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DRAFT <br />however, likely to occur primarily in the upper portions of the lake and is probably not evenly <br />distributed over the whole lake. <br /> <br />B. WATER QUALITY ASSESSMENT <br /> <br />1. Suspended Solids and Phosphorus <br /> <br />Flow- and time-weighted averages were calculated for total phosphorus, ortho-phosphorus, TSS, <br />VSS and TSS-VSS at monitoring stations: ERCR 15, TBCR 35, and the Lake Orono Dam (see <br />Appendix D). Average total phosphorus and TSS concentrations were 0.12 milligrams per liter <br />(mg/1) and 9 mg/l at ERCR 15, 0.15 mg/1 and 9 mg/1 at TBCR 35, and 0.11 mg/1 and 11 mg/1 at <br />the Lake Orono Dam. The MPCA has developed a water quality database from monitoring <br />minimally impacted streams from various ecoregions across Minnesota. The Elk River <br />watershed is within the North Central Hardwood Forest (NCHF) ecoregion. "Typical" values for <br />total phosphorus and TSS, within the NCHF ecoregion, range from 0.06 - 0.15 mg/1 and 4.8 - 16 <br />mg/l respectively. The above average concentrations are all within the "typical" ranges provided <br />by the MPCA. The average total phosphorus concentration monitored at TBCR 35 is on the high <br />end of the "typical" range for total phosphorus and is 25 percent higher than the average total <br />phosphorus concentration monitored at ERCR 15. <br /> <br />Storm event monitoring of minor tributaries to Lake Orono overall showed reasonably low total <br />phosphorus and TSS concentrations (See Table 2). Due to the very small local drainage <br />contribution to Lake Orono, the lake's water quality is dominated by the Elk River flow. <br /> <br />In-lake total phosphorus and TSS concentrations in Lake Orono are very high compared to <br />minimally impacted lakes within the NCHF ecoregion. "Typical" summer values for total <br />phosphorus and TSS, within the NCHF ecoregion, range from 0.023 - 0.050 mg/1 and 2-6 mg/1 <br /> <br />N :\0S 98\0 I~ELKRIVER. RPT-rlb 14 <br /> <br /> <br />