Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1.
Scope.
The phosphorus effluent limits in this part are in addition
to the effluent limits specified elsewhere in this chapter. In the event of any
conflict between this part and other applicable regulations, the more stringent
requirement applies.
Subp.
2.
Definitions. For the purposes of this part, the
following definitions apply. Other relevant definitions are found in part
7050.0150, subpart
4.
A. "Affects" means a measurable increase in
the adverse effects of phosphorus loading as determined by monitoring or
modeling, including, but not limited to, an increase in chlorophyll-a
concentrations, a decrease in water transparency, or an increase in the
frequency or duration of nuisance algae blooms, from an individual point source
discharge.
B. "Expanded discharge"
means a disposal system that after May 1, 2008, discharges more than 1,800
pounds of total phosphorus per year to a surface water on an annual average
basis, and increases in wastewater treatment capacity as indicated by an
increase in the:
(1) design average wet
weather flow for the wettest 30-day period for point source dischargers of
sewage with a continuous discharge, typically a mechanical facility;
(2) design average wet weather flow for the
wettest 180-day period for point source dischargers of sewage with a controlled
discharge, typically a pond facility; or
(3) design average daily flow rate for
dischargers of industrial or other wastes.
C. "Lake" means an enclosed basin filled or
partially filled with standing fresh water with a maximum depth greater than 15
feet. Lakes may have no inlet or outlet, an inlet or outlet, or both an inlet
and outlet.
D. "Measurable
increase" or "measurable impact" means a change in trophic status that can be
discerned above the normal variability in water quality data using a weight of
evidence approach. The change in trophic status does not require a
demonstration of statistical significance to be considered measurable.
Mathematical models may be used as a tool in the data analysis to help predict
changes in trophic status.
E. "New
discharge" means a discharge that was not in existence before May 1, 2008, and
discharges more than 1,800 pounds of total phosphorus per year.
F. "Reservoir" means a body of water in a
natural or artificial basin or water course where the outlet or flow is
artificially controlled by a structure such as a dam. Reservoirs are
distinguished from river systems by having a hydraulic residence time of at
least 14 days. For purposes of this item, residence time is determined using a
flow equal to the 122Q10 for the months of June through
September. "122Q10" has the meaning given in part
7053.0135, subpart 4b.
G. "Shallow lake" means an enclosed basin
filled or partially filled with standing fresh water with a maximum depth of 15
feet or less or with 80 percent or more of the lake area shallow enough to
support emergent and submerged rooted aquatic plants (the littoral zone). It is
uncommon for shallow lakes to thermally stratify during the summer. The quality
of shallow lakes will permit propagation and maintenance of a healthy
indigenous aquatic community, and the shallow lakes will be suitable for
boating and other forms of aquatic recreation for which they may be usable. For
purposes of this chapter, shallow lakes will be differentiated from wetlands
and lakes on a case-by-case basis. For purposes of this item, "wetlands" has
the meaning given in part
7050.0186, subpart
1a.
Subp. 3.
Total
phosphorus effluent limits.
A.
Phosphorus removal to one milligram per liter is required when subitem (1),
(2), or (3) applies:
(1) the discharge of
effluent is directly to or affects a lake, shallow lake, or
reservoir;
(2) the discharge is to
the specific basins and water bodies designated in subpart
5; or
(3) the discharge is new or expanded as
defined in subpart 2,
except when the discharger can demonstrate to the commissioner that the
discharger qualifies for an alternative phosphorus limit as provided in subpart
4.
B. If a phosphorus effluent limit is required
under item A, removal of nutrients from all wastes must be provided to the
fullest practicable extent wherever sources of nutrients are considered to be
actually or potentially detrimental to preservation or enhancement of the
designated water uses. Dischargers required to control nutrients under this
part are subject to the variance provisions of parts
7000.7000 and
7053.0195.
Subp. 4.
Alternative phosphorus
effluent limits for new or expanded discharges.
New or expanded discharges subject to a one milligram per
liter phosphorus effluent limit in subpart
3, item A, subitem (3), may
request an alternative limit or no limit if one or more of items A to C apply.
New or expanded discharges are defined in subpart
2. The exemptions in this
subpart do not apply to facilities that discharge directly to or affect a lake,
shallow lake, or reservoir or to discharges to the waters listed in subpart
5. Dischargers seeking an
alternative limit due to very high per capita treatment costs or economic
hardship must apply for a variance under parts
7000.7000 and
7053.0195.
The information submitted to the commissioner for
consideration of an alternative limit must include, at a minimum, a description
of the treatment technology used, influent and effluent total phosphorus
concentrations, a phosphorus management plan for the facility, descriptions of
any measures already taken to reduce phosphorus sources to the facility, and
expected reductions in phosphorus concentrations following implementation of
the phosphorus management plan. The discharger may qualify for an alternative
total phosphorus limit or no limit if it can demonstrate:
A. the discharge is to or upstream of a water
body listed on the applicable impaired water list, section 303(d) of the Clean
Water Act, and the subsequent total maximum daily load study is complete and
approved by the United States Environmental Protection Agency, as required by
Code of Federal Regulations, title 40, part 130, section 7, at the time the new
or expanding facility is in the planning and design phase. The total maximum
daily load study must have considered impacts from phosphorus loading on the
impaired water body. In this case, the total maximum daily load study will
determine the applicable phosphorus effluent limit;
B. the environmental benefits to be achieved
by meeting a phosphorus limit are outweighed or negated by the environmental
harm caused by meeting a limit; or
C. the treatment works, regardless of the
type of treatment technology, uses chemical addition to achieve compliance with
the one milligram per liter limit and the discharge is to a receiving stream in
a watershed listed in subitems (1) to (3). In this case the discharger may be
granted a seasonal one milligram per liter limit, applicable from May 1 through
September 30 and not applicable from October 1 through April 30:
(1) the lower Mississippi River and its
tributaries from the mouth of the Chippewa River in Wisconsin to the Minnesota
border;
(2) the Bois de Sioux and
Red Rivers and their tributaries from the southern end of Lake Traverse at
Browns Valley to the Canadian border; and
(3) the Missouri, Des Moines, and Cedar
Rivers and their tributaries in Minnesota.
Subp. 5.
Designated waters.
The one milligram per liter phosphorus limit established in
subpart 3
applies to the waters designated in items A to F.
A. All intrastate waters lying within the
drainage basin of Lake Superior in the counties of Aitkin, Carlton, Cook,
Itasca, Lake, Pine, and St. Louis (Townships 45 to 65 North, Ranges 7 East to
23 West).
B. The interstate waters
of Lake St. Croix in Washington County (Townships 26 to 30 North, Range 20
West).
C. The St. Louis River from
its source at Seven Beaver Lake (Township 58 North, Range 12 West) to and
including St. Louis Bay (Townships 49 and 50 North, Ranges 14 and 15 West) and
Superior Bay (Townships 49 and 50 North, Ranges 13 and 14 West).
D. The Mississippi River from its source to
the Blandin Dam at the outlet of Paper Mill Reservoir in the city of Grand
Rapids approximately 400 feet upstream from the bridge on U.S. Highway 169
including Lake Andrusia (Township 146 North, Range 31 West), Lake Bemidji
(Townships 146 and 147 North, Range 33 West), Cass Lake (Townships 145 and 146
North, Ranges 30 and 31 West), Lake Itasca (Township 143 North, Range 36 West),
Pokegama Lake (Townships 54 and 55 North, Ranges 25 and 26 West), and
Winnibigoshish Lake (Townships 145, 146, and 147 North, Ranges 27, 28, and 29
West).
E. The Little Minnesota
River and Big Stone Lake from the South Dakota border crossing to the outlet of
Big Stone Lake at the dam immediately upstream from the U.S. Highway 12 bridge
in Ortonville.
F. Albert Lea Lake
(Township 102 North, Ranges 20 and 21 West) in Freeborn County.
Subp. 6.
Averaging
period for phosphorus limit.
The phosphorus limit required under subpart
3 must be a calendar month
arithmetic mean unless the commissioner finds, after considering the criteria
listed in items A and B, that a different averaging period is acceptable. In no
case shall the one milligram per liter limit exceed a moving mean of 12 monthly
values reported on a monthly basis or a simple mean for a specified period, not
to exceed 12 months. Calendar month effluent limits in effect as of February 7,
2000, must remain in effect unless an assessment of the criteria listed in
items A and B indicate a different averaging period is acceptable. An averaging
period other than monthly is acceptable when:
A. there is no measurable or predictable
difference in the adverse effects of the phosphorus loading from the facility
on the receiving water or downstream water resources compared to the loading
that would result using a 30-day average limit; and
B. the treatment technologies being
considered offer environmental, financial, or other
benefits.
Statutory Authority: MS s
115.03;
115.44
