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Home My WebLink AboutHEWLETT-PACKARD C.I.C.D. RECEIVING AREA EXPANSION - I-L SITE PLAN REVIEW - 54-88A - CORRESPONDENCE - STORMWATER-RELATED DOCUMENTSauG z 9 11988 D Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 August 29, 1988 Mr. Richard S. Beardmore A-E Design Associates 323 South College Avenue, Suite 7 Fort Collins, Colorado 80524 Dear Mr. Beardmore: r This letter is prepared in response to your transmittal dated August 24, 1988. In that transmittal, you provided information concerning drainage facility construction proposed for the C.I.C.D. Receiving Area expansion. These new facilities will utilize the existing storm sewer system to convey stormwater runoff to the existing detention facilities in the southeast cor- ner of the Hewlett Packard site. RBD, Inc. is presently studying the impacts which the new Build- ing 6 (HPFC6) construction will have as well as those of a tem- porary building in the northwest portion of the HP site. The ex- isting storm sewer serving the C.I.C.D. RECEIVING Area is one of the storm sewers affected by the projects we are working on and the affect of your construction will be considered with our drainage work for HPFC 6. Stormwater runoff from the C.I.C.D. Receiving Area will be detained by the DAM POND located in the southeast corner of HP property. The detention capacity of this pond was addressed in a general discussion provided to the City of Fort Collins as a let- ter drainage report for the Temporary Building dated August 11, 1988. The general discussion would also apply to the C.I.C.D. Receiving Area expansion. The drainage report for HPFC6 (anticipated to be submitted to the City toward the end of=' September) will provide a detailed discussion of the current and future required capacity of the DAM POND. Adding additional stormwater--runoff to the existing onsite storm sewers will raise the hydraulic grade line of the stormsewer. Previous reports for the HP site stormsewers show they were designed to carry the peak flow when full. Additional runoff will require the sewers to flow under a pressure condition. Un- Other Offices: Vail, Colorado 3031476-6340 • Colorado Springs, Colorado 303/574-3504 5 der the worse / case, some temporary ponding will occur at the storm sewer inlets during the peak part of a 10-year frequency storm. Improvements made as part of HPFC6 construction will provide more capacity in the storm sewer serving the C.I.C.D. Receiving Area. Also, the temporary building is to be used while HPFC6 is being constructed - after which it will be removed. Consequently, any inconvenience caused by stormsewer surcharging will only be temporary. On the other hand, because of excess storage capacity in the DAM POND, the expansion of the C.I.C.D. Receiving Area will have no affect on the amount of stormwater runoff leaving the HP site. Sincerely, RBD, Inc. Joseph C. Goldbach, P.E. cc: 282-001 m A a m Z m M D 10 YEAR HISTORIC ._ ... -• . -MAME . .. -___= Figure 5 TYPICAL FORM FOR STORM DRAINAGE SYSTEM PRELIMINARY DESIGN DATA (From: Wright -McLaughlin Engineers. 1969) • w 0 m z 0 m M D 100 YEAR HISTORIC ION �■�■�©©�s©0000mmm®m®mmmmo®® ON INE NO ONIONENION NOWNEW MONSOON NO MONSOON ON INEWE NO WENNINNIONEW NO [NINNINE �� ■N ®� = r•0ar•�mummommom �INEENIO ENIONINENO � ►- NNION � NO ON ON ONEWINE INNINE INEWN ON ON ON ONNO NOWNINNINNINNINE ION INNEW NOW NNI■N INNINNEENINNINO SOON ON ON NORMINE MINION INNON NO ME NINE --- oNO NO NOUNIO UNION 10010 NO 1010 Figure 5-1 TYPICAL FORM FOR STORM DRAINAGE SYSTEM PRELIMINARY DESIGN DATA (From: Wright -McLaughlin Engineers, 1969)