Transcript Water Resources Extension at Penn State University

Wellhead Protection and
Land-Use
By Judy Muehl
Pennsylvania Rural Water Association
It’s Cheaper to Prevent Contamination
• Quantifiable costs
–
–
–
–
Treatment
Pollution clean-up
Litigation?
Loss of property value and tax
revenue
• Less quantifiable costs
– health costs from exposure
Contamination Can be Local or Widespread
Well Head
Contamination
Insects
Small mammals
Barnyard, yards, dumps, mines, septic systems, etc.
soil
Bedrock
Aquifer
Aquifer Contamination
Groundwater Flow
Surface water
Water Supply Protection Starts at Home!
Septic systems
Driveways
Fertilizer
Pesticides
Keep activities at least 50 feet or more from wellhead or spring box
Dispose of Household Chemicals Properly
Publicize
Household Hazardous
Waste Collection
Programs
Properly Locate the Water Supply
Wellhead protection zones
Greatest impact on well
Moderate impact on well
Some impact on well
stream
Direction of
Groundwater Movement
well
barn and barnyard
home and
septic system
Wellhead Protection Area
• A minimum of 50 feet in every direction
• Preferably more than 50 feet upgradient
from the well
• Why 50 feet?
– That’s the active recharge area for a typical home well
producing 200 gallons per day.
Wellhead Protection Zones for Public Water Supplies
Where is the water that needs protection?
Zone I
100 - 400 Ft
Zone II
Capture Zone
Zone III
Zone II + Zone III = Area of Contribution
Red = sources of potential contamination
Coliform Bacteria
“Indicator” organisms
•Indicate the “potential” for disease-causing bacteria
•E. coli is an example
•One of the most common problems in wells and springs
•Occur in about 50% of private water systems
•Can enter wells and springs from surface runoff,
human/animal waste, insects, etc.
•May occur from poor construction or aquifer
contamination
Seal the spring box to prevent insects,
animals and surface contamination
Proper Construction Can Prevent Wellhead Contamination
Sanitary well cap
Good casing
Soil
Grout seal
Bedrock
Water Table
Groundwater “aquifer”
Don’t Get Carried Away !
Photo by Tom McCarty
Grouting Reduces Bacterial Contamination
% Contaminated
100
Total Coliform
E. coli
80
60
40
20
0
No Grout
Grouted
(Zimmerman et al., 2002)
Sanitary Well Caps Also Help
Standard Well Cap
Sanitary Well Cap
Approximately 50% of private wells had obvious insect activity under cap
15% of wells with total coliform bacteria could be solved by installing a
sanitary well cap.
Even a Perfect Well Can Have Bacteria
Percent Contaminated
60
Coliform Bacteria
E. coli Bacteria
50
40
30
20
10
0
All New Wells
(n=24)
Carbonate
(n=6)
Non-carbonate
(n=18)
Larger Scale Groundwater Contamination
Agricultural
Acid Mine Drainage
Commerce/ Industry
Residences
Waste Management
Stormwater Runoff
Groundwater Moves !
Common Naturally Occurring
Problems in PA Groundwater
•
White residue, dull laundry – hardness
•
Reddish stains, metallic taste – iron
•
Black stains, metallic taste - manganese
•
Rotten egg odor - hydrogen sulfide gas
•
Blue stains, metallic taste - corrosive water
– 42% of wells and springs have hard water > 180 mg/L
– Especially in carbonate (limestone) areas
– Common in sandstone / shale aquifers
– Often occurs with iron
– Very common in wells in certain shale formations
– Generally caused by low pH and soft water
Percent Not Meeting Standard
Corrosivity and Low pH
100
Corrosive (RI > 7.5)
Low pH (<6.5)
75
50
25
0
NW
SW
NC
SC
Region of PA
NE
SE
Natural Problems Can Cause Other Pollutants
Percent Above 15 ppb
50
40
Lead in Private Water Supplies
•Based on 1,600 samples
•Comes mostly from corrosion of plumbing
•High correlation between blue stains, metallic taste and lead
30
20
10
0
NW
SW
NC
SC
Region of PA
NE
SE
Land Use Impacts Groundwater
Houses
Landfills
Organics, ?
Industry
Organics, Petroleum
Bacteria
Nitrate
Sediment
Yard Chemicals
Agriculture
Bacteria, Nitrate, Pesticides
Roads
Chloride, Sodium
Mining
Metals, pH
Water Testing Should Target Local Land Uses
Mining
Iron, Manganese, pH
Agriculture
Nitrate, bacteria, pesticides
Houses
Bacteria, nitrate
Gas / oil wells
Petroleum, sodium, chloride
Roads
Sodium, chloride
Dumps, industry
Organic scans
Routine water testing PRIOR to activities is important to document
water quality and may provide some legal protection !
How Close do Activities Need to Be?
• In general, homeowners should be
concerned about activities that are
visible from their home
• In limestone or gravel aquifers,
activities further from the home could
be important
Average Nitrate-N (mg/L)
Example of Land Use Impact
8
7
1,600 private water supplies in PA
6
5
4
3
2
1
0
0-100
100-500
500-1000
Distance to Cornfield (ft)
>1000
Occurrence of Nitrate in Private Water Supplies
Percent Above 10 mg/L
60
50
40
Nitrate most often occurs with intensive agriculture
30
20
10
0
NW
SW
NC
SC
Region of PA
NE
SE
Iron and Sulfate in Private Water Supplies
Percent Above Standard
50
40
Iron and sulfate are most prevalent in coal
mining regions
30
Iron > 0.3 mg/L
Sulfate > 500 mg/L
20
10
0
NW
SW
NC
SC
Region of PA
NE
SE
Other Health-Related Pollutants
• Giardia and Cryptosporidium
– Protozoans common in surface water
– Very rare in wells and springs
• Volatile Organic Compounds (VOC’s)
– Around industrials sites, gas stations, urban areas, etc.
– Examples – benzene, PCE, TCE, toluene
– Widespread in some areas, especially SE Pennsylvania
• Pesticides
– Occur in <5% of wells and springs that have been tested
– Atrazine is the most common pesticide detected
Land Use Can Also Affect
Water Quantity
• Reduces infiltration through compaction (yards) or
pavement (roads, sidewalks, driveways) causing less
recharge of groundwater
•Homes with wells and public sewer may remove
water from the aquifer
•Sprawl moves water use from cities to suburban or
rural areas = more users in traditionally rural areas
•Groundwater mining may occur = more withdrawal
than recharge
•Common misconception is that homowner owns
water under their property
Abandoned Wells
• May serve as a
pathway for future
contamination of
groundwater
Photo: Purdue Extension Service
• Should be plugged
by a licensed well
driller
Graphic: North Dakota State Univ.
Homeowner Actions
• Practice local wellhead protection on
their property
• Be aware of current and proposed land
use surrounding their property
• Test water annually for pollutants
associated with current or proposed
land uses