Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 260 - WATER QUALITY STANDARDS › Part II - Standards with More Specific Application › Section 9VAC25-260-185 - Criteria to protect designated uses from the impacts of nutrients and suspended sediment in the Chesapeake Bay and its tidal tributaries

Current through Register Vol. 40, No. 24, July 15, 2024
A. Dissolved
				  oxygen. The dissolved oxygen criteria in the following table apply to all
				  Chesapeake Bay waters according to their specified designated use and supersede
				  the dissolved oxygen criteria in
				  9VAC25-260-50.
Designated Use
Criteria Concentration/Duration
Temporal Application
Migratory fish spawning and nursery
7-day mean [GREATER THAN EQUAL TO] 6 mg/l (tidal
								habitats with 0-0.5 ppt salinity)
February 1 - May 31
Instantaneous minimum [GREATER THAN EQUAL TO] 5
								mg/l
Open
								water1
30-day mean [GREATER THAN EQUAL TO] 5.5 mg/l (tidal
								habitats with 0-0.5 ppt salinity)
year-round2
30-day mean [GREATER THAN EQUAL TO] 5 mg/l (tidal
								habitats with > 0.5 ppt salinity)
7-day mean [GREATER THAN EQUAL TO] 4
								mg/l
Instantaneous minimum [GREATER THAN EQUAL TO] 3.2
								mg/l at temperatures < 29°C
Instantaneous minimum [GREATER THAN EQUAL TO] 4.3
								mg/lat temperatures [GREATER THAN EQUAL TO] 29°C
Deep water
30-day mean [GREATER THAN EQUAL TO] 3
								mg/l
June 1 - September 30
1-day mean [GREATER THAN EQUAL TO] 2.3
								mg/l
Instantaneous minimum [GREATER THAN EQUAL TO] 1.7
								mg/l
Deep channel
Instantaneous minimum [GREATER THAN EQUAL TO] 1
								mg/l
June 1 - September 30
1In applying this open
								water instantaneous criterion to the Chesapeake Bay and its tidal tributaries
								where the existing water quality for dissolved oxygen exceeds an instantaneous
								minimum of 3.2 mg/l, that higher water quality for dissolved oxygen shall be
								provided antidegradation protection in accordance with
								9VAC25-260-30
								A 2.
2Open-water dissolved
								oxygen criteria attainment is assessed separately over two time periods: summer
								(June 1- September 30) and nonsummer (October 1-May 31) months.
B.
				  Submerged aquatic vegetation (SAV) and water clarity. Attainment of the
				  shallow-water submerged aquatic vegetation designated use shall be determined
				  using any one of the following criteria:
Designated Use
Chesapeake Bay Program
								Segment
SAV
								Acres1
Percent
								Light-Through-Water2
Water Clarity
								Acres1
Temporal Application
Shallow water submerged aquatic vegetation
								use
CB5MH
7,633
22%
14,514
April 1 - October 31
CB6PH
1,267
22%
3,168
March 1 - November 30
CB7PH
15,107
22%
34,085
March 1 - November 30
CB8PH
11
22%
28
March 1 - November 30
POTTF
2,093
13%
5,233
April 1 - October 31
POTOH
1,503
13%
3,758
April 1 - October 31
POTMH
4,250
22%
10,625
April 1 - October 31
RPPTF
66
13%
165
April 1 - October 31
RPPOH
4
13%
10
April 1 - October 31
RPPMH
5,380
22%
13,450
April 1 - October 31
CRRMH
768
22%
1,920
April 1 - October 31
PIAMH
3,479
22%
8,014
April 1 - October 31
MPNTF
85
13%
213
April 1 - October 31
MPNOH
-
-
-
-
PMKTF
187
13%
468
April 1 - October 31
PMKOH
-
-
-
-
YRKMH
239
22%
598
April 1 - October 31
YRKPH
2,793
22%
6,982
March 1 - November 30
MOBPH
15,901
22%
33,990
March 1 - November 30
JMSTF2
266
13%
665
April 1 - October 31
JMSTF1
1,333
13%
3,332
April 1 - October 31
APPTF
379
13%
948
April 1 - October 31
JMSOH
15
13%
38
April 1 - October 31
CHKOH
535
13%
1,338
April 1 - October 31
JMSMH
531
22%
1,328
April 1 - October 31
JMSPH
604
22%
1,510
March 1 - November 30
WBEMH
-
-
-
-
SBEMH
-
-
-
-
EBEMH
-
-
-
-
ELIPH
-
-
-
-
LYNPH
107
22%
268
March 1 - November 30
POCOH
-
-
-
-
POCMH
4,066
22%
9,368
April 1 - October 31
TANMH
13,579
22%
22,064
April 1 - October 31
1The assessment period
								for SAV and water clarity acres shall be the single best year in the most
								recent three consecutive years. When three consecutive years of data are not
								available, a minimum of three years within the data assessment window shall be
								used.
2Percent
								light-through-water = 100e(-KdZ) where
								Kd is water column light attenuation coefficient and can
								be measured directly or converted from a measured secchi depth where
								Kd = 1.45/secchi depth. Z = depth at location of
								measurement of Kd.
C.
				  Chlorophyll a.
Designated Use
Chlorophyll a Narrative Criterion
Temporal Application
Open water
Concentrations of chlorophyll a in free-floating
								microscopic aquatic plants (algae) shall not exceed levels that result in
								undesirable or nuisance aquatic plant life or render tidal waters unsuitable
								for the propagation and growth of a balanced, indigenous population of aquatic
								life or otherwise result in ecologically undesirable water quality conditions
								such as reduced water clarity, low dissolved oxygen, food supply imbalances,
								proliferation of species deemed potentially harmful to aquatic life or humans,
								or aesthetically objectionable conditions.
March 1 - September 30
See
								9VAC25-260-310
								special standard bb for numerical chlorophyll criteria for the tidal James
								River.
D.
				  Implementation.
1. Chesapeake Bay program
				  segmentation scheme as described in Chesapeake Bay Program, 2004 Chesapeake Bay
				  Program Analytical Segmentation Scheme-Revisions, Decisions and Rationales:
				  1983-2003, CBP/TRS 268/04, EPA 903-R-04-008, Chesapeake Bay Program, Annapolis,
				  Maryland, and the Chesapeake Bay Program published 2005 addendum (CBP/TRS
				  278-06; EPA 903-R-05-004) is listed in the following table and shall be used as
				  the spatial assessment unit to determine attainment of the criteria in this
				  section for each designated use.
Chesapeake Bay Segment Description
Segment
								Name1
Chesapeake Bay Segment Description
Segment
								Name1
Lower Central Chesapeake Bay
CB5MH
Mobjack Bay
MOBPH
Western Lower Chesapeake Bay
CB6PH
Upper Tidal Fresh James River
JMSTF2
Eastern Lower Chesapeake Bay
CB7PH
Lower Tidal Fresh James River
JMSTF1
Mouth of the Chesapeake Bay
CB8PH
Appomattox River
APPTF
Upper Potomac River
POTTF
Middle James River
JMSOH
Middle Potomac River
POTOH
Chickahominy River
CHKOH
Lower Potomac River
POTMH
Lower James River
JMSMH
Upper Rappahannock River
RPPTF
Mouth of the James River
JMSPH
Middle Rappahannock River
RPPOH
Western Branch Elizabeth River
WBEMH
Lower Rappahannock River
RPPMH
Southern Branch Elizabeth River
SBEMH
Corrotoman River
CRRMH
Eastern Branch Elizabeth River
EBEMH
Piankatank River
PIAMH
Lafayette River
LAFMH
Upper Mattaponi River
MPNTF
Mouth of the Elizabeth River
ELIPH
Lower Mattaponi River
MPNOH
Lynnhaven River
LYNPH
Upper Pamunkey River
PMKTF
Middle Pocomoke River
POCOH
Lower Pamunkey River
PMKOH
Lower Pocomoke River
POCMH
Middle York River
YRKMH
Tangier Sound
TANMH
Lower York River
YRKPH
1First three letters of
								segment name represent Chesapeake Bay segment description, letters four and
								five represent the salinity regime of that segment (TF = Tidal Fresh, OH =
								Oligohaline, MH = Mesohaline, and PH = Polyhaline) and a sixth space is
								reserved for subdivisions of that segment.
2.
				  The assessment period shall be the most recent three consecutive years. When
				  three consecutive years of data are not available, a minimum of three years
				  within the data assessment window shall be used.
3. Attainment of these criteria shall be
				  assessed through comparison of the generated cumulative frequency distribution
				  of the monitoring data to the applicable criteria reference curve for each
				  designated use. If the monitoring data cumulative frequency curve is completely
				  contained inside the reference curve, then the segment is in attainment of the
				  designated use. The reference curves and procedures to be followed are
				  published in the USEPA, Ambient Water Quality Criteria for Dissolved Oxygen,
				  Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal
				  Tributaries, EPA 903-R-03-002, April 2003 and the 2004 (EPA 903-R-03-002
				  October 2004), 2007 (CBP/TRS 285/07, EPA 903-R-07-003), 2007 (CBP/TRS 288/07,
				  EPA 903-R-07-005), 2008 (CBP/TRS 290-08, EPA 903-R-08-001), 2010 (CBP/TRS
				  301-10, EPA 903-R-10-002), and 2017 (CBP/TRS 320-17, EPA 903-R-17-002) addenda.
				  An exception to this requirement is in measuring attainment of the SAV and
				  water clarity acres, which are compared directly to the criteria.