COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT 
WATER QUALITY CONTROL COMMISSION 
5 CCR 1002-34
REGULATION NO. 34
CLASSIFICATIONS AND NUMERIC STANDARDS
FOR
SAN JUAN RIVER AND DOLORES RIVER BASINS
. . . .
34.6 	TABLES
. . . .
(2)	Abbreviations:
. . . .
(d)	Temporary Modification for Water + Fish Chronic Arsenic Standard
(i)	The temporary modification for chronic arsenic standards applied to segments with an arsenic standard of 0.02 mg/l that has been set to protect the Water+Fish qualifier is listed in the temporary modification and qualifiers column as As(ch)=hybrid.
(ii)	For discharges existing on or before 6/1/2013, the temporary modification is:  As(ch)=current condition, expiring on 12/31/2021.
(iii)	For new or increased discharges commencing on or after 6/1/2013, the temporary modification is:  As(ch)=0.02-3.0 mg/l (Trec), expiring on 12/31/2021.
(A)	The first number in the range is the health-based water quality standard previously adopted by the Commission for the segment.
(B)	The second number in the range is a technology based value established by the Commission for the purpose of this temporary modification.
(C)	Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range.
(3)	Table Value Standards
. . . .

REGION: 9

BASIN:  SAN JUAN RIVER	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS	

	
PHYSICAL
and
BIOLOGICAL	
INORGANIC

mg/l	
METALS

ug/l		

Stream Segment Description							

2.	Mainstem of the Navajo River from the Colorado/New Mexico border to the confluence with the San Juan River.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS

Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

4.	All tributaries to the San Juan River, Rio Blanco, and Navajo River including all wetlands which are within the Weminuche Wilderness area and South San Juan Wilderness Area.	

OW	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

5.	Mainstem of the San Juan River and the East Fork and West Fork of the San Juan River, from the boundary of the Weminuche Wilderness Area (West Fork) and the source (East Fork) to below the confluence with Fourmile Creek, including all wetlands and tributaries except for wetlands and tributaries included in Segment 4.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

6a.	Mainstem of the San Juan River from a point immediately below the confluence with Fourmile Creek to the Southern Ute Indian Reservation northern boundary.  Mainstem of Mill Creek from the source to the confluence with the San Juan River.  	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

REGION: 9

BASIN:  PIEDRA RIVER 	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS

	
	
PHYSICAL
and
BIOLOGICAL	
INORGANIC

mg/l	
METALS

ug/l		

Stream Segment Description							

1.	All tributaries to the Piedra River, including all wetlands, which are within the Weminuche Wilderness Area.	

OW	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

2a.	East Fork Piedra River and Middle Fork Piedra River, including all tributaries and wetlands, from the boundary of the Weminuche Wilderness Area to the confluence with the mainstem of the Piedra River, except for the specific listing in Segment 3.	
	
Aq Life Cold 1
Water Supply
Agriculture
Nov. 1 to March 31
Recreation N 

April 1 to Oct. 31
Recreation E	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
Nov. 1 to March 31
E.Coli=630/100ml

April 1 to Oct. 31
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

4b.	Mainstem of the Piedra River from the Southern Ute Indian Reservation boundary to Navajo Reservoir.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS
	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ch)=WS(dis)
Mn(ac/ch)=TVS
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

5.	All tributaries to the Piedra River, including all wetlands, from the boundary of the Weminuche Wilderness Area to a point immediately below the confluence with Devil Creek, except for the specific listing in Segment 2a and 3.  	
	
Aq Life Cold 1
Water Supply
Agriculture
Nov. 1 to April 30
Recreation N 

May 1 to Oct. 31
Recreation E	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
Nov. 1 to April 30
E.Coli=630/100ml

May 1 to Oct. 31
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

REGION: 9

BASIN:  LOS PINOS RIVER 	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS	

	
PHYSICAL
and
BIOLOGICAL	
INORGANIC

mg/l	
METALS

ug/l		

Stream Segment Description							

1.	All tributaries to the Los Pinos River, including all wetlands, which are within the Weminuche Wilderness Area.	

OW	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

2a.	Mainstem of the Los Pinos River from the boundary of the Weminuche Wilderness Area to the boundary of the Southern Ute Indian Reservation except for the specific listing in Segment 3.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

2b.	Mainstem of the Los Pinos River from the boundary of the Southern Ute Indian Reservation to the Colorado/New Mexico border.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

4a.	All tributaries to the Los Pinos River and Vallecito Reservoir, including all wetlands, from the boundary of the Weminuche Wilderness Area to a point immediately below the confluence with Bear Creek (T35N, R7W), except for the specific listing in Segment 5; mainstems of Beaver Creek, Ute Creek, and Spring Creek from their sources to  the boundary of the Southern Ute Indian Reservation.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

4b.	Mainstems of Beaver Creek, Ute Creek and Spring Creek from the boundaries of the Southern Ute Indian Reservation to their confluences with the Los Pinos River.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

REGION: 9

BASIN:  ANIMAS AND FLORIDA RIVER	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS	

	
PHYSICAL
and
BIOLOGICAL	
INORGANIC

mg/l	
METALS

ug/l		

Stream Segment Description							

4b.	Mainstem of the Animas River, including wetlands, from a point immediately above  the confluence with Deer Park Creek to Bakers Bridge.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml
	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
Al(ac/ch)=TVS
As(ch)=0.02(Trec)
As(ac)=340
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ch)=WS(dis)
Mn(ac/ch)=TVS
	
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

5a.	Mainstem of the Animas River, including wetlands, from Bakers Bridge to the Southern Ute Indian Reservation boundary.  	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
Al(ac/ch)=TVS
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
Ni(ac/ch)=TVS	
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

5b.	Mainstem of the Animas River, including wetlands, from the Southern Ute Indian Reservation boundary to the Colorado/New Mexico border.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
Al(ac/ch)=TVS
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
Ni(ac/ch)=TVS	
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

6.	Mainstem of the Animas River from the source to the outlet of Denver Lake.  Mainstem, including all tributaries and wetlands of Cinnamon Creek, Grouse Creek,  Picayne Gulch, and Minnie Gulch.  All tributaries and wetlands to the Animas River from immediately above Maggie Gulch to Elk Park except for those listed under segments 3c, 7, 8 and 9.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

10b.	Mainstem of the Florida River from the outlet of Lemon Reservoir to the Florida Farmers Canal Headgate.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O.= 6.0 mg/l
D.O.= 7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/cu)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS 
Zn (ch)=TVS(sc)

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

11a.	Mainstem of the Florida River from the Florida Farmers Canal Headgate to the Southern Ute Indian Reservation boundary.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

11b.	Mainstem of the Florida River from the Southern Ute Indian Reservation boundary to the confluence with the Animas River.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Southern Ute Indian Reservation.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

12a.	All tributaries to the Animas River from a point immediately above the confluence with Elk Creek to a point immediately below the confluence with Hermosa Creek except for specific listings in Segments 12b, 12c and 15.  All tributaries to the Florida River from the source to below the confluence with Mud Spring Creek, except the specific listing in Segment 1.  	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

13b.	 All tributaries to the Animas River from a point immediately below the confluence with Hermosa Creek to the Southern Ute Indian Reservation boundary except for the specific listings in Segments 12d, 13a, 14a and 14b; all tributaries to the Florida River, from a point immediately below the confluence with Mud Creek to the Southern Ute Indian Reservation boundary, except for specific listings in Segment 12d.	

Aq Life Cold 2
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O.= 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Water + Fish Standards
Temporary Modification for Coal Gulch, including all tributaries:
NH3=current condition. 
Type A
Expiration date 6/30/2014.

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

13c.	All tributaries to the Animas River from the  Southern Ute Indian Reservation boundary to the Colorado/New Mexico border, except for Segment 11b; all tributaries to the Florida River from the Southern Ute Indian Reservation boundary to the confluence with the Animas River.	

Aq Life Cold 2
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O.= 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	
Water + Fish Standards. Southern Ute Indian Reservation.
Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

14a.	Mainstem of Lightner Creek, including all tributaries, from the source to below the confluence with Deep Creek.	

Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

14b.	Mainstem of Lightner Creek from below the confluence with Deep Creek to the confluence with the Animas River.	

Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-II) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

REGION: 9

BASIN:  LA PLATA RIVER, MANCOS RIVER, McELMO CREEK, AND SAN JUAN RIVER IN MONTEZUMA COUNTY AND DOLORES COUNTY	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS	

	
PHYSICAL
and
BIOLOGICAL	
INORGANIC
mg/l	
METALS
ug/l		

Stream Segment Description							

1.	Mainstem of the La Plata River, including all wetlands and tributaries from the source to the Hay Gulch diversion south of Hesperus.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=205/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

4a.	Mainstem of the Mancos River, including all wetlands and tributaries, from the source of the East, West and Middle Forks to the San Juan National Forest Boundary.	

Aq Life Cold 1
Water Supply
Agriculture
Nov. 1 to April 30
Recreation N 

May 1 to Oct. 31
Recreation E	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O. (sp)=7.0 mg/l
pH = 6.5-9.0
Nov. 1 to April 30
E.Coli=630/100ml

May 1 to Oct. 31
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

REGION: 9

BASIN:  DOLORES RIVER	
Desig	
Classifications	
NUMERIC STANDARDS	
TEMPORARY
MODIFICATIONS
AND
QUALIFIERS	

	
PHYSICAL
and
BIOLOGICAL	
INORGANIC
mg/l	
METALS
ug/l		

Stream Segment Description							

8.	Mainstem of Horse Creek from the source to the confluence with the Dolores River.	
	
Aq Life Cold 1
Recreation E
Water Supply
Agriculture	
T=TVS(CS-I) oC
D.O. = 6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS
Cu(ac/ch)=TVS	
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ac/ch)=TVS
Mn(ch)=WS(dis)
Hg(ch)=0.01(tot)
Mo(ch)=160(Trec)
	
Ni(ac/ch)=TVS Se(ac/ch)=TVS
Ag(ac)=TVS
Ag(ch)=TVS(tr)
Zn(ac/ch)=TVS	

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.	

11.	All tributaries to the Dolores River, including all wetlands, from a point immediately below the confluence of the West Dolores River, to the bridge at Bradfield Ranch (Forest Route 505, near Montezuma/Dolores County Line), except for the specific listing in Segments 4 and 5.	
	
Aq Life Cold 2
Recreation E
Water Supply
Agriculture
	
T=TVS(CS-I) oC
D.O.=6.0 mg/l
D.O.(sp)=7.0 mg/l
pH = 6.5-9.0
E.Coli=126/100ml	
NH3(ac/ch)=TVS
Cl2(ac)=0.019
Cl2(ch)=0.011
CN=0.005	
S=0.002
B=0.75
NO2=0.05
NO3=10
Cl=250
SO4=WS	
As(ac)=340
As(ch)=0.02(Trec)
Cd(ac)=TVS(tr)
Cd(ch)=TVS
CrIII(ac)=50(Trec)
CrIII(ch)=TVS
CrVI(ac/ch)=TVS	
Cu(ac/ch)=TVS
Fe(ch)=WS(dis)
Fe(ch)=1000(Trec)
Pb(ac/ch)=TVS
Mn(ch)=WS(dis)
Mn(ac/ch)=TVS
Hg(ch)=0.01(tot) Mo(ch)=160(Trec)	
Ni(ac/ch)=TVS
Se(ac/ch)=TVS
Ag(ac/ch)=TVS
Zn(ac)=TVS 
Zn(ch)= TVS(sc)	
Water + Fish Standards

Temporary modification:
As(ch)=hybrid
Expiration date of 12/31/21.

. . . .
34.41	STATEMENT OF BASIS SPECIFIC STATUTORY AUTHORITY AND PURPOSE APRIL 8, 2013 RULEMAKING; FINAL ACTION MAY 13, 2013 EFFECTIVE DATE SEPTEMBER 30, 2013
The provisions of C.R S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specific statutory authority for adoption of these regulatory amendments.  The Commission also adopted in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
In August of 2005, the Commission adopted revisions to the Basic Standards and Methodologies for Surface Waters (Regulation #31) to add a Water + Fish (W+F) table value standard for chronic arsenic of 0.02 micrograms per liter (μg/L). W+F standards are numeric human health-based water quality standards that are calculated protective values that take into account the combined exposure from the pollutant in drinking water and the pollutant accumulated in fish flesh. This criterion automatically went into effect for Aquatic Life Class 1 waters which also have a Domestic Water Supply use, when the changes to the Basic Standards became effective.  It was also adopted on a segment by segment basis for Aquatic Life class 2 waters with Domestic Water Supply where the Commission determined there are fish of a catchable size of species that are normally consumed.  Because of the complicated nature of the arsenic standards, specific values were added to the basin tables in the basin hearings between 2006 and 2009.
In this hearing, the Commission adopted temporary modifications for W+F chronic arsenic where a permitted discharger with a water quality–based effluent limit compliance problem exists. The adopted temporary modification is listed in the regulation tables as “As(ch)=hybrid”. An explanation of the temporary modification and its expected implementation into control requirements, such as Colorado Discharge Permit System (CDPS) effluent limitations, is described in 34.6(2)(d). The temporary modification was established by the Commission to allow for a temporarily less stringent application of the chronic arsenic standard in control requirements for both existing discharges and new or increased discharges. 
For discharges existing on or before 6/1/2013, the temporary modification adopted for W+F chronic arsenic is “current condition”, expiring on 12/31/2021. The Commission intends that, when implementing the temporary modification of “current condition” in a CDPS permit, the Division will assess the current effluent quality, recognizing that it changes over time due to variability in treatment facility removal efficiency and influent loading from natural or anthropogenic sources, and due to changes in the influent flow and concentration over time. Maintaining the current condition will include maintaining permitted total arsenic loading to a treatment facility from arsenic contributors at the levels existing on the effective date of the temporary modification, while expressly allowing for variability in such loading due to changes in effluent quality as described above and due to changes in the influent flow and concentration over time within the permitted design flow of that facility. The Commission understands that the Division's past practice implementing this requirement in permits has been through reporting regarding the arsenic loading to the facility, and not through numeric effluent limitations. The Commission intends that the Division will continue this practice. For facilities that lack enough representative data to quantify arsenic loading, the permittee may satisfy reporting requirements through narrative descriptions of potential sources of arsenic. No permit action shall be approved that allows an increase in permitted total arsenic loading to a treatment facility. The expiration date of the temporary modification was set at 12/31/21 to allow for CDPS permits that are issued prior to the effective date of anticipated changes to the chronic arsenic standard in the 2016 Basic Standards Rulemaking to not have the temporary modification expire within the term of a permit. The Commission adopted this temporary modification to allow time for the Division, dischargers and stakeholders to continue a workgroup process to resolve the uncertainty regarding the appropriateness of the W+F chronic arsenic standard of 0.02 μg/L with respect to a technologically feasible level of treatment. 
For new or increased discharges that commence on or after 6/1/2013, the temporary modification adopted is As(ch) = 0.02–3.0 μg/L (Trec), expiring on 12/31/2021. The Commission decided that since the technologically achievable arsenic level is less stringent than the calculated W+F criterion, the temporary modification for new or increased discharges will be a range of 0.02-3.0 μg/L. The first number in the range is the health-based value, based on the Commission’s established methodology for human health-based standards that protect against the combined exposure of drinking water and eating fish. The second number in the range is the Commission’s initial determination of a technologically achievable value for arsenic, set at 3.0 μg/L. Control requirements, such as discharge permits effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end of pipe” discharge level more restrictive than the second number in the range during the effective period for this temporary modification. The expiration date of the temporary modification was set at 12/31/21 to allow for CDPS permits that are issued prior to the effective date of anticipated changes to the chronic arsenic standard in the 2016 Basic Standards Rulemaking to not have the temporary modification expire within the term of a permit. The Commission adopted this temporary modification to allow time for the Division, dischargers and stakeholders to continue a workgroup process to resolve the uncertainty regarding the appropriateness of the W+F chronic arsenic standard of 0.02 μg/L with respect to a technologically feasible level of treatment. 
The technologically feasible level of 3.0 μg/L for arsenic is based upon testimony heard by the Commission at the December 13, 2011 Emergency Revisions to Regulation #38. At the December 13, 2011 hearing, the Commission determined, as a practical manner, that 3.0 μg/L is the lowest level that is technologically achievable for common types of water treatment facilities. At the April 8, 2013 Rulemaking, the Commission heard testimony that concurred with the finding from December 13, 2011 that an initial reasonable  lower limit of treatment technology for arsenic is 3.0 μg/L, pending further investigation by the Division, dischargers and stakeholders. The Division intends to address the uncertainty of the W+F chronic arsenic standard with respect to a technologically feasible level of treatment through a continued workgroup process, and propose a revised W+F chronic arsenic standards as part of the 2016 Basic Standards Rulemaking Hearing
Temporary modifications were adopted on the following segments. The segments identified have the previously adopted W+F chronic arsenic standard of 0.02 μg/L and an identified CDPS permit or permits that discharge immediately to or directly above the identified segment. 
San Juan River 2
San Juan River 4
San Juan River 5
San Juan River 6a
Piedra River 1
Piedra River 2a
Piedra River 4b
Piedra River 5
Los Pinos River 1
Los Pinos River 2a
Los Pinos River 2b
Los Pinos River 4a
Los Pinos River 4b
Animas and Florida River 4b
Animas and Florida River 5a
Animas and Florida River 5b
Animas and Florida River 6
Animas and Florida River 10b
Animas and Florida River 11a
Animas and Florida River 11b
Animas and Florida River 12a
Animas and Florida River 13b
Animas and Florida River 13c
Animas and Florida River 14a
Animas and Florida River 14b
La Plata River, Mancos River, McElmo Creek, And San Juan River in Montezuma County and Dolores County 1
La Plata River, Mancos River, McElmo Creek, And San Juan River in Montezuma County and Dolores County 4a
Dolores River 8
Dolores River 11
PARTIES TO THE RULEMAKING HEARING
1.	Colorado Mining Association
2.	Union Gold, Inc.
3.	Colorado Department of Transportation
4.	City of Colorado Springs and Colorado Springs Utilities
5.	Town of Crested Butte
6.	Mountain Coal Company
7.	Centennial Water and Sanitation District
8.	MillerCoors, LLC
9.	Plum Creek Wastewater Authority
10.	Tri-State Generation & Transmission Association
11.	Climax Molybdenum Company
12.	Littleton/Englewood Wastewater Treatment Plant
13.	Eagle River Water and Sanitation District
14.	City of Boulder
15.	City and County of Denver
16.	Parker Water and Sanitation District
17.	U.S. Energy Corp.
18.	U.S. Environmental Protection Agency
19.	City of Greeley