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Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~...

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Page 1: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in
Page 2: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Nitrate Contamination: Nitrate Contamination: Tools, Insights, and Tools, Insights, and Potential SolutionsPotential Solutions

Christian A. Kropf Christian A. Kropf Sr. Hydrogeologist Sr. Hydrogeologist

Washoe County Dept. of Water ResourcesWashoe County Dept. of Water Resources

May 5, 2009May 5, 2009

Page 3: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Recipe for SuccessRecipe for Success

1. Apply for a large EPA Grant

2. Receive large EPA Grant

3. Hire the best scientists you can!

Page 4: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Presentation OutlinePresentation Outline

Nitrate: What’s the big deal?

Nitrate contamination case study

Characterization tools and insights

Applying this information regionally

Potential solutions

Page 5: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Background: NitrateBackground: Nitrate

Nitrate-N MCL is 10 ppm

Do not bind with soils & highly soluble

Travels with groundwater

Little or no retardation or degradation

Conservative solute that tends to accumulate in ground water

Page 6: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Background: NitrateBackground: Nitrate

One septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO3

18,000+ septic systems in Washoe County– 1.3 Billion gallons of septic effluent to groundwater annually– ~ 5.7 Billion gallons of groundwater to the MCL of 10 ppm annually– ~ 17,500 AFY or enough to serve ~ 50,000 homes!

Greatest potential for nitrate contamination of groundwater arises in areas of low rainfall recharge and high development density (Hantzsche and Finnemore, 1992)

Septic tanks are the most frequently reported cause of groundwater contamination associated with disease outbreaks (Yates, 2006)

Page 7: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Background: NitrateBackground: Nitrate

Methemoglobinemia (blue-baby syndrome):blood lacks the ability to carry oxygen throughout the body - especially in infants

Others: non-Hodgkin's lymphoma, gastric cancer, hypertension, thyroid disorder and birth defects.

Indicator contaminant: bacterial, viral, and pharmaceutical contamination

Page 8: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Loca

tion

Map

Loca

tion

Map

Page 9: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Site DescriptionSite Description

Reno-Sparks

Page 10: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Presentation OutlinePresentation OutlineSpanish Springs ValleySpanish Springs Valley

Page 11: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Recipe for ContaminationRecipe for Contamination

2,000+ homes on septic

½ within 2,000 ft of municipal wells

Increasing nitrate concentrations

Letter from the NDEP

Page 12: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Pre

viou

s C

ondi

tion

Pre

viou

s C

ondi

tion

July 2002

Page 13: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

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 2009

Date

Nitr

ate

- N (m

g/L)

Municipal Well ContaminationMunicipal Well Contamination

20081979

12

Page 14: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Characterization Tool KitCharacterization Tool Kit

TeamSoftwarePlanConceptual model Rough mass balance from septicsInitial characterizationFollow-up characterizationMunicipal well Quality and Flow profilesSource identification Source magnitudeVadose zone assessmentGroundwater flow & contaminant transport model

Page 15: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Team MembersTeam Members

GIS analyst - CountyModeler - DRIWQ specialist - CountyGeochemist – USGS/CountySoil scientist – UNRHydrogeologist – CountyDatabase specialist - CountyGrant writer!! – CountyInterns and graduate students!! – County and UNR

Page 16: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

SoftwareSoftware

AccessMS Office – Excel and PowerPoint!SurferGrapherArcGISAerial photosGMS – or any MODFLOW pre- & post-processorStatistical software – Excel, Origins, SAS

Page 17: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Conceptual ModelConceptual Model

Page 18: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

8.4 in./year Precipitation

5%In

filtr

atio

nNH4

+Biomass NO3-

Almost Complete Nitrification

0.4 in./year0.4 in./year0.4 in./year

Slow Shallow Gradient

Dilution

Little Denitrification

Municipal Pumping: 8 ppm10

-30

year

sIn

crea

sing

tim

e an

d ag

e of

gro

undw

ater

Dilution

Little Denitrification Mon

itor W

ell

Pum

ping

Wel

l

CLAY

Mon

itor W

ell

62 ppm ?

40 ppm ?

15 ppm ?

Mixing

17 ppm

3 ppm ?

Age?

Page 19: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Initi

alIn

itial

Cha

ract

eriz

atio

nC

hara

cter

izat

ion

Page 20: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

MW

04

MW

06

MW

13Li

ndbe

rgh MW

10

Cor

doba

MW

14M

W15

10 31

4

23

1811

1.1

5

Scale ~ 170 ft per Horizontal Unit

?

?

?

?

?

? CLAY

CLAY

NO3- Concentrations presented in ppm NO3

--N

Reality Mimics ConceptReality Mimics ConceptE-W Cross Section Through Spanish Springs Valley

Page 21: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Follo

wFo

llow

-- upup

Cha

ract

eriz

atio

nC

hara

cter

izat

ion

Page 22: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Reality Mimics Concept: Q3 2008Reality Mimics Concept: Q3 2008E-W Cross Section Through Spanish Springs Valley

4340

4360

4380

4400

4420

4440

4460

4480

4500

4520

4540

4560

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Horizontal Distance Units

Elev

atio

n (ft

asl

)

MW

04

MW

06

MW

13

Lind

berg

h

MW

10

Cor

dob

MW

14M

W15

6.0

5.3

9.4

16.2

5.7

Scale ~ 200 ft per Horizontal Unit

CLAY

NO3- Concentrations presented in ppm NO3

--N

MW

26M

W05

MW

28 MW

29

MW

17M

W30

9.8

12.016.1

2.8

8.439

4.9

8.495.3

CLAY

Page 23: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

0

5

10

15

20

25

Nitr

ate-

N (m

g/L)

Source IdentificationSource Identification

Inside

23.2

5.0

Outside

Page 24: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

SourceSourceIDID

WellLysimeter

Neutron

3 Homes1 Park1 School

49 Lysimeters10 Neutron Holes6 Monitor Wells4 Flux Meters

Page 25: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Nitrate Source StudyNitrate Source Study

Septic nitrate discharge from 1 to >500 mg/L as N

Median value of 44 mg/L Nitrate-N similar to the range of published values for septic tanks

Denitrification literature value of around 25% appears about right for Spanish Springs Valley septic tanks

Approximately 30 tons of N per year is being conveyed to the aquifer from septic tanks

Page 26: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Groundwater Age Dates, Nitrate, and Development in SSV

0

5

10

15

20

25

30

35

40

45

50

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005Date

Nitr

ate

- N (m

g/L)

Source ID: NOSource ID: NO33 & GW Age Date& GW Age Date

Start of Development

67% of Samples Above MCL

14% of Samples Above MCL

Shallow Sample Age Date & NitrateDeep Sample Age Date & Nitrate

Page 27: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

N vs O Isotopes

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

-15.00 -10.00 -5.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00Nitrate - 15N

Nitr

ate

- 18O

NO3 in Precipitation

NO3 fertilizer

NH4 in fertilizer & rain

Soil N Manure & Septic waste

(adapted from Kendall 2007)

Source Identification:Source Identification:N and O Isotopes in NitrateN and O Isotopes in Nitrate

Shallow WellsDeep Wells

Page 28: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

NO

NO

33S

ourc

e R

eS

ourc

e R

e --th

ink

thin

kSeptic Source?

Buried Swamp?

Soil cores refuted swamp

Recharge from a mining operation leaching naturally-occurring nitrate from vadosezone?

Plausible!

Page 29: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Source MagnitudeSource Magnitude

233 g/d/h from engineering estimate based on usage records

228 g/d/h from modeled estimate

INSIGHT! Don’t be afraid to recheck your data!– New data– New software– New processing ability

Page 30: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Source Magnitude: RecheckSource Magnitude: Recheck

SSV Septic Users Gallons per Day per House

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Gal

lons

per

Day

Average Gallons per Day

Page 31: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Nitrate - N (mg/L)

Vad

ose

Vad

ose

Zone

Nitr

ate

Zone

Nitr

ate

Tran

spor

t Mod

els

Tran

spor

t Mod

els SIMULATION

Modeled from soil cores230 gal/day/house44 mg/L Nitrate-N applied Accounts for precipitation and soil moistureAccounts for naturally occurring Nitrate in subsurface

Bottom of Trench

GroundwaterU

nsat

urat

ed S

oil Z

one

RESULTS2-3 yrs for leading edge6-10 yrs for max concentration

Page 32: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Gro

undw

ater

Nitr

ate

Gro

undw

ater

Nitr

ate

Tran

spor

t Mod

els

Tran

spor

t Mod

els

Page 33: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Expanding the Scope of Expanding the Scope of Investigation CountyInvestigation County--WideWide

SepticsWells– Municipal,

monitoring,domestic

Depth to WaterGeologyConcentration(Nitrate and others)Precipitation

GIS-BasedRegional

RiskAssessment

Page 34: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Regional Risk AssessmentRegional Risk Assessment

Literature review & compile data & data gapsID potential areas of concern (Project Areas)Prioritize Project Areas for further study

79% - 95% of all septic systems in a basin were found in these individual Project AreasDensities ranged from 50 – 350 septics/mile2

High Risk = High septic density, Shallow depth to water, Shortest distance to sensitive receptors

Page 35: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Sep

tic N

itrat

eS

eptic

Nitr

ate

Pro

ject

Are

asP

roje

ct A

reas

Page 36: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Met

hods

: Sep

tic D

ensi

tyM

etho

ds: S

eptic

Den

sity Basin Stats

Septics: 1,397Area: 29.5 mi2

Density: 47/mi2

NV Limit: 92 /mi2

Project AreaSeptics: 1,325Area: 7.5 mi2

Density: 177/mi2Max D: 350 /mi2

NV Limit: 92 /mi2

Page 37: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Potential SolutionsPotential Solutions

Continue monitoring of past projectsBaseline Dataset Creation – Fill data gaps, DTW, water quality (PPCP’s)

ASR or at least Recharge to dilute nitrateNo more RIBsWatering restrictions / efficiency Phased sewers through remediation districtNO MORE HIGH DENSITY SEPTICS!

Page 38: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Potential (THE!) SolutionPotential (THE!) Solution

Page 39: Nitrate Contamination: Potential Solutions · Background: Nitrate zOne septic tank contaminates ~ 900 gallons of water per day to the MCL of 10 ppm NO 3 z18,000+ septic systems in

Questions?Questions?


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