinct, shallow and deeper water-bearing sand zones,
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Mr. Anthony Pellecchia ~ WPA
May 14, 2003
Project No. 020167-003-01
respectively, that appears to be separated bY a low permeability clay horizon. Ground water
elevation and water quality data further support the two separate ground water zones.
Ground Water Elevation
Ground water flows fi:om areas of high head (elevation) to areas of low head. Ground water in
the project area is thought to be revving in a northerly direction and discharging into the Strait
of Juan De Fuca. Static groUnd water level data .collected at'the ti~ne of well completion
indicate a ground water level elevation of 22 feet and 5 feet, relative to mean sea level, for the
Pellecchia and McLaughlin wells, respectively. The data indicate that the Pellecchia water
level is about 17 feet higher in elevation than at the McLaughlin well. This water level data
indicate that the wells are completed in two different zones. If the wells were completed in the
same water-bearing horizon, the McLaughlin well, which is located south or upgradient of the
Pellecchia well, would have a higher ground water elevation.
Water Quality Data
Seawater intrusion can be evaluated by collecting water quality data at a well and performing
measurements for chloride. Ground water aquifers in direct hydraulic continuity, to the sea will
typically contain both fi:eshwater and saltwater. The freshwater, which is a lower density than .
the saltwater, will float on top of the denser saltwater. A mixing zone between the freshwater
and saltwater occurs as a result of hydrodynamic dispersion. This mixing zone typically
separates natural background freshwater (chloride levels typically <50 parts per million or
mg/1) from saltwater (chloride levels on the order of 19,000 mg/1) (Pacific Groundwater Group
& Parametrix, 2000).
Conductivity is a measure of the ability of water to conduct electricity hnd is measured in units
ofmicromohs per centimeter (Fmohs/cm) at 25 degrees Centigrade. Conductivity can be
easily measured with field monitoring equipment and proVides a good field-tool for evaluating
the relative level of dissolved compounds, such as chloride, in ground water.
Chloride and conductiVity has been analyzed at both the Pellecchia well and McLaughlin well
and are summarized in the following table.
Well Sample Date Conductivity Chloride (mg/l)
(~mhos/cm)
Pellecchia 11/5/2002 705 47.1
McLaughlin 11/2/2000 1870 326
The Pellecchia chloride sample was collected on' 11/5/2002, upon completion of a well yield
pump test after approximately 2.4 hours of pumping after a total withdrawal of 307 gallons of
water pumped fi:om the well. Conductivity was measured in the field throughout the well yield
test and stabilized after 100 minutes of pumping at a level around 700 [tmhos/cm. The
chloride level of 47.1 mg/1 is within the range of concentrations for natural freshwater
background and does not indicate seawater intrusion.
The sample collected at the McLaughlin well on-11/2/2000 contained chloride at 326 mg/1 and
conductivity at 1870 Fmhos/cm. This level of chloride would indicate that saltwater intrusion
Page 3
Mr. Anthony Pellecchia - WPA
May 14, 2003
Project No. 020167-003-01
is at an advanced stage in the deeper water-bearing sand zone that this well is completed in.
However, it is unclear, based on information reviewed for this report, as to how much water
was pumped or purged from the McLaughlin well PriOr to sample collection. Additional
ground water samples' analyzed for chloride are necessary to evaluate any trend in water ..
quality data and confirm with certainty that seawater intrusion is occurring at this well
location~ In our opinion, one single water quality sample does not form enough ora historical
data set to establish a High Risk SIPZ and its implications regarding surrounding land use.
The chloride data is another line of evidence that supports the fact that the Pellecchia well and
the McLaUghlin well are completed in different water-bearing zones. If the wells were
completed in the same groundwater system the Pellecchia well should exhibit an equal or
higher chloride concentration since the well is completed closer to-the sea than the McLaughlin
well. It appears that the upper sand horizon that the Peilecchia well is completed in contains a
much greater amount of freshwater. Chloride concentrations in ground water in the upper sand
horizon is within the range of naturally occurring background levels for freshwater.
Well Water Flow Test Data
A well water flow test on the Pellecchia well was conducted on 11/5/2002 by Peterson Pump
and Water Treatment (Peterson) of Port Hadlock, Washington. The well is outfitted with a
variable speed Grundfos pump with an above ground flow controller. The well was. pumped at
variable flow rates ranging between 1.75 and 3.5 gallons per minute (gpm) for a total period of
pumping of 145 minutes or 2.4 hours. Ground water level drawdown measurements, flow
measurements and conductivity measurements were recorded throughout the test. Attachment
7 contains the flow test data collected by Peterson. A graphical plot of the flow test data
showing drawdown at different pumping rates and conductivity reading for the duration of
pumping is shown in Attachment 8.
The flow test indicates that the Well is capable of producing about 3 gpm with a stabilized
drawdown at about 21 feet. As mentioned above, the conductivity readings also stabilized
during the 3 gpm pumping interval at about 700 ~mhos/cm. The conductivity reading '
collected throughout pumping do not show an increasing trend as would be expected if
saltwater intrusion was occurring.
Based on information obtained during well testing, a distance to the seaward or downgradient
stagnation point (area in the ground water flow field at which ground water is not moving
towards the well) can be calculated from the following equation (EPA, 1993):
Q
X~ 2zKbi
Where:
X~. = Downgradient distance to stagnation point
Q = Pumping rate (gpm) = 3 gpm
Kb = Hydraulic Conductivity x Aquifer Thickness = Transmissivity (gpd/ft)
Estimate T based on specific capacity (obtained by dividing pumping rate, Q
by drawdown, s (Q/s = 3 gpm/21 feet = 0.14 gpm/ti)
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Mr. Anthony Pellecchia - WPA
May 14, 2003
Project No. 020167-003-01
T = 1500'x Q/s (unconfined aquifer) (Driscoll, 1986) = 210 gpd/ft
i = GroUnd water gradient (unitleSs) = Ground water height above sea level/distance to
- Shoreline from well --.25 ft / 420 ft = 0.06
(3 gpm)(1440 min/day) ~ 55 feet
2(3.1416) (210 gpd!fi) (0.06)
The results of this analysis suggests that the Pellec~hia well pumping at a rate of 3 gpm will
draw ground water from the. downgradient or seaWard side at a distance of 55 feet from the
well. This indicates that the well will not draw in seawater and leaves about a 365--foot buffer
between the sea and the downgradient area of influence of the well.
Conclusions
The following conclusions are developed based on a review of the available hydrogeologic
data:
1. The Pellecchia well is completed in a shallow Water-bearing sand horizon which does not
appear to be connected to the zone that contributes ground water to the McLaughlin well.
A thick sequence of clay appears to provide a natural barrier that separates the shallow and
deep sand horizons.
2. Chloride and conductivity measurements collected from the Pellecchia well indicat& a fresh
ground water source that is within the range of naturally occurring background.
3. The Pellecchia well appears to be able tO sustain a pumping rate of 3 gpm and at that rate
the downgradient radius of influence would not extend to the sea.
4. An approximate 365-foot buffer exists between the downgradient radius of influence of the
Pellecchia well and the sea.
§. A variable speed pump is installed in-the Pellecchia well and could be adjusted to a lower
flow rate if future water quality readings warrant an adjustment.
6. A 1,000-gallon storage tank will be installed in the Pellecchia water system which will
allow for adequate storage and limit the overall pumping of the well.
?. The Pellecchia development plan intends to infiltrate storm water in an area between the
well and the sea which will further protect the shallow water-bearing horizon from
seawater intrusion.
Based on the data available for review, it appears that there is reasonable Probability that
pumping at the Pellecchia well will not cause further degradation to the deeper zone supplying
water to the McLaughlin well.
Page 5
Mr. AnthonY Pellecchia - WPA
May 14, 2003
Project No. 020167-003-01
References
Driscoll, Fletcher G., 1986, Groundwater and Wells, Johnson Division.
Environmental Protection Agency, February 1993, Wellhead Protection: A Guide for Small
Communities, EPA/625/R-93/002.
Pacific Groundwater Group and ParametriX, In&, June 2000, Groundwater Quality Data
Summary for Water Resources 'Inventory Area 17, prepared for Water Resources Inventory
Area 17 Planning Unit.
Limitations
Work for this project was performed and this report prepared in accordance with generally
accepted professional practices for the nature and conditions of work completed in the same or
similar localities, at the time the work was performed. 'It is' intended for the exclusive use of
Anthony Pellecchia for specific apPlication to the referenced property. This report does not
represent a legal opinion. Within the limitations of scope, schedule andbudget, our services
have been performed in accordance with generally accepted hydrogeology practices in effect in
this area at the time our report was prepared. No other warranty, expressed or implied, is
made. The statements presented in this letter-report were developed based on data readily
available or provided by Anthony Pellecchia for my review.·
Page 6
Mr. Anthony Pellecchia - WPA
May 14, 2003 Project No. 020167-003-01
!f you have any questions regarding information contained in this report, Please do not hesitate
to call me at (206) 780-9370.
SinCerely,
Aspect consulting, LLC
~ .~. I_.John Jacob
John J. Strunk,
Associate Geologist
j stmnk~aspectconsuiting.com
Attachments:
Table 1 - Well Records
Attachment 1 - Location Map
Attachment 2 - Parcel Map
Attachment 3 - Water Quality Reports
Attachment 4 - Distance from Pellecchia Well to McLaughlin Well Map
Attachment 5-- Well Logs
Attachment 6 - Cross Section
Attachment 7 - Flow Test Data
Attachment 8 - Pump Test and Conductivity Measurement Graph
W:\020167 Porter Lane Welrt020167-003-01 Hydrogeo Letter. doc
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information is based on the 1998 Comprehensive Plan Map and does not include changes made
the 1999 Comprehensive Plan amendment process~ Zoning designations must be confirmed with the
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Temperature o! water_
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Time Since Pumping Started (minutes)
::::j:::: ==================================== ::
. . ~ - - ~ : :. - : · -~- .- ~ .... ~ .... ~ .... ~ . . : : :
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Time Since Pumping Started (minutes)
Pump Test conducted on 11/5/02 by Marry Peterson of Peterson Pump & Water Treatment, Inc.
Well Depth 170 feet
Static Ground water Level 135.25 feet
Well Screen 154 - 159 feet
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