§ 93.7. Specific water quality criteria.

 (a)  Table 3 displays specific water quality criteria and associated critical uses. The criteria associated with the Statewide water uses listed in §  93.4, Table 2 apply to all surface waters, unless a specific exception is indicated in § §  93.9a—93.9z. These exceptions will be indicated on a stream-by-stream or segment-by-segment basis by the words ‘‘Add’’ or ‘‘Delete’’ followed by the appropriate symbols described elsewhere in this chapter. Other specific water quality criteria apply to surface waters as specified in § §  93.9a—93.9z. All applicable criteria shall be applied in accordance with this chapter, Chapter 96 (relating to water quality standards implementation) and other applicable State and Federal laws and regulations.


Critical Use*
Alkalinity Alk Minimum 20 mg/l as CaCO3, except where natural conditions are less. Where discharges are to waters with 20 mg/l or less alkalinity, the discharge should not further reduce the alkalinity of the receiving waters. CWF,
Am The maximum total ammonia nitrogen concentration (in mg/L) at all times shall be the numerical value given by: un-ionized ammonia nitrogen (NH3-N) x (log-1[pKT-pH] + 1), where:
un-ionized ammonia nitrogen = 0.12 x f(T)/f(pH)
f(pH) = 1 + 101.03(7.32-pH)
f(T) = 1, T ›= 10°C
f(T) = 1 + 10(9.73-pH) , T ‹ 10°C
1 + 10(pKT-pH)
pKT =

, the dissociation 0.090 +…constant for

ammonia in water.

(T + 273.2)

The average total ammonia nitrogen concentration over any 30 consecutive days shall be less than or equal to the numerical value given by:
un-ionized ammonia nitrogen (NH3-N) x (log-1[pKT-pH] + 1), where:
un-ionized ammonia nitrogen = 0.025 x f(T)/f(pH)
f(pH) = 1, pH ›= 7.7
f(pH) = 100.74(7.7-pH), pH ‹ 7.7
f(T) = 1, T ›= 10°C
f(T) = 1 + 10(9.73-pH) , T ‹ 10°C
1 + 10(pKT-pH)
The pH and temperature used to derive the appropriate ammonia criteria shall be determined by one of the following methods:
1) Instream measurements, representative of median pH and temperature—July through September.
2) Estimates of median pH and temperature—July through September—based upon available data or values determined by the Department.
For purposes of calculating effluent limitations based on this value the accepted design stream flow shall be the actual or estimated lowest 30-consecutive-day average flow that occurs once in 10 years.
Bacteria Bac1 (Fecal coliforms/ 100 ml)—During the swimming season (May 1 through September 30), the maximum fecal coliform level shall be a geometric mean of 200 per 100 milliliters (ml) based on a minimum of five consecutive samples each sample collected on different days during a 30-day period. No more than 10% of the total samples taken during a 30-day period may exceed 400 per 100 ml. For the remainder of the year, the maximum fecal coliform level shall be a geometric mean of 2,000 per 100 milliliters (ml) based on a minimum of five consecutive samples collected on different days during a 30-day period. WC
Bac2 (Coliforms/100 ml)—Maximum of 5,000/100 ml as a monthly average value, no more than this number in more than 20 of the samples collected during a month, nor more than 20,000/100 ml in more than 5% of the samples. PWS
Chloride Ch Maximum 250 mg/l. PWS
ColorColMaximum 75 units on the platinum-cobalt scale; no other colors perceptible to the human eye.PWS
Dissolved Oxygen The following specific dissolved oxygen criteria recognize the natural process of stratification in lakes, ponds and impoundments. These criteria apply to flowing freshwater and to the epilimnion of a naturally stratified lake, pond or impoundment. The hypolimnion in a naturally stratified lake, pond or impoundment is protected by the narrative water quality criteria in §  93.6 (relating to general water quality criteria). For nonstratified lakes, ponds or impoundments, the dissolved oxygen criteria apply throughout the lake, pond or impoundment to protect the critical uses.
DO1 For flowing waters, 7-day average 6.0 mg/l; minimum 5.0 mg/l. For naturally reproducing salmonid early life stages, applied in accordance with subsection (b), 7-day average 9.0 mg/l; minimum 8.0 mg/l. For lakes, ponds and impoundments, minimum 5.0 mg/l. CWF
DO2 7-day average 5.5 mg/l; minimum 5.0 mg/l. WWF
DO3 For the period February 15 to July 31 of any year, 7-day average 6.0 mg/l; minimum 5.0 mg/l. For the remainder of the year, 7-day average 5.5 mg/l; minimum 5.0 mg/l. TSF
Fluoride F Daily average 2.0 mg/l. PWS
Iron Fe1 30-day average 1.5 mg/l as total recoverable. CWF, WWF, TSF, MF
Fe2 Maximum 0.3 mg/l as dissolved. PWS
Manganese Mn Maximum 1.0 mg/l, as total recoverable. PWS
Nitrite plus Nitrate N Maximum 10 mg/l as nitrogen. PWS
Osmotic Pressure OP Maximum 50 milliosmoles per kilogram. CWF, WWF, TSF, MF
pH pH From 6.0 to 9.0 inclusive. CWF, WWF, TSF, MF
Phenolics (except
§  307(a)(1) (33
U.S.C.A. §  1317(a)(1)),
Priority Pollutants)
Phen Maximum 0.005 mg/l. PWS
Sulfate Sul Maximum 250 mg/l. PWS
Temperature Maximum temperatures in the receiving water body resulting from heated waste sources regulated under Chapters 92a, 96 and other sources where temperature limits are necessary to protect designated and existing uses. See the following table.

January 1-31 38 40 40
February 1-29 38 40 40
March 1-31 42 46 46
April 1-15 48 52 52
April 16-30 52 58 58
May 1-15 54 64 64
May 16-31 58 72 68
June 1-15 60 80 70
June 16-30 64 84 72
July 1-31 66 87 74
August 1-15 66 87 80
August 16-30 66 87 87
September 1-15 64 84 84
September 16-30 60 78 78
October 1-15 54 72 72
October 16-31 50 66 66
November 1-15 46 58 58
November 16-30 42 50 50
December 1-31 40 42 42

Critical Use*
Total Dissolved Solids TDS 500 mg/l as a monthly average value; maximum 750 mg/l. PWS
Total Residual Chlorine TRC Four-day average 0.011 mg/l; 1-hour average 0.019 mg/l. CWF,

   * Critical Use: The designated or existing use the criteria are designed to protect. More stringent site-specific criteria may be developed to protect other more sensitive, intervening uses.

 (b)  For naturally reproducing salmonids, protected early life stages include embryonic and larval stages and juvenile forms to 30 days after hatching. The DO1 standard for naturally reproducing salmonid early life stages applies October 1 through May 31. The DO1 standard for naturally reproducing salmonid early life stages applies unless it can be demonstrated to the Department’s satisfaction, that the following conditions are documented: 1) the absence of young of the year salmonids measuring less than 150 mm in the surface water; and 2) the absence of multiple age classes of salmonids in the surface water. These conditions only apply to salmonids resulting from natural reproduction occurring in the surface waters. Additional biological information may be considered by the Department which evaluates the presence or absence of early life stages.

 (c)  The list of specific water quality criteria does not include all possible substances that could cause pollution. For substances not listed, the general criterion that these substances may not be inimical or injurious to the existing or designated water uses applies. The Department will develop a criterion for any substance not listed in Table 3 that is determined to be inimical or injurious to existing or designated water uses using the best available scientific information, as determined by the Department.

 (d)  If the Department determines that natural quality of a surface water segment is of lower quality than the applicable aquatic life criteria in Table 3 or 5, the natural quality shall constitute the aquatic life criteria for that segment. All draft natural quality determinations will be published in the Pennsylvania Bulletin and be subject to a minimum 30-day comment period. The Department will maintain a publicly available list of surface waters and parameters where this subsection applies, and will, from time to time, submit appropriate amendments to § §  93.9a—93.9z.


   The provisions of this §  93.7 amended under sections 5(b)(1) and 402 of The Clean Streams Law (35 P. S. § §  691.5(b)(1) and 691.402); and section 1920-A of The Administrative Code of 1929 (71 P. S. §  510-20).


   The provisions of this §  93.7 amended through March 8, 1985, effective February 16, 1985, 15 Pa.B. 907; amended March 10, 1989, effective March 11, 1989, 19 Pa.B. 968; amended February 11, 1994, effective February 12, 1994, 24 Pa.B. 832; amended April 3, 1998, effective November 4, 1995, 28 Pa.B. 1633; amended July 16, 1999, effective July 17, 1999, 29 Pa.B. 3720; amended November 17, 2000, effective November 18, 2000, 30 Pa.B. 6059; amended February 11, 2005, effective February 12, 2005, 35 Pa.B. 1197; amended January 5, 2007, effective January 6, 2007, 37 Pa.B. 11; amended May 15, 2009, effective May 16, 2009, 39 Pa.B. 2523; amended July 19, 2013, effective July 20, 2013, 43 Pa.B. 4080. Immediately preceding text appears at serial pages (343950) to (343955).

Notes of Decisions

   The Department of Environmental Resources is not required to consider the economic consequences to a discharger in establishing water-quality based effluent limitations in a National Pollutant Discharge Elimination System (NPDES) Permit. Mathies Coal Company v. Department of Environmental Resources, 559 A.2d 506 (Pa. 1989).

   The water quality standards in 25 Pa. Code §  93.7 are to be considered only as one of the major factors in developing discharge limitations, and neither these standards nor effluent limitations based on them in case-by-case DER determinations require a presumption of validity. Lucas v. Department of Environmental Resources, 420 A.2d 1 (Pa. Cmwlth. 1980).

Cross References

   This section cited in 25 Pa. Code §  93.4b (relating to qualifying as High Quality or Exceptional Value Waters); 25 Pa. Code §  93.8d (relating to development on site-specific water quality criteria); and 25 Pa. Code §  96.3 (relating to water quality protection requirements).

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