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HomeMy WebLinkAbout2000-03-08 NSP Ltr to OPH03/08/00 WED 10:53 FAX 612 731 7305 NSP 2002 Kris Danielson, Community Development Director City of oak Park Heights 14168 Noah 57" Street P.O. Box 2007 Oak Park Heights, Mho 55082 -2007 Dear Kris, [Northern States Power company Allen S. King Plant 1103 King Plant Road Bayport, Mlit 55003 -1000 March 8, 2000 Please find the letter f received from Terry Winherg, project construction superintendent for the cooling tower addition at King plant, attached. This explains the need for the additional increase in overall height of the new tower of 12 inches. All drawings the city received are accurate to specifications with the exception of 12 additional inches of aggregate. l apologize for the late notice for this changed 1 received the information for the need late yesterday, Tuesday, March 7, 2000. If there are any questions, Kris, please let me know. Thank you, 03/08/00 IVED 10:54 FAX 612 7.31. 7305 NSP .,+.� .. �, ., [ „[,. 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Wed nesday, March 08, 2000 8:21 AM To: Knutson, Darrell G Subject; FW NSP Cooling Tower Basin original Message---._ - From: Weber, Cathy A. LELM TP:WeberCA@bV.00M J Senn Wednesday, March O 2000 7;43 AM To: 'Dave Swanberg @ N5 P', `Wi nberg, Terry @ NSP Cc: Shaw, Mark D.; Schmidt, Dare L.; Campbell, Patricia L. (Lynn); Gib, Russ @ NSP Subject: NSP Cooling Tower Basin B&V File 96750-14,0200/62.0601170.0000 Dave/Terry, Auer many discussions on the cooling tower basin floor /curb elevations over the past few days, I've tried to summa B &V's recommendations as follows: - -Mark Shaw sent an email on 2129100 stating several options for NSP to consider based on the actual water elevation being higher than the original design drawings /specifications had 'Indicated. Option 3 was rejected by Mark Holmberg because of the negative effect on performance. Option 2 (Marley increasing their columns by 1 foot) was rejected because of the 2 to 4 week dela in the schedule. That left us with option 1 (raising the basin floor 1 foot) as our only feasible option. Our hydraulic engineer has recalculated the water surface elevations based on raising the basin floor by one foot, and he feels the effect on the water elevation will be nominal. His calculated water elevations are dependent on the water elevation at the north end of the existing basin which he assumed to be at Elevation 585.5` based on NSP's visual determination. With the water elevation at 685.5' at the north end of the existing basin and 50,000 gpm coming in at the new tower, the elevation at the north end of the new basin was calculated to be 685.62 which would provide 0.88 feet of freeboard if we left the top of basin curb at Elevation 685.5. Since the water elevation in the new basin is dependent on the water elevation at the existing basin he also reran his model for a worst case scenario in which the water elevation at the north end of existing basin was set at 685.25' (3 inches below the top of extended existing wall) and calculated a water elevation at the north end of the new basin of 6$6.31' which leaves 0.19 feet for freeboard based on the wall elevation of 586.5'. It appears that the water profile in the new basin is close to flat; therefore, if the new basin wall height matches the existing extended wall height of 6865 we should have sufficient freeboard even with the floor being raised by 1 foot. Because the basin has already been excavated, 24 inches of aggregate will be required beneath the basin in lieu of the original 12 inches. Since the grade elevation is at approximately 663 feet, fill from the basin excavation will be required around the perimeter of the basin to avoid exposing the aggregate. I recommend building up the grade along the outside of basin to about 634 feet and then sloping down to the existing grade at a 2:1 slope. Towards the north end of basin, the existing grade drops and there will be more fill required but, per Terry `ll inberg, we have sufficient space to make the slope without affecting the wetlands to the northeast. We are proceeding with raising the basin floor up one foot and maintaining ? 00 03/08/00 WED 10:54 FAX 612 731 7305 NSP the basin wail height at 686.5 feet. We will be reissuing the cooling tower basin drawing this meek. Please call if you have any questions, Cathy Cathy Weber Tel (913) 458 -2283 Fax (913) 458 -2934 weberca @bv.com 2004