The URL can be used to link to this page

Home My WebLink AboutGARDENS ON SPRING CREEK MAJOR AMENDMENT - FDP - FDP160029 - SUBMITTAL DOCUMENTS - ROUND 1 - STORMWATER-RELATED DOCUMENTSBOULDER I FORT COLLINS I WINTER PARK JVA, Incorporated 25 Old Town Square Suite 200 Fort Collins, CO 80524 Ph: 970.225.9099 Fax: 970.225.6923 Toll Free: 877.444.1951 Web site: www.jvajva.com E-mail: info@jvajva.com Date: June 28, 2016 To: Mark Taylor, P.E., CFM – Fort Collins Floodplain Administrator From: Karen Brigman, Brian Campbell, P.E. RE: Gardens on Spring Creek Floodplain Memo 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 10-45, and; • Section 10-105 – outdoor storage of materials is prohibited. Gardens on Spring Creek – Floodplain Memo June 28, 2016 2 of 5 BOULDER I FORT COLLINS I WINTER PARK 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 4995.69 4998.86 19686* 4995.27 4998.44 19620* 4995.25 4998.42 19496* 4995.24 4998.41 19392 4995.23 4998.40 19266* 4995.22 4998.39 18938* 4995.20 4998.37 18809 4995.20 4998.37 *New cross sections Gardens on Spring Creek – Floodplain Memo June 28, 2016 3 of 5 BOULDER I FORT COLLINS I WINTER PARK 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. *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 4999.42 ft NAVD88 - 12 inches above the BFE of 4998.42 ft NAVD88. The proposed finished elevation of the new bandstand/stage deck (the lowest floor level of the structure) is 4999.50 ft NAVD88, above the required RFPE. Compensatory Storage 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, Table 2 Proposed Project BFEs vs. Existing Condition BFEs HEC-RAS W.S. Elev (ft – NAVD88) Δ from Section Proposed Existing Ex. Cond. (ft) 19776 4998.86 4998.86 0.00 19686 4998.44 4998.44 0.00 19620* 4998.42 4998.42 0.00 19496 4998.41 4998.41 0.00 19392 4998.40 4998.40 0.00 19266 4998.39 4998.39 0.00 18938 4998.37 4998.37 0.00 18809 4998.37 4998.37 0.00 Gardens on Spring Creek – Floodplain Memo June 28, 2016 4 of 5 BOULDER I FORT COLLINS I WINTER PARK 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 685 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 365 cubic yards of import. From the current documented available volume in the detention pond of 1,120 cubic yards, the proposed improvements result in a remaining 170 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 4998.42 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. Gardens on Spring Creek – Floodplain Memo June 28, 2016 5 of 5 BOULDER I FORT COLLINS I WINTER PARK Please feel free to contact JVA to discuss any questions you may have. Sincerely, JVA, INCORPORATED By: __________________________ Karen Brigman Project Engineer By: ________________________________ Brian Campbell, P.E. Regional Manager ________________________________ Brian Campbell, P.E. Regional Manager ________________________________ Brian Campbell, P.E. Regional Manager Bi r c h S t St Ave M o n t e V i s t a Pl Mant z Ave Av e S t Summer Smit h St Rust Dr Con Pl acer A Wa g o n Boze Ct Rocky C Ct Ni g h t h a wk Fl i c k e r Avocet Rd K i l l d e e r D r Long ho r n Ct Ci r l l deer Dr Dr Foot hi l l s Cant e r bur y Ra i nt r ee Cr o c k e t t St Sweeney Ln H i l l P GARDENS PROPERTY ATTACHMENT B GARDENS PROPERTY ATTACHMENT B S LEGEND CONDITION FOR 100—YR FLOODPLAIN FROM PROPOSED 1/2—FOOT FLOODWAY 2006 SPRING CREEK CLOMR PONDED ARE& ONLY COMPENSATORY STORAGE VOLUME REQUIRED (EXCEPT ALONG SPRING CREEK CHANNEL WHERE HYDRAULIC ANALYSIS IS ALSO REQUIRED) k INEFFECTIVE FLOW ARE& ONLY ‘\ COMPENSATORY STORAGE VOLUME REQUIRED CONVEYANCE ZONE COMPLETE HYDRAULIC ANALYSIS REQUIRED ALONG WITH COMPENSATORY STORAGE VOLUME I I / / - - \\ z4 b CflY OF SHEET NUMBER C JVA, INC DATE: JOB NUMBER: CHECKED BY: DRAWN BY: DESIGNED BY: NO. DATE DRAWN DESIGNED REVISION / ISSUE DESCRIPTION JVA, Incorporated 25 Old Town Square Suite 200 Fort Collins, CO 80524 E-mail: info@jvajva.com Phone: 970.225.9099 Fax: 970.225.6963 CONSULTING ENGINEERS CENTRE FOR ADVANCED TECHNOLOGY 22ND FILING COMMUNITY HORTICULTURE CENTER MAJOR AMENDMENT - FINAL UTILITY PLANS 2257c JUNE 2016 BJC KRB CRH FLOODPLAIN EXHIBIT C1.3 CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: Date Date Date Date Date Date City of Fort Collins, Colorado UTILITY PLAN APPROVAL Parks and Recreation Traffic Engineer Stormwater Utility Water & Wastewater Utility City Engineer CHECKED BY: APPROVED: Date Environmental Planner ATTACHMENT D Item Quantity Material Total Size (CF) Notes Bridge Structure 2 Steel/wood 602 Lookout Structure 1 Wood 75 Ticket Booth 1 Wood 100 Boardwalk 1 Wood 300 Signage - General Wayfinding 10 Steel 25 Planting Containers 20 Concrete 150 (7)-60" pots; (6) 36" pots (7) 24" pots Tables/Chairs 1 Steel 100 Boulders 1 Stone 2,100 Trees 305 Plant material 2,440 Shrubs 1 Plant material 6,000 11,892 Item Quantity Material Notes Chairs 200 max. Steel 600 Tents 2 Steel/Fabric 1,000 Sound Monitor Station tent 1 Steel/Fabric 200 Food Truck 3 Misc. 4,800 6,600 18,492 CF 685 CY GARDENS ON SPRING CREEK Item Size (Cubic feet - CF) Item Size (Cubic feet - CF) Location Location Total for all Permanent Structures = 75 100 Throughout gardens Throughout gardens Café Grove Total Volume of ALL Structures = 6000 Throughout gardens Prairie Garden Prairie Garden Throughout gardens Café Grove 300 2.5 7.5 301 Great Lawn 1600 Adjacent to great lawn and foothills garden Total for all Temporary Structures = 3 500 200 Foothills Garden Permanent Structures Temporary Structures 100 Adjacent to great lawn and foothills garden 2100 8 Great Lawn Behind stage ATTACHMENT E FORT COWNS FORESTRY AND HORTICULTURE DIVISION GARDENS ON SPRING CREEK FLOODPLAIN MANAGEMENT PLAN ATTACHMENT C on Gilgalal Way S he e l y Ln Bay Dr J ohnson Dr Da r t mout h v e r S t Heat her Heat her i dge Av e A v e Av e El l i s St St Ci r Junco Ct Ri ngneck Dr Dr Dr St Worthington Centre Dr w h eel A l a m o A v e Ct A n n a b e l S COLLEGE AVE DRAKE ROAD Sioux Blvd Way Sharps Laredo Lyman Gatlin St Ottawa W Swallow Rd Nottingham Rocky Mountain Way Dr Nez Perce Spring Creek Bennett Rd Westward Lakewood Dr City Park W Myrtle St W Coy Wagner E Coy University St W Myrtle St W Laurel St North Dr Meridian Ave South Dr University Ave Isotope Dr Norte Del Ave Armstrong Rembrandt Dr Old Main Dr Oval Drive West Dr Burton Ct W Lake St Blevins Ct James Ct St Braiden W Pitkin St East Dr Edison Dr "A" St Center Ave Prospect Balsam Ln Juniper Ln Prospect Ct Birky Pl Sheely Dr W a l l e n b u r g Dr Hobbit St Tamasag Dr Waters Edge Winterberry Way d Rd Trail Wind Spring Ct Arthur Dr Meadowlark Princeton Rd Dr Davidson Winchester Dr Powderhorn Dr Rocky Mountain Way Cha p a rall r Tumbleweed Ln Cimarron Ct Mor se man Stagecoach Ct Frontier Ct man Mtn Redwing Rd Dr Meadowlark Ave Blue jay St Eagle Dr McClelland Dr Bobolink Ct Robin Ct Cardinal Bluebird Fairplay Dr Silv e r t h orne Dr Blue Ho Swallow Rd Crestmore Pl Miller Dr W Stuart St Cir e r Pl Dr Baystone Dr Aster St Ellis Dr Chetwood Dr Mathews Zuni Ct Swallow Pl Swallow Bend Parkview Stover Cir Parkview Ct E Swal lo w Southmoor Dr Alexander Ct Strachen Dundee Ct Stover St Stanford Rd Leisure Dr Tulane Dr Mathews St Harvard St Allen St Mae St Ruth St Thunderbird Dr Harvard St Del Clair Rd Li n d a Ln E Swallow Rd Phoenix Dr Remington St Cortez St Marquette St Hartford Cir Queens Ct Vanderbi lt Ct Camb r idge Ct Baylor ST Princeton Rd Brown Ave Tulane Dr Columbia Rd Cornell Ave Stanford Rd Duke Ln Sq Kiowa Ct Apache Ct Shawnee Ct Harvard St Yale St Mathews St Yale Way Rutgers Ave Vasser Ave Loyola Ave Purdue Rd Dar t mou th Ln Villanova Ct Cir Remington Spring Park Dr Busch Ct Cheyenne Dr Osage St Mohawk Chey e n e n h er o ke e C Choctaw Way Mathews St Smith Pl Deines Ct Person Ct Peterson Pl Peterson St Alpert Ct Parker St Whedbee St Morningside Ct Alpert Ct Bristol Ct Stuart St B. Ct B. C i r Peterson St E Lake St Buckeye St Circle Dr Newsom St Lake St Buckeye St Morgan Garfield St E l l is St Edwards St E Myrtle St E Laurel St E Plum St Locust St E Elizabeth St Garfield St Edwards St Mathews St Remington St Whedbee St Colorado St Eastdale Dr Kenroy Ct Locust Cowan St E Pitkin St Daisy Columbine St Bluebell St Rd Ave Delmar St Stuart St COLORADO & SOUTHERN RAILROAD Spring Creek Spring Creek E PROSPECT RD CSU S SHIELDS ST JVA, Incorporated 25 Old Town Square Suite 200 Fort Collins, CO 80524 Phone: 970.225.9099 Fax: 970.225.6963 E-mail: info@jvajva.com CONSULTING ENGINEERS GARDENS ON SPRING CREEK VICINITY MAP PROJECT SCALE: 1"=1500' ATTACHMENT A