Section 185. Criteria to protect designated uses from the impacts of nutrients and suspended sediment in the Chesapeake Bay and its tidal tributaries  


Latest version.
  • 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.