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Home My WebLink AboutRIDGEVIEW CLASSICAL SCHOOL - SPAR - 16-01 - CORRESPONDENCE - DRAINAGE REPORTSent By: ZP; 303 455 3708; Jul-19-01 11:58AM; Page 5/5 07/19/01 Ridgeview School Storm Detention Response Page 2 of 2 provide water quality storage in addition to the storm drainage. We will therefore request a variance for the water quality. 6. Contour elevation 101.5 feet around the existing detention pond B already extends within the R.O.W. and the proposed grades only maintained this maximum limit. However, since the west side of the lot will be regraded for the addition and the pond we will revise the grades and keep the detention out of the R.O.W. The dashed line around the perimeter of the site is not an easement but a building set back. Neither detention ponds are within an easement. However trailer 5 does encroach into one of the obsolete access easements through the site_ These easements are going to be abandoned and revised so that they will work with the final site configuration. 7. We have not proposed revised outlet restrictions because the as -built outlet configurations are not known at this time. We will verify these issues and address them. The outlet pipe from detention pond B, the west pond, is a 6-inch D.I.P. and is connected directly to the street storm inlet and is labeled on the current drawing_ 8. The surveyor supplied the assumed datum. At this time we do not know the city datum relation to the site and will have to resolve this issue with the surveyor at a latter date. 9. I sized the pond based on the intensities from figures 3-1, 3-la and 3-Ib out of the city's drainage manual, dated revised April 16, 1999. The city figures are limited to 120 minutes. The usual mass detention method will extend beyond 120 minutes and for this site it is around 130 to 135 minutes. I derived the following formula by curve fitting the given city data and extrapolating the required intensities. I_100= 85.29/(tc+9.59)^0.80 for the 100-year event. If this is not satisfactory, I will need the city to provide the correct values. If you have any questions, please feel free to call. Thank you. Zeiler -Pennock, Inc./OHA f.. 2�/01;il �2 William J. Logan, .E. Project Engineer cc. Cameron Gloss, City Planner Brian Grubb, City Planner Sent By: ZP; 303 455 3708; Jul-19-01 11:57AM; Page 4/5 ZEILER-PENNOCK,INC. /OHA Lioq'.� %� A R C H I T E C T S E N G I N E E R S �J July 19, 2001 PRINCIPALS PAUL R. PENNOCK W. KELLY OLIYER JOfLNC. NELLOREN Mr. Glen Schlueter City of Fortcollins Storm Water Utility P.O. Box 580 Fort Collins, CO 80522 Re: Ridgeview Classical School — Stormwater Comments Dear Mr. Schlueter; Thank you for the quick response from Wednesday July, 18, 2001 to our drainage proposal. I appreciate you quick turn around I would like to follow up with our phone conversation from yesterday and provide you with my response to your issues. I hope this will provide the necessary information and you will be able support the proposed drainage concept for this existing site. The school board wants to work with the city and it would be helpful to them if they know we can resolve the site drainage issues. The revised drawings will address all these issues. Item Response 1. The finished floor elevation is 103.0 feet plus or minus 0.1 foot around the door openings. The top of the west pond is at 101.5 feet Ieaving a 1.5 foot free board. 2. We agree with your concern with the location of trailer 3 and it's impact on the northeast detention pond. Our client directs the trailer locations and we will discuss these issues with them. There are a number of additional issues in addition to the trailers - parking and site access - that will need to be resolved before alternate locations can be proposed. 3. The grade lines will be shown on the grading plan. The extent of the grades will range from 101.5 feet down to 100.50 feet for detention pond B. 4. The trash enclosure will be relocated and drainage around the garages will remain original. This should allow for drainage through this area. 5. As we discussed, due to the existing building location and elevation, street elevations, detached sidewalk and other conditions we can not change, it will not be possible to 2727 BRYANT ST. SUITE 600 DENVER, CO 80211 (303)/553322 FAX (303)455.3708 Sent By: ZP; 303 455 3708; Jul-19-01 11:57AM; Page 3/5 ....- .. ....... ..c... . -- cri rnyv c 7. The drawings and letter for this project are vague regarding drainage outlets. The letter mentions `outlet reconfigurations" but it is not specified on the drawings or anywhere else. Please clarify. The outlet from pond A is currently a CW pipe to a sidewalk chase. Please replace this pipe with RCP if possible and provide the details for connecting the pipe flows to the sidewalk chase. Pond B shows inlet protection but no structure or pipe is located on the drawings. Please provide details for this area. Pond B occupies part of the parking lot in a 100yr event. Please provide a curb cut so flows may freely move between the parking and graded areas. RESPONSE: 8. Currently the plans use an assumed datum. Please use the established City datum and reference a City of Fort Collins benchmark. RESPONSE: 9. The calculations for the pond sizing use slightly different Intensities than the Ft. Collins IDF curve. Please provide complete calculations (full duration) and check 100 yr. storm intensities. Also the area of each imperviousness on the calculations does not match the areas quoted on the plans. Please revise calculations or plans accordingly. RESPONSE: Please refer to the redlined plans and report for additional comments. rgdn-sengreen-2.doc Page 2 of Sent By: ZP; I 303 455 3708; Jul-19-01 11:56AM; Page 2/5 l eS - Vit -��j Fox 303- 4155--3>og Ridgeview Classical Schools- Stormwater Comments 7/18/01 1.Please show the lowest opening/ finished floor for all buildings. Also, please show that there is V freeboard for each pond to the lowest opening. , o K ' RESPONSE: 2. Trailer 3 has a trickle pan running underneath it and resides in the deepest part of detention pond A. The trailer will obstruct flows to and in the detention pond. Other possible problems with temporary buildings in detention area are problems with the structure's utilities, hazards to the occupants, and damage to the structure during a runoff event. Please consider relocation of the trailers in the detention area or provide details on how to handle the aforementioned issues. If you have any questions please contact Wes Lamarque at 416-2418. RESPONSE: 3. The grade lines in pond R are not marked and do not show the pond elevation in relation to the buildings. Please clarify this grading and check that the slopes meet requirements. RESPONSE: 4. Currently as designed, water will pond at the garage area with no outlet. Please provide a curb chase or other means of outlet for this runoff. Please do not route this runoff thru the trash enclosure for water quality reasons. RESPONSE: 5. Please provide water quality for this site. If none is provided, please request a variance and state the reasons. 1« RESPONSE: 6. Currently buildings and ponds are shown in the easements and R.O.W. Please relocate and regrade areas so as not to encroach into easements and to be clear of R.O.W. RESPONSE: Sent By: ZP; 303 455 3708; Jul-19-01 11:56AM; Page 1/5 I.N ZEILER-PENNOCK,INC./OHA ��%� A R C H I T E C T S - E N G I N E E R S FAX COVER SHEET To: Brian Grubb Company: City of Fort Collins - Planning No. Pages: 5 Regarding: Ridgeview Classical School Date: 7-19-01 Fax No: 970-416-2020 Comments: For your information to the Utility Departments issues with the storm drainage. From: Bill Logan 2727 11RVANT ST. SUITE 600 DENVER, COLORADO 90211 (303) 455-3322 FAX - 455-3709