2021-Appendix-V-II--Algal-Bloom---Press-Release-Information

Chowan – Appendix V-II 1 2/18/2021

Appendix V-II
Table V-II.1. DWR Chowan River Basin Algal Bloom Assessment for Years 2015-2019.
Location Date
Sampled Basin
Micro-
cystin
(ug/L)
Toxin
Chl a
µg/L County Cell Density +
Cells/mL
Density +
Units/mL
Biovolume +
mm3/m3
Algal Group/
Dominant Taxa Latitude Longitude
Reason
Reported
Station/Sample Code/ID
Bloom ID
& Notes
2015 Blooms:
Chowan River
Edenhouse
D9490000
6/29/2015 Cho ND 68 Chowan T-83,000
C-79,00
T-6,500
C-2,600
T-5,000
C-4,300
CYA
Anabaena
planctonica
36.0476 -76.69611 Discolored
water
CHO018/
Smplid10914-2015/
Bloom ID 2015027/AC20626
Chowan River
West side nr
Colerain
9/16/2015 Cho ND 500 Bertie T-2,738,000
C-2,738,000
T-3,800
C-3,100
T-82,000
C-82,000
CYA
Microcystis
36.2001 -76.74994 Discolored
Water
CRABWR91615/
11112-2015
2015056/AC22649
2016 Blooms:
Chowan River
Indian Creek 7/20/2016 Cho NA NA Chowan T-12,000
C-12,000
T-2,500
C-2,400
T-800
C-800
CYA
Anabaena
36.235 -76.67 Discolored
Water Indian Creek/11526-2016
Chowan River
Between
Arrowhead and
Edenhouse
8/10/2016 Cho ND 100 Chowan T-139,000
C-138,000
T-5,400
C-4,400
T-15,000
C-14,000
CYA
Anabaena
36.13868 -76.7294 Discolored
Water
CRBR081016/
11543-2016
2016036/AC31536
Chowan River
Channel Marker 7
nr Colerain
D8950000
9/7/2016 Cho NA NA Chowan NA T-12,000 NA CYA
Microcystis
NA NA Discolored
Water
According to USGS- Channel
Marker 7 is near Colerain
2017 Blooms:
Chowan River
Edenhouse
D9490000
6/12/2017 Cho ND ND Chowan T-80,000
C-56,000
T-4,500
C-2,700
T-7,000
C-5,500
CYA
Dolichospermum
36.0476 -76.6961 Discolored
Water
D9490000/CHO018/
11953-2017
2017011/AC39626
Edenton Bay 6/12/2017 Cho ND 160 Chowan T-240,000
C-157,000
T-24,000
C-5,700
T-29,000
C-15,000
CRY
Dolichospermum
36.06077 -76.6092 Discolored
Water
EB61217/
11952-2017/ 2017010
AC39625/EB061217
Chowan River
Colerain
D8950000
6/22/2017 Cho ND 320 Bertie T-561,000
C-560,000
T-18,000
C-17,000
T-54,000
C-54,000
CYA
Dolichospermum
36.20983 -76.7268 Discolored
Water
D8950000/CHO016/
11987-2017
2017018/AC39209
Chowan River
nr Rockyhock 7/10/2017 Cho ND ND Chowan T-162,000
C-161,000
T-13,000
C-12,000
T-14,000
C-14,000
CYA
Dolichospermum 36.17994 -76.722 Discolored
Water
CRRH071017/
12012-2017
2017025/AC40697
Chowan River
nr Whites Landing
Rd.
10/16/201
7 Cho ND 24 Chowan T-6,500
C-5,800
T-700
C-100
T-700
C-400
DIN
Scrippsiella
36.16778 -76.7211 Foam WLAB101617/12222-2017
AC43966
2018 Blooms:
Chowan River
Colerain
D8950000
6/25/2018 Cho ND 54 Chowan T - 170,556
C -162,190
T- 9,900
C-7,100
T-7,400
C-6,700
CYA
Dolichospermum,
Polycystis
36.209830 -76.726770 Discolored
Water
D8950000/CHO016
Bloom ID 2018023
AC51154/ D8950000_PHO
Chowan – Appendix V-II 2 2/18/2021

Location Date
Sampled Basin
Micro-
cystin
(ug/L)
Toxin
Chl a
µg/L County Cell Density +
Cells/mL
Density +
Units/mL
Biovolume +
mm3/m3
Algal Group/
Dominant Taxa
Latitude Longitude Reason
Reported
Station/Sample Code/ID
Bloom ID
& Notes
Chowan River near
Leary Landing 6/27/2018 Cho 0.44 5,400 Bertie T-7,334,000
C-7,334,000
T-259,000
C-259,000
T-474,000
C-474,000
CYA
Dolichospermum,
Aphanizomenon
36.131761 -76.749140 Discolored
Water
CRLL62718/CRAB062718
Bloom ID 2018024/AC52530
Verified Chl a conc with Chem
Lab Ŧ – 5,400 µg/L
Chowan River
near Rockyhock 7/17/2018 Cho 0.72 28 Chowan NA NA NA NA NA NA NA No additional information
available on this sample
Chowan River
Johnson Point 7/19/2018 Cho NA NA Chowan T-27,000
C-22,000
T-3,600
C-1,800
T-2,100
C-650
CYA
Dolichospermum
36.19954 -76.7181 Discolored
Water CRAB071818/12520-2018
Chowan River near
Colerain
D8950000
8/7/2018 Cho 1.40 120 Chowan T-162,000
C-158,000
T-5,800
C-2,100
T-8,400
C-6,700
CYA
Dolichospermum,
Microcystis
36.209830 -76.726770 Discolored
Water
D8950000/CHO016
Bloom ID 2018035
AC53266/ D8950000_PHO
Chowan River
Edenhouse/Wharf
Landing
8/7/2018 Cho 14.0* ND Chowan T-918,000
C-913,000
T-25,000
C-20,000
T-61,000
C-60,000
CYA/
Dolichospermum,
Microcystis
36.053500 -76.682020 Discolored
Water
WLAB080718
Bloom ID 2018033
AC53686/Station: WARO_NLC.
Note: Resampled 8/28/18 – CYA
Biovolume dropped to 3,600;
not listed in bloom datasheets.
Chowan River
Edenhouse/Wharf
Landing
8/27/2018 Cho 6.4 120 Chowan T-118,000
C-114,000
T-4,700
C-2,300
T-4,500
C-3,600
CYA
Pseudanabaena,
Dolichospermum
36.05353 -76.682 Discolored
Water
WLAB082818/
12712-2018/AC54653
2019 Blooms:
Chowan River near
Harrellsville and
Colerain
5/13/19 Cho 0.4^ 610 Hertford T-698,000
C-697,000
T-19,400
C-18,400
T-9,800
C-9,800
CYA/ Aphanizomenon 36.3220 -76.7376
Discolored
water/Surf
ace Scum
AC62831/WARO_NLC
CRAB051319
Bloom ID 2019001
Some spreadsheets have it as
5/3/19 instead
Chowan River
Edenton (Hwy 17)
D94900NS
5/15/19 Cho 0.4^ 10 Chowan NA NA NA NA 36.0536 -76.6841 NA
AC62842/D94900NS
Not on Blooms 2019 list.
Sampled for microcystin.
Chowan River
Colerain (CM7)
D8950000
5/29/19 Cho 0.4^ 50 Chowan T-66,000
C-59,000
T-4,800
C-1,600
T-4,800
C-2,900
CHL/Eudorina,
Dolichospermum 36.2098 -76.7268 Discolored
Water AC62375/D8950000/CHO016
AC62376/D8950000_PHO
Chowan River near
Harrellsville 6/5/19 Cho NA 51 Hertford T-101,000
C-96,000
T-4,100
C-2,100
T-6,400
C-4,700
CYA/Dolicho-
spermum 36.3220 -76.7382
Discolored
Water/
Green
Flecks
CRHV0619
Bloom ID 2019007/AC63911
Data from 2019 algal bloom/fish
kill table

Chowan River near
Johnson Point 6/5/19 Cho NA ND Chowan T-48,000
C-41,000
T-6,500
C-3,600
T-3,100
C-1,000
CYA/Chroococcus,
Dolichospermum 36.1990 -76.7157
Discolored
water/
Bloom
complaint
CRSF0619/AC63912
Data from 2019 algal bloom/fish
kill table
Chowan – Appendix V-II 3 2/18/2021

Location Date
Sampled Basin
Micro-
cystin
(ug/L)
Toxin
Chl a
µg/L County Cell Density +
Cells/mL
Density +
Units/mL
Biovolume +
mm3/m3
Algal Group/
Dominant Taxa
Latitude Longitude Reason
Reported
Station/Sample Code/ID
Bloom ID
& Notes
Chowan River
Edenton (Hwy 17)
D94900NS
6/12/19 Cho 0.4U 20 Bertie NA NA NA NA 36.0536 -76.6841 Discolored
Water
AC63976/D94900NS
Not on Blooms 2019 list.
Sampled for microcystin.
Chowan River
Edenton (Hwy 17)
D94900NS
6/18/19 Cho 0.4U 94 Bertie T-81,000
C-76,000
T-7,600
C-4,300
T-6,900
C-6,200
CYA/
Dolichospermum 36.0536 -76.6841 Discolored
Water
AC64937/D94900NS
Bloom ID 2019010
Chowan River
Colerain
D8950000
6/27/19 Cho NA 57 Chowan T-37,000
C-20,000
T-8,000
C-1,300
T-5,600
C-500
BAC/centrics 36.2098 -76.7268
Green
Flecks/
Elevated
DO & pH
D8950000/CHO016
Bloom ID 2019011
(Non HAB bloom)
AMS monitoring date.
Chowan River
Edenton (Hwy 17)
D9490000
6/27/19 Cho 0.4U 58 Bertie T-54,000
C-36,000
T-9,400
C-1,800
T-3,800
C-1,000
BAC/centrics 36.0470 -76.6970
Green
Flecks/
Elevated
DO & pH
AC63584/D9490000/CHO018
Chowan River
Edenton (Hwy 17)
D94900NS
7/17/19 Cho 0.4U 24 Bertie NA NA NA NA 36.0536 -76.6841
Not on
bloom
report
spreadshe
et
AC65470/D94900NS
Included on Microcystin table

Chowan River near
Arrowhead Beach
Shawnee Trail
Canal
7/17/19 Cho 310* 984 Chowan T-853,000
C-852,000
T-7,900
C-7,200
T-32,000
C-31,000
CYA/
Microcystis

36.2246 -76.7069
Surface
Scum/
Bluish
White
Scum
AC65469/WARO_NLC/
CRST71719
Bloom ID 2019021
Chowan River near
Arrowhead Beach
Shawnee Trail
Canal
7/23/19 Cho 21* 72 Chowan T-338,000
C-332,000
T-5,600
C-2,700
T-12,000
C-9,800
CYA/
Microcystis 36.2247 -76.7068 Discolored
Water
AC65469/WARO_NLC/
STCR72319
Bloom ID 2019024
Chowan River at
Leary Landing 7/29/19 Cho 190* 630 Bertie T-9,097,000
C-9,093,000
T-9,600
C-6,797
T-280,000
C-273,000
CYA/
Microcystis 36.1386 -76.7515
Discolored
Water/
Surface
Scum with
Clumps
AC66286/WARO_NLC/ESLL1907
29/LLCR72919
Bloom ID 2019025
Chowan River
Colerain (CM7)
D8950000
7/31/19 Cho 3.3 9 Chowan NA NA NA NA 36.2098 -76.7268 NA
AC64446/D8950000
Included on Microcystin table
AC64447/D8950000_PHO
Chowan River
Edenton (Hwy 17)
D94900NS
8/13/19 Cho 0.4U 17 Bertie NA NA NA NA 36.0536 -76.6841 NA AC66433/D94900NS
Included on Microcystin table
Chowan
River/Indian Creek
(Dillard Cr.)
8/13/19 Cho 620* ND Chowan T-18,596,000
C-18,570,000
T-13,4000
C-13,300
T-557,000
C-557,000
CYA/
Microcystis 36.2349 -76.6946
Discolored
Water/
Surface
Scum
AC66435/ESIC190813/
ICCR190813
Bloom ID 2019030
Chowan – Appendix V-II 4 2/18/2021

Location Date
Sampled Basin
Micro-
cystin
(ug/L)
Toxin
Chl a
µg/L County Cell Density +
Cells/mL
Density +
Units/mL
Biovolume +
mm3/m3
Algal Group/
Dominant Taxa
Latitude Longitude
Reason
Reported

Station/Sample Code/ID
Bloom ID
& Notes
Chowan
River/Indian Creek
(Dillard Cr.)
8/19/19 Cho 9.3 32 Chowan T-235,000
C-231,000
T-2,600
C-400
T-7,900
C-6,900
CYA/
Microcystis
36.2327 -76.6950 Discolored
Water
AC66641/WARO_NLC/
Dillard Creek
Bloom ID 2019032
Chowan River Bess
Landing
9/11 or
9/12/19 Cho 0.4U 18 Bertie T-61,000
C-59,000
T-5,100
C-3,000
T-2,600
C-1,500
CYA/
Microcystis
36.1432 -76.7539 Discolored
Water
AC67977/BLAB91219/
ESCR190911_2
* WHO (World Health Organization): Exceeds guideline of 10 ug/L indicating moderate probability of acute health effects from recreational exposure;
^ QA/QC issues;
+ T=Total Algae & C=Cyanobacteria/Bluegreen Algae;
Ŧ = April Williams, personal communication, May 18, 2020;
ND = Sheet was found, but no analytical data was found;
NA= Not available;
U = sample detection limit;
Q1 = sample holding time issue.

Chowan – Appendix V-II 5 2/18/2021

Table V-II.2. DWR and DHHS Press Release/Algal Bloom Recreational Advisories for the Chowan and Pasquotank River Basins (2015-2019).
Ref # Date Agency Bloom Reported Warning Provided
Chowan River /Albemarle
Sound Bloom Locations
Identified in Public New
Release
Algal bloom
species identified
in the area
Microcystin Toxin
Concentration
(µg/L)
2015
2015-1 July 23,
2015
DEQ No specific date
of bloom was
provided in the
notice.
Avoid contact with
potentially harmful algal
blooms; prevent children
and pets from swimming
or ingesting water.
Albemarle Sound and
Chowan River near Queen
Ann’s Creek.
Cyanobacteria/
bluegreen algae;
pHAB Anabaena
planctonica
Sample sent to
public health lab for
microcystin testing.
2015-2 September
18, 2015
DEQ No specific date
of bloom was
provided in the
notice.
Avoid contact with toxic
algal blooms/large
accumulations of the
algae; prevent children
and pets from swimming
or ingesting water.
In and around the
Albemarle Sound; Chowan
River. Blooms have turned
up in waters in Bertie,
Chowan, Herford,
Perquimans and
Washington Counties.
Cyanobacteria/
bluegreen algae;
pHAB Microcystin
aeruginosa
Sample sent to
DHHS and toxin was
identified. No
concentration
provided in the
press release.
(Colerain Chl a =
500 µg/L)
2016
2016-1 July 22,
2016
DEQ Since late June,
2016
Avoid contact with
potentially harmful algal
blooms; prevent children
and pets from swimming
or ingesting water.
Now concentrated in
Edenton Bay, Chowan
County.
Cyanobacteria/
bluegreen algae;
pHAB
Dolechospermum
planctonicum
Indicates these are
potential harmful
blooms.
2016-2 September
9, 2016
DEQ Blooms since June
2016; lingering
Avoid contact with green
water/large accumulations
of algae; prevent children
and pets from swimming
or ingesting water.
Chowan River from
Colerain to Edenton Bay.
Cyanobacteria/
bluegreen algae;
pHAB Microcystin
and Anabaena
Indicates these are
potential toxic
blooms
2017
2017-1 June 23,
2017
DEQ Bloom since June
12, 2017
Avoid contact with green
or blue water; prevent
children and pets from
swimming or ingesting
water.
Chowan River, Arrowhead
Beach area south to
Edenton, beyond NC Hwy
32 bridge (this is in the
Albemarle Sound).
Cyanobacteria/
bluegreen algae;
pHAB Anabaena
No toxin
assessment
discussed.
Chowan – Appendix V-II 6 2/18/2021

Ref # Date Agency Bloom Reported Warning Provided
Chowan River /Albemarle
Sound Bloom Locations
Identified in Public New
Release
Algal bloom
species identified
in the area
Microcystin Toxin
Concentration µg/L
2018
2018-1 July 3,
2018
DEQ Bloom since June
20, 2018
Avoid contact with green
or blue water; prevent
children and pets from
swimming or ingesting
water.
Chowan River about 12
miles upstream of
Edenton, however, can
easily move to other areas.
Cyanobacteria/
bluegreen algae;
pHAB
Dolechospermum
6/27/18-Learly
Landing = 0.44 µg/L
2018-2 August 8,
2018
DEQ Bloom lingering
since June 20,
2018
Avoid contact with green
or blue water; prevent
children and pets from
swimming or ingesting
water.
Bertie and Chowan
Counties, with reports of
the blooms along the
eastern and western
shorelines from
Harrellsville downstream
to Edenton Bay, including
the Colerain and
Rockyhock areas
Cyanobacteria/
bluegreen algae;
pHABs
Dolechospermum
and microcystis
7/17/18 –
Rockyhock = 0.72
µg/L;
8/7/18-Wharf
Landing = 14 µg/L*;
8/7/18- Colerain =
1.4 µg/L
2019
2019-1 June 11,
2019
DEQ Bloom since May
14, 2019
Avoid contact with green
or blue water; prevent
children and pets from
swimming or ingesting
water.
Albemarle Sound and
adjoining waterbodies
(Perquimans River,
Pasquotank River near
Elizabeth City; western
shore of the Chowan River.
Currently affecting Bertie,
Chowan, Pasquotank and
Perquimans Counties.
Cyanobacteria/
bluegreen algae;
pHAB
Dolechospermum
No toxin identified
in blooms, however
there where QA/QC
issues with the
tests. No toxin
samples collected
on other dates.
2019-2 July 3,
2019
DEQ Bloom since May
14, 2019
Avoid contact with green
or blue water; prevent
children and pets from
swimming or ingesting
water.
Albemarle Sound and
adjoining waterbodies
including the Chowan
River; affecting Bertie and
Chowan Counties.
Cyanobacteria/
bluegreen algae;
pHAB
Dolechospermum
Toxin was not
detected above the
PQL or not sampled.
See photo of bloom
on 7/2/19 in the
Chowan (below).
2019-3 July 19,
2019
DHHS Bloom since May,
2019
Avoid an algal bloom on
the east side of Chowan
River because of a toxin
called Microcystin. Prevent
children and pets from
swimming or ingesting
water.
Eastern side of Chowan
River and Arrowhead
Beach in Edenton
Cyanobacteria/
bluegreen algae;
pHAB Microcyctis
Preliminary results
5-10 µg/L
microcystin. Low
level rick from
recreational
exposure.

Chowan – Appendix V-II 7 2/18/2021

Ref # Date Agency Bloom Reported Warning Provided
Chowan River /Albemarle
Sound Bloom Locations
Identified in Public New
Release
Algal bloom
species identified
in the area
Microcystin Toxin
Concentration µg/L
2019-4 July 23,
2019
DHHS Numerous
blooms since May
2019; report of
specific bloom on
July 17th.
Stay out of the Chowan
River near Arrowhead
Beach because of an algal
bloom producing a toxin.
Included a list of
safeguards to take.
Chowan River near
Arrowhead Beach
Cyanobacteria/
bluegreen algae;
pHAB Microcyctis
Report indicated
readings >250 µg/L
(High risk); DWR lab
reported
concentrations:
7/17/19 – 310 µg/L*
&
7/23/19 – 21 µg/L*
2019-5 August 5,
2919
DHHS Numerous
blooms since May
2019; report of
specific bloom on
July 29, 2019
Stay out of the Chowan
River near Leary Landing
because of an algal bloom
producing a toxin.
Included a list of
safeguards to take.
Chowan River near Leary
Landing and Arrowhead
Beach
Cyanobacteria/
bluegreen algae;
pHAB Microcyctis
7/29/19 - Leary
Landing = 190 µg/L
(high risk);
7/23/19 -
Arrowhead Beach =
21 µg/L (high risk)
2019-6 August 16,
2019
DHHS No date of bloom
indicated in press
release. Provided
link to DWR
interactive bloom
map.
Stay out of the Chowan
River near Indian Creek
because of an algal bloom
producing the highest
levels of toxin recorded
this year. Stay away from
all blooms as they are
more common in the late
summer.
Included a list of
safeguards to take.
Chowan River near Indian
Creek; Note: Blooms are
more common during late
summer due to war water
temperatures and
stagnant bodies of
water. Because toxicity
levels can change rapidly
over time and location, it is
best to stay away from all
blooms whenever
possible.
Cyanobacteria/
bluegreen algae;
pHAB Microcyctis
8/13/19 - 620 µg/L*
(Extremely high risk)
*WHO (World Health Organization): Exceeds guideline of 10 ug/L indicating moderate probability of acute health effects from recreational exposure.

Links to DWR/DHHS Press Releases:
Future press releases here - https://deq.nc.gov/about/divisions/water-resources/water-resources-data/water-sciences-home-page/ecosystems-branch/algal-
blooms
2015-2019 press releases -
2015-1: July 23, 2015 – https://deq.nc.gov/press-release/algal-blooms-fish-kills-occurring-across-portions-state
2015-2: September 18, 2015 – https://deq.nc.gov/press-release/people-urged-avoid-toxic-algal-blooms-eastern-north-carolina-waters
2016-1: July 22, 2016 - https://deq.nc.gov/press-release/people-urged-avoid-contact-algal-bloom-edenton-bay
Chowan – Appendix V-II 8 2/18/2021

2016-2: September 9, 2016 - https://deq.nc.gov/press-release/state-reminds-public-avoid-algal-blooms-chowan-river-area
2017-1: June 23, 2017 - https://deq.nc.gov/state-urges-public-avoid-algal-blooms-chowan-river-area
2018-1: July 3, 2018 – https://deq.nc.gov/news/press-releases/2018/07/03/public-urged-avoid-algal-blooms-chowan-river-area
2018-2: August 8, 2018 - https://deq.nc.gov/news/press-releases/2018/08/08/state-reminds-public-avoid-algal-blooms-chowan-river-area
2019-1: June 11, 2019 – https://deq.nc.gov/news/press-releases/2019/06/11/public-urged-avoid-algal-blooms-albemarle-sound-area
2019-2: July 3, 2019 – https://deq.nc.gov/news/press-releases/2019/07/03/public-still-urged-avoid-widespread-algal-blooms-albemarle-sound-area
2019-3: July 19, 2019 – https://deq.nc.gov/news/press-releases/2019/07/19/public-cautioned-avoid-toxin-producing-algal-bloom-chowan-river
2019-4: July 23, 2019 – https://www.ncdhhs.gov/news/press-releases/test-results-indicate-high-health-risk-contact-chowan-river-algal-bloom
2019-5: August 5, 2019 – https://www.ncdhhs.gov/news/press-releases/reported-algal-bloom-west-side-chowan-river
2019-6: August 16, 2019 – https://www.ncdhhs.gov/news/press-releases/test-results-show-highest-toxic-algae-levels-recorded-chowan-river-year

State of NC website links:
NC DWR Algal Blooms page with link to Interactive Algal Bloom Map - https://deq.nc.gov/about/divisions/water-resources/water-resources-data/water-
sciences-home-page/ecosystems-branch/algal-blooms
NC DHHS – Cyanobacteria, Protecting Children & Dogs - https://epi.dph.ncdhhs.gov/oee/algae/protect.html
NC DHHS – Occupational & Environmental Epidemiology (Cyanobacteria) - https://epi.dph.ncdhhs.gov/oee/a_z/algae.html
Other Website links:
Dolichospermum bloom, Chowan River (7/2/18)
Chowan – Appendix V-II 9 2/18/2021

CDC – Harmful Algal Bloom (HAB)-Associated Illness - https://www.cdc.gov/habs/index.html

Website links for WHO cyanobacteria/microcystin information:
Guidelines for safe recreational water environments. Volume 1: Coastal and fresh waters (2003).
Full document: https://www.who.int/water_sanitation_health/publications/srwe1/en/
Chapter 8 (Algae and cyanobacteria in fresh water): https://www.who.int/water_sanitation_health/bathing/srwe1-chap8.pdf
EPA – WHO 1999 Guideline Values for Cyanobacteria in Freshwater - https://www.epa.gov/cyanohabs/world-health-organization-who-1999-guideline-values-
cyanobacteria-freshwater
Table V-II.3. World Health Organization (WHO) 2003 Cyanobacteria/Microcystin Risk Table Summary from Guidelines for safe recreational water environments.
Volume 1: Coastal and fresh waters (2003).
Relative Probability of
Acute Health Effects
Cyanobacteria
(cells/mL)
Microcystin
(µg/L)
Chlorophyll-a
(µg/L)
Low < 20,000 <10 <10
Moderate 20,000-100,000 10-20 10-50
High 100,000-10,000,000 20-2,000 50-5,000
Very High > 10,000,000 >2,000 >5,000