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HomeMy WebLinkAboutGOOD SAMARITAN VILLAGE - ODP - 27-96A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTr IIJunr- c w 4 3.3 Future Phase Improvements The primary improvements for Phase 2 include a detention pond at the Southeast comer of the site, an outlet system for discharge to the existing culvert at Constellation Drive, and replacing and rerouting the existing 12" HDPE pipe. There may be some grading in the low area in front of the existing building. The parking lot for the multi -family facility will be graded for positive drainage. No major drainage facilities will be necessary for the Phase 3 development. There will be some grading immediately around the proposed long term care facility to assure positive drainage. 3-2 3.1 3.2 SECTION 3 - PROPOSED DRAINAGE IMPROVEMENTS Drainage Concept The intent is to limit the total developed runoff from the site to the historic runoff. The runoff from the drainage area to the Northeast comer of the site will be detained and released at a rate not to exceed the present capacity of Constellation Drive. Additional volume needed to restrict the release to the street capacity will be incorporated in a detention pond at the Northwest comer of the site via a cross storm drain pipe. The runoff from the drainage area to the Northwest comer of the site will be detained by an interior pond and the Northwest comer detention pond. Discharge from the Northwest detention pond will be limited to the net total historic runoff rate. The owner of the downstream property is the Burlington Northern Railroad (C & S Railroad). A drainage easement or license will be obtained from the railroad, although the runoff from the drainage area sheet flows across the railroad property. The railroad embankment directs the sheet runoff to Lang Gulch. Improvements on the railroad property will include erosion mitigation as necessary. Grading along the North and West property lines will direct runoff to the detention ponds to mitigate offsite sheet runoff. Runoff from the South area of the site will continue to utilize the existing culvert under Constellation Drive and the existing roadside ditch along Trilby Road to the East. A detention facility at the Southeast comer of the site is proposed. Release from this detention pond would be limited to the historic runoff rate. The Louden Ditch Company will be contacted to confirm that they will continue to accept the historic runoff from this property. The detention ponds, other drainage improvements and basin boundaries are shown on the Drainage Plan Proposed Improvements exhibit. Preliminary detention volumes are also shown on the exhibit with the computations in the Appendix. Phase 1 Improvements The Phase 1 Improvements include the detention ponds at the Northeast and Northwest comers of the site and the interior pond. Chase inlet and outlet would be installed to control flow in Constellation Drive. Inlets, storm drain piping, drainage pans and swales would be constructed to direct the runoff to the respective detention ponds. The detention pond outlet structures and . cross piping would also be installed. The detention ponds would be sized for the total development proposed as part of the ODP. No major drainage improvements are planned for the southerly portion of the site as the Phase 1 development virtually does not impact the historic runoff at the Southeast corner of the site. The low area in front of the existing building, the existing 12" HDPE pipe and the existing culvert at Constellation Drive would continue to be utilized to direct the historic runoff to the Trilby Road roadside ditch. 3-1 I 1 2.3 1 1 Offsite Drainage The site is bounded on the South by Ridgewood Hills PUD First Filing, on the West by Fossil Crest Subdivision First Filing and the railroad property, on the North by Skyview South Second Filing, and on the West by Skyview South First Filing. (Reference Drainage Plan - Existing Condition). Within the context of the Fossil Creek Drainage Basin, Trilby Road is a ridge line. Runoff from the property on the South side of Trilby is in an East to Southeast direction. Runoff from the property on the North side of Trilby Road is a North to Northeast direction. The only offsite runoff onto the site is from a very small adjacent area on the West side of the site in the Fossil Crest Subdivision. Runoff from the Skyview South First Filing is basically an East direction away from the site. Site runoff onto offsite property is limited to Skyview South Second Filing and the railroad ' property. There is a very small area (0.07 ac.) that sheet flows onto the Fossil Creek Subdivision. Most of the site is contributory to Constellation Drive. The Southerly site area is contributing to the Trilby Road roadside ditch. 2.4 Historic Runoff I The historic runoff from the site is shown on the Drainage Plan -Existing Conditions exhibit. Computations are shown in the Appendix. 2-2 I I SECTION 2 - EXISTING DRAINAGE CONDITION 2.1 Major Drainage Basin The site lies in the Fossil Creek Drainage Basin for which a master drainageway planning study has been adopted. The Northerly portion of the site (11.22 ac.) is contributory to Reach 7, the Lang Gulch tributary. (Reference Fossil Creek Study Area Map). ' The historic runoff is conveyed to Lang Gulch by Constellation Drive and the street system North of the site to a point where Lang Gulch crosses the Colorado and Southern Railroad (aka Burlington Northern). There are several cul-de-sacs off of Constellation that slope in a Westerly ' direction toward the railroad property. Runoff is collected by small non-standard units and pipe discharged onto the railroad property. Other than these inlets and discharge piping, there are no storm drainage facilities. The Northwest corner of the site (0.92 ac.) sheet flows onto the railroad ' property. The railroad embankment directs the sheet runoff in Northerly direction to Lang Gulch. The historic runoff from the Southerly portion of site (1.75 ac.) is conveyed by a roadside ditch ' on the North side of Trilby Toad to the Louden Ditch and an unnamed tributary. The unnamed tributary crosses U.S. Highway 287 (College Avenue) approximately 1,500 North of Trilby Road and flows Easterly to Fossil Creek. This Southerly portion of the site was apparently missed by ' the Master Drainage Study. The site is not in the floodplain nor is onsite detention required per the study. However, ' developed runoff is subject to the criteria that downstream property is not impacted and a system is in place to convey any increased runoff. 2.2 . Existing Topography t The Southerly portion of the site especially around the existing building is relatively flat and lies slightly lower than Trilby Road. There is a low area in front of the existing building. Runoff collects in the low area and piped via an existing 12" HDPE to the Trilby Road - Constellation ' Drive intersection. The remainder of the Southerly site area sheet flows toward the intersection and toward Constellation Drive. The roadside ditch on the North side of Trilby Road slopes in an Easterly direction. There are ' several existing culverts for the roadside ditch. Two are the access to the site and the third is at the Trilby Road - Constellation Drive intersection. ' There is knoll near the center of the site. From the knoll the land slopes in a Northeast, North, and Northwest direction. In the Northeast direction toward Constellation Drive, the grade is approximately 3.3%. In the North and Northwest direction toward Skyview South Second Filing ' and the railroad's property, the grade is approximately 5.8%. ODP DRAINAGE REPORT FOR ' FORT COLLINS GOOD SAMARITAN VILLAGE . SECTION 1 - PROJECT DESCRIPTION 1.1 Existing Facility ' The Fort Collins Good Samaritan Village is a well established senior living center that provides full time nursing care and assisted care and independent care residential units. The existing facility is on a 13.89 acre site bounded on the South by Trilby Road and on the East by Constellation Drive. The existing facility is a combination one story and four story buildings on the Southerly 6.6 acres ' of the site. The North 7.3 acres is presently vacant covered with mature grass and vegetation. The present access to the facility is off Trilby Road. ' The previous zoning was M, a Larimer County designation. 1.2 Proposed Development The proposed development is planned in phases. Phase 1 is expected to occur within the next five ' years. Phase 2 is expected to be developed and completed in the next five to ten years. Phase 3 is expected to by developed and completed in ten plus years. The development will be constructed on the existing 13.89 acre site. fThe Phase 1 development consist of a maximum of 36 single family attached residential units on the North 6.42 acres. A 3000 S.F. physical therapy addition on the Northeast side of the existing building and a 3000 S.F. storage and maintenance building on the Northwest side of the existing building is also included in Phase 1. The North side of Trilby Road and the West side of Constellation Drive will be improved during Phase 1. A 28 foot wide private interior drive with I a five foot sidewalk will "loop" through the residential area. A new access of Constellation and a redesigned access off Trilby will be included with the looped private drive. The associated parking lots for the physical therapy addition and the storage and maintenance building will be improved. Phase 2 consists of an independent living apartment complex with a maximum 55 units on the Southeast 2.34 acres. The administrative area (approximately 3000 S.F.) and kitchen and dining ' area (approximately 2000 S.F.) will be expanded in Phase 2. The expansions will be immediately adjacent to the existing building. ' Phase 3 consists of a 16 to 20 bed expansion of the long term care facility (approximately 15,000 S.F.) immediately on the North side of the existing building. Additional administrative office space will be included in the expansion. II The current zoning is a MMN as designed through the City's annexation process. 1-1 II TABLE OF CONTENTS SECTION 1 PROJECT DESCRIPTION 1.1 Existing Facility 1.2 Proposed Development SECTION 2 EXISTING DRAINAGE CONDITION 2.1 Major Drainage Basin 2.2 Existing Topography 2.3 Offsite Drainage 2.4 Historic Runoff SECTION 3 PROPOSED DRAINAGE IMPROVEMENTS 3.1 Drainage Concept 3.2 Phase 1 Improvements 3.3 Future Phase Improvements EXHIBITS Fossil Creek Study Area Map Drainage Plan - Existing Conditions Drainage Plan - Proposed Improvements APPENDIX Historic Runoff Detention Volumes Page Number 2-1 2-1 2-2 2-2 3-1 3-1 3-2 I hereby certify that this ODP Drainage Report for the Fort Collins Good Samaritan Village was prepared Iby me or under my direct supervision in accordance with the provisions of the City of Fort Collins Storm Drainage Criteria for the Owners thereof. ' The purpose of this ODP Drainage Report is too satisfy the submittal requirements of the City of Fort Collins ODP development process. More specifically, the existing drainage conditions are ascertained and ' drainage improvements are evaluated to the extent they will function as intended for the site development. Subsequent preliminary and drainage reports will. be submitted during the development review process. The reports will be prepared in accordance with the City's design criteria with the appropriate supporting documentation. � m� TIuunnngi1' ^ _ MAl- �A osy /�0/ /94WW: O. Patrick M. Mestas ,vA� P Colo. P.E. 13886 '�i,���FDF C�, Oe1��� . ODP DRAINAGE REPORT FOR FORT COLLINS GOOD SAMARITAN VILLAGE Prepared For: Fort Collins Good Samaritan Village 508 W. Trilby Road Fort Collins, CO 80525 Date: December 8, 1995 Project No. FTCG-6G8B-04-216 Landmark Engineering Ltd. 3521 West Eisenhower Boulevard Loveland, CO 80537 Landmark