' O "
PRO^°
NONPOINT SOURCE SUCCESS STORY
™ Minnesota
Watershed and In-Lake Treatment Approaches Improve Bryant Lake
Water Quality
Waterbody Improved
Bryant Lake is a 161-acre lake in Eden Prairie, Minnesota. The lake
is used primarily for recreation and fishing, and provides some
wildlife habitat. Bryant Lake was placed on Minnesota's Clean Water Act (CWA) section 303(d) list of
impaired waters in 2008 for exceeding eutrophication criteria. In lieu of developing a total maximum
daily load (TMDL) to address this issue, a two-phased in-lake alum treatment was implemented in
2008 and 2013. Wetland restoration and other various stormwater best management practices
were also implemented. As a result of this work, Bryant Lake now meets water quality standards
and was proposed for delisting in 2018.
Problem
Bryant Lake (27-0067-00), is a 161-acre lake in the city
of Eden Prairie in Hennepin County, Minnesota
(Figure 1). it is defined as a deep lake, and has a
maximum depth of 45 feet. Bryant Lake is in the North
Central Hardwood Forests (NCHF) ecoreglon. The
lake Is used primarily for recreation and fishing and
provides some wildlife habitat as well. The Bryant Lake
watershed encompasses a combination of residential
and mixed-use developments, as well as parks and
recreational areas, including Bryant Lake Regional
Park on the northeast shore. This diversity of land use
generates multiple sources of nutrient-rich overland
runoff that contribute to elevated phosphorus concen-
trations in the lake.
Phosphorus levels exceeding the deep lake NCHF
eutrophication standard (growing season averages of
40 micrograms per liter (|ig/L) total phosphorus,
14 |ig/L chlorophyll o, and not less than 1.4 meter [m]
Secchi disk depth) were observed in Bryant Lake. The
data in 2007 showed growing season averages of
57 ng/L total phosphorus, 34.5 |ig/L chlorophyll a and
1.2 m Secchi disk depth. For this reason, Bryant Lake
was listed as impaired in 2008.
Story Highlights
Actions that contributed to reduction in phosphorus
loading include both in-lake management and
external loading reduction projects implemented
Figure 1. Bryant Lake is in eastern Minnesota.
by the Nine Mile Creek Watershed District and local
partners. To address nutrient loading from surround-
ing residential and commercial land uses, multiple
watershed-scale best management practices (BMPs)
were implemented. Wetland restoration occurred in
the subwatershed west of Bryant Lake, and included
the construction of permeable weirs, runoff diver-
sion structures, and permanent pool storage areas.
Additional stormwater BMPs, including the construc-
tion of wet detention ponds, were completed in
subwatersheds both north and east of Bryant Lake.
Collectively, these external BMPs were designed to
address 47 percent of annual phosphorus loading to
Bryant Lake.
Technology Dr
Sources: Esri, HERE, DeLorme, lntermap; increment P Corp, GEBCO, USGS, FAO, NPS, NRCAN, GeoBase:
IGN, KadasterNL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, Mapmylndia, (c)
OpenStreetMap contributors, and the GIS User Community
Minnesota
SSKS

-------
Additionally, a two-phased in-lake alum treatment was
employed in 2008 and 2013 to address in-lake phos-
phorus loading resulting from sediment phosphorus
release and recycling (Figure 2). In-lake phosphorus
inputs from the lake's bottom sediment contribute to
roughly 26 percent of Bryant Lake's annual phosphorus
load. The first treatment occurred before the wetland
restoration and stormwater BMPs were completed;
the second treatment occurred after the external
loading reduction projects were completed.
In-lake water quality monitoring will continue in Bryant
Lake to evaluate trends over time and to inform the
need to modify in-lake management. Additionally,
opportunities for additional stormwater treatment will
continue to be explored.
Results
Recent water quality data (2009-2015) collected in
Bryant Lake indicates growing season averages of
29 jig/1, total phosphorus, 8.6 [ig/L chlorophyll a
and 2.6 m Secchi disk depth. This data shows that
Bryant Lake now meets the phosphorus water quality
standard, along with the standards for both response
variables (chlorophyll a or Secchi disk). For this reason,
the lake was proposed for delisting on the draft 2018
CWA section 303(d) list of impaired waters.
Partners and Funding
Bryant Lake restoration project relied on multiple
partners including the Nine Mile Watershed District, the
City of Eden Prairie, and the Three Rivers Park District.
Figure 2. Alum treatment in progress on Bryant Lake.
£
I

r-<
*1 PRO^
U1
O
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-19-001PP
November 2019
For additional information contact:
Tim Schwarz
Minnesota Pollution Control Agency
651-757-2426 • timothy.schwarz@state.mn.us
Randy Anhorn, District Administrator
Nine Mile Creek Watershed District
952-835-2078 • ranhorn@ninemilecreek.org

-------