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Home My WebLink About20120183 r I 8 5 1 2 0 I 1 COPY PUBLIC WORKS DEPARTMENT 1111 H STREET, P.O. BOX 758 GREELEY, COLORADO 80632 WEBSITE: WWW.CO.WELD.CO.US PHONE: (970) 356-4000, EXT. 3750 W E L D__-€ � N T Y FAX: (970) 304-6497 RECEIVED December 30, 2011 JAN 0 5 7m? Aggregate Industries Attention: Connie Davis Weld County (tanning Department 1707 Cole Blvd GREELEY OFFICE Suite 100 Golden, CO 80401 Re: Flood Hazard Development Permit application (FHDP-742) Dear Ms. Davis, The Weld County Public Works Department, Planning Services, Building Inspection Department, and Environmental Health Services have reviewed the requested Flood Hazard Development Permit (FHDP) application for the Tull Pit and conveyor crossing. The current FHDP application is conditionally approved based on the comments and requirements below. Applicant: Aggregate Industries Attention: Connie Davis 1707 Cole Blvd Suite 100 Golden, CO 80401 Legal: Part of the Section 32, T3N, R67W, Sixth P.M., Weld County, Colorado Location: North of and adjacent to CR 20.5 and approximately 0.75 miles west of CR 7 FEMA Panels: 080266-0850C dated September 28, 1982 Parcel No's.: 1313-16-0-00-031, 1313-09-0-00-003, 1313-09-0-00-004, 1313-08-0-00-030 COMMENTS Department of Planning Services Special Use Permit No. USR-1046, was approved by the Board of County Commissioners on June 15, 1994 for an open pit sand and gravel mine, including concrete and asphalt batch plants in the Agricultural Zone district as submitted in the application materials. The narrative for this application indicates that the property owner, Aggregate Industries (Al) intends to mine alluvial sand and gravel from the property, creating water storage reservoirs post reclamation within a 200-acre site located adjacent to Boulder Creek. From the submitted application materials and letter dated July 27, 2011 from W. Schenderlein of Blue Earth Mr. Schenderlein states the mining operation and associated conveyor bridge is allowed under Use by Special Review permit (USR-1046); per research by staff and review of the application Page 1 of 5 2012-0183 M:\PLANNING—DEVELOPMENT REVIEWFHDP-Flood Hazard Development Permit\742 Ag Industries Tull Pit\FHDP-742 Ag Ind Tull Pit Conditional Approval 12-30-11.doc govra,nicatinuo 1-0,- 2.0i2.. PLOW( materials and narrative, this is not an accurate statement as this permit does not address conveyance of any material across regulated water bodies, i.e., Boulder Creek. The current permit, USR-1046 does not address the exporting of materials, and does not address a conveyor bridge spanning the Boulder Creek allowing for the transport of the mined materials to the existing processing facility operated by Al and identified as the Distel facility [4th AmUSR-877]. Further, 4th AmUSR-877 does not address the conveyor and does not indicate that the importing of material from an off-property location is permitted. At a minimum, and prior to the approval of this Flood Hazard Development Permit, it is requested that representatives for Al meet with Weld County staff to ascertain if an amendment to both Special Use Permits is warranted. Further, the application identifies four parcels to be incorporated into Flood Hazard Development Permit No. 742. It is important to state that two parcels included with this application are not included in the existing permit boundary (1313-08-0-00-030 and 1313-09-0-00- 003); and parcel number 1313-08-0-00-030 is not in Weld County's jurisdiction, as the property has been annexed into the City of Longmont. Should it be the intention of Al to include parcel 1313-09-0- 00-003 having a surface property ownership with Temperature Processing Company, an amendment to permit number USR-1046 will be required. For this amendment to the permit, a pre-application meeting between representatives for Al and Weld County staff will be required. Please refer to the REQUIREMENTS section of this memorandum for specific instructions. Building Department Please refer to the REQUIREMENTS section of this memorandum for specific instructions. Public Works Department The applicant's engineer, Blue Earth, submitted a FHDP application for review on August 9, 2011. The application was returned for more information on August 24, 2011. The application was resubmitted on December 14, 2011. The FHDP maps and narrative were stamped, signed, and dated by William Schenderlein, P.E. # 38161. The FHDP application was submitted for a gravel mining operation known as the Tull Pit. The subject property is located north of and adjacent to CR 20.5 and approximately 0.75 miles west of CR 7 in Section 32, T3N, R67W, Sixth P.M., Weld County, Colorado. The entire property is located in the Boulder Creek Special Flood Hazard Area (SFHA), also known as the 100-year floodplain and is designated as Zone A on Flood Insurance Rate Map (FIRM) Panel 080266-0850C. This designation indicates that there are no published base flood elevations (BFEs) and floodway boundaries established for Boulder Creek on the current effective FIRM dated September 28, 1982. All FIRMs and FBFMs are prepared, distributed, managed, and revised by the Federal Emergency Management Agency (FEMA). For purposes of this application, it was assumed that the entire mine site is located in the floodway of Boulder Creek. This assumption is supported by an unpublished Army Corps of Engineers study dating to the early 1980s. The application indicates that the majority of the mining activity and material stockpiling that will occur in the floodway will be below existing grade in the bottom of the pit. The material stockpiling is not expected to cause a rise in the 100-year water surface elevations as it will be located below existing grade. The application also indicates that the only berms to be located above the existing grade will be located at the eastern edge of the property as far away from Boulder Creek as possible. The berms will be oriented parallel to the flood flows in Boulder Creek. The applicant's engineer provided HEC-RAS modeling showing the location of the floodway and the floodplain boundaries. The HEC-RAS model was based on site specific topographic data surveyed within the property and NED USGS topographic data for areas outside of the property. The HEC- Page 2 of 5 M:\PLANNING—DEVELOPMENT REVIEW\FHDP-Flood Hazard Development Permit\742 Ag Industries Tull Pit\FHDP-742 Ag Industries Tull Pit Conditional Approval 12-30-11.doc RAS cross section data contains information regarding the specific stations for which the site specific and USGS data was used. It should be noted that the bridge for CR 20.5 was improperly entered into the HEC-RAS model. The applicant's engineer did not extend the bridge roadway deck entirely across the floodplain as is standard FEMA modeling procedure. It was determined that while not technically correct; the improper modeling of the bridge would not adversely impact the water surface elevations in the vicinity of the bridge. The application also states that a conveyor will be used to export material from the Tull Pit across Boulder Creek to the west to the Distel Pit batch plant. The application materials state the conveyor will be designed and constructed to be above the regulatory flood datum (BFE+1ft) and will be adequately constructed to withstand the impact of flood debris such as logs. An As-built elevation certificate for the conveyor will be required. It should be noted that development activities located in a FEMA regulatory floodplain or floodway are subject to the requirements of Title 44 of the Code of Federal Regulations (CFR), Parts 60 and 65. The proposed sand and gravel operations will include a gravel pit, material stockpiles, overburden stockpiles, top soil stockpiles, conveyor, and on-site parking. Because more than 5 acres of land are being disturbed, FEMA in letters dated January 13, 2011 and June 17, 2011, informed the County that a Letter of Map Revision was required in order for Weld County to remain in compliance with FEMA's National Flood Insurance Program. Therefore, at the conclusion of mining the applicant shall be required to provide a Letter of Map Revision based on as-built topography to document and formalize any changes that may have occurred to the floodplain and floodway during mining activity. The FHDP application includes the following documentation: 1. Flood Hazard Development Permit Application 2. Flood Evaluation Report that is stamped, signed, and dated by William Schenderlein, P.E. No. 38161 3. FHDP maps that has been stamped, signed, and dated by William Schenderlein, P.E. No. 38161 4. FHDP Standards 5. Letter from application allowing Blue Earth to act as agent 6. Deeds for the property 7. Conveyor crossing plans 8. USR-1406 Plat 9. Copy of FEMA FIRM Panel 080266-0850C 10. Copy of Avocet Subdivision Floodplain Analysis 11. Copy of USACOE unpublished floodplain study 12. HEC-RAS summary tables 13. Impact calculations for conveyor crossing 14. Floodplain maps 15. CD containing HEC-RAS and CAD files The following information was added to the file: 1. Letter to the applicant outlining the identified deficiencies dated August 24, 2011 2. Letter from FEMA to Weld County dated January 13, 2011 3. Letter from FEMA to Environment, Inc dated June 17, 2011 4. Comments from Planning Services, Building Department, and Environmental Health Services 5. GIS Map showing the extents of the current effective FEMA floodplain 6. Copy of FEMA FIRMette showing the approximate location of the pit 7. Copy of MSHA berming requirements Please refer to the Requirements section of this memorandum for specific instructions. Page 3 of 5 M:\PLANNING—DEVELOPMENT REVIEW\FHDP-Flood Hazard Development Permit\742 Ag Industries Tull Pit\FHDP-742 Ag Industries Tull Pit Conditional Approval 12-30-11.doc Environmental Health Services Please refer to the Requirements section of this memorandum for specific instructions. REQUIREMENTS: Department of Planning Services 1. All proposed structures must be appropriately permitted for the use of the building or structure, including evidence of compliance with the Flood Plain regulations. 2. Stockpiling of any material in the floodway is not permitted due to the highly erosional nature of placement of said material in this location. 3. Appropriate anchoring of transient equipment including temporary structures shall be required per established Codes and Ordinances from the appropriate regulatory agency. 4. Construction shall comply with all requirements/conditions of the Weld County Building Code. Installation of utilities shall comply with the requirements listed in the Weld County Code. 5. All proposed or existing structures will or do meet the minimum setback and offset requirements for the zone district in which the property is located. 6. New construction must meet the minimum requirements for setback from oil and gas encumbrances. No building or structure as defined and limited to those occupancies listed as Groups A, B, E, F, H, I, M and R in Section 302.1 of the 2006 International Building Code, shall be constructed within a 200-foot radius of any tank battery or within a 150-foot radius of any wellhead. Any construction within a 200-foot radius of any tank battery or 150-foot radius of any wellhead shall require a variance from the terms of the Section 23-3-10 of the Weld County Code. 7. Any future structures or uses on site must obtain the appropriate zoning and building permits. 8. Low water crossings, including access roads, shall not impede floodwaters, potentially adversely impacting downstream properties and/ or conditions. Building Department 1. Any new structures and any electrical work will require appropriate building permits. 2. All electrical and mechanical equipment shall be elevated a minimum of 1 foot above the BFE or shall be waterproofed to prevent the entry of floodwaters into the electrical and mechanical equipment. Public Works Department 1. A letter of map revision shall be submitted to Weld County and FEMA for review and acceptance by the gravel pit operator within 60 days of final bond release from DRMS and prior to the request for the vacation of the USR. The LOMR shall depict the impact of mining activity to the floodplain boundaries, floodway boundaries, and BFEs. 2. Any new buildings or structures to be placed in the floodplain or any existing buildings/structures in the floodplain that will be used by the mine operator shall obtain a FHDP prior to the use or placement of such structure or building. 3. The current FHDP application must be amended for future reclamation development, or for any changes to the mine plan as shown on the FHDP maps date stamped December 14, 2011. 4. Prior to the finalization of the building permit for the conveyor, an As-Built Elevation Certificate shall be provided to Public Works. The As-Built Elevation Certificate shall include photos of the conveyor and shall be stamped, signed, and dated by a registered Professional Land Surveyor licensed in the state of Colorado. 5. Any proposed development activities in the FEMA-defined 100-year floodplain and/or floodway may not cause an adverse rise in the BFE on adjacent or upstream properties or structures. Any flooding impacts must be quantified in the amended FHDP documentation, Page 4 of 5 MI PLANNING—DEVELOPMENT REVIEWTHDP-Flood Hazard Development Permit\742 Ag Industries Tull Pit\FHDP-742 Ag Industries Tull Pit Conditional Approval 12-30-11.doc clearly identified on pertinent work maps stamped by a registered P.E., and be accompanied by written approval from impacted landowners. 6. Any future proposed stockpiles, berms, levees, or riverbank protection features not identified on the current effective FIRM maps must be approved through the amended FHDP (AmFHDP) process and FEMA's LOMR Process. Future stockpiles, berms, levees, or riverbank protection features will not be allowed in the floodway and will only be allowed in the flood fringe if they are permitted with an AmFHDP and are oriented parallel to the direction of flow in the floodplain. 7. Portable toilets located in the flood plain shall be anchored to resist flotation and lateral forces associated with flood waters. 8. No tanks such as fueling tanks will be allowed in the floodway and tanks placed in the flood fringe will have to be anchored, protected with a fuel containment berm whose top of wall elevation is a minimum of one foot above the BFE, and permitted with an amended FHDP application. 9. AmFHDP applications will be subject to the rules and regulations in effect at the time of future application. 10. Pursuant to Chapter 15, Articles I and II of the Weld County Code, if noxious weeds exist on the property or become established as a result of the proposed development, the applicant/landowner shall be responsible for controlling the noxious weeds. All vegetation, other than grasses, needs to be maintained at a maximum height of 12 inches until the area is completely developed. Environmental Health Services 1. The future installation of any septic system within the 100-year floodplain shall comply with the Weld County I.S.D.S. floodplain regulations. Specifically, if the septic tank lids are not above the floodplain elevation, then the access to the tank manhole lids must be covered with 20 ml PVC and sealed with plumbers cement. In addition, a one-way valve must be installed on the effluent line between the tank and the absorption field. Therefore, any future pumping of the septic tank will require that the tank lids be sealed prior to backfilling, and any future upgrade of the septic system will require that a one-way valve be installed on the effluent line. 2. In accordance with the Colorado I.S.D.S. Regulations, no septic systems shall be installed within the floodway. RECOMMENDATIONS: The Weld County Public Works Department recommends conditional approval of this FHDP application, subject to all Comments and Requirements included in this letter. Sincerely, F 1%Av hvw/4 1. Clay Kimmi, P.E., CFM Weld County Public Works Original: Aggregate Industries,Applicant CC to Files: USR-1046 FHDP-742 PC by Post: Kim Ogle, Planning Services Frank Piacentino,Building inspections Dept. Lauren Light,Environmental Health Lin Dodge.Planning Services William Schenderlein,Blue Earth,P.O.Box 973, Fort Collins, CO 80522 Page 5 of 5 M:\PLANNING—DEVELOPMENT REVIEW\FHDP-Flood Hazard Development Permit\742 Ag Industries Tull Pit\FHDP-742 Ag Industries Tull Pit Conditional Approval 12-30-11.doc F- k DP-- -7 qa LONGMONT OPERATION Application For Flood Hazard Development Permit WELD COUNTY, COLORADO itt Cu re ST!'4 a, 41409 -..41-ti) ;y„. NNeasi IMF PA/S:is --V II-W: fr . i vi . s v r'{, .., f f i y M1 E - f' ,• �- a . . .w a _J _ ..�r- - M - 1•Ara- r AGGREGATE INDUSTRIES - WCR, Inc. 1587 County Road 20'V2 Longmont, Colorado 80504 T...., __. .„ I LE c is, U l.JelL DEC 1 4 9011 DECEMBER 12, 2011 WELD COUN fY PUBLIC WORKS nFP1 BLUE EARTH 0 CERTIFICATION Engineer I hereby certify that this Application for a Flood Hazard Development Permit for sand and gravel mining operations on the Aggregate Industries Longmont Tull site was prepared by me or under my direct supervision in accordance with the Weld County Floodplain Management Standards. Wi is c enderlein =�OAADO(taN Registered Professional Engineer s State of Colorado No. 38161 ;' 38161 c / ` 4 Certified Floodplain Manager No. US-05-01642 iI o `‘‘sS/ONA----- 12/12/2011 TABLE OF CONTENTS PROPOSED PROJECT DESCRIPTION 4 HEC-RAS MODEL DATA AND ASSUMPTIONS 7 Existing Condition 7 Proposed Condition 8 Floodway 9 Discussion of HEC-RAS Errors,Warnings, and Notes 9 FLOODPLAIN MANAGEMENT STANDARDS SUMMARY 11 REFERENCES 21 FIGURES 22 FHDP Application 22 Deed and Legal Right to Enter 22 Existing Conditions Site Map(Full Scale) 22 Existing Conditions Site Map(Project Area) 22 FHDP Map(Proposed Condition, Full Scale) 22 FHDP Map(Proposed Condition, Project Area) 22 Conveyor Bridge Typical Plans 22 Preliminary Reclamation Plan 22 APPENDIX A. EXISTING FLOOD INFORMATION 23 FEMA Flood Insurance Rate Map(FIRMETTE) 23 Avocet Subdivision LOMR Study Report 23 1977 Army Corps of Engineers"Technical Write-Up St. Vrain Creek and Boulder Creek, Colorado." 23 APPENDIX B. CALCULATIONS 24 HEC-RAS Summary Tables 24 Hydrodynamic Force Calculations 24 APPENDIX C. DIGITAL FILES (CD) 25 AutoCAD workmaps 25 HEC-RAS files 25 3 PROPOSED PROJECT DESCRIPTION This application is submitted on behalf of Aggregate Industries - WCR, Inc. to fulfill the Weld County Department of Public Works Flood Hazard Development Permit requirements for proposed aggregate mining and reclamation activities on the Tull Property. Aggregate Industries proposes to mine alluvial sand and gravel from the property with reclamation activities potentially creating below-grade water storage. The 200 acre site is located adjacent to Boulder Creek just north of Weld County Road 20'A, three quarters of a mile west of Weld County Road 7 and approximately five miles east of the town of Longmont (see Vicinity Map). The entire site is within the Zone A 100-year approximate floodplain for Boulder Creek as shown on the Weld County, Colorado Unincorporated Area Flood Insurance Rate Map (FIRM) Panel 080266 0850, revised September 28, 1982 (Appendix A). Vicinity Map 9 e a a _ " _—�'- ±� r T`_. n : • , n • n ri I o , �1 • U ,95„ \____„-------c\ 610 J • - , - - - - 40 'SC r; .. >--\ ). .N. vir /7-----„_ a • II KMD68+ 11 (\ijall Iiik 4 -- -tep p—<860 4bI• ..j. n 4 q '4 Cjj n ye y la + p'' a 'l • A. I n It Jessum• 4892 Ih. 8MM i - R 2Q.5 17 16 : n t, `1%- --Th \ �, A P PP OXIMA?E ..u: a : .. • T U L L- E Gtt� • \_ PROPER"".. wcNt---,,_ / ,v— :- r , ( .. �nr��s o k a A bole' 4937 �' 1b. .,r- _ • as;r 4 During active mining, a conveyor bridge will span Boulder Creek approximately 2600 feet north of County Road 20% in order to transport mined material to existing processing facilities to the west. The conveyor will be loaded by hopper below grade in the mine pit, exit the active mine site, and extend approximately 2300 feet west to the Aggregate Industries Longmont-Distel processing facility. All fuels, oils, lubricants, and other potentially hazardous materials for mining and reclamation operations will be supplied by trucks as needed, and will not be stored on-site. No domestic water supply, treatment, or additional structures are planned for the mine site. Temporary stockpiling of aggregate product and topsoil and overburden suitable for reclamation will be a part of active mining operations. Since the conveyor will transport aggregate product off-site, stockpiles of this material will be small and exist only briefly. These stockpiles will be located in the bottom of the pit below the existing ground surface. As mining operations progress, reclamation will be performed in the mined out areas of the pit. Therefore, most of the topsoil and overburden to be used during reclamation will be staged on-site for a brief period. Some reclamation material, however, will be stockpiled in areas where it will remain for the majority of the mining operation. These stockpiles will be placed on the eastern side of the property, as far from Boulder Creek as is practical. They will be aligned in a north-south configuration, parallel with potential Boulder Creek flood flows. The stockpiles will be a maximum of 300 feet in length and adjacent stockpiles will be separated by a minimum of 50 feet. Topsoil and overburden material to be used for concurrent reclamation will typically be placed without stockpiling. Topsoil and overburden stripped from the site ahead of the mining operation will generally be transported directly to the pit bottom and placed to create reclamation side slopes. To expose the underlying aggregate material, stripping the topsoil and overburden will lower the grade adjacent to the active mine pit approximately 3 to 6 feet below the existing ground surface. 5 Temporary berms will be placed for safety purposes along active mine face high-walls in accordance with Mine Safety and Health Administration (MSHA) code 30 CFR § 56.9300. The location of safety berms will move with the active mine face. In order to prevent any impacts in the floodway, the berms will be placed below the existing ground surface, within the areas where topsoil and overburden have been stripped for mining. Figure 1 illustrates the typical construction of below-grade safety berms. Figure 1. MSHA Safety Berm Construction 100'Typical Existing ground surface MSHA- Safety Berm r 1 ( Excm tdtapsoho.ettmrden —13'- 6' Proposed ground surface 4'- 12' (top of aggregate deposit) Active Mining Face Highwall MSHA Safety berms to be placed such that top of berm is at or below existing grade. 6 HEC-RAS MODEL DATA AND ASSUMPTIONS The project site is located within the Zone A approximate floodplain encompassing St. Vrain Creek, Boulder Creek, and Idaho Creek (see FEMA firmette, Appendix A). Approximate floodplain zones have no defined base flood elevations (BFE's) and no designated floodway boundaries; therefore, hydraulic analysis was performed in order to establish relative base flood elevations, and the associated 100-yr floodplain boundary. Additionally, the 100-yr 1-foot and 1/2-foot floodways were analyzed. After establishing a baseline "existing condition" model, the conveyor bridge, proposed pit, and temporary stockpiles were added in order to reflect proposed conditions. Both of these models were built using collected site topography, Boulder Creek channel survey data, and best available off-site topographic and hydrologic data. The hydraulic models are used only for relative comparison of existing and proposed conditions. The HEC-RAS modeling submitted with this application contains the following plans and geometries: -r1w Pia Filo w 3 3 =`.70.C4 . Existing Condition Agg_Ind_TuIl10.p03 Agg_Ind_TuIII0.g02 Proposed Condition Agg_Ind_Tu1110.p02 Agg_Ind_Tulll0.g04 Existing Condition The Army Corps of Engineers one-dimensional standard step backwater program (HEC-RAS v 4.1 January 2010) was used to determine existing water surface elevations and extents (see Existing Conditions Site Map). The 100-yr flow for Boulder Creek (QIoo= 12,250 cfs) was taken from a LOMR study for the Avocet subdivision entitled "Floodplain Analysis-Boulder Creek, Avocet Subdivision Town of Frederick Weld County, Colorado" prepared by QED Consultants March 7, 2008 (see Appendix A). This flow originally came from the hydrologic analysis presented in the Boulder County Flood Insurance Study (FIS). On-site topographic information was taken from 2008 aerial mapping provided by Aggregate Industries. Additionally, the Boulder Creek channel was surveyed in January 2011 within the property. Outside of the property boundary, it was necessary to use USGS 1/3 arc-second NED data. All topographic information is on Colorado North State Plane coordinates, NAD 83 horizontal datum, NAVD 88 vertical datum. These three data sources were used to create a composite digital terrain model (DTM). This DTM was then used to create cross-sections for HEC-RAS. Specific topography source data locations are given in the description field for each cross-section in HEC-RAS. At the direction of Weld County Public Works staff, St. Vrain Creek was not considered in the analysis, and Idaho Creek was not modeled separately from Boulder Creek. The portions of the cross-sections that represent St. Vrain Creek were modeled as blocked obstructions. In order to see if any impacts extended beyond the property, an additional 2 sections were added on both the upstream and downstream model extents. These sections are based solely on USGS NED data in the overbank. The channel portion of these sections was extrapolated from the nearest surveyed section at the prevailing bed slope. 7 Manning's n values were taken from the HEC-2 model (Bould97.dat) obtained from Weld County, which was the basis for the 1977 Army Corps of Engineers "Technical Write-Up St Vrain Creek and Boulder Creek, Colorado"(see Appendix A). These n-values (0.04 channel, 0.075 overbank) seem reasonable and consistent with the site based on engineering judgment. Roadway deck elevations for County Road 20'1 were taken from the aerial mapping. Additional geometric information for the bridge opening was determined during a January 2011 site visit. Ineffective flow areas in existing ponds and mine sites were placed based on aerial photos and ground topography. The current floodplain in the project area is Zone A approximate and has no published water surface elevations. Since this is the case, normal depth based on the average bed slope (0.00245 ft/ft) was used as the boundary condition for the HEC-RAS floodplain modeling at cross-section 351.44. Known water surface elevations were entered as downstream reach boundary conditions for the 1-foot floodway and %2-foot floodway profiles. These elevations were determined by taking the computed water surface at the downstream section for the base 100-yr floodplain model and adding 1 foot for the 1-foot floodway profile, and 1/2-foot for the % foot floodway. Proposed Condition The proposed condition HEC-RAS model includes geometry representing the conveyor bridge, future pit, and temporary stockpiles for storage of reclamation material (see Flood Hazard Development Plan Map). The conveyor bridge was modeled as a simple bridge with an open span of 120 feet going across Boulder Creek. The low chord elevation was set to 4873 feet above mean sea level (amsl) providing a little over 3 feet of freeboard above the calculated 100-yr water surface elevation. Outside of the clear span across Boulder Creek, the conveyor was modeled as continuous ground without any openings. In reality, the conveyor will be an open structure; therefore, the HEC-RAS model represents the most conservative approximation. The pit area was modeled based on preliminary reclamation plans and represents the ultimate condition. Pit side-slopes were placed at 3H:1 V extending to a maximum depth of 26 feet below existing grade. The pit area was modeled as ineffective flow area except for the very top (2 feet or less) in order to reflect storage but not active conveyance. Temporary stockpiles comprised of material suitable for final reclamation that will likely be in place for the life of the mine will be located on the eastern side of the property, as far from Boulder Creek as is practical. These stockpiles will be aligned in a north-south configuration, parallel with potential Boulder Creek flood flows. The stockpiles will be a maximum of 300 feet in length and adjacent stockpiles will be separated by a minimum of 50 feet. In HEC-RAS, potential stockpiles were modeled as a blocked obstruction 26-feet wide and 8-feet tall running the length of the eastern property boundary. This configuration gives a conservative approximation. 8 Material used adjacent to the mine pit for safety berms was not included in the modeling. Topsoil and overburden will be stripped adjacent to the mine pit to expose the aggregate product, lowering the preexisting ground surface where the safety berms are placed. The material stripping and placement of safety berm material will change frequently as mining operations progress making it unpractical to create realistic layouts on the site plan for modeling. The modeling assumes that the preexisting ground surface extends to the edge of the mine pit. Since the actual grade and safety berms will be at or below the preexisting ground surface, the modeling approach still provides a conservative representation of conditions. None of the proposed project features modeled result in any increase in the intermediate regional flood (100-yr). Floodwav The project area lies within the floodplain and most likely between the floodways of two drainageways, Boulder Creek and Idaho Creek. For the purpose of this permit application, the entire floodplain was modeled as a single section containing both drainageways in order to contain 100-year flows. The HEC-RAS floodway encroachment modeling routine removes area from the left and right edges of each cross section, and cannot define two separate floodways concurrently. Limitations in topographic and hydrologic data prevented the use of split flow modeling which is likely the only way to define two discreet floodways. Based on these limitations, along with the extent of current Zone A 100-year approximate floodplain boundary, the project site is considered to be within the floodway. Nevertheless, the proposed conveyor bridge and temporary stockpiles do not cause any rise in the intermediate regional flood elevations. Discussion of HEC-RAS Errors. Warnings, and Notes There are a number of warnings and notes reported by HEC-RAS for the existing and proposed conditions models. Warning's and notes are typically not considered to be major problems with the model. Error messages indicate problems with the model that potentially produce invalid solutions. None of the profiles contained any Error messages. A discussion of reported notes and warnings is presented below. • Divided flow computed for this section This warning indicates that there are flow areas separated by high ground not inundated for the given section. This is the case for our site and is the result of modeling two drainageways in one section (Boulder Creek and Idaho Creek). Due to the lack of hydrology information for each specific drainage, as well as the fact that the current approximate Zone A mapping shows both creeks occupying one large floodplain, it was determined that this simplification was acceptable. 9 • The conveyance ratio (upstream conveyance divide by downstream conveyance) is less than 0.7 or greater than 1.4. This may indicate a need for additional cross sections. This warning was determined to be acceptable. When n values are consistent from one section to the next, the conveyance is primarily a function of area. If there are multiple conveyance areas (divided flow) this warning is likely to occur as the area associated with a given n value (channel or overbank) may vary greatly from one section to the next. If the model is rerun with interpolated cross sections every 50 ft., the warning is not posted, but the resulting water surface profile is not any more accurate and the profile is a lot less smooth. Bridge Notes • The energy upstream of the bridge computed by the orifice equation was below critical depth. The pressure solution has been disregarded. • The weir over a bridge is submerged, the energy answer was used. • Yarnell answer is not valid if the water surface is above the low chord or if there is weir flow. The Yarnell answer has been disregarded. • Momentum answer is not valid if the water surface is above the low chord or if there is weir flow. The momentum answer has been disregarded. • The downstream water surface is above the minimum elevation required for orifice flow. The orifice flow equation was used for pressure flow. The HEC-RAS default bridge modeling approach was used for both bridges on the project. This method checks for pressure and weir flow, and looks for the highest energy answer. When piers are present it uses the Yarnell method to determine associated losses. The various notes listed above are reported to tell the user which routines were employed in computing the water surface at bridge sections. The highest energy solution was selected for both bridges, representing a conservative calculation of water surface elevation. • Multiple critical depths were found at this location. The critical depth with the lowest, valid,water surface was used. This warning occurs at sections where critical depth occurs and there is divided flow. In such cases HEC-RAS defaults to the lowest critical depth. This warning is considered to be acceptable since the approach was taken to model sections covering the entire floodplain. 10 • The energy equation could not be balanced within the specified number of iterations. The program used critical depth for the water surface and continued on with the calculations. • The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross section. This may indicate the need for additional cross sections. • During the standard step iterations, when the assumed water surface was set equal to critical depth, the calculated water surface came back below critical depth. This indicates that there is not a valid subcritical answer. The program defaulted to critical depth. These warnings occur at sections 5540.66 and 5455.77. These sections are both immediately downstream from the County Road 20%2 Bridge. There may be a hydraulic jump here; however, running the model in mixed mode did not yield a significantly different solution. Likewise, adding interpolated cross-sections did not have a great influence on the solution. In any case, a critical water surface at these locations would be more conservative than a supercritical water surface and the warnings are considered to be acceptable. FLOODPLAIN MANAGEMENT STANDARDS SUMMARY The mining operation, and associated conveyor bridge is allowed under the Use by Special Review Permit(USR-1046) provided for by Weld County Code Sec. 23-3-40 (A.3 open pit mining and material processing). Specific requirements for the Flood Hazard Development Permit are defined in Sec. 23-2- 480, 23-2-490, 23-5-250, and 23-5-260. A summary of applicable requirements follows. Sec. 23-2-480. Standards. The Department of Planning Services shall not issue a FLOOD HAZARD Development Permit until it has determined that all applicable standards specified in this Subsection have been met by the applicant. Any USE or DEVELOPMENT which results only in the ALTERATION OR RELOCATION OF A WATERCOURSE and does not require a building permit need only meet the standards listed in Subsection I below. A. The applicant has met all applicable conditions listed in Section 23-5-250 or 23-5-260 of this Chapter. See discussion of 23-5-250, 23-5-260 later in this report. B. If a STRUCTURE is to be ELEVATED in order to meet the floodproofing requirements, the property owner shall certify that the LOWEST FLOOR is ELEVATED (for existing STRUCTURES which are being SUBSTANTIALLY IMPROVED or replaced) or will be built (for new STRUCTURES) to the level, or above, of the REGULATORY FLOOD DATUM. The certificate shall include the elevation of the ground and the existing (for SUBSTANTIALLY IMPROVED STRUCTURES) or proposed (for new STRUCTURES) elevation of the lowest floor of the STRUCTURE. The ground elevation and elevation of 11 the LOWEST FLOOR of any existing STRUCTURE shall be certified to be accurate by a licensed surveyor or registered professional engineer. The conveyor bridge is the only new structure proposed, and it will be elevated. The computed intermediate regional flood elevation at the bridge is 4869.61'. The regulatory flood datum is defined to be 1 foot above the intermediate regional food elevation (i.e. 4870.61). The conveyor bridge is to be constructed such that the low chord elevation is 4873'. This elevation will be certified by a licensed surveyor upon construction. C. For all new construction and SUBSTANTIAL IMPROVEMENTS, fully enclosed areas below the lowest floor that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following criteria: 1. A minimum of two (2) openings having a total net area of not less than one (1) square inch for every foot of enclosed area subject to flooding shall be provided. 2. The bottom of all openings shall be no higher than one (1) foot above grade. 3. Openings may be equipped with screens, louvers or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters. Portions of the conveyor from the pit to the bridge and from the bridge to the processing area will stand on legs that allow water to flow through. D. A registered professional engineer shall certify that all STRUCTURES which are not ELEVATED in order to be FLOODPROOFED are designed so the STRUCTURE is WATERTIGHT below the elevation of the REGULATORY FLOOD DATUM and that the STRUCTURES are designed to be capable of resisting the hydrostatic and hydrodynamic forces expected at the BUILDING site during an INTERMEDIATE REGIONAL FLOOD. The certification shall include the elevation above Mean Sea Level of the REGULATORY FLOOD DATUM at the BUILDING site and the proposed elevation of the lowest floor of the STRUCTURE. All electrical components associated with the conveyor below the regulatory flood datum (4870.61') will be designed and constructed to be watertight. Hydrodynamic force calculations (Appendix B) verify that the bridge portion of the conveyor and associated abutments will be able to resist the overturning moment that could be produced by the impact of floating logs in the event of a large flood A similar moment calculation is presented verifying that the bridge and abutments will be able to withstand the hydrodynamic pressure exerted by a large log/debris hung up on the bridge. Table 1.presents a summary of hydrodynamic forces. 12 Table 1. Hydrodynamic Force Summary .. , 4 , , Impact 143,216 309,058 Pressure 188,590 309,058 I. If the proposed USE or STRUCTURE is to be located in the FW (Floodway) District, a registered professional engineer shall certify that the proposed USE or STRUCTURE, when built, will not cause any increase in floodwater levels during an INTERMEDIATE REGIONAL FLOOD. The project area lies within the floodplain and most likely between the floodways of two drainageways, Boulder Creek and Idaho Creek. Limitations in topographic and hydrologic data prevented the use of split flow modeling which is likely the only way to define two conconcurrent floodways. Based on these limitations, the project site is considered to be within the floodway The proposed conveyor bridge and temporary stockpiles do not cause any rise in the intermediate regional flood elevations. Table 2.presents a comparison of existing and proposed intermediate regional flood water surface elevations. 13 Table 2. Existing vs. Proposed Water Surface Elevations r rt: 4 Y i Ma'Mg 47, 6400 4882.71 4882.71 0.00 5895 4882.59 4882.59 0.00 5594.68 4882.57 4882.57 0.00 5545 4882.42 4882.42 0.00 CR 20.5 Bridge 5540.66 4881.93 4881.93 0.00 5506.34 4877.54 4877.54 0.00 5455.77 4877.31 4876.98 -0.33 5357.54 4876.79 4876.33 -0.46 5175.85 4876.41 4875.87 -0.54 4912.18 4876.01 4875.38 -0.63 4600.3 4875.48 4874.77 -0.71 4280.67 4874.9 4874.1 -0.80 3927.49 4874.11 4873.34 -0.77 3573.17 4873.38 4872.57 -0.81 3223.99 4871.75 4871.58 -0.17 2955.51 4870.82 4870.66 -0.16 2677.52 4869.9 4869.77 -0.13 2639.72 4869.82 4869.68 -0.14 2629.54 4869.79 4869.61 -0.18 Conveyor Bridge 2594.5 4869.68 4869.44 -0.24 2579.37 4869.64 4869.42 -0.22 2355.83 4868.92 4868.65 -0.27 2201.69 4868.53 4868.01 -0.52 2110.87 4868.34 4867.71 -0.63 1883.91 4866.92 4866.87 -0.05 1716.88 4866.58 4866.37 -0.21 1570.7 4866.35 4865.97 -0.38 1295.08 4865.79 4865.62 -0.17 1151.02 4865.36 4865.36 0.00 983.17 4865.2 4865.2 0.00 686.86 4864.82 4864.82 0 351.44 4864.12 4864.12 0.00 14 J. No encroachments, including fill, NEW CONSTRUCTION, replacement of existing structures, SUBSTANTIAL IMPROVEMENTS and other Development shall be permitted unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of an INTERMEDIATE REGIONAL FLOOD. Temporary stockpiling of aggregate product and other materials suitable for reclamation will be a part of active mining operations. Since the conveyor will transport aggregate product off-site, stockpiles of this material will be small and exist only briefly. These stockpiles will be located in the bottom of the pit below the existing ground surface. As mining operations progress, reclamation will be performed concurrently in the mined out areas of the pit. Most of the topsoil and overburden will be used for concurrent reclamation, however, some material will be stockpiled in areas where it will remain for the majority of the mining operation. These stockpiles will be placed on the eastern side of the property, as far from Boulder Creek as is practical. Stockpiles will be placed in a north-south configuration, parallel with potential flood flows. The stockpiles will be a maximum of 300 feet in length and adjacent stockpiles will he separated by a minimum of 50 feet to allow flow passage. The stockpiles are represented in HEC-RAS as blocked obstructions located on the east side of the property on cross sections (5455.77-983.17), and can be seen on the eastern edge of the mine site on the proposed conditions FHDP maps. Temporary stockpiles do not result in any rise in the intermediate regional flood elevations. See the water surface comparison presented above (Table 2.). 15 K. If FILL material is to be used in the FP-1 or FP-2 (Floodprone) Districts, a registered professional engineer shall certify that the FILL material is designed to withstand the erosional forces associated with an INTERMEDIATE REGIONAL FLOOD. HEC-RAS modeling for the proposed condition shows that the temporary stockpiles along the eastern edge of the property experience typical inundation depths between 0 and 2 feet, with velocities in the 0 —2 ft/s range. The average depth is 0.6ft and the average velocity is 0.9 ft/s. While a flood may cause some small local erosion, the temporary stockpiles will be vegetated and should be able to withstand these relatively small depth and velocity conditions. Table 3. below summarizes the values. Table 3. Detth and Veloctt' at Stockpiles. + � Y*'�^¢ �"m Y• „r Yt3: �'z'Nh ,cis y�"`"no�' x rtfirglinr7 5357.54 0.74 1.33 5175.85 1.87 1.05 4912.18 1.38 1 4600.3 1.77 1.1 4280.67 1.1 1.14 3927.49 1.34 1.22 3573.17 1.64 1.26 3223.99 1.58 1.61 2955.51 1.66 1.44 2677.52 1.77 1.47 2639.72 1.68 1.55 2629.54 0.62 1.95 Conveyor Bridge 2594.5 1.14 1.9 2579.37 0 0 2355.83 0.65 1.65 2201.69 0.72 1.85 2110.87 0 0 1883.91 0 0 1716.88 0 0 1570.7 0 0 1295.08 0 0 1151.02 0 0 983.17 0 0 16 L. Any USE or DEVELOPMENT which causes or results in an ALTERATION OR RELOCATION OF A WATER COURSE shall comply with the requirements listed below. If the USE or DEVELOPMENT does not include any new construction or SUBSTANTIAL IMPROVEMENT of STRUCTURES and it only includes the ALTERATION OR RELOCATION OF A WATERCOURSE, compliance with the following standards is the only requirement which needs to be met before the Department of Planning Services may issue a Flood Hazard Development Permit. The applicant shall provide evidence that: 1. Municipalities within a three-mile radius of the proposed ALTERATION or RELOCATION have been notified in writing of the proposed ALTERATION or RELOCATION. 2. The Colorado Water Conservation Board has been notified in writing of the proposed ALTERATION or RELOCATION. 3. The Insurance and Mitigation Division of the Federal Emergency Management Agency has been notified in writing of the proposed ALTERATION or RELOCATION. 4. A registered professional engineer shall certify that the flood-carrying capacity within the ALTERED or RELOCATED portion of the WATERCOURSE will remain the same after the ALTERATION or RELOCATION as existed prior to the ALTERATION or RELOCATION. The certification shall also provide evidence which substantiates that the ALTERATION or RELOCATION shall not adversely affect landowners upstream or downstream from the ALTERATION or RELOCATION. (Weld County Codification Ordinance 2000-I) This project is strictly for aggregate mining in the floodplain. Upon completion, the site is likely to become a below grade reservoir. Since the project site is within the floodplain, it is considered to be an alteration of the watercourse. Once active mining and reclamation has been completed, a Letter of Map Revision (LOMR) will be conducted in order to revise the FEMA floodplain to reflect post project conditions. At that point in time, the conditions specified in section L. of the floodplain management standards will be satisfied. 17 Sec. 23-5-250. FW(Floodway)District. A. The FW (Floodway) District is an extremely hazardous area due to the velocity of FLOOD waters which carry debris, potential projectiles and erosion potential. B. No development shall occur in the Floodway District with the exception of FLOODPROOFED agricultural exempt buildings. Agricultural exempt buildings are defined in Chapter 29. (Weld County Codification Ordinance 2000-1; Weld County Code Ordinance 2001-1) For the duration of mining, the conveyor bridge and temporary stockpiles will be the only above-grade development on the site. As previously mentioned, the project area is bounded by Boulder Creek and Idaho Creek, and portions of the site are likely to be in the Floodway of one or both of these drainages. Since detailed split flow modeling was not performed, the project area is considered to be within the Floodway. Temporary stockpiles for reclamation will be placed on the extreme eastern edge of the property. Neither the conveyor bridges nor the stock piles cause any rise in intermediate regional flood elevations. Following mining and reclamation, the site will likely become a below grade reservoir. No further development beyond mining is proposed. Sec. 23-5-260. Uses permitted in FP-1 and FP-2 (Floodprone) Districts. USES listed as allowed by right, ACCESSORY USES and Uses by Special Review in the UNDERLYING ZONING DISTRICT may be permitted in the FP-1 and FP-2 (Floodprone) Districts subject to the following conditions: A. USES allowed shall conform to the requirements of the UNDERLYING ZONING DISTRICT. The project site is specified as Zone A (agricultural). Open pit mining is allowable by Use by Special Review 23-3-40 section A.3., 23-4-250. The owner has a USR permit in place (USR-1046) for the project site. B. USES allowed in the UNDERLYING ZONING DISTRICT which require a building permit or mobile home permit shall, in addition, obtain a Flood Hazard Development Permit. Any USE which results in an ALTERATION OR RELOCATION OF A WATERCOURSE within the FP-1 and FP-2 (Floodprone) Districts shall apply for and receive approval of a Flood Hazard Development Permit. This application is in pursuit of obtaining an FHDP. 18 C. All new construction, replacement or SUBSTANTIAL IMPROVEMENT of DWELLING UNITS shall have the LOWEST FLOOR, including the BASEMENT floor, ELEVATED to or above the REGULATORY FLOOD DATUM. NEW CONSTRUCTION, replacement or SUBSTANTIAL IMPROVEMENT of STRUCTURES other than DWELLING UNITS shall be FLOODPROOFED either by ELEVATING the STRUCTURE or by making the STRUCTURE WATERTIGHT below the REGULATORY FLOOD DATUM. The conveyor bridge is the only new construction proposed for the project. The low chord of the conveyor bridge is to be at elevation 4873' (see conveyor typical section). This is above the computed regulatory flood datum (4870.61). Portions of the conveyor from the pit to the bridge and from the bridge to the processing area will stand on legs that allow water to flow through. All electrical components associated with the conveyor below the regulatory flood datum will be designed and constructed to be watertight. D. STRUCTURES which are designed to be WATERTIGHT below the level of the REGULATORY FLOOD DATUM shall be designed and built to be capable of resisting the hydrostatic and hydrodynamic forces expected at the BUILDING site during an INTERMEDIATE REGIONAL FLOOD. Portions of the conveyor from the pit to the bridge and from the bridge to the processing area will stand on legs that allow water to flow through. Hydrodynamic force calculations are presented in (Appendix B). G. For all NEW CONSTRUCTION, replacement of existing structures and SUBSTANTIAL IMPROVEMENTS, fully enclosed areas below the LOWEST FLOOR that are subject to flooding shall be designed to automatically equalize hydrostatic FLOOD forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must be certified by either a registered professional engineer or architect and must meet or exceed the following minimum criteria: A minimum of two (2) openings having a total net area of not less than one (1) square inch for every one (1) square foot of enclosed area subject to flooding shall be provided. The bottom of all openings shall be no higher than one (1) foot above grade. Openings may be equipped with screens, louvers or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters. Portions of the conveyor from the pit to the bridge and from the bridge to the processing area will stand on legs that allow water to flow through. The spacing of these legs will exceed the minimum requirements to allow for passage offlood waters. H. Electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities shall be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding. The only electrical systems proposed for the project are associated with the conveyor bridge. All electrical components below the regulatory flood datum will be designed and constructed to be watertight. 19 1. All NEW CONSTRUCTION and SUBSTANTIAL IMPROVEMENTS shall be constructed with materials and utility equipment resistant to FLOOD damage. The conveyor, and conveyor bridge components will be constructed with flood resistant materials (steel, aluminum, concrete). J. All NEW CONSTRUCTION, replacement of existing structures and SUBSTANTIAL IMPROVEMENTS shall be constructed using methods and practices that minimize FLOOD damage. All construction, mining, and reclamation activities will be carried out in a manner which will minimize potential flood damages. The project will not increase intermediate regional flood elevations (see Table 2.). K. All NEW CONSTRUCTION, replacement of existing structures and SUBSTANTIAL IMPROVEMENTS shall be anchored to prevent flotation, collapse or lateral movement of the STRUCTURE and to withstand hydrodynamic loads. The conveyor bridge itself will be anchored to the abutments, and will have slightly more than three feet of freeboard compared to the intermediate regional flood elevation (low chord = 4873, IRF w.s -- 4869.61). Hydrodynamic force calculations are summarized in Table 1. and presented in (Appendix B). Portions of the conveyor leading up to, and away from the bridge could potentially fall in a large storm, but due to the relatively shallow flood depth (0-1 foot in the overbank), low velocity (1-2,ft/s in the overbank), and weight of the conveyor, it is unlikely to travel significantly. Additionally, since the conveyor only occupies a small portion of the total floodplain width, water will have the opportunity to move around the conveyor. O. All NEW CONSTRUCTION, replacement of existing structures and SUBSTANTIAL IMPROVEMENTS within any AO Zone shall have the LOWEST FLOOR, including the BASEMENT floor or MOBILE HOME PAD, ELEVATED to or above the REGULATORY FLOOD DATUM. The conveyor is the only new construction proposed for the project, and the conveyor bridge is elevated above the regulatory flood datum (low chord= 4873, RFD= 4870.61). 20 REFERENCES U.S.Army Corps of Engineers, 1977. "Technical Write-Up St. Vrain and Boulder Creek, Colorado" U.S.Army Corps of Engineers, 2010. "HEC-RAS River Analysis System, User's Manual," The Hydrologic Engineering Center, Davis, CA, Version 4.1, January. QED Associates, March 7, 2008. "Floodplain Analysis—Boulder Creek,Town of Frederick Weld County, Colorado" p. 5. Mine Safety and Health Administration, "30 CFR § 56.9300 Berms or guardrails," Department of Labor, Davis, CA, Retrieved June 2011 from httn://www.msha.gov/30cfr/56.9300.htm Weld County Code "Sec. 23-2-480, 23-2-490, 23-5-250, 23-5-260" Retrieved June 2011 from http://www.colocode.com/weld/weld_23_a2.pdf Chean Chin Ngo, Kurt Grammol , "Fluid Mechanics Example" Retrieved June 2011 from http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=fl&chap_sec=02.3&page=example C.R. Nave , "Forces in Car Crashes" Retrieved June 2011 from http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html#cc 1 21 FIGURES • FHDP Application • Deed and Legal Right to Enter • Existing Conditions Site Map (Full Scale) • Existing Conditions Site Map (Project Area) • FHDP Map (Proposed Condition, Full Scale) • FHDP Map (Proposed Condition, Project Area) • Conveyor Bridge Typical Plans • Preliminary Reclamation Plan 22 FLOOD HAZARD DEVELOPMENT PERMIT (FHDP) APPLICATION FOR PUBLIC WORKS DEPARTMENT USE DATE RECEIVED: RECEIPT/AMOUNT# 1$ CASE#ASSIGNED:_ APPLICATION RECEIVED BY PUBLIC WORKS REVIEWER: Parcel Number: 1313-16-0-00-031, 1313-09-0-00-004, 1313-09-0-00-003, 1313-08-0-00-030 (12 digit number-found on Tax I.D.information,obtainable et the Weld County Assess or's office,orwww.co.weld,co.us). Waterway Name: Boulder Creek — Flood Insurance Rate Map (FIRM) Panel#: 080266-0850-C Legal Description AlI of the SE 1/4 of the SW 1/4 of , Section 16 , Township 02 North, Range 68 West * see attached legal description FEE OWNER(S)OF THE PROPERTY: Name: Aggregate Industries Work Phone# 970-396-5252 Home Phone# _ Email Address Connie.Davis@aggregate=us.com Street Address: 1 707 Cole Blvd, Suite 100 _ City/State/Zip Code Golden, CO 80401 _ APPLICANT OR AUTHORIZED AGENT(Sae se+ow:Autheezeeee must eccompeny aN appricabons signed by Authorized Agent) Name: Blue Earth Work Phone# 970-227-2803 Home Phone# Email Address bill@fiywatcr.com Street Address:] Lj3ox 973 City/State/Zip Code Fort Collins, CO 80522 1. General Description of Proposed Development: (Please check all that apply) Residential Non-Residential Manufactured of Mobile Home D New Construction ® New Construction D On Single Lot ❑ Addition or improvements ❑Addition or Improvements 0 In Mobile Home Park Li In Subdivision ❑x Fill Material U Fill Material ❑ Fill Material ❑ Watercourse Alteration ❑ In Mobile Home Subdivision Other 2. Brief Narrative Description of Proposed Development: Owner proposes to mine and process mineral resources __-_- at the property. _-- 3. Property located in designated FW(Floodway) District? Yes No X - (If yes, certification and engineering calculations shall be provided by a registered Professional Engineer(P.E.)that the property use or structure,when built, will not cause any increase in floodwater levels during an intermediate regional flood (100-year flood)and will not limit or restrict the flow capacity of the tloodway.) Site is within ZONE A(appx.) Floodplain. No official floodway delineated. See attached HEC-RAS sales. 4. Is the property located in a designated FP-1 (100-yr Floodplain)or FP-2(500-yr Floodplain) District? Yes No it ' _ONE A(appx.)ap 100-yr Floodplain, Agent Qate Signature: Owner or Authorized Agent Date Signature: O er or Authorized g g g (If an Authorized Agent signs,a letter of authorization from all fee owners must be included with the application.If a corporation is the fee owner, notarized evidence must be included showing the signatory has to legal authority to sign for the corporation.) Updated 03-13-2008 6 July 18,2011 AAk Mr. Clay Kimmi Weld County Department of Public Works AGGREGATE P.O. Box 758 INDUSTRIES Greeley, Colorado 80632 RE: Authorization Letter for Blue Earth d/b/a FlyWater,inc.; Aggregate Industries— WCR, Inc.; Tull Property FHDP Dear Clay: We authorize Blue Earth, P.O. Box 973. Fort Collins, Colorado, 80522, to perform work and submit material for the Tull Property Flood Hazard Development Permit application on behalf of Aggregate Industries- WCR, Inc. Aggregate Industries - WCR, Inc. Name(Printed) Name(Signature) Title Z— //f.-- Date Aggregate Industries w.st Contra'Raglan,Inc. 1707 Cole Blvd.,Suite 100 Golden, CO 80401 An Equal Opportunity Employ.r Telephone:303-985-1070 i<li OWNER'S POLICY OF TITLE INSURANCE • sSUE.D igv TRANSAMERICA TITLE INSURANCE COMPANY i : SUBJECT TO THE EXCLUSIONS FROM COVERAGE.THE EXCEPTIONS FROM COVERAGE CONTAINED IN SCHEDULE B AND THE CONDITIONS AND STIPULATIONS.TRANSAMERICA TITLE INSURANCE COMPAdIY,a California corporation,herein called the Comps• try.insures,as of Date of Policy sham In Schedule A.against loss or damage.not exceeding the Amount of Insurancesrned in Schedule A.sustained or tuned by the tenured by twos of: I. Tole to the ate a brined de tbd is Schedule A being vested other this as surd therein: 2. Any detest is a km or eacuminame oe the lid& J. UnmarketaNBty of the We; 4. Leek of a right of moat to sad from the lad. The Company till also pay the ebb attorneys'fees and expenses Incurred in defense of the title,as insured.but only to the ateat provided in the Conditieea and Stipulation& IN WITNESS WHEREOF.TRANSAMERICA TITLE INSURANCE COMPANY has caused its corporate name and seal to be hereunto affixed by its duly authorized olfscers,the Policy to become valid when countersigned by an authorized officer or agent of the Company. TRANSAMERICA TITLE INSURANCE UR ,L COMPANY if. `4`-a imflP�,w gy�,��/i/�4'sG�L+ By: _ i��I /_ _ _ . JI s -anima Authorized zed Countesigeaarc gswtfd/P/raPresident %, aaya&yea � 'e Attest: Secretary EXCLUSIONS FROM COVERAGE The following mamas art expressly taeltded from the coverage of this policy and the Company will not pay km or damage,at,attorneys' fees or expect which aria by meson of: I. (a)Any law,ordinance or governmental regulate (trading but not limited to building and zoning lam, ordinances. or regulatioes) misting.regulating,Prohrliting or relating to()the occupancy,os,in esgjoyment of the lend;(tai)the character,dimensions or location of any improvement now or hereafter meted on the land;(iii)•separation in ownership or a cbaage in the dimensions or are of the land or say parcel of which the bed la a was a part;or(m)env ronmental protection.a the effect of any violation of these lam,ordinances or treatments]regulations,except to the extent that a notice of the enforcement thereof a a notice of a defect,bee or encumbrance resting from a violation a alleged violate effecting Nc land has been recorded in the public tecosde at Date of Pokey. (b)Any perienents1 pot punier sot adudd by(a)above,ate to the eteat that a notice of the ester thing or a norice of a defect lien or eneumbesea resulting from a violation or alleged violation alfeetlne the Mad has hex traded in the pubic records at Data of Policy. 2. Rights of tint domain odes notice of the anon thereof has bees recorded in the public nude as Dee of Policy,but not excluding from coverage any taking which has otrund prior to Date of Policy which would be binding on the sights of a purchaser for value without knowledge. 3. Defect.Its,encumbnse,adverse claims or other mantra (a)mated,leered,assumed or to by the inured claimant; (b)not known to the Company,sot recorded in the public records at Date of Policy.but known to the insured dalwnt and not disclosed la writing to dm Companyby the bound&t nt prior to the date the brand claimant became en bumf under this policy; (o)eking in so Ion or tone to the insured claimant: ii (d)attaching or crud ebeequent to Date of Policy;or (e)resulting In loss or damage which would sot have been s aiad d the imbed&beast bad paid value tot the estate a interest insured by ibis pokey. Et I Mrbss Lund it Associate Owner%Policy(102147) Valid Only If Schedule A,Band Cover Are Attached ' Foos Paps t • TRANSAMERICA TITLE INSURANCE COMPANY • POLICY OP TITLE INSURANCE SCHEDULE A Amount of Insurance: Policy No. : 8033230 Date of Policy: November 19, ' 1993 at 7:00 A.M. . : 1. Name of Insured: Cooley Gravel Company, an Indiana Corporation 2. The estate or interest in the land described herein and which is covered by this policy is: FEE SIMPLE The estate or interest referred to herein is at Date of Policy vested in: Cooley Gravel Company, an Indiana Corporation 4. The land referred to in this Policy is described as follows: (SEE ATTACHED PAGE FOR LEGAL DESCRIPTION) ' I • • • TRANSAMERICA TITLE INSURANCE COMPANY Policy NO. 1 8033230 LEGAL DESCRIPTION All of the SE1/4 of the SW1/4 of Section 9 and all that portion of the NW1/4 of Section 16 and the E1/2 of the NE1/4 of Section 17, all in Township 2 North, Range 68 West of the 6th P.M. County of Weld, State of Colorado, lying Easterly of the following described line: Commencing at the W1/4 corner of said Section 16, thence North 89 degrees 45 minutes 11 seconds West 537.53 feet along the South line of the SE1/4 of the NE1/4 of said Section 17 to the True Point of Beginning; thence North 30 degrees 38 minutes West, 150.48 feet; thence North 6 degrees 00 minutes West, 246.93 feet; thence North 2 degrees 39 minutes East, 138.97 feet; thence North 4 degrees 55 minutes East, 98.72 feet; thence North 19 degrees 27 minutes East, 264.79 feet; thence North 30 degrees 30 minutes East, 527.03 feat; thence North 39 degrees 50 minutes East, 201.97 feet; thence North 31 degrees 04 minutes East, 214.87 feet; thence North 29 degrees 51 minutes East, 192.91 feet; hence North 32 degrees 34 minutes East, 189.73 feet; ence North 29 degrees 10 minutes East, 104.43 feet ence North 8 degrees 14 minutes East, 277.70 feet; thence North 10 degrees 20 minutes East, 113.48 feet; thence North 27 degrees 51 minutes East, 196.67 feet to the North line of the NW1/4 of said Section 16 and the Point of Termination from which the Northwest corner of said Section 16 bears South 89 degrees 30 minutes 16 seconds West, 327.96 feet. 41 Page 2 z For el tics use only 012 0#14011Yeti a:Ssareery of ILta Copaa5aas tseBaa Please include a typed 7500 Ereeday,Sulu 200 sex eddmessd ahnvelope Denver,Co 51202 p03)swum ; 961169375 C $25.00 • KNIT OE TYPED Fax (303)ISb2242 SECRETARY OF STATE FLSG FEE:$25.00 12-30-96 08:54 MUST tCOPIES FM(o10skt APFUCATION FOR AMENDED AUTHORITY Pursued to the provisions of the Colorado Business Corporation Ad.the urdersisned aaporallon hereby apples for an Amended Au5horly and dries: FIRST: The net*al the corporation is Cooley Grand Cowpony SECOND: If the carponde name was not avaAYfk.the assumed name of the corporation c THIRD: ❑ (Check NAppsoable) The corporate name of the oonporatlon has become available in Colorado and the corporation dere to amend is Authority to rated the corporate name on the records dive Secretary ofStele. ❑ The corporation has evaded the pedal d duration In Its Adidas of *corporation to: X The corporation hes dhenprt i name to CAMAS Cots WC. ❑ The name which f elects to use in Colorado is: Of Its corporate name is not avdlabk to use in Colorado) ❑ The oapastion ha redaneetkaad from to FOURT1t This eppkatlon is accompanied by■Certificate of Fact,ddy aultanYoMed by the proper nicer in the stele or country of inoapondlon(a redonasYos&on as theme cony be)cen yin0 the detemrgs)made above. Comet OMvaaCoerPrAm QOMPUIER U O TE COMPLETE Titre Y • eV STAIR Or DRUM oprlca OP Tae Y11QAaT OW STATE AIMICISS OF A1a7OOr To Wba These Presents Comm, Cresting: WHEREAS, there has been presented to me at this office, Articles of Amsodsant for: COOLIE MATTE, OMAR and said Articles of Amendment have been prepared and signed is accordance with the provisions of the Indiana Business Corporation Lew, as amended. The Dena of the corporation is amended as follows: CAMS COLORADO, INC. NOW, MIRROR, I. SUE ANNE GILROT, Secretary of State of Indiana, hereby certify that I have this day filed said articles in this office. The effective date of these Articles of Amendment is December 31, 1996. /6 �� i •(�....••.••••••• In Witness Whereof, I have hereunto set my /44.-/ t _ ,/ t••gl,I hand and affixed the seal of the State of :Z led* 1 Indiana, Indianapolis,at the City of Indianapolis, this sr* 0 Twenty-third day of December , 1996. I W.� ;._ ilb •••,t • - #,� SUE ANNE GILEOY, Secretar f State ly0�x./ CAMAS America,Inc. 3333 South Wadsworth BcSsnrd Suite 210 Lakewood Colorado 10227 Telephone(303)907.2300-Fan4M.(303)987.9079 Novanber2l, 1996 7 ak • TO WHOM IT MAY CONCERN: CAtNAS A DUO 0 p1� CAMAS ine, Delaware corporation,dba in Colorado as CAMAS America,Inc.,does hereby consent to the use.of.Manama,CAMAS Colorado,.lnc.by its affiliate,Cooley Gravel Company, an Indiana corporation. CAMAS inc understands that Cooley Gravel Company is tiling arequest-furreservation lathe name CAMAS.Colorado,Inc.and will,indue worse,change itrnane. Sincerely, . / RANDALL R.BEESO Vice President Financial Administration CAMAS inc dba CAMAS America,Inc. g:\tax\cailspecproj\res W 14 aYwa-1,q,_s Cando AN ew, Cooley Gael Company lame.u.r. aw>,Minn"a.aa.Pk*arvn 1.,.a° .ARTICLES OF MERGER c %memrt tommesocreval or Or 19@lniE DAB OF °ig"Z v. CAMAS COLORADO,INC„�Qtt \y��\Oy5o5\aLgph_ an Indiana corporation AND AGGREGATE INDUSTRIES-WCR, INC.AQC 1.AOO\1cJt'L%y a Colorado corporation 16W�1bO'R-� 20001253933 C To the Secretary of State f 110.00 State of Colorado SECRETARY OF STATE... 12-27-2000 14:31:18 Pursuant to the provisions of Section 7-111-105 of the Colorado Business Corporation Act, the domestic business corporation and the foreign . business corporation herein named do hereby submit the following Articles of Merger. 1. The name and state of incorporation of each of the constituent corporations participating in the merger is as follows: Name of Corporation State of Incorporation CAMAS Colorado,Inc. Indiana ("CAMAS") Aggregate Industries -WCR,Inc. Colorado ("AI-WCR") 2. Annexed hereto and made a part hereof is the Plan of Merger for. merging CAMAS. an Indiana corporation with and into AI - WCR, a Colorado • corporation as approved by Unanimous Written Consent of the Board of Directors of • CAMAS on December 22, 2000, by Written Consent of the Sole Shariholder of CAMAS on December 22, 2000, by Unanimous Written Consent of the Board of Directors of AI-WCR on December 22. 2000, and by Written Consent of the Sole. Shareholder of AI-WCR on December 22,2000. 3. The number of votes cast for the Plan of Merger by each voting group of CAMAS entitled to vote separately on the merger was sufficient for approval by that voting group. 4. 'The number of votes cast for the Plan of Merger by each voting group of AI-WCR entitled to vote separately on the merger was sufficient for approval by that voting group. COMPbrat UPDA7a 0QMPc.ETE • • • • 5. The merger herein provided for.is permitted by the laws of the • jurisdiction of organization of CAMAS and is in compliance with said laws. 6. AI-WCR will continue its existence u the surviving corporation upon the effective date of the merger pursuant to the provisions of the Colorado Business Corporations Act. 1. The executed Plan of Merger is on file at the principal office of AI- WCR,which is located at 3605 S.Teller Street,Lakewood,Colorado 80235. 8. The effective time of the Plan of Merger shall be 11:59 p.m.M.S.T. on December 31,2000. • [SIGNATURE PAGE FOLLOWS] • • • • • • • 2' • The foregoing Articles of Merger are hereby agreed to and executed. CAMAS COLORADO,INC., an Indiana corporation BY: FMy-iJ"` . CA.L.ie - M.Addams,President AGGREGATE INDUSTRIES:WCR,INC., a Colorado corporation By: tiAOS AS.. Chita- - M:Addams,President • PLAN OF MERGER OF. CAMAS COLORADO,INC.,an Iatlaoa=pondfen WITH AND IlYTO AGGREGATE INDUSTRIES-WCR,Met a Cobras acportlfes PLAN OF MERGER approved on December 22,2000 by CAMAS Colorado,Inc., a business commotion&S Sots of Indiana("CAMAS"),and by resolution adopted by ha Beard of Direct=on said dad and approved on December 22,20011 by Aggregate Industries-WM.2m.. a business caparadoo agonized under the laws of the State of Colorado ("AI-wCI"), and by resolution adopted by its Board ofDirectors on acid date. 1. M 11:59'p.m. M.S.T. on December 31, 2000 (the "effective time.and date") CAMAS shall, pesos to the provisions of the Indio*Badness Carpoatiat Law end of the Colorado Busies Capered= Act, be.merged with and into AI-WCR, which loll be the surviving corporation et the effective time and sire of the merger and which is sometimes hereinafter tdamd to as the 'surviving''corpotadon", end which shall continue to exist as said surviving corporation under its present none pass to the provisions of the Colorado Business Corporation Act. The seprae existence of CAMAS,which is sometimes bemire teuefeued to as • the"taem+.dng copporntion , shall cease at the effective time and date in accordance with the provisions of the Ivdana.Bnsi.esa Corporation Law. 2. The Articles of Incorporation of the surviving corporation as in free and effect • at the elective tine and date of the merger hi the State of Colorado shell be the Articles of Yacarpostion of said surviving corporation and said Midas of Iocapariou shall eon.=in sal force and.ofhat wall=coded aid=aged in the maws pauaaibed by the laws.of the Stye of Colon= • • 3. The bylaws of the surviving corporation a in face sad tact at the eflbcdve time and date oldie merger will be the bylaws of rid surviving mpoad=and will continue in lull farce and effect mil di epd, egged, or amended sa detain provided and iu the manner peeettibed bythe provide.'of the laws tithe Sete of Caaando. 4. The.drectars aid officers in office of the surviving corporation upon tie effective de of the mew shall be the mambas of'the fiat Bard of Directors and.die first soma of the surviving corporation,all of whom shall hold their di reetaa'hipa mod aurora until due election and qualfadat of their respeetve success=or until their ammo is otherwise amino= in accedence with the bylaws of the surviving corporal= 5. Each Sand shwa of the ter>®rdng corporation IS!!.upon the active dais of the mags be convened into five shares of the'arriving wrporatoa,and the land'hatm of the • =abutting cognition shall be canceled. The issued"hares of the surviving c pon.=shall not be converted in any maser. 6. The elan of Merger herein made and*roved shall be submitted to the sole shareholder of the tenninoing couplan for its g1O°d or rejection in the moiler panscdbed by the provisions of the fathom Bu®eae Capitation Law and to the sobs slrreholder of the surviving of the State of asaspersion for its appeals' a mjecdcn in the asermer pneribed by the laws 7. Edo Plan of Merger shell have been approved by the sole shareholder of the aarminedng corporation in thermoset prescribed by the provisions of the bdIsoa BMWS Capaadoo Law and by the sole sheadeader of the surviving carpaadon in amphorae with the laws of the Sale of Colossd%the terminating corpsman and the:riving corporation hereby stipulate tit they will cane to be executed and filed and/or mcaded any doatment a document proem-beet by the laws of she Sate of Indiana and by the State of Colorado.and that they will cause to be perfmrtoal ail necessary act therein and elsewhere to effectuate the merger. 8. The Board of Dheaas and the proper officers of the floating n end to do of the aaviving cotpontien,teepeadv'ely,ate hereby authorized,empowered. and climessd any and all ads and thing, and to make. exeasse, deliver, fibs, and/or mooed any and all instruments,papers,and documents which shall be or became aeaaa"Y,proper.a convenient to say out a!rat into effect any of the provisions of this Plan of Meagr or of the merger herein provided for. 9. The effective time and elms of the merger Stein provided for in the State of Indiana shall be 11:59 p.m.M.S.T.co December 31,2001). • [SIGNATURE PAGE POILOVISJ • • t Isnot P\ZD-01.3 M x4\ra re'O•s' ew\m•s.l.la..IT a..n.••(s—.4q vw.or art is-l• a.2 ,• u WI - vM-SO t.a.o mw ICS cw-aa+sq Iw-naj frs-+U fm-l.tal PAM filviilig mil('(/'?Yi ) c /! // • C� s \ -I 1 -. / i / 1 „ �+ a I __142--,,p) 1r k ' f#* V{. ,.7 / I ~. 1 �' '( } , %I / �, ' ; , �� I kI' t rr J I } II 111 , / , /_ `. L� , ` -V�� < w . 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O aY 34 / / *.E. s N �� O�xJ�p � 1 I Q w Laoj i Yom ¢a $ C !f \\ Y F z s� \ Y!E I 0 o x inaa il �.�.' a i T Y /r ,�, \\\S .... -�-t 8 7 I -\ S / \J j \ i APPENDIX A. EXISTING FLOOD INFORMATION • FEMA Flood Insurance Rate Map (FIRMETTE) • Avocet Subdivision LOMR Study Report • 1977 Army Corps of Engineers "Technical Write-Up St. Vrain Creek and Boulder Creek, Colorado." 23 } I lI KEY TO MAP 1 nI \ ), SOO Va.'load toondary - • _ i ki ..' 1 Yi I �, +- IbarurMoodtel,nd.n• _ ZONE t, i 2,rn.0eY velour.• QV \T r 1 a i LOO yea flmd totnavv ZONE B w 3' 1 SOD e...Mood toenelety - CO f r BeM Flood Elevation Lint SF7.• Mtn[onto.in 1 ste• � •'' --- .1— to 2 r - — � tea Floe(Lie...M feel 1E096( 17-ins..„ 1 I I Whet Undo.,Widdn Zo..•• - q Memel.tekonu Mars RM7x • ( tin, Moe eMl.b -T.., LIBERTY •' "• •� •I _ �;`1� •N.terMcad to thr ration.,Geodetic vu focal OaNII of 1929 1 `� 'p �L_- ___ i - 1- -_ --,,__.- -_ 7, : �' i •'CXPLANATIONOF LONE OISIGNATIONS _` 1:.__ I I — q-7;r I I 'n ��F� 2000 E%II ANATMN r -� `1 1'' a Area,sr 10Zy.a• lead Oise Rood Nava:km.NS 1 ,I TORO.u,.0 leetannut dolt-,wed. 2 `r•.%t I' an Area.or 106Teer dm.. O.n.o. ..ere .00,1I Tl t aa oetroen OM(I)$00 I04,!1)reef( 11R depth, of 1yndaten are NOrn•but no reed hazard letters 3 2T i le determined �' . ', AK Are. M IODy.r Nadu. flooding where deptnt II ; X; ZH ti !0 !' an xwsn one I II 00$t Ylr«^oodteat, (.0no.factors 4l ea.p.n.s 4.l,,rood no 1. , ZONE C ''f. y - ' Al.Am A..a,or :00wr Rood,bete need flees..and 1- I flood hatard fKte.1 de%nT.red. .) /So'do'm I 1 1 - ' I R•reamer ' Alt Areal or 1 ly year flood o ha o0norflot,••10 noted - J I �� em..� uoflor hazard t 10 flood ' '- � � I I - � d and rd remote net eeaemww6 I / I Wm ,,. t Ann.,between 'nrl,of Lee'00,.,1 Rood and SOD- '__--_ L_ -- --t__- i. ._ ". --- . _ __ - year g*IN enemy deputen then one I(00,00 When 1I �KIRKLAND .-�r•.. .1 I. If �� I--? UM emplewlnh ain�.Arta It Iett Nan one...re 11 I •k,or Ner protected by la..from Ora Ore rood 'I 11 I . (, (MMNm Wading] I, I I C Monist mini.]$110041.0 INo 101.104) I0 Are.,oh vndoloo000&bur po..br..flood Numd, I V Moo of'00-year Do.*rood woeh a achy(w1. I _ • (1 ea..);bae Rood elevator.and flood heard 1.1,04, not d.xrmmld. V1 850 Area of i®-Von,co,a1M need 0110 mans'tame t4 35 m r 0.4 Idolt•eak and flood Nerve fatten g( Lfj !3 II F NOTES TO USER I ''�� -. lr Cent.Amos not in W.TWIT!ROW hn✓6 moat(tor.A and VI F ,:I. 45 may k noaacted by Rood 0001001,vuam.u. l�y /., t Mils map N roe flood Wewanee pvrpe,e on,T,1t dou not..tea '• _J L -="� - ----- - -,i .J .`. tartly Oro.m tnao unbent to flooding in the oarwmu0Ny o• I .10....., r.___ T r _ __._ _ Ir _. __.. -``._.-. _. _ i "j, �I pWrbeUdt ketone ovoid.tpeeo'/Mod hazard areas. 1710 r� i" I I -1t., For Ad...mop pawls,tea so meardY premed Indav TO Mao \`�\ j I'emlt • _ --__ I fit�� 0ESit° I 1 I I T.'` x 4 �� INITIwARCH 1In 1978 — MARCH:1.1070 F I ^ (1000 IOUN0ANY MAP REVIZ1004 II LI J \l, F i � II it - If I ii •- I oLOOD rYtuwANGt doll MAI EFFECT', l.� _ _ MARCH'8 '980 - �.,_O 1 _ . 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'''II I'edam Mnerpanly mene8emen,awn 7y "A MICHAEL BAKER JR.[INC FRAME FLOODPLAIN ANALYSIS - BOULDER CREEK AVOCET SUBDIVISION TOWN OF FREDERICK WELD COUNTY, COLORADO Prepared for: LUKE STROMQUIST 1649 METROPOLITAN DRIVE LONGMONT, CO 80504 Prepared by: QED Associates QED ASSOCIATES 204 WALNUT STREET, SUITE C FORT COLLINS, CO 80524 MARCH 7, 2008 TABLE OF CONTENTS Table of Contents 2 Project Description 3 Project Scope 4 Hydrologic Analysis 5 Methodology 5 Results 5 Hydraulic Analysis 6 Methodology 6 Results 6 Appendices 7 Page 2 3/7/2008 PROJECT DESCRIPTION The Avocet Subdivision project is a proposed 10 lot minor subdivision located in recently annexed areas of the Town of Frederick, Colorado. The project site is located near the intersection of Weld County Road (WCR) 5 and WCR 18 as shown in the following vicinity map: 40nymont 1 1 i 3�.�Y4 ! `" ' i,,,,' v-.I� I Flreston fj} :.: . ? ric_ G} j 4 �� Ilr f .. a r 'S 4 1 Pi , i, ISl f j> ITEI .4 , I a; N.T.S. r L �' I � ;g ;. I The project can be characterized as a large lot rural subdivision. The proposed land use is single-family residential. A portion of the project is located within the approximate Zone A regulatory floodplain along Boulder Creek. As currently planned, lots I, 2 and 3 are located within this 100-year floodplain. The remaining 7 lots are located outside of the floodplain. This area is shown on Flood Insurance Rate Map (FIRM) Panel 080266 0850C for Weld County, Colorado It should also be noted that the areas along Boulder Creek has experienced significant mining activity subsequent to the currently effective approximate floodplain delineation. Much of this mining activity has occurred within the floodplain limits, resulting in significant topographic changes within the study area. This has also resulted in floodplain topography that is extremely variable and irregular. Page 3 3/7/2008 PROJECT DESCRIPTION The Avocet Subdivision project is a proposed 10 lot minor subdivision located in recently annexed areas of the Town of Frederick, Colorado. The project site is located near the intersection of Weld County Road (WCR) 5 and WCR 18 as shown in the following vicinity map: I i longmoNl i If`i f f• S ., j A ' lit ' E. ) r ii I I I I j r I i 1 ITE ;' 4\be. N.11.S. E �. I (1 4 ' , I t , l I /J The project can be characterized as a large lot rural subdivision. The proposed land use is single-family residential. A portion of the project is located within the approximate Zone A regulatory floodplain along Boulder Creek. As currently planned, lots I, 2 and 3 are located within this 100-year floodplain. The remaining 7 lots are located outside of the floodplain. This area is shown on Flood Insurance Rate Map (FIRM) Panel 080266 0850C for Weld County, Colorado It should also be noted that the areas along Boulder Creek has experienced significant mining activity subsequent to the currently effective approximate floodplain delineation. Much of this mining activity has occurred within the floodplain limits, resulting in significant topographic changes within the study area. This has also resulted in floodplain topography that is extremely variable and irregular. Page 3 3/7/2008 PROJECT SCOPE The purpose of this study is to incorporate new topographic and hydrologic information into the currently effective approximate floodplain analysis in support of a Letter of Map Revision (LOMR). This will provide a more accurate floodplain boundary and Base Flood Elevations (BFEs) along the portion of Boulder Creek that affects the Avocet Subdivision. These BFEs will ultimately be used to support a Conditional Letter of Map Revision Based on Fill (CLOMR/F) or a Letter of Map Amendment (LOMA) depending on the final results of the LOMR. Boulder Creek is not currently studied in detail throughout Weld County, which includes the area of interest. The 5.5 mile reach of Boulder Creek lying with Weld County is shown as approximate Zone A. However, the upstream portions of the creek that lie within Boulder County were studied in detail as shown on the currently effective Flood Insurance Study (FIS) for Boulder County, Colorado. The downstream limit of study for the hydraulic model is located at the county line, which is located approximately 3 miles upstream of the Avocet Subdivision. Although the hydraulic model does not extend downstream to the area of interest, the hydrologic study extends all the way to the mouth of the creek, which is located approximately 2.5 miles downstream of the Avocet Subdivision. Therefore, currently effective hydraulic information is not available, but currently effective hydrologic information is available throughout the area of interest. The scope of this study is to use the currently effective hydrologic information in conjunction with new hydraulic modeling to define the 100-year floodplain for the portion of Boulder Creek that affects the Avocet Subdivision. The appropriate FEMA forms for a Letter of Map Revision are included in the Appendix. Page 4 3/7/2008 HYDROLOGIC ANALYSIS METHODOLOGY Boulder Creek is not currently studied in detail throughout Weld County. However, the upstream portions of the creek that lie within Boulder County were studied in detail as documented in the Boulder County Flood Insurance Study (FIS). The hydrologic analysis for Boulder Creek encompassed the entire creek, all the way to its confluence with St. Vrain Creek. The area of interest for the Avocet Subdivision lies totally within the limits of this currently effective hydrologic analysis. This new floodplain analysis does not propose to modify the hydrologic results of the currently effective Boulder County hydrologic analysis. RESULTS The 100-year flowrate as presented in the previously described hydrologic study is 12,250 cubic feet per second (CFS). Page 5 3/7/2008 HYDRAULIC ANALYSIS METHODOLOGY 100-year flood water surface elevations, also known as Base Flood Elevations (BFEs), are calculated using version 3.1.3 of the Corps of Engineers' HEC-RAS computer program. This program uses a step backwater methodology to estimate water surface elevations from geometric, elevation and other data in the study area. Topographic data for the areas surrounding the Avocet Subdivision are obtained via a new field survey. In order to tie in the results of this study to the currently effective floodplain boundary, it is necessary to use topographic date from USGS quadrangle topographic mapping in the upstream and downstream portions of this study. Using these two sources of data, a composite digital terrain model (DTM) is created within Land Development Desktop 2006. This DTM is used to create cross section station/elevation data for input into HEC-RAS. Manning's roughness coefficients are estimated based on field observation, using standard hydraulic engineering references as a guideline. It should be noted that much of the overbank conveyance areas have been extensively mined, resulting in groundwater and/or lined mining lakes in the overbank areas. This results in unusual cross-sections, where the channel itself is the only remaining "natural" area and the overbank areas are very irregular. The bottom portions of these mining lakes in the overbank areas are modeled as ineffective flow where appropriate. Since the bottom surface of the actual effective overbank flow areas are water, Manning's roughness coefficients in many overbank areas are somewhat lower than those for the channel. Although unusual, this is appropriate in this case because the bottom surface of these overbank conveyance areas is water while the channel itself is lined with native grasses and intermittent light brush. The final proposed HEC-RAS model was checked using FEMA's CHECKRAS program, version 1.4. The HEC-RAS and CHECKRAS output is included in the Appendix, RESULTS The results of the hydraulic analysis are shown graphically on the Floodplain Map and the annotated FIRM, included In the Appendix. The Floodplain map shows the revised delineation and BFE's for the 100-year floodplain. The revised floodplain ties into the currently effective floodplain boundary at cross-sections 120+99 and 167+58, which are the downstream and upstream limits of this floodplain study. Page 6 3/7/2008 TECHNICAL WRITE-UP ST. VRAIN CREEK AND BOULDER CREEK, COLORADO tl, A. Areas Studied St. Vrain Creek was studied in detail from its mouth at the South Platte River upstream to the Weld-Boulder County line. Boulder Creek was studied in detail from its mouth at St. Vrain Creek upstream to Valley View Road near the east edge of Boulder, Colorado. The length of the streams studied was 19.3 miles on St. Vrain Creek and 19.2 miles on Boulder Creek. Stream bed elevations range from 4739 feet above mean sea level (m.s. l . ) to 4889 feet m.s. l . on St. Vrain Creek and from 4843 feet m.s. l . to 5189 feet m.s. l . on Boulder Creek for the reaches studied. Stream bed slopes range from 0.0008 ft/ft (4 feet/mile) to 0.0028 ft/ft ( 15 feet/mile) on St. Vrain Creek and from 0.0035 ft/ft ( 18 feet/mile) to 0.004 ft/ft (21 feet/mile) an Boulder Creek. B. Sources of Data and Records Information on past floods was obtained from the Corps of Engineers and the U.S. Geological Survey (USGS) publication entitled Floods in Colorado,' Water Supply Paoer 997. Stream caging records maintained by the U.S. Geological Survey on St. Vrain Creek and Boulder Creek are described in Table 1 . Cross section data and topographic mapping were provided by the Colorado Water Conservation Board, Weld County, Boulder County, and the Urban Drainage and Flood Control District. The •. r� : t? reach extended from a point approximately 5f miles upstream from the mouth of St. Vrain Creek upstream along St. Vrain Creek and Boulder Creek to the Weld-Boulder County line. Topographic mapping having a contour interval of 2 feet and a scale of l"=400' and l"=200' was established by photogrammetric methods from flights made onliiWt6077,w, The igagewaludy reach extended along St. Vrain Creek from the mouth of St. Vrain Creek upstream approximately 5f miles. Topographic mapping having a contour interval of 2 feet and a scale of 1"=200' was established by photogrammetric methods from flights made onllegrilir TheAMID& extended along Boulder Creek from the Boulder-Weld County line through Boulder County upstream to Valley View Road near the east edge of Boulder, Colorado. Topographic mapping having a contour interval of 2 feet and a scale of l"=200' was established by photo- grammetric methods from flights made onlIMMIIIIPAIN USGS 7.5 minute quadrangle mapping with 10 feet contour intervals at a scale of 1 :24,000 was also used in the study. Bridge data were supplied by Weld County, Boulder Country, the Colorado Water Conservation Board, and the Corps of Engineers. Table I St. Vrain Creek Stream Gaoe Data Approximate Stream Location Drainage Area Gagino Records (sq. mi . ) St. Vrain Creek Lyons 212 Aug 1887 to Sep 1891 ; Jun 1895 to present St. Vrain Creek Longmont 424 Oct 1976 to present St. Vrain Creek Platteville 976 Jul 1 90 1t5 4 to Dec 1906; Apr-Dec Mar 1927 to present Boulder Creek Stream Gage Data Approximate Stream Location Drainage Area Gaging Records (sq. mi . ) Boulder Creek Orodell 102 Aug-Oct 1887; Apr-Oct 1888; 1906-1914; 1916-present Boulder Creek Boulder 129 1889- 1892; 1895-1901 ; 1905-1908 Boulder Creek Longmont 439 Mar 1927 to Sep 1949; May 1951 to Sep 1955; Oct 1978 to present C. Flood History Floods in the St. Vrain Creek and Boulder Creek basins are produced by intense rainfall during either isolated or general storm systems. In addition, there is normally an increase in flows during the mountain snowmelt period which is frequently augmented by rainfall runoff. 2 St. Vrain Creek - Early records of floods in the study reach are fragmented and lacking in detail . Flooding occurred along St. Vrain Creek In 1864, 1876, 1894, 1919, 1921 , 1938, 1941 , 1949, 1951 , 1957 and 1969. Descriptions of past floods that may have affected St. Vrain Creek through the study reach are presented below. June 1864 and 1876 - The storm of June 1864 resulted in a flood the effects of which reportedly "were felt severely" in the St. Vrain valley. The Golden, Colorado Tribune on 31 May 1876 described a flood during that month as covering farmlands from "bluff to bluff" at the junction of St. Vrain and Left Hand Creeks, at Longmont. 30-31 July 1919 - In late July 1919 a series of severe thunderstorms caused flash flooding along St. Vrain Creek. From the Lyons Recorder dated 2 August 1919: "The heaviest and most destructive cloudburst. . . in the memory of the oldest inhabitant visited Lyons on Wednesday (July 30) between 2:30 and 3:45 p.m. It took out all the bridges on the North St. Vrain for about 5 miles up and 5 miles downstream. The Longmont and Lyons water mains up the canyon were torn out in many places. . .miles of roads were torn out along the narrow canyon. The people living. . . along the banks of the river were flooded out, and many abandoned their homes for higher ground and safety. . . .homes ( in the lower part of town) . . .were in a roaring sea of water 2 and 3 feet deep." Another crest on the following day again flooded houses in the lower areas of town and washed out 300 yards of railroad track east of Lyons. The peak discharge on 30 July was later computed to be J c.f.s. The right bank of North St. Vrain Creek was flooded to a width of 300 feet. 22 June 1941 - The largest peak discharge of record on St. Vrain Creek at Lyons is 10,500 c.f.s. on 22 June 1941 . This flood originated mostly on South St. Vrain Creek and the creek peaked very rapidly with floodwaters receding quickly. It is assumed that an extremely localized cloudburst occurred over St. Vrain Creek a short distance upstream from Lyons. 4 June 1949 - The effects of this flood were felt largely downstream of Lyons. Prolonged rainfall and heavy snowmelt runoff kept St. Vrain Creek out of its banks in the rural areas during most of the month of June and bridges, roads, and irrigation headworks were damaged. 3 3 Auoust 1951 - Lyons received 6.3 inches of rain from a cloudburst type storm that began about 6 p.m. on 3 August. This combined with general heavy rains over the basin caused flooding from Lyons to the mouth of St. Vrain Creek. Flood duration was less than 12 hours. Severe damage resulted to the highway along South St. Vrain Creek. In the rural areas downstream from Lyons much shocked grain was washed from the fields. 9 May 1957 - During the night of 8 and 9 May approximately 3 to 5 inches of rain fell over the entire basin of St. Vrain Creek. The rain began about 10 p.m. and stopped about 6 a.m. with St. Vrain Creek peaking at Lyons about I a.m. on 9 May at 3,060 cubic feet per second. The flood damaged and destroyed irrigation diversion works and bridges downstream from Lyons. May and June 1969 - Heavy rainfall combined with snowmelt runoff caused prolonged high flows on St. Vrain Creek. The worst flooding occurred on 7 and 8 May and from 15 to 21 June. Roads and bridges along the stream were extensively damaged, stream banks were eroded, farmlands were flooded. The peak discharge at Lyons was 2,900 cubic feet per second on 7 May. Boulder Creek - Flooding has occurred along Boulder Creek in 1864, 1876, 1894, 1914, 1923, 1938, and 1969. Descriptions of major floods that may have affected the study reach are presented below. 21-23 May 1876 - A general storm over the Boulder Creek basin created flooding on the plains of reportedly 1>i miles wide. Railroad service to Boulder was disrupted. 29 Mav-2 June 1894 - Heavy rains fell over the mountains extending from the Colorado-Wyoming border southward into the Republican and Arkansas • River basins. Rainfall over the Boulder and South Boulder Creek basins was particularly heavy. Rainfall records for a 96-hour period ending at 3 a.m. on 2 June 1894 indicate that the mountain drainage area received from 4.5 to 6.0 inches of precipitation. Rainfall amounts over the high plains gradually decreased from west to east and varied from 5 inches at Boulder to approximately 2.5 inches at the mouth. The mountain rainfall combined with the snowmelt runoff produced the greatest flood known at 4 Boulder inundating the valley during the night of 30 May 1894. Buildings, bridges, roads and railroads were washed away. Computations made 18 years later produced estimates of the peak discharge in Boulder that ranged from 9,000 cubic feet per second to 13,600 cubic feet per second. 1-2 June 1914 - This flood was caused by rainfall on 1 June of more than I-inch in the North Boulder Creek basin near Silver Lake at an elevation of 10,200 feet, thus hastening the mountain snowmelt. The flood, described as the worst since 1894, washed out numerous bridges between Colburn Mill and Boulder Falls. Several hundred feet of main line for Boulder's water system were destroyed. The peak discharge in Boulder was estimated at 5,000 cubic feet per second. 4 September 1938 - A large storm system produced general rains over all the eastern Colorado. The largest amount of precipitation occurred in the mountains where over 6 inches was reported west of Eldorado Springs. Boulder reported 3.62 inches of precipitation from 31 August to 4 September with 2.32 inches falling on 2 September. Eldorado Springs located in the South Boulder Creek basin had 4.42 inches of rainfall . A maximum discharge of 4,410 cubic feet per second occurred near the mouth of Boulder Creek at noon on 3 September. 6-8 May 1969 - This flood was the result of long duration rainfall . Precipitation was heaviest in the mountains, part of which fell as snow. In the Boulder and South Boulder Creek basins, the rainfall continued at a moderate rate for nearly 4 days. Total precipitation for the storm amounted to 7.60 inches at Boulder and 9.34 inches at the Boulder Hydro- electric Plant located about 3 miles up the canyon from Boulder. Precipita- tion amounts totaled 8. 11 inches at Eldorado Springs and 10.05 inches at Gross Reservoir on South Boulder Creek. Peak flooding occurred on the 7th of May on both Boulder and South Boulder Creeks. That gaging station at Orodell recorded a peak discharge of 1 ,220 cubic feet per second. In Boulder, local inflow increased the Boulder Creek peak discharge to an estimated 3,000 cubic feet per second. The peak discharge on South Boulder Creek at Eldorado Springs was 1 ,690 cubic feet per second. Flooding below the confluence of these two streams extended over large portions of the floodplain. 5 D. Hydrology . ✓ LOWER BOULDER CREEK HYDROLOGY ) BOULDER AND WELD COUNTIES, COLORADO 1. GENERAL. This report is a continuation of the Boulder Creek hydrologic studies presented in Volume 5, Appendix H, of the Metronolitan Denver and South Platte River and Tributaries study, which was prepared by the Omaha District, U.S. Army Corps of Engineers, in September 1977. Reference is made to pages 42 through 45 of the study for a description and flood history of the Boulder Creek basin. Plate 61 contains discharge profiles for Boulder .Creek from below Fourmile Creek to above South Boulder Creek. The additional -hydrologic studies presented in the lower Boulder Creek report provide 10—, --50—, 100—, and 500—year discharge profiles for Boulder Creek from South • Boulder to the mouth. 2. PRELIMINARY DISCHARGE PROBABILITY AT GAGE SITE. A preliminary discharge C •probability analysis was made for Boulder Creek at a discontinued U.S.G.S. gaging station located approximately 2 miles upstream from the mouth. Guide— lines presented in Bulletin No. 17 of the Water Resources Council (WRC) were • -..used for the probability analysis. Twenty—eight years of record, from 1927 through 1949, and from 1951 through 1955, are available at the gage site. The largest recorded discharge of 4,410 cubic feet per second occurred on 3 September 1938. A generalized skew coefficient of +1 obtained from a Lorps of Engineers regional study of similar streams in Colorado was used to help shape the distribution. The resulting curve, with confidence limits rand adjustments for length of record, is shown on attachment 1. S. MODELING STUDIES. a. General. Lower Boulder Creek was modeled in the same manner as was Upper Boulder. The EPA Storm Water Management Model (SWNM) was used to model rainfall—runoff characteristics of the basin. Tributary hydrographs developed from SWMM were routed along Boulder Creek by using the Missouri River Division version of Harder' s diffusion routing model. b. Rainfall. Rainfall values for the 10—, 50—, and 100—year 6—hour events were obtained from the Precipitation—Frequency Atlas of the Western United States, Atlas 2, Volume III, Colorado, published by the National Oceanic and Atmospheric Administration in 1973. In each case, a 500—year value was estimated by extrapolating the selected Atlas values on semi— logarithmic paper. Adjustments for depth—area were based on the depth—area relationship presented in the NOAA publication. Adjustments for length of record were made on logarithmic probability paper using•Beard's table of expected probability_ .adjustments for various lengths of record. The spatial variation of the rainfall potential shown in the Atlas for the Boulder Creek basin was simulated by SWMM through the introduction of several hyetographs. The time variation of the 6—hour rainfall for each hyetograph was based on a study of hourly precipitation data recorded during major storms in the South Platte River basin. . Rainfall was distributed over the 440 square miles of the Boulder Creek basin in 1-hour intervals. Shorter time intervals result in rainfall intensities that are not likely to occur simultaneously over basins as large as Boulder Creek. The 6-hour rainfall distribution is given in Table 1 below. • • • TABLE 1 6-HOUR RAINFALL DISTRIBUTION Period Incremental Rainfall Hours) (Percent) • -0-1 4 1-2 8 2-3 19 3-4 50 4-5 11 5-6 8 c. Losses. Mountain losses used in this study were the same as those reported in the Metropolitan Denver and South Platte River and Tributaries -study. These losses are a uniform infiltration rate of 1 inch per hour and a detention storage of 0.05 inch. The infiltration map prepared for the -Missouri River Basin Comprehensive Framework Study indicated infiltration rates ranging from 0.6 to 2.0 inches per hour for the high plains portion of the Boulder Creek basin. A uniform infiltration rate of 1.0 inch per Chour was selected as being representative of the area. (See discussion of losses in the Supplemental Report of the 1976 Flood in the Big Thompson River Basin.) A value of 0.3 inch for high plains detention storage was chosen on a trial and error basis in order to calibrate the model. d. Calibration. The WRC frequency analysis of the gaged data near the -mouth of Boulder Creek was used in the calibration of the SWMM and Harder's routing models. Ten SWMM models provided inflow hydrographs for the Harder's routing model of Boulder Creek from Fourmile Creek to the mouth. Rainfall -was applied to the entire 440 square mile Boulder Creek basin. Infiltration rates and mountain detention storage were selected as described in paragraph 3.c. above. Conveyances for the routing model from South Boulder Creek to the mouth reflected a channel Manning's "n" of .050 and an overbank "n" of .080. A trial and crror analysis of high plains detention storage indicated • .3 Cthat a value of 0.3 inch produced a modeled discharge of 12,730 cubic feet per second at the gage for the 100—year event. After adjusting for an average annual May base flow of 170 cubic feet per second, the resulting 100—year model discharge was 12,900 cubic feet per second. The same procedure was used to determine the 10—, 50—, and 500—year events. The discharge frequency ~° curve derived from these runs can be seen on attachment 1. This curve fits the WRC frequency curve very well. 4. ADOPTED DISCHARGE PROBABILITY PROFILES. The 10—, 50—, 100—, and 500—year modeled discharges (including base flow) were plotted on logarithmic probability paper for the points of interest and a "smoothed" discharge for each of the events was obtained from the frequency curve. These discharges are presented in Table 2 and are shown on attachment 2 as discharge profiles. TABLE 2 CBOULDER CREEK — PERTINENT DISCHARGES Drainage Station Area 10-Year 50-Year 100-Year 500-Year (sq.mi. ) (c.f.s. ) (c.f.s. ) (c.f.s. ) (c.f.s. ) Boulder Cr Below South Boulder Cr 291 3,500 9,400 13,300 27,200 Above Fourmile . "Canyon Creek • 291 3,400 9,400 13,300 27,200 Below Fourmile Canyon Creek 302 3,700 10,200 14,500 29,800 Above Dry Creek 312 2,900 8,900 12,900 27,500 Below Dry Creek 325 3,100 9,200 13,400 28,500 Above Bullhead Gulch 331 2,800 8,600 12,700 27,800 Below Bullhead Gulch 340 2,800 8,600 12,700 27,800 ' Above Coal Creek 347 2,600 8,300 12,200 27,000 ✓ Below Coal Creek 429 3,000 9,400 14,000 31,800 Former Gage Site 438 2,300 7,800 12,500 31,500 Mouth 440 2,000 7,200 11,900 31,400 V N e4 4 N • opoo .1, .. ..i 1 .. T 1 I 1 II I .I 1 , '. I I I., 1 I 1 1 ' , 1 _ ICI I 1 _J 11 , { I I ! j - - - I - I —� 1 =— L = - 1 •-•--.---1--z- I- -. }- 7.--'1 { _ I - .I .. - 1 _ _ - f _ I r_ �_ 1 _ = _ 1 V- -,z:::77-.-.1--=_,-7, L rf--� n .,17 7 — — r -. �.I _ -- — r t �L70 0 F z^EA5? FsDVI �. 7 T / --- f 1 1 1 1 - I. `' �1 I . . 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'_»_..=_._....:� . r ' ......-..... . .... "•N CST. VRAIN CREEK HYDROLOGY BOULDER AND WELD COUNTIES, COLORADO 1. GENERAL. This report is the hydrologic portion of a special study that is being made for Weld County, Colorado. Since the entire St. Vrain Creek basin was modeled in this study, the results are applicable to 4144 Boulder County as well. Discharges for the 10—, 50—, 100—, and 500—year floods are given for St. Vrain Creek from Lyons, Colorado, to the mouth. A map of the St. Vrain basin is shown on attachment 1. • 2. ' BASIN DESCRIPTION. St. Vrain Creek, a left bank tributary to the South Platte River, has its source in the Rocky Mountains west of Long— mont, Colorado. North St. Vrain and South St. Vrain Creeks, which drain approximately 211 square miles of mountain area, join in .the foothills at Lyons, Colorado to form St. Vrain Creek. A gaging station is located C 0.4 mile downstream from the confluence of North and South St. Vrain Creeks. From Lyons, St. Vrain Creek flows in a southeasterly direction to Longmont. Lefchand Creek, a 68 square mile right bank tributary, enters St. Vrain Creek south of Longmont. Flowing in an easterly direction, St. Vrain Creek is joined by Dry Creek and Spring Gulch 3 miles downstream from Longmont. Approximately 1.5 miles downstream from this point, the major tributary, Boulder Creek, enters St. Vrain Creek. The drainage area of Boulder Creek basin is approximately 440 square miles. From the mouth of Boulder Creek, St. Vrain Creek flows 15 miles in a northeasterly direction to its confluence with the South Platte River. A stream gage located 1.2 miles upstream from the mouth of St. Vrain has Ca drainage area of 976 square miles. Elevations in the basin range from 4,740 to 14,250 feet above mean sea level. 3. EXISTING STRUCTURES . Button Rock, Barker, and Gross Dams are the three major structures in the St. Vrain basin. Although none of the reservoirs has a specific flood control function, they provide some residual flood control effects downstream. Button Rock Dam, located 6 miles west of Lyons on North St. Vrain Creek, was completed in 1969 by the City of Longmont and is used for municipal water supply. Barker Dam, located on Boulder Creek 12 miles above the city of Boulder, was built in 1910. Gross Dam was constructed in" 1953 on South Boulder Creek approximately 8 miles upstream from Eldorado Springs. The reservoir is used for storage as a part of Denver's municipal water supply system. CNumerous smaller reservoirs having uses other than flood control are located throughout the St. Vrain Creek basin. Some of these reservoirs provide residual flood control effects, but to a lesser degree than the major reservoirs discussed above. 4. PRELIMINARY DISCHARGE PROBABILITY AT GAGE SITES. a. General. A preliminary discharge probability analysis was made for St. Vrain Creek at the U.S.G.S. gaging stations located at Lyons and at the mouth near Platteville, Colorado. The analytical methods presented • in Bulletin No. 17 published by the Water Recources Council (WRC) were used for each analysis. The results of these studies are discussed in the following paragraphs. • • • • / b. At Lyons. Located below the confluence of North and South St. Vrain Creeks, this gage has records available from 1888 to 1977. The U.S.G.S., in a 1939 field investigation of the 31 May 1894 flood, esti— mated a peak discharge of 9,800 cubic feet per second for this event, which was treated as a high outlier. Since Button Rock Dam has a con— trolling affect on peak discharges at the Lyons gage, only the period of record preceding its full time operation was used in the discharge probability analysis. Button Rock Reservoir was in the process of filling during the 7 May 1969 flood and an estimate of the uncontrolled peak was made for use in the frequency analysis. The 2,900 cubic feet per second peak discharge recorded at the gage was adjusted to 6,000 cubic feet per second by using unit hydrograph ratios. The resulting - frequency curve with a +1.1 computed skew, expected probability adjust— ments, and confidence limits is shown on attachment 2. c. At Mouth Near Platteville. Fifty—three years of record, 1905, 1906, and 1927 thru 1977 were used in the WRC frequency analysis. The 1969 event was adjusted from 10,300 cubic feet per second to 13,400 cubic feet per second in order to reflect an uncontrolled condition. Peak dis— .charges since 1969 appear to have been generated from the lower portion of the basin and did not require adjustment to reflect effects from • Button Rock. The estimated 1894 peak discharge of 15,500 cubic feet per second was treated as an historic event. The computed skew of —.04 was weighted with a generalized skew coefficient of +1.0 obtained from a Corps of Engineers regional study of mountain streams in Colorado. L 3 • Frequency data for these streams is shown on attachment 3. The resulting curve, with a +0.2 adopted skew, expected probability adjustments, and confidence limits .is shown on attachment 4. 5. MODELING STUDIES. a. General. Hydrology for Boulder ?reek was developed in previous studies (September 1977, October 1978, and November 1978) by utilizing the EPA Storm Water Management Model (SWMM) and. the Missouri River Division version of Harder's diffusion routing model. Rainfall—runoff characteristics for the remaining portion of the St. Vrain basin were also modeled by SWMM. Tributary hydrographs generated from SWMM and from the Boulder Creek model were routed by a Harder's model of St. , Vrain Creek. The routing model extends from Lyons to the mouth of St. Vrain Creek. b. Rainfall. Rainfall values for the 10—, 50—, and 100—year 6—hour events were obtained from the "Precipitation—Frequency Atlas of the Western United States, Atlas 2, Volume III, Colorado," published by the National Oceanic and Atmospheric Administration in 1973. In each case, a 500—year value was estimated by extrapolating the selected Atlas values on semi— logarithmic paper. Adjustments for depth—area were based on the depth— area relationship presented in the NOAA publication. Adjustments for length of record were made on logarithmic probability paper using Beard's table of expected probability adjustments for various lengths of record. The spatial variation of the rainfall potential shown in the Atlas for the St. Vrain Creek basin was simulated by SWMM through the introduction of several hyetographs. The time variation of the 6—hour rainfall for 4. \ each hyetogragh was based on a study of hourly precipitation data recorded during major storms in the South Platte River basin. The rainfall distri— bution is given in Table 1 below. TABLE 1 6—HOUR RAINFALL DISTRIBUTION ' Period Incremental Rainfall (Hours) (Percent) 0-1 4 • 1-2 8 2-3 19 3-4 50 4-5 11 5-6 8 c. Losses. Losses reported in previous Boulder Creek model studies were used for the Boulder basin in this study. These losses are a uniform infiltration rate of 1 inch per hour in the mountains and plains, 0.05 _ C . inch mountain detention storage, and 0.3 inch plains detention storage. The detention storage values were chosen on a trial and error basis in order to calibrate the Boulder Creek model. Calibration of the St. Vrain SWMM models (excluding Boulder Creek) also required adjustment of deten— tion storage values. Values of 0.15 inch mountain and 0.10 inch plains detention storage were selected by trial and error. Mountain infiltration rates were set at a uniform rate of 1 inch per hour. In order to cali— brate the St. Vrain model to the Platteville gage, it was necessary to use a. plains area infiltration rate of 0.5 inch per hour. d. Calibration. The WRC frequency analysis of the gaged data at .Lyons was used in the- calibration -of the SWMM model of North and South St. Vrain Creeks. Button Rock Dam was not modeled in the calibration studies because the WRC curve reflects an uncontrolled condition. Infiltration C rates and detention storage for the mountains were selected as described in paragraph 3.c. above. An average annual June base flow of 500 cubic • Cfeet per second was added to obtain the modeled frequency curves shown on attachment 2. The modeled curve without Button Rock Dam fits the WRC curve very well. Calibration of the model to the Platteville gage at the mouth of St. Vrain Creek was accomplished by varying infiltration rates and de— tention storage values on the plains area. The average annual June base flow of 600 cubic feet per second was added to obtain the modeled dis- charges shown on attachment 4. 6. ADOPTED DISCHARGE PROBABILITY. Button Rock Dam was inserted in the calibrated SWMM model of St. Vrain Creek at the Lyons gage and rainfall was applied to the 211 square miles of mountain area. The resulting fre— quency curve is shown on attachment 2. It was found that 6-hour rainfall over South St. Vrain Creek and North St. Vrain Creek below Button Rock Dam generated higher discharges at Lyons than did rainfall over the entire - mountain area. The adopted frequency curve at Lyons therefore does not reflect any contribution to peak discharges from the 109 square miles above Button Rock. The adopted frequency curve at the mouth (attachment 4) was modeled by applying 6-hour rainfall to the 924 square miles of contributing basin area. This curve was developed for existing conditions and with Button Rock Dam in place. Two different 6-hour storms were used in deter- mining the 10-, 50-, 100-, and 500-year discharge profiles shown on attach- ment 5. The profiles above Boulder Creek were produced by centering a storm over the St. Vrain basin above Boulder Creek, excluding the area above Button Rock Dam. From the mouth of Boulder Creek to the mouth of St. Vrain Creek, the discharge profiles were developed by applying rainfall to the entire contributing area of the basin. Table 2 below lists the St. Vrain Creek C- discharges that are shown as discharge profiles on attachment 5. 6 TABLE 2 - ( ST. VRAIN CREEK DISCHARGES Distance Drainage from Station Area Mouth 10-Year 50-Year 100-Year 500-Year ' (sq.mi .) (miles) (c.f.s.) (c.f.s. ) (c.f .s.) (c.f.s.) Confluence, No 211, 102* 31.27 2,040 5,570 8,880 20,260 & So St Vrain r_a Lyons Gage 212, 103* 30.95 2,030 5,560 8,830 20,140 Tributaries Above 111* 27.31 2,480 6,060 8,970 20,270 Below 120* 3,050 6,850 9,750 21,440 Lykins Gulch Above 132* • 21.76 3 ,160 6,890 9,580 19,680 Below 143* 3,690 7,610 10,160 20,500 Dry Creek Above 144* 20.60 3,660 7,430 9,820 19,940 Below 156* 4,110 8,240 10,580 21,200 Lefthand Cr & Above 157* 20.08 4,110 8,240 10,580 21,200 The Slough Below 242* 5,250 10,950 14,850 28,670 Dr; Creek & Above 245* 16.97 5,120 10,790- 14,610 - 28,470 CSpring Gulch Below 274* 6,010 ----12,580 ----16,440 - 31,790 --- Boulder Creek Above 277* 16.37 6,010 --- -12,500 16,440 -_. 31,790 Below 825** _6,110 12 ,500 -16,630 -42,400-- Idaho Creek Above 837** 13.45 .5,910 - 12,140 --- - 16,320 -- 41,590 Below 849** .=6,070 12,500 16,510 - 41 ,960 Right Bank Tribs Above 850** 11.33 5,760 12,350 - 16,350 . . - 41 ,360 v/ Below 881** -5,920 12,900 16,760 41 ,900 ' Left Bank Tribs Above .904** 3.60 5,510 12,370 16,530 40,520L7- . 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V_L r ,s------T p7 cT.t7 .i_ L :--- o- — .1 -L.::—..12-1:::. _ .=-1" .Kt: MQ-.`Ti.i 1--r• r - _ �1-t i_1,-.7r `-i I - - 1 U L-C 1 I I r 1 .1' ; F _- ' '...I,- I .A '.L.i 7..-.7,; / 1. 1 : . . r m N Q� 2 0 0 o 0 0 0 0 0 0 0 0 Or T 0; ChM W 01 CO F CC r0 P 17 N T N N n m m G ter. — �I•- ICr�QUET.ICY IN /o ATT:,C Wt."r 17 /'---- 1 i�Lf— - I I • , C, • - N,� ; , ... ; •.11.\31,b—J �.. .� 1 ;4... 1• f• • I r' r r '' .s.” L.. 3 • I' ::_ j • I 'k j. L:. • ,� '.j..: SBldj VhtiR 1J3� ..._ i 1 ...........»......« ....... -_.•...... .. . ' • _,- _1 r.....,—......:---..-.7.-i...:-:. ... . . 1. 'ti. i.. ...jc.. .. . . --- --- -Y _ :--;.. ..—_ --,re,• ,-..- r . I. .-l::.:-r.-.t;..j,;-.,_ m. __ -•--7.:•••••:-1.7.. ::::::-, — �•. .• — .:: _ is r;: r•--...._... 4:—. _ .. • .I -- = _ — — —! --- ... I; '''''. .I:;:-.7.7 -.••I. •'P ...-- _ - .•I: ......I.: L L.:—.1..,I..,.i...'••••,1- --D �'ii!111 xNvi is ..._ _ - . .i�.1..:,,:.,*•:.1 4;• _' S. 1.. T,• i . - .. I: . . ... •_-1.:_..L • :_ t _:_ Pr: • •--- ...... • •- -. - t ..-7-"": -- -•-• .., - -.-r~ ..•:1:.. .., •;-.. .--,-.1,-. !-=.1:33•.: 0;:t-ti ••• . .• " _•!1.,�:..._ � ..•_ :ms s, y `:i4: ..�. .E.• '•s::.- •U1 - - •_ _ - - - -I: =-'''':..1...1..... .:.::.'...::".i' - • - -- I,.:_ :$:: J_ 7. ' C • E - j Mgrt'yg a- i ___ G.-- _ __I 1_ O •- x32,O AbG b • {l • 2 q _.. i Ill ef er ; K 4 r.. '1 W m a c sc a 1 lJJ G T..'...".. • • q 4 1 11 CC O r > .� W - c7 y a r r L [— . .. .— . V i.: 4 6 0 4 , v N q W ,,, Q 4 CC CC Z L.1 y C ._... ; '. ; !- .,) IJ C A t 1 .• *.:. .io r.e.illa .113!'1•: . .. —.. • l .i• rJ ,• a c o .I c • , E. Hydraulics Water surface elevations for the 10-, 50-, 100-, and 500-year floods were computed using the U.S. Army Corps of Engineers step-backwater computer program HEC-2. The version used was the HEC-2 release dated November 1976 updated August 1977, error correction 01 , 02, modifications 50, 51 , 52, and 53. No high water marks were located from which to calibrate the hydraulic 4 model on St. Vrain Creek and Boulder Creek. Stream gaging data collected at the U.S. Geological Survey stream gage on St. Vrain Creek at Platteville and on Boulder Creek upstream from the mouth were used to compare results from the hydraulic model . Manning's "n" value of 0.040 was used in the - - channel for St. Vrain Creek and Boulder Creek. Overbank "n" values range from 0.070 to 0. 150. Adjustments were necessary in the hydraulic model for overbank roughness and geometry due to the extensive use of the flood- plains for gravel mining. Starting water surface elevations for St. Vrain Creek were established from stage-discharge relationships on the South Platte River developed from Special Flood Hazard Information, South Platte River, Volume I Weld County, Colorado, published by the Corps of Engineers to April 1977. -Starting water surface elevations for Boulder Creek were established from stage-discharge relationships developed for St. Vrain Creek as a part of this study. Bridges in this study were analyzed in accordance with the U.S. Department of Transportation/Federal Highway Administration's publication entitled Hydraulics of Bridge Waterways, dated 1970. The determination of water surface profiles and flood boundaries was especially complicated along portions of Boulder Creek because of the extensive modification of the floodplain due to gravel mining operations. These- operations have resulted in a floodplain typified by dikes and ponds of irregular shape and size. Because the integrity of these diking systems is unknown when subjected to floodwaters, the most conservative analysis was utilized. This consisted of assuming the diking system was intact for computation of flood discharge. 7 !-4-r--4--,- t, . , 1_. .. ,J-DTI. ' ..-.t..+-1-i- j-{ ± . _ - 1t' ' I j !""F}'y'Tt" t I r-•--. 1 .T-Y_ -.."' ' ''' :I 1 s Sf- 4 __l_ Ili, , , 1 1 , } ! '---t- , -1-1—Y-1"t_ - *---4--1---0- i - �a� u' -4---;,- __-_,_r___-___! _ _i I T __.." ( �"1- . -.�- _>--i 1 1 __.-Li --1_ Imo_ 7 Nr• —± -i,- + H -1-+---r---1---t_- 1-i-F--- F-7-r-r--+' -r ■r - m - . -t- �'�- 1-1 • �' Iii i iii li,-_; �; -i -LI IS ti Hi- - ' ' 1 4.--- -r- 1 f ' I rt-r- -414+4'1 ; r - I -'--r'1- -�r• 4l 11,41"+ a1 NI r' AA-RT i � 1 - l I I I I � , I e,-}�- -t-o ■ ■ ■ ; ' 1fi It I - - T ' { I ■ f 1 ' — - ■i■ ■ f ■ I ' 1 ■ i ■ 1 I rr I -- r I - ■■■■aa■ ■ ■ ■■ra ■� ■ I I I i -H 7 t 1 I ! -r� -r--oo ■ ■ ■■ ■■ - ■ i- _.] } ' i ' 14: 1 - 1 ; I ' I. INIaBI ff r i ___ _4. - ill I f it. i 1 1 ti 1 I ' I s i1 aaa jai a of iI iI 1 , �; i1i I 1 +-1--!,-r-: f I i t I-i , . . -, I,-r 1 • i , H- - -;-r- : -i_ -t- a ' . t I i I I 1 N r I 7- -t-i'i-' '1-r-r-- -"-� ---�- r r -+ 1--1-i- I �-t-}' ti-.-- i'*'- 1._,_,.. Y I IT�yf. 4 4 y1 ,1 ' JJ-;---H--4- 7 ( t ---.--Y-+4 L-t-'-+-; l 14 -+ a i 1 T- . yT� -1.-i-f-f, -`?-1 L,■i n d 1-1* -t-a�+ ' 1 T` 1 1 __ -re-s-7- r- --i-,--,------4--1-4..--t - -'-,-----t - -r '--4 ' 1- -Hi --� , ' ■ ' urw ■r■��i -1-. , i ` , SIT ,�!i 1 i .{ -4 -4-. 1 i i y-' r --I ' 1 (-.+r f- -' t • ' ■ i .-...-,.-,_`l ' 1 -�—i-^-- -r -hi-V-4-74-4 _;- a-_`H 1.-- -i 1 f �- r_r : -4-+ ' I I t t ** 1-:-+-�. '1-t-r-{- -'-t-r-r- -r 1 - T 1-,-Y' -4-t' -I-, . i i 1 _ I ' ' - --4-,-14 I Y---f 1-y-1 •4-f- Wit_ 1 , 1-,- f-*-' `__ ■■� T '`'( -1 1 -_I-+- • -i-t -� -1-4 -" "rte-` 1T� i. 1 I I F---j-1 .-_, .'_lam t~ - 1 ��11"'n. ■ +-r i Y--I ti� 1-�.'�' y- t.'y.�- �..' i ,- 4 { -4--r f-�•r- - I J 1 � a } .1 k- r ,; ; L • __4_1_,_. 1 t'I ; r cr. --t — i 7.71--1-1.1-ti- I t 1 / -tl-it--± f ! '►m"'i"'l- ft-4' -f-f I '.'t- +1- ! 1't 1 • 7 , -y�-, - T 1-1,- -4-4- I ' I 1 -71.p_11_-_-;+1F »-r '-;- t i r N f { ■ I i _,- 4-?-t-`. • -!--117- -1-f--E -1-_+11-t-_ .i__,..,___,__, 4_ _ _-T y f i )_ -l; �_�. ■a / 7 t a z' a■i t H . .a: 1-{--1-r I I 1 , , mam -1-+-'- I '' t1- 'i- +r -+" , r '-i I [ •±-+,'i- 1 ■r■ i i t i 11 { + i I _ l r o ua �i i "' 1 a■■r�aW . i t I k —t_ i, t ■ � ■ � ■ urn -(- _ — i (....__T-A-1.. I._ -4-HiI-Z;a-----I ' --_--4:11-1------44C-ill-Ht:,44-; l_f_. - — 4.- - -.i-f4-+-`_1-i-- 1_-- .y i.-++4 I _l. -r -! f.± .1- --.,-1-. -1-1 . - -1 1 1 I i -ate.' -,.. - 1-r. fi.'-- -1 Ty-++if Z- 1-+' t 'I:: t 1_-1 .11,7_1-,7_-r- -'!- 7r4-:;_ :742,-.4._f!. ,_+47],_ *�y-- -1-1 l rH I t-_I.�_}_�__.__}."'_, T-1--f-~ !-1-' 1'1 --A�r d .3; -� i..1_ta l r` .; w -} . , I . I , 7--i- 1 f'-. . - .4 - _I.1.�. t�` -777 APPENDIX B. CALCULATIONS • HEC-RAS Summary Tables • Hydrodynamic Force Calculations 24 N CO P m 0 m CO a 0 m m N w P LO ✓1 CO n a a a O 1.11 N Ian m a a m m a H NOON a Vl 1/1 m a m N m V1 a a a 0 0 0 0 00000000000000000000 .. m m m 0 m m m s W 0 00 C- u- = .-. P N m m in m P N I, P m N in N n N a T 10 m m H N N. N m m a N w P N 41 4-, m a m a a 0 W P CO P N CO P rl n el W N CO m Ln or P P P M P 9 v m e N •n V ton,m 01 „ l Cl N In VD •m m W• N V • N y h • m N a a .v 10 3 N n P 0 N N 0 rl N w O ✓1 N 0 0 a 0 a d N HOG' 1O N V1 0 CO 10 a N a T n a N a rl T a N N 0 N Cl m n e1 N P a 10 P P P CO V1 10 1D 'D n CO 00 N u1 a a Cr a a a a a 0 N N N NCO 00 0 l- O r. m 0 N ei P N 1O 0 LOCO Fro CO P Wm m 0 W 0 CO CO n N CO CO N a w e1 a el L V • b rl P CO P CO m W n m a N P N 0 CO CO P rl n in 0 m N a or N V1 N 001 0 CO N N N N m N 0 CO 10 CO a P a 1D m a a P 0 N N CO m 0 N Cr H N 0 0 CO O N CO CO 1D N a CD N N 0 01 N CO 3 n 1D N n NC D .0 •101 .*a P a to LA 0 a m D1 0 a 000000011/10. .-IN r0 v N n m e~1 N N 1D 0 P 0 0 0 P P a N V1 V1 'D 1010 ID N P a 0 0 W 10 r1 el el m P Lc M P a m 4101 a 10 m n N e1 L m w w N N 0 ei 'O V1 m m a m w N P C V1 m N D1 n ON N n V1 N W a P wa0 10 1D 1D 0 m 0 W w • Ce 4-i 1n •H O v 10 In 10 10 • v m v 1n vi e w v 1n a a a a 10 • v e 4- el m m v m 1• n e u, I v > W e. 1D 10 P W 0 P 01 e1 m m 10 w N P N N a P rl N O N m V1 V1 N m 1D rl CL= NN a CO V 10 W „ N O n 10 O N ' N LA a ei N P e1 N 10 N P m n O 4- 10 m m P 0 w 1D W w V N m 00 10 n 'O w N .0 N V1 n a 100. 0 a 0 0 0 0 N a V1 of N e4 0 rl a m m N ew4 el rl N N m N Vf V 0000 0000000000 0 0 0 0 0 0 0 0 m 0 0 0 0 0 0 0 1F 0 0 0 0 0• c m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V' v 0000 0000000000000000000000000000 iv >i-t. LAO N N 0 0 N P V1 1D W N e1 m a 0 N m N 0 p N W N 1D m 0 W V N a a01 a 0 a P N a N P ei P 01 N n 0 m a or 'D n1 w a NO N w v NNNN 010• N10 1D 10 N a a T N 0 0 0 P P P P w w N 1010 N w N a a w 0 W W ON n N N N N N N N N n w 1010 10 1D 1D 1D 101010 10 10 1D 0 0000• C 0000000000000000000000000000000 T V' a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a 0 w 0 H a ma Oaei CD N N Y 0 P n NCI Lf101 a N rl 0 N el e. W N Ina aaa •W-I 3 v W • • • • • P00 n 1D 10 1D 4.0 10 10 1D 1c W „ CO CO CO 00 000 000 CO o a a a a s a s a a a a C C R V > rl N N N m N ei P e4 w 0 e1 w V1 N 0 N P W a N m m N w V1 P 1D m N N W Y Co a CO ON a CO a P e1 n CO P W N 1/40 10 01 a P Ln rn N m N CO 41 OD H4- NNNN e4 n n 1D `D a of a in 4-I CD P P P P P w w CO 10 1D 10 m Ln N Cr or w 3 0003030 CONNNNINNNNNNN 10 N LOW 1010 1010 WOW 0101000 0 0 00 LCl N• a a a a DOCO a a a a a a a a a a a a a a a a a a a a a a a a a a a a ~ 3 rn 0 HI n el HO e1 e4 01 HI (DC D1 in m CO CO C. m m 0 n 01 P 00 w N O N W m w m 0 W w V T 0 m N to 10 N N W a a w T N 10 4D w P N N N w m 0 a nw . . . . . . . . . . . . . . . . . . . . m L m 14 0 0 0 P 0 0 CO CO w 0 1D V1 N m m m m m m m 14 0 e4 CO N P CO P N N N V v n n n n 10 Co .D 0 1D 1D 10 10 10 1D 10 1D 1D 1D `D 10 1D 10 10 0 V1 Vl N 03030000 0000000000000000000000000000000000 a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a CO W rl 0000 W 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 m m m 0 0 0 0 m m a 0 0 0 0 0D 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 414- o V m 0 0 0 H m m N 0 0 0 0 m 0 0 0 m m 0 0 0 0 VI in Ln Ln m N 0 0 VI Ln m m N N 0 0 0 OD 0) ~ v N N N N O N N N N N N N N N N N N N N N N N N N N N N a N N N N N 3 a el e-4 e-4 -Ni el eel ti Hot e1 e-I -1 - H M M Hl I eN1 N M 1N4 r_l eN1 el e4 eH4 1N4 e_4 1N4 M rl Al m N rci H C L C C L L L L C C L C L L C C C C L C C L L L C T T >0 T T T T T >1 T T T >1 >1 T T T >1 T T T >1 T >1 >0 >0 >0 >0 > > >' T el r 14-• 0 0 0 0 0000000000000000000000000000 W W aC 0000 00000000 00000 000000000000000 r 1r-IN el elr-Irl e44-1 HeIrloi 0 H C 0 O .ti L V O 0 .rl a C C C 1C L I V CO 10 m n N a W N P N P H N N N 0 N T P rl w W N y V• V a VD 0 n CO H m 1D V e4 P a n CO a CO 01 CO n m m N a a m CO 14 HIM 4141 L W 0 V1 of V1 N 0 m N N N 0 0 N m N N CA N a N in CO m 10 N m N II II II II II > 0 P P a N a minim N HI m N N N N N P N in CD CO N N P m 0 HI W N N L N P 10 N P m N N N N N N NHCON N T „ N H w W a H W ✓i A' 1D N N V1 Vl V1 a a a m m N N N N N N N rl e1 P 10 m a .„ C CO % L ~ w 0 vl C OD 00 00 00 00 CO 00 00 OD 00 00 00 00 00 00 00 00 00 00 00 CO 00 00 00 OD 00 00 DO 00 00 00 00 OD V WO W W W W W W W W W W W W W W 01 W W W N W 0 W 01 W W W W W W W W 01 W o C 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 a V CO L CO 0 CO COT COCO0 COCOR 00 0 F CO 00 4-, c1 U 10 L L L L L L L L L L L L L L L L L L L L L L O 11. .l Vut H H F F F F F F r 1— H H H F H H I— F' H H F 1— f H r r F H F F F H l- 0 = N d m m T m m m T T m m m m m m m m m m m m m m m m 0 m m gl C 0 L N e HI mi m �4 em1 1T4 m rl ei e1 e4 ei 14 M rl e4 rl ei rl e1 rl nri ¢ W C ≥ ry o a 0 m 0 0 0 m 0 0 0 m m 0 0 m 0 0 m m 0 m m m m 0 m m 0 0 0 m m 0 b `C r_4 '0- L m m m n m lot m n m m rt. m m m m m n l'.. m n n m m n m m Inn m n rcln m Inn n n O U CLi) W = w w W 00 N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N I1 = * * lilt * n m 0 N m m el ei N a ON N m n N a en HO N N a m N O N 1n H N m m N a DO Vl m m a a a a N a N a VI a a N a N m a u . . . . . . . . . . . "1. . . . . . . . . . . . . . . . . . . . . m# m m m 000000000000000 0000000000000 w 00 L H. P V1 m m m o o m V1 N N N N CO MA P T n Oc4- 0 N e N a 0 m m N Y Y CD N a N CD en m N m 0 Al AlN N N el P n rl ei `O a m m P 04- m v ry N ..400 ,-IN• v N 10 m w 0 1 .• 0 m ei• a 00 m m V Fn O• D In N H a• O e. O 3 N V1 N P N el a ry P P a P N N P '1 m HI o N o N. ✓i 0 N 0 0 CO o N N V1 N N In/1 N 0 H m 0 ern a a N CO N M P a N P P 01 CO N a N m CO N N N HW CON N a V VI a s N N N N N N CO m 0 F R 0 m N m m 0 P m ei N H P o N N N a LAO m m N Vl 0 T P ei a a i+ m 0 MT!' a m a N N m a W m m N 0 a P m a N m 0 N m N N a Lb, Q N LAN m 10 p N 1n 1c m m en V H H m m m o N a0 m O N e l m m N N 0 N 0 N o H m 0 LAO W N a 0 W N N P m N W T ei O N P N 3 N o N N NO P P 0 m n P a m W N N n N N ei N N m N O• ' N N 0 el n N a N OH OM m W 0 0 0 o LA N o 0 V1 P CO el el m N CO P u. P a M H P P H m N m H H m N N N m W 0 m 0 m 0 P 0 N V1 N 0 N P H ONO n N W n N m m P 0 N 0 P 0 M H P CO CO 11 Y Me-1 m a 0 N CO N a M a a V V a N Vl a Vl N a 0 N V1 N a a N N Al a N k I v J W 010 P n1COLn 0 al, NN •tC0 y n W N N 0 m a N 0 m C N N n N 0-10 ,-I NCOHNul O H- 0000 00 H 0 0 N 0 N m H VI 0 a HUD UnCOLIDLOUIMNInct en 0 N N N 0 N N 0 a N 0 a 0000 Nr.10 .9" NeINNNNmrnenence a N •t N a N N 0 N 0 N V11-1 0 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 0 0000000000000 V 0000 C3006700000040 ,9000 0000000000000 0 0000 000000000000000 000000 0 0 0 0 0 0 0 >• - N N N VO1 N 0 M N „ m N 0 H H N M N 0 P m 0 N a y N o m W V n 0 a P a m a 0 N W P N n N N H m 0 •40 •10 NON w v NNNN N N N o N Vf a a en N H 0 P P P P P W W N N o LO Cn V1 Vl a s W W CO CO ON n N N N n h n 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 • 0000000 CO 1:003003 00030300030300000 CO 0000000000000 ≥1 0 a a a a a aaaaaaaaaaaaa a a a a a a a a a a a a a a mw 0 HN en De CO N CD ul CD FO rn 0 N Y 0 P P P N N a Oat a N H m ti 3 •�-• N m n 0 CO 00 00 1a0 00 0D 0 V Y CO m CO m CO 00 m W W W CO o a a a a a a s a a a a a a a V > H N N a CO M N m N CO a,1 N 0 0 N CO y N H N. N0 0 N W V n a 01 V1 P M m N H o N 0 0 4400 n W T P 0 N m m H v w NNNN H N 0 0 V1 V1 a a M N H 0 P 0 0 P 01 W W N 0 0 N Vl N V1 a s CU 3 0000 0 n n n n n h n n n n 0 0 0 0000 0 0 0 0 0 0 0 0 0 1p • 0 co co co m m m m W co 0 m m co co W co 0 0 co 0 W co co m m 0 co W W W W 0 L in a a a a Cr aaaaaaaaaaaaa a a a a a a a a a a a a a a H 3 m elel H T 0 0 P m N 0 0 P m M 0 N 0000 N N W N m 0 m 0 W w V mom N a M o N N m a a 0 H m N 0 0 00 N N W V1 H 0 a N v NI NI . • H 0 0 01 P 0 P 0 W 0 0 o V1 V1 M M mn m M H 0 H 0 P N N N W N N V mN N FO 0N000000000000 0 0 0 0 0 0 0 0 000 ,0000 V1 0 0 0 0 000000000000000 0000000000000 c a a a a a aaaaaaaaaaaaa a a a a a a a a a a a a a a .c f m 00 H .� 00000i000000000000000 0000000000000 0000000000000000000000000 t m m 0 0 0 0 m m 0 0 0 0 0 u o m m m m H m 0 0 0 0 0 0 0 0 0 m m m m m H 0 0 m m m m m m m m m m 0 OD r •-. 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P = T S+A�(r � /2 � Sao0.0 fr 6.2. /pi _e"/SC SG3...44)/2, . 426,3. /3;.", it/t/ 1 d= 5.94/ • $ + �Z . y'" ,x_ 5.28 /• Gp9_ � - - s g 8,if5L r z 9 4 N M y" 1`' 75 ' , „,z _ j. fy _ _ ��. --�- --r -• Lo (Pf"S- 1j I.7 2 2S6 t� Z . /, '/ 5 ,)/ Z ; Li 38 LrO� • y / 2 //2 7-i y-z6OM7 — y.. z, 71#141 7) '-- 012, 8q 1,0(7. 4q) ( /`,530 + JJJ 11100 + 12, 000) (7. 7Li) 1 / 381 5 9O / L6 -4- 30'9, ci!5,8 APPENDIX C. DIGITAL FILES (CD) • AutoCAD workmaps • HEC-RAS files Aas deer' re 4ed d4 rnrni` d %d/cc 6/0 rx5DeevolMeE f 25 Hello