ENTRAINED AIR EVALUATION - Clear Creek...
Transcript of ENTRAINED AIR EVALUATION - Clear Creek...
May 7, 2015
Group of 4 public supply wells near the Agua Fria produce milky water that appears to be the result of entrained air
The cause and when it was first observed are unknown
The make up of the entrained air was also unknown
What was known is that customers do not like milky tap water!
Well #1
Well #4
Well #2
Well #3
1 Mile
Union Hills Rd
Beardsley Rd
83rd
Ave
91st
Ave
Pinnacle Peak Rd
Well/pump related
Cascading water
Holes in column pipe
Excessive drawdown close to pump intake
Leaking air relief valves
Chemical/physical reactions
Acidic waters mixing with carbonate formations
Depressurization of very deep groundwater
VZ recharge of surface water
Surface waters typically contains higher DO concentrations than GW
As the recharge water percolates through the vadose zone it picks up additional CO2
As the water mounds, pressure helps increase the amount of dissolved gasses in the water
When the DO/CO2 laden GW is extracted, the gas is released from solution
Review effected well data
Pump each well and collect WQ and
WL data
Collect raw groundwater samples for
laboratory analyses
Analyze the data and develop an
opinion as to its potential source(s)
including CAP recharge at nearby
Agua Fria Recharge Project (AFRP)
Closest upgradient recharge project
Recharge water has high DO
Recharge rates along river nearly 4 ft/d
High volumes recharge/flow down river
(>100,000 gpm)
Linear recharge increases amount of
vadose zone the water comes in contact
with (literally many thousands of feet)
Structures along river aerate water
CAP 2013 Annual Water Quality Report
DO concentrations in CAP Water
Ave DO ~9.5 mg/L
Well #1 Well #4 Well #2 Well #3
Pump each well for 4 hours
Monitor pumping rates and water levels
Collect WQ parameters every 15 mins
Visually observe groundwater
conditions every 15 mins
Track entrained air dissipation rates in
sealed and open sample containers
Well Screened
Interval
(ft bls)
Pump
Setting
(ft bls)
Pumping
WL
(ft bls)
pH EC
(µs/cm)
ORP
(m/V)
DO
(mg/L)
Temp
(°C/°F)
Field Sample
Observations
#1 698-1,200 680 547 7.11 436 333.1 8.57 22.8/73.0 Clear after 30
seconds
#2 700-1,050 761 548 7.52 494 223.4 8.52 23.4/74.1 Clear after 60
seconds
#3 739-1,010 720 NA 7.40 637 210.7 7.26 24.0/75.2 Clear after 15
seconds
#4 850-1,300 ~800 555 7.63 550 166.1 4.98 25.3/77.5 Clear after 15
seconds
DO at or near saturation in 3 of 4 wells
Elevated ORP corresponds to high DO
measurements
While DO in groundwater can fluctuate
and varies from place to place, typical
concentrations at these depths would
be expected to be much lower on the
order of 2 to 4 mg/L
Each raw water sample analyzed for
suite of analyses including
Cations/anions
Dissolved Oxygen & CO2
Total Dissolved Solids
Bromide
Tritium
CAP tracer compound
Sample SO4
(mg/L)
Cl
(mg/L)
Ca
(mg/L)
Na
(mg/L)
Mg
(mg/L)
K
(mg/L)
Background GW 27 29 43 30 20 3.3
Well #1 43 17 40 30 19 2.3
Well #2 48 28 48 34 22 2.7
Well #3 74 63 64 40 28 3.1
Well #4 53 45 42 42 22 3.5
Recharge Water 248 87 83 82 22 4.3
Recharge Water
Signature
Groundwater
Signature
Well #3
Signature
Well #3 signature is
closer to Recharge
water than
Groundwater
Analytical results consistent with
field measurements
Saturation at Wells #1 and #2 and
near saturation at #3. Well #4,
the deepest well was lower
DO concentrations much more
consistent with CAP water than
groundwater
Detected at concentrations ranged from 0.88 mg/L (Well #4) to 2.2 mg/L (Well #1)
CAP water at or below detection limit
Groundwater concentrations have decreased over time (> 75% since 2004 at Well #3)
Decreases of N in GW may be attributed to dilution by CAP water
Concentrations ranged from 300 mg/L
(Well #1) to 420 mg/L (Well #3)
CAP water averages about 660 mg/L
Groundwater concentrations have
increased nearly 40% since 2000
Increases of TDS may be
attributed to mixing of
CAP water
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Analytical results for bromide were ND, consistent with typical groundwater
Ratios for GW calculated using ½- the detection limit for bromide
Ratios for evaluated wells ranged between 68 and 252
Ratios of CAP water typically range between 950 and 1150
Higher ratios in groundwater noted at wells closer to the AFRP
Substance released to atmosphere from
the detonation of nuclear bombs in
1950s
Can be identified in groundwater
recharged within past 50 years
Detected in each GW sample
Higher concentrations were reported in
wells closer to AFRP
Recharge water is known to have low
concentrations of a compound from
the Hawthorn, NV Superfund Site
Low level detected in raw water
collected from Well #3 which
is most impacted by AFRP
Not detected in any of the
other wells
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Well #3 Raw Water Tap
Uniformity of entrained air between wells
suggests that it originates from aquifer
as opposed to a pump/well issue
All PWLs above well screen eliminate cause
related to cascading water within well
All PWLs far above pump intakes
Recent pump replacements confirm integrity
of column pipe
All vacuum/air relief valves functioning
properly
WQ data indicate CAP water has mixed with groundwater and the blended water has reached the wells with entrained air to varying degrees
ORP values indicate highly oxidative state of the groundwater
Nitrate concentrations have decreased
TDS concentrations have increased
Chloride:bromide ratios greatest in wells most impacted by recharge
Tritium concentrations greatest in wells most impacted by recharge
The presence of CAP tracer in groundwater confirms influence from surface water recharge
The wells with the greatest DO & CO2
concentrations had the slowest
entrained air dissipation rates
While a direct correlation between the
presence of entrained air in these
wells and nearby artificial recharge
cannot be made, qualitative evidence
suggests the two may be linked
Clear Creek Associates would like to
thank the City of Peoria for supporting
the development of this presentation for
the 88th Annual AZWater Conference and
Exhibition
“Statements of fact and opinion
expressed are those of the author(s) /
presenter(s).
AZ Water, AZAWWA, and AZWEA assume
no responsibility for the content, nor do
they represent official policy of the
Association.”