Lafayette Bay (DNR ID: 27-0133-02)
Sampling Location GPS Coordinates: Surface Area: 460 acres Max. Depth: 62 ft
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Lafayette Bay is located near the city of Minnetonka Beach. Head east on Minnetonka Blvd, and turn left on Co Rd 101 S. Turn right at Grays Bay Blvd and continue on Bushaway Rd. Turn left on Eastman Ln/Shady Ln, then a slight right at E Circle Dr. Next take a slight left at Lake St. E. Turn left at Ferndale Rd S and continue on Shoreline Dr. Turn right at Northshore Dr. North Arm public boat access is located off of Northshore Drive two miles west from Shoreline Drive.
Lafayette Bay is on Lake Minnetonka which is a class 2B lake protected for aquatic life and recreation. Water quality information is available beginning in 1997. MCWD staff have been monitoring the site on Lafayette Bay on a bi-weekly basis from the time of ice out (April) to the time of fall mixing (mid-October) since 2006.
See Previous Reports.
Monitoring season started in late April and ended in late October. A YSI multi-probe sonde was used to measure dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom. Additionally, water samples were collected within the first two meters of the surface with a 2-meter composite sampling tube. Samples one meter above the bottom were collected with a Van Doran water sampler. Surface sample were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), where the bottom samples were analyzed for TP and SRP. Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded.
| 2009 Summer Water Quality Summary |
| Parameters | Range | Mean | TSI Value | Lake Grade |
| Months | June - Sept. | May - Sept. | ||
| Secchi Depth (m) | 2.9 - 3.9 | 3.3 | 43 | A |
| Surface TP (µg/L) | 16 - 24 | 17.5 | 45 | A |
| Chlorophyll-a (µg/L) | 1 - 8 | 3.8 | 44 | A |
| Overall Score | 44 | A |
The following summary refers to Figure 3.23 (a-d).
- Secchi disk depth remained above the standard (> 1.4 m) throughout the season
fluctuating between 2.9 m and 3.9 m. - Chlorophyll-a concentrations peaked four times throughout the season: late May
(8 μg/L), the middle of July (4 μg/L), late August (8 μg/L), and early October (14 μg/L).
Early October was the only sample that chlorophyll-a concentrations equaled, but did not
exceed the standard limit (standard < 14 μg/L). - Surface TP concentrations were below the standard limit for the season (< 40 μg/L) and
fluctuated between 13 μg/L and 35 μg/L. Surface SRP concentrations were below
detection limit (< 0.005 μg/L) for the entire season. - Bottom TP concentrations fluctuated between 15 μg/L and 37 μg/L throughout the
season. The highest concentrations occurred in the middle of August. Bottom SRP
concentrations were below detection limit (< 0.005 μg/L) except in the middle of August
and late September.
Lake Grades and Historical Monitoring Summaries
When available, previous reports are linked to applicable year. Additional lake data previous to 2007 may be available in the applicable year's hydrodata report. If you have additional questions or you are looking for specific information please contact MCWD's Water Quality Staff.
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