Loading...
HomeMy WebLinkAboutGARDENS ON SPRING CREEK - MAJOR AMENDMENT (SUPPLEMENTAL DOCUMENTS) - MJA150006 - SUBMITTAL DOCUMENTS - ROUND 3 - STORMWATER-RELATED DOCUMENTSATTACHMENT GARDENS ON SPRING CREEK Item Quantity Material Item Size (Cubic feet - CF) Total Size [CF) Location Notes Bridge Structure 1 Steel/wood 300 300 Foothills Garden Lookout Structure 1 Wood 75 75 Prairie Garden Ticket Booth 1 Wood 100 100 Adjacent to great lawn and foothills garden Boardwalk 1 Wood 300 300 Prairie Garden Signage General Wayfinding 10 Steel 2.5 25 Throughout gardens (7)-60" pots; (6) 36" pots (7) Planting Containers 10 Concrete 7.5 150 Cafe Grove 24" pots Tables/Chairs 1 Steel 100 100 Cafe Grove Boulders 1 Stone 2100 2,100 Throughout gardens Trees 305 Plant material 8 2,440 Throughoutgardens Shrubs 1 Plant material 6000 6,000 Throughout gardens Total for all Permanent Structures = 11,590 Item Quantity Material Item Size (Cubic feet - CFI Location Notes Chairs 200 max. Steel 3 E00 Great Lawn Tents 2 Steel/Fabric 500 1,000 Behind stage Sound Monitor Station tent 1 Steel/Fabric 200 200 Great Lawn Food Truck 3 Misc. 1600 4,800 Adjacent to great lawn and foothills garden Total for all Temporary Structures= 6,600 Total Volume of ALL Structures = 18,190 CF 4 CY r=�. ...... �Jy:"�:� a Il ~I i ' -• l \`9�1�1 �'; ` k �� '� r C"'P a IA VII "' �!L i _ I- __'__\ �1 4 , I �� ILI -1i � + . E . � 'e`•wi via®.. �l t .I, G V11tm M.w M9N0Vµ < \.\ J%' -•\ \�'� \ / ,� � ♦ - �_� ®. mac.—T od No Text ATTACHMENT B Nam TO awes a;, I MD LLE r • j� .� a � O Y. _3S -_— GKROENS PROPERTY �7t7I'!1-�IhS!�nl�r ' ATTACHMENT B IIIIIi� � ku, 11����■ �IIII©1111. IIII�IIIIIIIIIC111111► � �11111�1�1■1111111 III:IIIIII�IIIICIIIIIIII_=� Ilium PR OR Q�'�111111" C UM ATTACHMENT A U A6nt 6 3 P� es A Est tV� � c� o S Dr i Ave sawed Ave wo Dr Ee° amen Ie r Rd W m Ct V4aurkl St E _ Ok i Dr O r Q ..toper Dr < 3 B gunr eret, Ave s �'k WRhan CSU W Lake St Blev�a 6 Ct RD s Bass. Ln E L Jsl St N 2 E Lake St a a Bay Or w 0 u rA a Deidea i l Jun rLn m He al nerl dge Hoods St Clr Beky PI v_ U Sneery Or EN i yy b ° AI en ct V WSI rt51/°°0urg Dr R IX € B��°I SNaR St 0. Slosh Spnng Creek were Edge Sump Spd 0db Ln ch° ertY Way Johnson ; e , pt ngr Or Cheyenne s°neWied al GVgMaWelN and CneMood AMU, - ink W. Or PROJECT r D. ` - �$ F Rutgers Ave Q°�b �n m 5a S Duke v° LU as < < t K `ys�A / j ° n Cdumbla a` Rd re - Worth o ¢ W VMe Way Co ndl Ave Camar Wga P e '^ V Cr Or Or cemr° I J k aetlem'` m g J O sQu- enT"" Ave x a m g ° re0 V T IX 0 f Prinorson L > Pnnc �' Baylor ST DRAKE ROAD Rd Or g a � FI I ck er u� `d Davidson 6 WlrxMaterD g a G ci TnunderGrd Or o He a[Rar n ° Wgonvi — d m _ " _ w paM` StSt ° r� Ct n Was a RgckY a 3 F- °r de e er a: ti oy C afar mop Or. Harvard 51 Rud• AJekander ° Fj 9e 2— E 0 `Nay qua Y o `3 Dal CS., Rd Ct L V E NI pht narM 0r S Ann ye S C` g 65 8 ° ° F 1P Li rasa 7 Orr 10 WS.Ul Rd Frn�bar Junco Q ¢ G Gr oGWf c o P ouk BM ti i `o < 0 d'. Swalbw y ESwMl. Rd n p Nat Porn ° Z a r Q' O BOOOIink Pan,>< a N CO °9 ° r SCALE:1"=1500' m o 3 r tr �Q c Cardnal JVA, Incorporated GARDENS ON SPRING CREEK 25 Old Town Square will ` 1` Sulte 200 VICINITY MAP `J`fFan Collins, CO 90524 `��� Phone: 9707359099 Fax: 970.335.6963 E-maiP iid°p'n .ram Gardens on Spring Creek — Floodplain Memo September 8, 2015 5 of 5 Please feel free to contact NA to discuss any questions you may have. Sincerely, NA, INCORPORATED Kare rEen7r I� By: e2v.,ZY Brian ell, P.E. Regiolial Manager BOULDER I FORT COLLINS I WINTER PARK Gardens on Spring Creek — F000dplain Memo September 8, 2015 4 of 5 the maximum probable volume occupied by the shed was calculated to be 10.6 cubic yards, leaving a remainder of 1,120 cubic yards of excess storage volume. These values are recorded and tracked on a spreadsheet located on the S-drive at Fort Collins Stormwater Utility for the Centre Avenue Pond. The displacing volume below the BFE of all temporary and permanent structures proposed on site, including trees & shrubs, planters, tables & chairs, food trucks, etc., must be accounted for in addition to the change in earthwork volumes as a result of grading activities. The total volume (below the BFE) occupied by all structures on site is 674 cubic yards (note that the stage structure, sound walls, and all seat walls are located above BFE). See Attachment E for the volume table prepared jointly by Russell Mills Studios and JVA, Inc. Based on the current proposed grading of the site, there is a net volume of 67 cubic yards of export. From the current documented available volume in the detention pond of 1,120 cubic yards, the proposed improvements result in a remaining 379 cubic yards of excess storage volume. Before the site can be certified, as -built records of the final constructed improvements must be provided to the City to verify no -rise in BFEs and maintenance of compensatory storage in the detention pond. All structures, permanent and temporary, must be securely anchored to resist floatation per Section 10- 39 (7). Onsite floatable materials such as chairs, tents, and band equipment, will be secured by cabling. Washable Architecture: Portions of the walls of the bandstand/stage structure below the Regulatory Flood Protection Elevation of 4996.25 ft NAVD88 will be constructed of Class 4 and 5 flood resistant materials as defined in FEMA Technical Bulletin 2: Flood Damage -Resistant Materials Requirements and as required per Section 10-39 (5) of the Municipal Code. Compliance with City Code: • Section 10-16 — development; the proposed work is acknowledged herein as floodway development, and; • Section 10-27 —permits + certification; this document, no -rise certification, and floodplain use permit provide sufficient evidence to permit the accessory structure and proposed improvements and will supersede the non -compliant FPUP #10828 for the Rock Garden, and; • Section 10-45 — no -rise; the proposed improvements will create no increase in the BFE, no change in the floodway or floodfringe boundaries, and will not reduce the required regulatory storage volume in the Centre Avenue Pond by the attached documentation, and; • Section 10-103 — accessory structure construction; the stage is elevated above the RFPE in accordance with Section 10-37 and potential storage volume in the Centre Avenue Pond is offset by the Rock Garden excavation permitted by FPUP #10828, and; • Section 10-105 — outdoor storage; all outdoor materials will be confined inside latched utility sheds behind the stage and within the Horticulture Center maintenance/service yard buildings. BOULDER I FORT COLLINS I WINTER PARK Gardens on Spring Creek - Floodplain Memo September 8, 2015 3 of 5 Proposed Project Model A proposed project model was developed from the existing conditions model to verify that the proposed development does not adversely affect the floodway boundaries, does not increase BFEs, does not drop BFEs more than 0.30', and is consistent with City of Fort Collins requirements. The eight total cross sections running through the site were modified to include the elevated stage, meandering natural trails, gardens, and wetlands basin. Overbank roughness coefficients remained the same as in the current effective Spring Creek model. The results of the proposed project model are shown in Table 2. No rise in base flood elevations and no more than 0.30 feet drop in BFE were calculated. Table 2 Proposed Project BFEs vs. Existing Condition BFEs HEC-RAS W.S. Elev (ft - NAVD88) 0 from Proposed Existing Section Ex. Cond. (ft) 19776 4995.69 4995.69 0.00 19686 4995.27 4995.27 0.00 19620* 4995.25 4995.25 0.00 19496 4995.23 4995.24 -0.01 19392 4995.23 4995.23 0.00 19266 4995.22 4995.22 0.00 18938 4995.20 4995.20 0.00 18809 1 4995.20 1 4995.20 1 0.00 *Cross section through proposed bandstand/stage The Regulatory Flood Protection Elevation (RFPE) is the elevation to which a structure located within a FEMA floodway must be elevated, floodproofed, or vented per Section 10-103 of Municipal Code. The RFPE for the bandstand/stage is 4996.25 ft NAVD88 - 12 inches above the FIFE of 4995.25 ft NAVD88. The proposed finished elevation of the new bandstand/stage deck (the lowest floor level of the structure) is 4998.50 ft NAVD88, well above the required RFPE. Compensatory Storaee Volume in Centre Avenue Pond As documented in the Floodplain Management Plan prepared by Anderson, all proposed improvements within the floodplain/floodway east of the conveyance line are required to provide compensatory storage to ensure that the necessary stormwater detention volume is maintained. The improvements completed as part of the Rock Garden addition to the site in 2009 resulted in a net export of earth excavation and corresponding increase in available storage volume of 1,131 cubic yards, as documented in Floodplain Use Permit #10828 (note that this FPUP was never re -certified after construction and is therefore currently out of compliance with City Code - recertification of the proposed final Gardens improvements will include the Rock Garden in order to rectify this violation). Later in 2009, City crews installed a garden shed on site without a floodplain use permit or no -rise certification. Brian Varella, City floodplain manager at the time, obtained survey records and as -built information to certify the shed, as documented in Floodplain Use Permit #11134. The garden shed was constructed to vent floodwaters in accordance with Chapter 10 of the Municipal Code. In the event that the vents become obstructed, BOULDER I FORT COLLINS I WINTER PARK Gardens on Spring Creek — Floodplain Memo September 8, 2015 2 of 5 Vertical Datum The City of Fort Collins has converted from the NGVD 1929 to the NAVD 1988 as its standard vertical datum. Elevations shown on the plans are NAVD88, however the hydraulic model used to calculate base flood elevations uses the NGVD29 datum. The shift between datums is made using information from the current City of Fort Collins Vertical Control and the nearest benchmark to the project, 14-97. The conversion for elevations at the project site is -3.17 feet from NAVD88 to NGVD29. Current Effective Hydraulic Information The majority of this work will be located within the FEMA regulatory 100-year floodway for Spring Creek, as shown on the two annotated FEMA FIRMettes included herein as Attachment B. The current effective hydraulic model for Spring Creek, revised to reflect the recent FEMA approval of the Choice Center LOMR (City of Fort Collins Case No. 13-08-1143P, effective date July 25, 2014), uses the Hydrologic Engineering Center River Analysis System (HEC-RAS, USACE 2005) Version 4.1.0 software and was provided by the City of Fort Collins. Three existing cross sections divide the ponding area west of Centre Avenue, with Section 19776 representing the floodway conveyance line and western ponding limits, and Section 18809 adjacent to the eastern embankment formed by Centre Avenue. The proposed Gardens improvements do not extend west beyond Section 19776 and into the "zone of effective conveyance" as described in the Floodplain Management Plan by Anderson, but do lie directly adjacent to the Spring Creek channel within the ponded area and require both a hydraulic analysis to prove no increase in 100-year water surface elevations as well as provisions for accommodating adequate compensatory storage volume. See excerpted map from Anderson's Floodplain Management Plan in Attachment C. An existing conditions model was prepared by adding five additional cross sections at key locations through the site, allowing a more definitive comparison between existing and proposed conditions in order to evaluate the effect of the proposed project on hydraulic conditions in Spring Creek. One foot interval topographic contour information used to generate the cross sections was taken from the City of Fort Collins LiDAR survey data. Construction of the Rock Garden (reference Floodplain Use Permit #10828) was completed after the date of the current effective model but has been incorporated into the existing conditions model for comprehensive analysis. Existing condition base flood elevations (BFEs) are summarized in Table 1 below. Refer to Attachment D: Floodplain Exhibit for the project site plan with cross section locations and floodway boundaries. Table 1 Existing Condition Model BFEs HEC-RAS 100-yr W.S. Elevation (ft) Section NGVD29 NAVD88 19776 4992.52 4995.69 19686* 4992.10 4995.27 19620* 4992.08 4995.25 19496* 4992.06 4995.23 19392 4992.06 4995.23 19266* 4992.05 4995.22 18938* 4992.03 4995.20 18809 1 4992.03 1 4995.20 *New cross sections BOULDER I FORT COLLINS I WINTER PARK JVA, Incorporated 25 Old Town Square Suite 200 Fort Collins, CO 80524 Ph: 970.225.9099 Date: September 8, 2015 Fax 970.225.6923 To: Mark Taylor, P.E., CFM — Fort Collins Floodplain Administrator Toll Free: 677.444.1951 Web site: From: Karen Brigman, Brian Campbell, P.E. www.jvajva.com RE: Gardens on Sppring Creek Floodplain Memo E-mail:nf@ara.com m JVA PN: 2257c Purpose & Background The City of Fort Collins Community Horticulture Center, also known as the Gardens on Spring Creek (The Gardens), is proposing a new non-residential accessory bandstand/stage along with an extensive trail system & gardens expansion on its existing property located in the Federal Emergency Management Agency (FEMA) regulatory 100-year floodway for Spring Creek. The 18.3 acre Gardens site is located west of Centre Avenue and south of Prospect Road, in a ponding area designated by City floodplain management for storage and detention of the stormwater runoff volume needed to attenuate the 100-year flow leaving the BNRR Detention Pond downstream to the east (refer to the "Gardens on Spring Creek Floodplain Management Plan" prepared by Anderson Consulting Engineers, dated July 10, 2009). The site is currently occupied by the Horticulture Center building and outdoor classrooms, visitor parking lot, and several demonstration and community gardens. In general, as part of this project, the proposed site improvements will consist of the construction of a stage structure opposite a Great Lawn and bounded by sound mitigation walls to the west and raised seat walls to the south, as well as numerous themed gardens, interconnecting trails, and an expanded stormwater detention pond/wetlands demonstration site to the east. See Attachment A - Vicinity Map. All development activities on all properties located within a FEMA regulatory floodway are subject to the requirements of Chapter 10 of City Municipal Code. This memorandum, attachments, and associated floodplain use permit are intended to provide adequate documentation to demonstrate compliance with Code. Applicable Floodplain Ordinance The following sections of Chapter 10 apply to construction of the new non-residential accessory structure in a FEMA floodway: • Section 10-16 — all new construction of structures and filling, excavation, or grading associated with site work in the floodplain are considered development, and; • Section 10-27 — development work must be preceded by an approved floodplain use permit and supporting documentation, and; • Section 10-45 — a no -rise certification and supporting documentation must be provided from a registered P.E. and/or P.L.S. for work proposed within the floodway, and; • Section 10-103 — all new non-residential accessory structures must be elevated or flood vented to or above the regulatory flood protection elevation (RFPE), which is defined as 12 inches above the base flood elevation (BFE), and must satisfy the no -rise standards of Section 1045, and; • Section 10-105 — outdoor storage of materials is prohibited. BOULDER I FORTCOLLINS I WINTER PARK