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TECHN/CAL MEMORANDUM <br /> HDR ENG/NEERING, INC. <br /> Table 1- Summary of Pond Level Measurements <br /> Staff Location �taff R�ading *HI , Ei�vs�an ' <br /> (�) ��� ��� <br /> "*Invert of the d/s end of the outlet structure 9.54 943.85 934.31 <br /> To of the d/s end of the outlet structure 8.00 943.85 935.85 <br /> Invert of stand i e 8.82 943.85 935.03 <br /> Invert of Inlet PE i e 8.36 943.85 935.49 <br /> To of Inlet PE i e 7.04 943.85 936.81 <br /> Ed e of water 8.63 943.85 935.22 <br /> Ed e of water 8.62 943.85 935.23 <br /> Bottom of ond 5 ft from outlet 11.22 943.85 932.63 <br /> Bottom of ond 8-10 ft from outlet 11.42 943.85 932.43 <br /> Ed e of water 8.72 943.85 935.13 <br /> Bottom of ond 5 ft from inlet 10.95 943.85 932.90 <br /> Bottom of ond 8-10 ft from inlet 10.98 943.85 932.87 <br /> '`HI=HEIGHT OF THE INSTRUMENT. <br /> "'`INVERT OF THE DOWNSTREAM END OF OUTLET STRUCTURE WAS KNOWN(934.31 FT). <br /> Based on the measurements taken during the survey, the amount of sediment accumulation in the <br /> Orono pond appears to be negligible. Given that the water surFace elevation in the pond is not <br /> above the design elevation, the pond outlet (standpipe) appears to be functioning and appropriately <br /> draining the pond. <br /> Overall Assessment <br /> Given that the Orono wet detention pond was constructed in early 2002 and has been in operation <br /> for approximately 2.5-years, it appears to be in good shape and is functioning as intended. The <br /> presence of vegetation along the boundary of the pond indicates that influent storm water brings <br /> plentiful amounts of nutrients and some percentage of these nutrients is being removed from the <br /> storm water discharge flows. Although the side bank near the inlet structure has undergone erosion <br /> and needs immediate attention, it appears that almost all of the storm water pond components are <br /> present, intact, and functioning. The amount of sediment in the pond is negligible. <br /> RECOMMENDATIONS <br /> Based on HDR's inspection and assessment of the pond conditions, few recommendations are <br /> proposed to improve or sustain the pond's performance. The recommendations are presented in a <br /> tabular format in Table 2. Additional discussion relating to an action item is noted in the Comment <br /> Item column and the related comments are provided following the table. <br /> 11/4/2005 <br /> HDR PRo.IECT#32560 5 HENNEPIN COUNTY,MINNESOTA <br /> ORONO TRUCK STATION FACILITY <br /> STORM WATER POND EVALUATION <br />