accomack county planning overview of ground water on the ... · 4/22/2014 · overview of ground...

Accomack County Planning Commission

Overview of Ground Water on the Eastern Shore Curt Smith Director of Planning Accomack-Northampton Planning District Commission April 22, 2014

A-NPDC Overview and Purpose • Commonwealth created 21 PDCs in 1970 to address

regional issues by fostering cooperation amongst localities and cooperation between state & localities

• Accomack-Northampton District: • Members: 2 Counties and Town of Chincoteague • Also provides services to 18 other towns

• Affiliate Organizations: • A-N Regional Housing Authority provides privately or authority-

owned rental housing • ESV Housing Alliance improving housing for homeowners • A-NPDC

• Community Development • Economic Development • Transportation Planning • Environmental Planning Ground Water Committee; Climate

Adaptation Working Group

Accomack-Northampton Planning District Commission

Presentation Overview

1. Geologic/Hydrogeologic Framework Evolution

2. Ground Water Conditions

3. Ground Water Use

4. Threats to Ground Water Quality

5. Ground Water Management and Water Supply Planning


Geologic/Hydrogeologic Framework Evolution

• Timeline: i. Opening of Atlantic Ocean & Salisbury Embayment – ≈180 Million

Years Ago (MYA)

ii. Filling of Salisbury Embayment (Potomac Formation) – ≈180 to 35.5 MYA

iii. Bolide impact & removal of pre-impact sediments – ≈35.5 MYA

iv. Deposition of post-impact sediments – ≈35.5 MYA – Present

v. Reworking of surficial sediments & progradation of peninsula – ≈200,000 YA – Present

vi. Sea level reaches elevation of modern Chesapeake Bay transitioning system from riverine to estuarine - ≈8,000 YA

vii. Sea level continues to rise and inundate the Chesapeake Bay watershed and the Chesapeake Bay begins to take its modern appearance we currently recognize - ≈3,000 YA



Ward and Powars, 1991

Development of Salisbury Embayment

Millions of Years AgoMillions of Years Ago

• Basin feature in bedrock created by tectonic forces during the opening of Atlantic Ocean

• Bound by arches, or elevated regions, of bedrock

• Basin filled by intermittent marine overlap and sediment deposition


Bailey and Johnson, 1999

Opening of Atlantic Ocean



USGS PP#1688

In-Filling of Salisbury Embayment


Hampton Accomac • Sea level highstands =

• Shoreline west of area • Shallow sea conditions

here • Deposition of marine

sediments • Fine sediments settle out

during normal conditions

• Punctuated by deposition of larger-grained sediments (silts/sands) during storm events

• Shoreline transgressions & regressions = • When ocean shoreline

migrates over area • High energy = reworking

of sediments, deposition of sands and “flushing” of fines


Olsson (1980), Powars & Bruce (1999), Owens & Gohn, 1985), Kolwecz (2008)

Chesapeake Bay Impact Structure


Virginian Pilot USGS


USGS Chesapeake Bay Evolution Animation (Bratton et. al, 2009)


Development of Eastern Shore & Chesapeake Bay

Colman et al (1990)

Hobbs (2004)

Scott (2006)


Surficial Features: Relict Shorelines

Cintos (2012)

Mappsburg Scarp

Cheriton Scarp

Pungoteague Scarp

Bailey (2009)

Suffolk Scarp

Ames Ridge


2-D view of

LiDAR data

ground

elevation only

South-Central Accomack County (Melfa, Keller, & Painter)

The Nature Conservancy (2011)

2-D view of

LiDAR data

ground

elevation only

Chincoteague


2D view of LiDAR data

ground elevation only

Saxis/Sanford

2-D view of LiDAR data

ground elevation only



Surficial Features: Carolina Bays

Cintos (2012)

• Over 700 shallow, elliptical depressions • Similar orientation

(NW-SE) • Variable size (1 – 1,000

acres) • Some overlapping • Coarse-grained rims • Fine-grained floors

• Variable ages (100,000-<5,000 years)

• Debated origin • Wind & Water

• Shock wave from bolide explosion

NASA-WFF

Accomack-Northampton Planning District Commission 16


Cintos (2012)







November 6, 2013

Parksley

Accomack-Northampton Planning District Commission 17


Cintos (2012)







November 6, 2013

Onancock

Ground Water Conditions on the Eastern Shore


Ground Water is not like an underground river!

• Groundwater flows through porous soils and sediment that includes gravels, sands, silts, and clay.


Soil/Sediment type determines if it can be used as a source of water

Any coarse grained material (sand, gravel) that can supply sufficient water for a beneficial use

A Confining Unit Impedes Movement of A Confining Unit Impedes Movement of Groundwater and is: Groundwater and is:

Any fine grained material (silt, clay) that can significantly restrict vertical movement of groundwater such that the

resulting groundwater is under pressure.

An Aquifer is a Source for Groundwater and is:An Aquifer is a Source for Groundwater and is:


• Water Table • Water is not “under pressure”

• Well yield is lower than comparable confined aquifers

• Replenished (recharged) directly by precipitation

• More vulnerable to contamination from surface activities

• Confined aquifer • Water is under pressure, confined by an overlying layer(s) of silt and

clay

• Replenished from vertical flow through the confining unit (recharge is much lower than a water table aquifer)

• More vulnerable to saltwater intrusion

Aquifers are defined by where they appear relative to a confining layer



All Groundwater Aquifers on the Eastern Shore

S N Kiptopeke Cape

Charles Exmore Jenkins Bridge

Water Table

Yorktown-Eastover

St Marys

Piney Point

Potomac

Source: McFarland and Bruce, 2006

• Fresh Groundwater is restricted

to the Columbia (Water Table)

aquifer and significant portions

of the Yorktown-Eastover aquifer

• Brackish groundwater is found in

portions of the Yorktown-

Eastover, all of the St. Marys

Aquifer, Piney Point, and

Potomac aquifers

• The Columbia, Yorktown-

Eastover, and Piney Point

aquifers are found throughout

the Eastern Shore

• St. Marys and Potomac Aquifers

are absent in the southern

portion of the Shore


WEST Water Table Surface

Confining Unit

Freshwater Aquifer

Saltwater Aquifer

Estimated Recharge to Water Table Aquifer = 625 MGD approx Estimated Recharge to Yorktown-Eastover Aquifer = 9 MGD approx (based on USGS Eastern Shore Model)

Water Table and Fresh Water Confined Aquifers on the Eastern Shore

Fresh ground water is restricted to depths less than 350 feet


Movement through the Groundwater System

• Horizontal flow typically toward a surface water body. Gradient is often low and the actual flow rate is low

• Vertical flow typically downward and very low


Hydraulic Gradient Under Confined Pumping Conditions

• Horizontal flow may be re-oriented toward well. Gradient (flow rate) is often significantly increased

• Vertical flow remains downward but rate often significantly increased


Groundwater Levels under no Pumping

Confined Aquifer

Water Table Aquifer Level (no Pumping)

The pressure in the aquifer changes with distance from the well.

Confining Layer

Confined Aquifer Level no Pumping)


Pumping from a confined aquifer with little leakance through the confining layer

Confined Aquifer

Water Table Aquifer Level

(Pumping)


Confining Layer

Confined Aquifer Level

(Pumping)


Pumping from a confined aquifer with significant leakance through the confining layer

Confined Aquifer

Water Table Aquifer Level

(Pumping)


Confining Layer

Confined Aquifer Level

(Pumping)


Multiple Wells Additively Increase

Water Level Declines

Static Water LevelStatic Water Level

DrawdownDrawdown

in the in the

Pumping WellPumping Well

Cone of Cone of

DepressionDepression

(Single Well)(Single Well)

Drawdown in AdjacentDrawdown in Adjacent

(Non(Non--Pumping) WellPumping) Well Drawdown Due to PumpingDrawdown Due to Pumping

Adds to Existing DrawdownAdds to Existing Drawdown Cone of Depression is Cone of Depression is

Superimposed on the Superimposed on the

Existing Cone of Depression Existing Cone of Depression

AquiferAquifer

The Cone of Depression is The Cone of Depression is

the Sum of Each Well’sthe Sum of Each Well’s

Cone of Depression Cone of Depression

How Much Water Recharges the Aquifers?

• All fresh water comes from precipitation falling directly on the Shore

• About 88% of the precipitation never infiltrates to the groundwater

Total Rainfall

Recharge to Water Table

Recharge to Yorktown Aquifer


How Much Water Recharges the Aquifers?

• Most of the rainfall never infiltrates to the groundwater and is lost through: •Evaporation • Interception (on plants and trees) •Direct runoff

•Evapotranspiration


Of the water infiltrating to the water table, only a small amount reaches the Yorktown aquifer

• Limited Recharge: • Of the 44-inches of annual precipitation only 5 to 6

inches infiltrate to the water table (625 MGD)

• And only about 0.05 in/year make it to the confined aquifer (9 MGD)

Total Estimated Recharge to Water Table Aquifer = 625 MGD 15%

1%

84%

Evapotranspiration

Discharge to Surface Water

Leakage to Yorktown Aquifer


Recharge amounts vary across the Shore

Recharge to Surficial Aq Location of Paleochannels Recharge to Y-E Aq

Recharge to the water table is a function of soil type, slope, and location

Estimated Recharge Rates

Source: USGS

Potential Recharge areas (based on soil type and slope)

Source: USGS


Recharge to the Yorktown depends more on where pumping from the aquifer is occurring

Estimated in 1900 (pre-pumping)

Estimated in 2003 (Effects of pumping)


Recharge rate to the Yorktown has increased over time due to pumping

0

2

4

6

8

10

12

1900 1920 1940 1960 1980 2000

Mil

lio

ns o

f G

all

on

s p

er

Day

YearSource: USGS Eastern Shore Model

• Current Yorktown-Eastover Aquifer use

exceeds recharge by approximately 1

MGD

• Recharge will

increase as use

increases – but

will NOT keep

pace with

pumping


Estimated Water Ages Reflect Recharge Rates Water Table Upper Yorktown Middle Yorktown LowerYorktown


Water Table / Yorktown Dilemma

WATER TABLE AQUIFER WATER TABLE AQUIFER DEEP AQUIFER DEEP AQUIFER

Little Storage

Low Inflow

High Use High Use Little Use Little Use

Large Storage

High Inflow


WEST Water Table Surface

Confining Unit

Freshwater Aquifer

Saltwater Aquifer

Estimated Recharge to Water Table Aquifer = 625 MGD approx Estimated Recharge to Yorktown-Eastover Aquifer = 9 MGD approx (based on USGS Eastern Shore Model)

Ultimately the Balance of Recharge to Use Dictates Stability of the Fresh Water Lens

Fresh ground water is restricted to depths less than 350 feet


Groundwater Use on the Eastern Shore

DEQ Permitted Wells

Public Water Supply

Commercial

Industrial

Irrigation


Ground Water Use and Ground Water Level Measurements

• Ground Water Use for permitted wells (wells pumping greater than 300,000 gallons-per-month) are submitted to VDEQ

• Ground Water Levels are routinely measured in Observation Wells by the USGS


Non-Agricultural Ground Water Use Trends

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Annu

al G

roun

d W

ater

Use

(MGD

ave

rage

)

Accomac County

Northampton County


All Permitted Ground Water Use

0

1

2

3

4

5

6

7

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Northampton Agricultural

Accomack Agricultural

Northampton Public/Commercial/Industrial

Accomack Public/Commercial/Industrial


Types of Groundwater Use

18%

62%

20%

Irrigation

Commercial/Industrial

Municipal

Groundwater Use DistributionFrom Calendar Year 2002

Why Measure Ground Water Levels?

• Ground water use: • Lowers ground water levels, reducing available water to other

ground water users

• Reduces the size of the freshwater lens

• Impact of ground water use can be evaluated: • Indirectly using models

• Measured directly from pumping wells and observation wells


Water Level Change and Monthly Use

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000 0

10

20

30

40

50

60

70

80 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Mo

nth

ly W

ate

r U

se

(G

PD

ave

rag

e)

De

pth

Be

low

Gro

un

d S

urf

ac

e (

ft)

67M 13 SOW 115D - Screen Depth = 239-249 ft Chincoteague Water Use


Ground Water Levels Near Perdue Farms 0

20

40

60

80

100

120

140 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Dep

th B

elo

w G

rou

nd

Su

rfac

e (

ft)

65K 30 SOW 114S - Screen Depth = 30-40 ft

65K 27 SOW 114A - Screen Depth = 150-160 ft

65K 28 SOW 114B - Screen Depth = 220-230 ft

65K 29 SOW 114C - Screen Depth = 305-315 ft

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@A@A@A@A @A@A@A

@A@A@A@A

@A@A@A@A

Accomack County Office Buildings Waterworks

Perdue Farms Incorporated

Shore Life Care at Parksley

Byrd

Rew Farm

Burton Farm

Accawmacke Ornamentals

65K 26 SOW 109S

65K 25 SOW 109B

65K 24 SOW 109A 65K 30 SOW 114S65K 29 SOW 114C

65K 28 SOW 114B

65K 27 SOW 114A

66K 2 SOW 101C

66K 4 SOW 101A

65K 62 SOW 183D

65K 61 SOW 183C

1 inch equals 4,000 feet

¢0 0.5 1 1.5 20.25

Miles

Legend

# Agricultural

# Industrial/Commercial

! Municipal

@A USGS Observation Well


Water Level Change and Annual Use Near Perdue Farms

1,200,000

1,300,000

1,400,000

1,500,000

1,600,000

1,700,000

1,800,000

1,900,000 20

25

30

35

40

45

50

55

60 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

An

nu

al

Gro

un

date

r U

se

(G

PD

ave

rag

e)

Dep

th B

elo

w G

rou

nd

Su

rfa

ce

(ft

)

Year

65K 27 SOW 114A - Screen Depth = 150-160 ft Perdue Farms Water Use


Effect of Irrigation Use

15

20

25

30

35

40

45 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Dep

th B

elo

w G

rou

nd

Su

rfa

ce

(ft

)

63J 1 SOW 113A - Screen Depth = 110-120 ft

63J 2 SOW 113B - Screen Depth = 215-225 ft

63J 3 SOW 113C - Screen Depth = 280-290 ft

Observation Wells SOW 113 West of Wardtown

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YMCA Family Campground

Northampton Accomack Memorial Hospital

Grapeland Farm

Davids Nursery

James Wharf Farm

Silver Beach Farm

Guy Produce Farms

Marshall/Johnson Farm63J 3 SOW 113C

63J 2 SOW 113B

63J 1 SOW 113A


¢0 0.5 1 1.5 20.25

Miles

Legend

# Agricultural


! Municipal


Long Term Decline from Irrigation Use

15

20

25

30

35

40

45 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Dep

th B

elo

w G

rou

nd

Su

rfa

ce

(ft

)

63J 1 SOW 113A - Screen Depth = 110-120 ft

Observation Wells SOW 113 West of Wardtown

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YMCA Family Campground

Northampton Accomack Memorial Hospital

Grapeland Farm

Davids Nursery

James Wharf Farm

Silver Beach Farm

Guy Produce Farms

Marshall/Johnson Farm63J 3 SOW 113C

63J 2 SOW 113B

63J 1 SOW 113A


¢0 0.5 1 1.5 20.25

Miles

Legend

# Agricultural


! Municipal



Amount of water level decline in the Lower Yorktown Aquifer

Legend

DEQ Permitted Wells

Agricultural

Industrial/Commercial


Municipal

Legend

Model Predicted Drawdown (2003) - Lower Yorktown

DEQ Permitted Wells

Agricultural



Municipal


• Water Table Aq. •Quality Surface Activities • Quantity Drought

• Confined Aq. • Quality Over-pumping

• Quantity Over-pumping



Threats to Ground Water Quality & Quantity on the Eastern Shore

WATER TABLE AQUIFER

CONFINING UNIT

SEPTIC FIELD FERTILIZER PESTICIDES

HOUSEHOLD

CHEMICALS

Potential Threats To Water Table Water Quality

Sources: Agriculture / Livestock Nutrients (Fertilizers) Pesticides / Herbicides On-site waste disposal

Waste Units Septic Systems / Drain Fields Public Sewers Underground Storage Tanks

(USTs) Residential Nutrients / Pesticides -

Herbicides Petroleum and solvents

Function of amount (loading) and area of application

CONFINED AQUIFER


Potential Threats to Yorktown-Eastover Aquifer Water Quality

Freshwater aquifer

Confining unit

Salt water aquifer

Freshwater aquifer

Confining unit

Salt water aquifer

Sea level

Salt waterFreshwater

Water Table

Yorktown

Aquifers

Sea level

Salt waterFreshwater

Water Table

Yorktown

Aquifers

Land Surface


Chloride Increase With Depth Upshur Neck Seaside Example

0

50

100

150

200

250

300

3500 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750

Chloride Level (mg/L)

De

pth

Be

low

Gro

un

d S

urf

ac

e(

fee

t)

Drinking Water MCL (fresh/brackish)

Over a vertical distance of only 150 feet the chloride concentrations

increase by almost 5,000 percent

Fresh Ground Water

Brackish Ground Water


Why the Eastern Shore of Virginia?

Most likely cause for a loss of fresh ground water is salt water intrusion due to over pumping

100,000

115,000

130,000

145,000

160,000

175,000

190,000

100

150

200

250

300

350

400

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

An

nu

al

Wa

ter

Use

(G

PD

ave

rag

e)

Ch

lori

de

Co

nc

en

tra

tio

n (

mg

/L)

Cape Charles Tower Well Chlorides

Drinking Water MCL

Cape Charles Use


• ESVA Ground Water Committee

• ESVA Ground Water Resource Protection and Preservation Plan

• Water Supply Plans – Accomack & Northampton Cos.



Ground Water Management and Water Supply Planning

ESVA Ground Water Committee • Formed in 1990 by Accomack & Northampton to study and plan for

ground water protection and management

• 11-member Committee meets monthly • 2 County Administrators, 4 County Supervisors, 4 County-appointed

members, A-NPDC Executive Director

• Coordinated by A-NPDC with funding from Counties & VA Coastal Zone Management Program

• Contracts consulting hydrogeologist to advise Committee

• Activities: • Develop protection and management plans • Ground Water Research: USGS, VA Tech, Randolph-Macon • Public Workshops & Educational Materials • Review/comment on state withdrawal permit applications and federal

environmental assessments • Coordinate with state/federal governments on ground water-related

regulations • ESVA Ground Water Model • ESVA Ground Water Award Program • Household Hazardous Waste Collection


ESVA Ground Water Resource Protection and Preservation Plan

• Originally adopted in 1992 and Updated in 2013

• Purpose: • Ensure that adequate and safe drinking water is available to all

citizens of the commonwealth • Encourage, promote, and protect all other beneficial uses • Encourage, promote, and develop incentives for alternative

water sources, included but not limited to desalinization

• Components of Plan • Water Resources: Current understanding of water resources. Will

periodically update as new research is available. • Land and Water Resource Use: Water use will be updated

annually. • Resource Vulnerability: • Saltwater Intrusion: Water quality trends updated annually.

Modeling and other research updated periodically. • Water Level Declines: Updated annually. • Land Use Activities: Updated periodically based on research. • Sustainability Plan


Component Summary

• Institutional Controls: Federal / State / Local

• Research: • Hydraulic Characteristics: Paleochannels; Confining Units;

Deeper Aquifers

• Water Quality: Freshwater/Saltwater Transition; Agricultural Nutrients; On-Site Systems; Emerging Contaminants

• Climate Change

• Monitoring: Water Use; Groundwater Levels; Water Quality

• Alternate Source Development: Columbia (Water Table); Membrane Treatment; Reuse; ARS

• Conservation and Reduction


Highlights • Relevant components of the 1992 plan have been retained.

• Sections of the plan will be updated, some as frequently as annually to maintain current. Plan and various components such as monitoring data and research publications will be linked on the internet to improve accessibility.


Highlights

• Better understanding of the groundwater resource: Columbia aquifer is replenished at much higher rates than the Yorktown-Eastover. With lower withdrawals, the Columbia is an underused resource.

WATER TABLE AQUIFER WATER TABLE AQUIFER DEEP AQUIFER DEEP AQUIFER

Little Storage

Low Inflow

High Use High Use Little Use Little Use

Large Storage

High Inflow


Highlights

• Better understating of the vulnerability: Improved models for the Shore provide greater insight on flow dynamics. Yorktown-Eastover more vulnerable near the Bayside and Seaside, less vulnerable near the spine than previously thought.


Highlights

• Research needs are more focused and will be periodically revised.


Accomack County Water Supply Plan

• Regulations: 9 VAC 25-780 • Adopted in 2011 • Required to be reviewed every 5 years and rewritten every 10 years

• Purpose: • Ensure that adequate and safe drinking water is available to all

citizens of the commonwealth • Encourage, promote, and protect all other beneficial uses • Encourage, promote, and develop incentives for alternative

water sources, included but not limited to desalinization

• Components of Plan • Existing Water Sources (Description of water systems) • Existing Water Use (Description of current and historical use) • Existing Water Resource Conditions (Groundwater Resource, Natural Resoruces) • Projected Water Demand (Future water use) • Water Demand Management (Water Conservation and Management) • Drought Response and Contingency Plan • Statement of Need and Alternatives (Use / Resource Constraints; alternate sources /

technologies)


Curt Smith Director of Planning Accomack-Northampton Planning District Commission

[email protected] 757-787-2936

Thank You!

mailto:[email protected]



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