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Nitrates in
Groundwater:
The Path to a
SolutionWhat We Have ♦ What We Need
Overview
• Ensure clean drinking water for affected communities
• Nitrate management has been a priority for years, and we’re making progress
• California must base proposed solutions on reliable data and analysis
• More information would better inform decisions
• We are committed to working with you 1
SB X2-1 Mandate Is Not Yet Met
The SWRCB in consultation with other
agencies…shall develop pilot projects in
the Tulare Lake Basin and the Salinas
Valley…that focus on nitrate
contamination and do all of the following:
(a)(1) In collaboration with relevant
agencies and utilizing existing data…2
Uncited Studies
• “California GAMA Special Study: Nitrate Fate and Transport in the
Salinas Valley,” 2011, Lawrence Livermore National Laboratory and
California State University, East Bay
• “California GAMA Domestic Wells: Nitrate and Water Isotopic Data
for Tulare County,” 2010, Lawrence Livermore National Laboratory
• “Ground-Water Quality Data in the Monterey Bay and Salinas Valley
Basins,” 2007, California, 2005—Results from the California GAMA
Program: U.S. Geological Survey Data Series 258
• “Nitrate dynamics within the Pajaro River, a nutrient-rich, losing
stream,” University of California–Santa Cruz, 2006
• “Nitrate Contamination in California Groundwater: An Integrated
Approach to Basin Assessment and Resource Protection,” 2002,
Lawrence Livermore National Laboratory 3
Where Better Analysis Will Be Helpful
60.6%
31.7%
7.7%
Total Samples-Low
Total Samples-Medium
Total Samples-High
77.5%
16.7%
5.8%
Unique Samples-Low
Unique Samples-Medium
Unique Samples-High
Total Tests with Repeats
Sample Data Set
Unique Wells Only
Sample Data Set
Source: SWRCB GeoTracker/GAMA MCDPH Public Service Wells with 15+ Connections 1980–2012
4
Where Better Analysis Will Be Helpful
0 13
29
12
42
91
0 13
96
14
21
0
10
20
30
40
50
60
70
80
90
100
1980 1985 1990 1995 2000 2005 2010
Nu
mb
er
of
We
lls
in
Ea
ch
Ye
ar
Ex
ce
ed
ing
MC
L
Total Samples with Repeats Unique Well Samples
Source: SWRCB GeoTracker/GAMA MCDPH Public Service Wells with 15+ Connections 1980–2012
5
Where Better Analysis Will Be Helpful
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
18.0%
20.0%
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Discrete YearsMethod
Report Method
Linear RegressionTrend
Percentage of 200 Monterey Co. Wells with NO3 Levels > MCL 2002-2010
36 of 200
0 of 3 > MCL
6 of 46
10 of 62
13 of 84
9 of 50
6 of 43
4 of 39
8 of 477 of 43
4 of 51
9 of 76
13 of 92
0 of 5
6
U.S.G.S. Geospatial Sample Grid
• The USGS relies upon a spatially unbiased grid to select its well locations to assess aquifer-scale groundwater quality in the Salinas Valley.
• CDPH well data are used to identify well contaminants, extrapolate within grid cells, and perform spatially-weighted calculations at aquifer scale.
• Use of this methodology prevents statistical distortions caused by numerous areas in the CDPH databases with heavy clusters of exceedence wells, such as that seen north of the city of Salinas.
Source: United States Geological Survey, 2011
7
Where Better Analysis Will Be Helpful
• Alternate sources may be significant
• Nitrate dilution does occur
• Experts say Salinas Valley and Tulare Lake Basin
should be analyzed separately
• USGS
• Lawrence Livermore Lab
• Monterey County Regional Water Authority
8
Alternate Causation: Chualar Canyon
The report fails to
adequately explain high
groundwater nitrates
found in natural
vegetation areas distant
from manmade sources
of nitrates.
This local small system
well east of Chualar
tested 97 mg/l NO3 in
2011, over double the
nitrate MCL.
Source: 971 Local Small Water System Wells with 2-4 Connections, Monterey County Department of Public Health, 2011
9
Alternate Causation: Hudson Landing Rd.
10
The exceeding wells are located in the
drainage flow from a hilltop at Pajaro
Valley Golf Course to the lowlands below.
Golf courses apply nitrate fertilizers to
their turf.
Sources: Small System Wells: Monterey County Department of Health, 2011; Base Maps: Google Earth and
Google Terrain
Scientific Validation is Critical
• Independent peer review can resolve concerns
about:
• Data integrity and gaps
• Statistical analysis
• Inconsistencies with other studies
• Errors and omissions
11
Summary
The State Water Board must have the benefit of a
scientifically defensible study that meets the
legislative mandate and has been validated in peer
review before sending a report to the Legislature.
12
We Are Committed To A Solution
• Agricultural practices have evolved and today are
reducing nitrates in groundwater
• We have a track record of working toward
solutions and achieving results
• This will be no exception
13
