I-26_Ambient Troubleshooting Memo July 2020 to April 2021 _Final

CITY OF
DURHAM
Date: July 13t", 2021
Memo
To: John V. Loperfido- Asst. Water Quality Manager
From: Joseph Smith- Environmental Planning and Compliance Analyst
Subject: Timeline of Ambient Troubleshooting, July 2020 to April 2021
Executive Summary
The following details issues with Ambient Monitoring chemistry data quality documented
from June 2020 to March 2021. In the fall of 2020, questionable values for nutrient and
metals parameters were observed by the Monitoring and Assessment Team. To determine
the cause of data quality issues, split samples were collected for comparison between South
Durham Water Reclamation Facility Laboratory (SDWRF) and ENCO Laboratories. Data
issues included clustered non -detects of nutrient parameters, higher detections of
dissolved fractions of metals than reported total fractions of metals, and elevated
concentrations of metals without obvious explanation. Comparisons between ENCO and
SDWRF laboratories made in January and February indicated that the above issues were no
longer observed. Perhaps, coincidental to the issue, the SDWRF relocated its laboratory to a
newly constructed building in July, 2021. An additional data quality issue noted that was
not related to those described above included detection of ammonia and nitrate + nitrite
parameters above acceptable levels in field blanks from January to March. This was
determined to be caused by contaminated lots of deionized water used in the preparation
of field blanks. As of April 13th, 2021 ammonia and nitrate + nitrite have not been detected
in field blank results.
July 2020
Due to the ongoing response to COVID-19 sampling for the Ambient program was limited
to core "Nutrient Loading" sites only (Seven sites, one duplicate, and one field blank
sample). In review of June data Christine Cailleret (EP&C Coordinator on the Monitoring
and Assessment team) noted that a majority of copper (Cu) and zinc (Zn) results had higher
values for dissolved vs. total results, an unreasonable result. Results were confirmed as
reported by James Blake (SDWRF Sr. Laboratory Manager). The majority of results were J
qualified (Estimated- The reported value is less than the laboratory Method Reporting
Limit (MRL) but greater than or equal to the Method Detection Limit (MDL)). It should be
noted that the SDWRF Laboratory moved from its old location to a newly constructed
building on July 1st, 2020.
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September 2020
July and August data was received on September 16th, 2020. July nutrient data had more
results reported below the detection limit than typically observed. These results were U
qualified (the contaminant was not detected at a concentration greater than the detection
limit). Four results for ammonia were <0.04 mg/L on July 7th, 2020. Four total phosphorous
(TP) results were < 0.02 mg/L on July 14th, 2020. While non detects do occur in results
from time to time, ammonia and TP are commonly found in Durham streams and clusters
of non- detects can be indicative of issues with lab analyses. Field notes indicate rain in the
past 24 hours on both days, and moderate turbidities of 3 to 25.5 NTU on July 71h, 2020 and
2.5 to 295 NTU on July 141h, 2020, further indicating that TP likely may have been above
detection limits. Field blank results did not indicate contamination in TP or any other
nutrient parameters. Metals results for ambient samples and field blanks continued to
show higher dissolved than total results at most sites. Due to this and other potential
quality issues 96 of 112 results for total and dissolved copper and zinc were Z qualified
(sample results are rejected due to serious deficiencies in the ability to analyze the sample
and meet QC criteria. The presence or absence of the analyte can't be verified).
Ammonia was reported at <0.04 in all samples on August 111h, 2020 and in eight of nine
samples on August 18th, 2020. Ammonia was not detected in field blanks for all three days.
Considering issues were previously noted in July, Ammonia values for August 11th and 18th,
2020 were Z qualified. Nitrate + nitrite (NOx) was not detected in seven of eight samples on
August 111h, 2020. These values were also Z qualified. Metals results appeared to
normalize, with results showing higher total metals concentrations than dissolved metals
concentrations.
October 2020
Sampling for the Laboratory Quality Assurance Split Sampling Study was conducted on
October 27th, 2020. Laboratories involved included SDWRF, ENCO, and the NCDWR Central
Laboratory. This sampling is summarized in the 2020 Laboratory Quality Assurance Split
Sampling Study Report. It should be noted that results from the SDWRF for the split
sampling study did not include NOx results due to a computer hard drive failure and
dissolved CU and dissolved ZN due to a chain of custody form error.
December 2020
October and November ambient data was received on December 16th, 2020. Ammonia was
not detected in 21 out of 29 samples in October, and 19 out of 29 samples for November.
Nitrate + Nitrite concentrations appeared to within the range typically observed, with
concentrations ranging from not detected at 0.04 to 1.48 mg/L in for the month of October,
and not detected at 0.04 to 1.60 mg/L for November. Total Kjeldahl nitrogen was not
detected in seven of eight samples on November 41h, 2020. On the same day NOx was not
detected in three of eight samples. Total phosphorous was not detected in five of nine
samples on October 16th, 2020. November TP concentrations appeared to normalize, with
results ranging from 0.01 to 0.34 mg/L. Field blank results on November 3rd, 2020 showed
a concentration of 0.27 mg/L for TKN. No other nutrient parameters detections were
observed in field blanks for October or November. The deionized water lot number for
November 3rd, 2020 was #200818A. A dissolved Zn value of 6,284 mg/L was reported at
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TF2.5TCTC in November, while the reported total Zn was only 0.05 and J qualified. There
were elevated total Cu and total Zn of 120 and 162 mg/L respectively at TF4.4TC. This
sample was collected downstream of an WQI that occurred five days later at Forest Hills
where blue/ gray water reported, so the sample result and the investigation could have
been related.
Due to numerous perceived issues with data quality, additional split samples were
collected in January and February for nutrient and metals parameters to be analyzed by
SDWRF and ENCO laboratories. January split samples included analysis for ammonia, NOx,
as well as total and dissolved Cu and Zn. February split samples included analysis for NOx,
total Kjeldahl nitrogen (TKN), calcium (Ca), magnesium (Mg), as well as dissolved Cu and
Zn. These parameters were deemed high priority due to their impact on the Water Quality
Index.
January 2021
December ambient data was received on January 21St, 2021. Ammonia was not detected at
the MRL of 0.04 mg/L in five of 26 samples, and detected but J qualified at 0.04 mg/L in
another nine of 26 samples. Concentrations for ammonia detected above the MRL ranged
from 0.05 to 4.27 mg/L. Nitrate + nitrite and TP concentrations appeared to normalize for
all three days. Nitrate + nitrite results ranged from 0.12 to 3.54 mg/L, while TP ranged
from not detected at 0.003 to 0.93 mg/L. Total phosphorous was not detected above the
MRL in 3 of 26 results. Total Kjeldahl nitrogen results normalized with a range of 0.42 to
5.97 mg/L. Contamination was not detected for any parameters in field blanks.
February 2021
In review of split samples collected during January, two field blanks submitted to SDWRF
were reported with unqualified ammonia values of 0.21 mg/L and 0.24 mg/L on January
5th and January 19th, 2021. This resulted in rejecting all subsequent data for those days.
Field blank contamination was evident in ENCO results with a detection of 0.17 mg/L on
January 12th, 2021. Half of the reported NOx values were also automatically rejected for
blank contamination on January 12th, 2021. NOx field blank values were reported at 0.05
mg/L, when the detection limit is 0.04 mg/L. Comparison of relative percent difference
values for other NOx values from the same day between SDWRF and ENCO were 5.5%,
indicating general agreement between labs for those reported values. ENCOs did not detect
NOx in field blank samples submitted. TKN was not detected in any results from SDWRF on
January 121h, 2020. Comparisons of the relative percent difference (RPD) were made
between total and dissolved Cu and Zn reported concentrations. Total and dissolved Cu had
an average RPD of -9%, while total and dissolved Zn had an average RPD of -46 %. Previous
studies by the City and State have had acceptable ranges of 20% to 40% RPD in
comparisons between laboratory data sets. Due to the issues with field blank
contamination and the consistency of values at both laboratories, the EP&C Analyst initially
believed that there may have been cross contamination at the point of collection from field
staff. Field staff were notified of the contamination and field notes were reviewed. No
deviances from standard operating procedures were noted by staff. Staff were reminded of
proper sample bottle handling.
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March 2021
Split sampling with SDWRF and ENCO was discontinued for the month of March. Following
receipt of February ambient data from both SDWRF and ENCO laboratories comparisons of
RPD were again made between reported concentrations of NOx, TKN, calcium, magnesium,
dissolved copper and dissolved zinc. Overall good agreement was observed between the
two laboratories., with average RPD of 10.8% for NOx, 17.4% for TKN, 2.0% for calcium,
1.3% for magnesium, 2.5% for dissolved copper, and -3.3% for dissolved zinc. Ammonia
contamination was still evident in SDWRF non -qualified field blank samples analyzed at
relatively consistent levels of 0.23, 0.23, and 0.22 mg/L on all three ambient days.
Ammonia was not detected above the MDL at six of 11 sites on February 2nd, 2021.
Detected concentrations were initially rejected due to field blank contamination. Ammonia
was not detected above the MDL at any site on February 161h, 2021. Field blank
contamination was also observed for NOx on February 9th, 2021 with unqualified values of
0.05 mg/L. Three of eight accompanying NOx results were initially rejected based on
internal quality assurance guidelines due to concentrations not being greater than five
times the detected concentration from a field blank on February 9th. The remaining five
values were qualified as J7 (Estimated- Blank contamination evident, value may not be
accurate) by SDWRF staff. Given that the values detected in field blanks for multiple
months were consistently in the 0.20-0.25 mg/L range for ammonia, and at 0.05 mg/L for
NOx, contamination by field staff was deemed unlikely. Contamination from improper
sample handling would be expected to have high variance and occur intermittently. In
review of field notes and data from January and February, deionized water from lot #
201117 was noted to consistently associated with observed field blank contamination
(Table 1).
Table 1 Ammonia concentrations detected infield blanks, January and February, 2021.
Date
DI Lot #
SDWRF Result,
mg/L
ENCO Result,
mg/L
1/5/2021
201117
0.21
-
1/12/2021
200818A
0.04
0.04
1/19/2021
201117
0.25
0.25
2/2/2021
201117
0.23
-
2/9/2021
201117
0.23
-
2/16/2021
201117
0.22
-
Lot # 201117 was deemed potentially contaminated, and removed from use after March
2nd, 2021. A new lot of deionized water was used for the remaining two days of ambient
sampling in March. This lot, lot # 210127B, was used for field blanks on March 9thand
March 23rd, 2021. A lab blank was prepared in the stormwater lab using lot # 201117 to
confirm contamination and submitted alongside samples on March 23rd, 2021.
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April 2021
In review of March data on April 12th, 2021, the prepared lab blank of lot # 201117 was reported at 0.19 mg1L, confirming
contamination of our field blank source water from previous months and infield blank source water used on March 2nd 2021.
However, field blank contamination for ammonia was still present at 0.09 mg1L on March 9th and 23rd (
Table 2) associated with the replacement lot # 210127B.
Table 2 Ammonia concentrations detected infield blanks, March 2021.
Date
DI Lot #
SDWRF Result,
mg/L
3/2/2021
201117
0.26
3/9/2021
210127B
0.09
3/23/2021
210127B
0.09
Lot # 210127B had already been used for the field blank on April 6th, 2021. Laboratory
results from SDWRF for this sample were reported at 0.06 mg/L for ammonia. This lot was
also deemed contaminated, and removed from further use. Exaxol Corp. was contacted, and
agreed to replace the contaminated deionized water. In the interim ENCO Laboratories also
supplied deionized water for use on April 131h, 2021. A new lot of deionized water was
received from Exaxol corp., and used in sampling on April 20th, 2021. Lab results from both
of these days were below the detection limit for ammonia (0.04 mg/L). NOx was detected
above the detection limit in field blanks on April 131h, at O.OS mg/L, however these results
were J qualified, and not considered indicative of source water contamination on behalf of
ENCO Laboratories. It should be noted the Exaxol Corp. states that their deionized water is
ACS Reagent Grade, which does not have a specified ammonia limit. To meet ACS Reagent
grade, deionized water is expected to have nitrate (NO3-) levels <_ 0.4 mg/L, among other
limitations. The Monitoring & Assessment group will continue to monitor field blanks for
any contamination issues. As of April 131h, 2021, all ambient data quality issues are
believed to have been resolved and new Exaxol water lots have been used for ambient
sampling without issue.
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