Virginia Administrative Code (Last Updated: January 10, 2017) |
Title 9. Environment |
Agency 25. State Water Control Board |
Chapter 260. Water Quality Standards |
Section 185. Criteria to protect designated uses from the impacts of nutrients and suspended sediment in the Chesapeake Bay and its tidal tributaries
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A. Dissolved oxygen.
Designated Use
Criteria Concentration/Duration
Temporal Application
Migratory fish spawning and nursery
7-day mean ≥ 6 mg/l (tidal habitats with 0-0.5 ppt salinity)
February 1 - May 31
Instantaneous minimum ≥ 5 mg/l
Open water1
30 day mean ≥ 5.5 mg/l (tidal habitats with 0-0.5 ppt salinity)
year-round2
30 day mean ≥ 5 mg/l (tidal habitats with > 0.5 ppt salinity)
7 day mean ≥ 4 mg/l
Instantaneous minimum ≥ 3.2 mg/l at temperatures < 29°C
Instantaneous minimum ≥ 4.3 mg/l at temperatures ≥ 29°C
Deep water
30 day mean ≥ 3 mg/l
June 1 - September 30
1 day mean ≥ 2.3 mg/l
Instantaneous minimum ≥ 1.7 mg/l
Deep channel
Instantaneous minimum ≥ 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 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
1700
22%
5000
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
200
13%
500
April 1 - October 31
JMSTF1
1000
13%
2500
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
200
22%
500
April 1 - October 31
JMSPH
300
22%
750
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 below 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), and 2010 (CBP/TRS 301-10, EPA 903-R-10-002) addenda. An exception to this requirement is in measuring attainment of the SAV and water clarity acres, which are compared directly to the criteria.
Historical Notes
Derived from Volume 21, Issue 23, eff. June 24, 2005; amended, Volume 26, Issue 12, eff. February 1, 2010; Volume 27, Issue 06, eff. January 6, 2011.
Statutory Authority
§ 62.1-44.15 of the Code of Virginia; 33 USC § 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.