Section 7
Methodology Development for the Cahokia Canal/Horseshoe Lake Watershed
DRAFT 7-13
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7.2.4 BATHTUB Development for Frank Holten Lakes
The BATHTUB model was used to develop the total phosphorus TMDL for the Frank
Holten Lakes. Frank Holten Lakes 1, 2, and 3 are connected and were modeled as three
segments of a contiguous waterbody. All of the Frank Holten Lakes are listed on the
2004 303(d) list for impairments caused by total phosphorus. In addition, Frank Holten
Lake 3 has had two dissolved oxygen samples collected that were below the 5.0 mg/L
instantaneous minimum standard. There are no known sources of oxygen demanding
materials to the lakes and it is therefore assumed that reducing total phosphorus will
likely result in improved dissolved oxygen levels.
7.2.4.1 Operation of Frank Holten Lakes and Watershed Delineation
Frank Holten State Park contains three small lakes, Frank Holten Lake 1, 2, and 3.
These lakes are the remains of an old oxbow lake of the Mississippi River. Lakes 1 and
2 together are commonly known as Whispering Willow Lake and Lake 3 is known as
Grand Marais Lake. The lakes and the park are managed by the Illinois Department of
Conservation (IDOC).
The Frank Holten Lakes consists of three distinct lakes as shown on Figure 7-7. Under
normal conditions, Lake 1 flows into Lake 2, Lake 2 flows into Lake 3 via a
connection channel, and then Lake 3 drains to Harding Ditch. The only connection
between the lakes and Harding Ditch is at the outlet at the southern end of Lake 3. The
connection channel and Harding Ditch are directed through culverts beneath I-255.
There is no water level control at the outlet, and therefore during wet weather, when
the water level in Harding Ditch is rising, it flows freely into Lake 3. When the water
level in Harding Ditch is falling, Lake 3 flows freely into Harding Ditch. The area
drained by Harding Ditch is 23,755 acres.
The area drained directly by the Frank Holten Lakes is approximately 3,300 acres.
There are two sources of inflows into the Frank Holten Lakes:
Stormwater runoff from surrounding residential sites
Wet weather flows from Harding Ditch
Stormwater runoff from low-density residential areas and a high school discharges into
Lake 1 via three drainage district culverts. Also, direct overland runoff from the other
areas surrounding the lakes contributes flows to the lakes.
The modeling approach for the Frank Holten Lakes is based on two distinct "seasons";
a dry and a wet season. Two separate models have been developed, one for each
season. The wet season includes March through May, the high flow portion of the year,
when Harding Ditch can backflow into Lake 3. The dry season is defined as the other 9
months of the year, during which flows are lower.
7.2.4.2 Global Inputs
Global inputs represent the averaging period, precipitation, evaporation, and
atmospheric contribution of phosphorus. The averaging period for the Frank Holten
