Proposed Text
9VAC25-260-185. Criteria to protect designated uses from the impacts of nutrients and suspended sediment in the Chesapeake Bay and its tidal tributaries.
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 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: 19832003, 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 |
RPPOH |
Western Branch Elizabeth River |
WBEMH |
Lower |
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 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) and
, 2007 (CBA/TRS (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.
DOCUMENTS INCORPORATED BY REFERENCE (9VAC25-260)