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Home My WebLink About20063342.tiff Add to Weld County Storm Drainage Criteria Ordinance 2006-7 Volume 1, Drainage Policy, Section 4.5 Detention and Retention Storage Add to Section 8-11-30, Item 16: Weld County will not approve any detention or retention pond that does not drain in less than 72 hours, or causes injury to water rights, or is in violation of State or Federal law. Volume 2, Storage, Section 3.3.4 Retention Facilities Add to Section 8-11-40, Item 10: Weld County will not approve any detention or retention pond that does not drain in less than 72 hours, or causes injury to water rights, or is in violation of State or Federal law. Volume 3, Structural BMPs, Section 5.3 Outlet Protection Add to Section 8-11-50, Item 18: Weld County will not approve any detention or retention pond that does not drain in less than 72 hours, or causes injury to water rights, or is in violation of State or Federal law. Volume 3, Structural BMPs, Section 9.0 Retention Pond—Sedimentation Facility Add to Section 8-11-50, Item 20: Weld County will not approve any detention or retention pond that does not drain in less than 72 hours, or causes injury to water rights, or is in violation of State or Federal law. A new item for the Addendum: Volume 1, Drainage Policy, Section 4.3.1 Channelization Add to Section 8-11-30, - to be in sequence would be between Items 15 and 16: It shall be the policy of Weld County to review proposed channel designs on a case-by- case basis. Proposed modifications to natural channels shall be approved only if the proposed work causes no injury to water rights and is not in violation of State or Federal law. ( VV) I>1(CZ-- -7 EXHIBIT 2006-3342 ..ter- WzooG-7 2,4- ARTICLE XI Weld County Storm Drainage Criteria Division 1 General Provisions 2c Section 8-11-It Adoption of storm drainage standards—short title. The Denver, Colorado Urban Drainage & Flood Control District's "Urban Storm Drainage Criteria Manual," consisting of Volume 1 (June 2001), Volume 2 (June 2001), and Volume 3, Best Management Practices September 1999), is hereby adopted by reference, with the amendments which are set forth ' me • he rgvisions of this Article 11 shall be known as the\Weld County Storm Drainage Criteria ' . All facilities for storm drainage on properties located within the unincorporated lands of Weld County, whether public or private, shall be designed and constructed in accordance with such criteria, unless quired otherwise by an applicable master drainage plan approved by Weld County. s • of the "Urban Storm Drainage Criteria Manual" shall be kept on file in the office of the Weld County Clerk to the Board of County Commissip er o inspection during regular business hours. It may be downloaded by visiting the 3M web site at www.udfcd.org, or ordered by contacting the UD&FCD at 303-455-6277. %O �, 3 Section 8-11-1Q: Purpose and authority. Thi\s CSDE•is adopted in order to provide minimum standards to preserve and protect the public health, safety and general welfare in the unincorporated lands of Weld County, pursuant to authority granted by Part 4 of Article 15 of Title 30, and Article 35 of Title 30, C.R.S. Section 8-11-$. Enforcement responsibility. It shall be the duty of the Weld County Public Works Department to enforce provisions of the WCSDC, and is responsible for the interpretation of provisions of the WCSDC using the following guidelines: A. In the interpretation and application, the provisions of the WCSDC shall be held as the minimum requirements for promotion of the health, safety, and general welfare of the community. B. The WCSDC is not intended to interfere with, abrogate, or annul any other regulation, statue, or other provision of law. C. Where any provision of the WCSDC impose restrictions different from those imposed by any other provisions of the WCSDC or any other regulation, or provision of law, that provision which is more restrictive or imposes higher standards shall govern. 6/29/2006 D. The WCSDC is not intended to abrogate any easement, covenant, or any other private agreement or restriction, provided that where the provisions of the WCSDC are more restrictive or impose higher standards or requirements than such easement, covenant, or other private agreement or restriction, the provisions of these Regulations shall govern. so - v.4e , vcAL3 Section 8-11-40. 'Exceptions. O1'pz'aLX The We ounty Board of C ommissioners may at its-discretion grant exce�ph to the regulatid of the WCS accordance wit provisions of Chap 8, 22, 23, 24, 26, d,27 of this Code. Div. II Drainage Planning Submittal Requirements Section 8-11-100. Review process. All new developments and subdivisions within the jurisdiction of the WCSDC shall submit drainage reports, construction drawings, existing condition and as-built information in accordance with the requirements of this Article. Section 8-11-110. Sketch plan drainage report. The purpose of the Sketch Plan Drainage Report, submitted at the Sketch Plan Review stage of the Planning Review process, is to identify and define conceptual solutions to storm drainage problems, which may occur on-site and off-site as a result of the proposed development. In addition, those problems that exist on-site prior to development must be addressed during the conceptual phase. For proposed projects that will have rural levels of development the Public Works Department will review the site, surroundings, and proposed improvements and advise the applicant as to what additional information and or engineering design may be required for Change of Zon and Final Plat approvals. All repo its shall be typed on 8-1/2" x 11" paper and bound. Drawings 24" x 36" may be included as needed. The drawings shall be bound within the report or included within a pocket attached inside the back cover of the report. The report needs to stand-alone and therefore all important reference material and supporting documents and calculations should be copied and included within the report appendix. The report shall include a cover letter presenting the conceptual design for review and shall be prepared by or supervised by an engineer licensed in Colorado. Only original documents sealed in ink will be accepted. The sealed report shall contain a certification sheet as follows: 2 6/29/2006 "I hereby certify that this report for the conceptual drainage design of(Name of Development) was prepared by me (or under my direct supervision) in accordance with the provisions of the Weld County storm drainage criteria for the owners thereof" Registered Professional Engineer State of Colorado No. (Affix Seal) B\ Sketch Plan Drainage Report Contents. Sketch Plan Drainage Reports shall be prepared in accordance with the following outline and contain the applicable information listed: 1. General Location and Description. a. Location. i. Township, Range, Section, Quarter Section. 1. Local streets within and adjacent to the development. if. Major open channels, lakes, streams, irrigation and other water resource facilities within and adjacent to the proposed development. iv. Names of surrounding developments including jurisdictions (municipalities). b. Description of Property i. Area in acres. 1. Ground cover. if. Major open channels and ownership. v.. General project description. v. Irrigation facilities and ownership information. 4. Groundwater characteristics (where applicable). 3 6/29/2006 2. Drainage Basins and Sub-Basins. a. Major Basin Description. Reference to applicable Weld County or adjacent county Master Drainage Plan(s). ii. Major basin drainage characteristics. Identification of all irrigation facilities within 200-feet of the property boundary. Identification of all FEMA-defined 100-year floodplains and ( floodways affecting the property. b. Sub-Basin Description. Historic drainage patterns on the subject property and CJ adjacent properties. ii. Off-site drainage flow patterns and impacts on the subject property. 3. Drainage Facility Design. a. General Proposed Concept. Proposed concept and typical drainage patterns. i'. Compliance with offsite runoff considerations and constraints. i. Anticipated and proposed drainage patterns. Identify all requests for variance from Weld County Storm Drainage Criteria. b. Specific Details. Describe design storms and source of design storm depth information(NOAA Atlas, UD&FCD maps, etc.). Drainage problems encountered and proposed solutions at specific locations. ii. Maintenance access and aspects of the proposed design. 4 6/29/2006 Cam, Sketch Plan Drainage Report Drawing Contents. 1. A General Location (vicinity) Map shall be provided at a scale of 1" = 2000' or larger in sufficient detail to identify upstream off-site drainage areas flowing into the proposed development and general drainage patterns. 2. A Drainage Plan of the proposed development shall be provided at a scale from 1" = 100' or 1" = 200' on a 24" x 36" drawing. The plan shall show the following information: a. Existing contours at 2-feet maximum intervals, contours should extend at least 200 feet from all project boundaries or further if necessary to show upstream and downstream drainage relationships impacting the proposed development. b. Property lines, existing and proposed lot lines, and existing and proposed easements. c. Streets with names. d. Existing drainage facilities, pipes, structures, irrigation facilities, and sizes. e. Overall drainage area boundary and sub-area boundaries. f. Proposed flow directions using arrows. g. Conceptual location of storm sewers, swales, open channels, culverts, detention ponds, and other appurtenances. h. Identification of outfall locations and receiving waters. i. Location of all defined 100-year floodplains affecting the property. j. Any other items so noted within the Drainage Report. Section 8-11-120. Change of Zone Drainage Report. The purpose of the Change of Zone Drainage Report is to identify and define preliminary solutions to problems, which may occur on-site and off-site as a result of the proposed development. In addition, those pFeb,teps that exist on-site prior to development must be addressed during the preliminary phase h reports shall be typed on 8-1/2" x 11" paper and bound. Drawings 24" x 36" shall be included as needed. The drawings shall be bound within the report or included within a pocket attached inside the back cover of the report. The Change of Zone Drainage Report needs to stand-alone and therefore all important reference material should be copied and included within 5 6/29/2006 the report appendix. The report shall include a cover letter presenting the preliminary design for review and shall be prepared by or supervised by an engineer licensed in Colorado. Only original documents sealed in ink will be accepted. The sealed report shall contain a certification sheet as follows: -I I "I hereby certify that this report for the preliminary drainage design of(Name of Development) was prepared by me (or under my direct supervision) in accordance with the provisions of the Weld County storm drainage criteria for the owners thereof" Registered Professional Engineer State of Colorado No. (Affix Seal) a`A. Change of Zone Drainage Report Contents. The Change of Zone Drainage Report shall be in accordance with the following outline and contain the applicable information listed: 1. General Location and Description. a. Location. is Township, Range, Section, Quarter Section. ii Local streets within and adjacent to the development. i Major open channels, lakes, streams, irrigation and other water resource facilities within and adjacent to the proposed development. vi. Names of surrounding developments including jurisdiction (municipalities). b. Description of Property. i. Area in acres. ii. Ground cover. iii. Major open channels and ownership. 6 6/29/2006 v General project description. v. Existing irrigation facilities and utilities and ownership information. vi Groundwater characteristics (where applicable) 2. Drainage Basins and Sub-Basins. a. Major Basin Description. * Reference to Weld County Master Drainage Plan(s) where applicable. i. Major basin drainage characteristics. ii. Identification of all irrigation facilities and utilities within 200-feet of the property boundary. b. Sub-Basin Description. i� Historic drainage patterns on the subject property. i. Off-site drainage flow patterns and impacts on the subject development. 3. Drainage Design Criteria. a. Regulations: Discussion of the optional criteria selected or the deviation from the WCSDC if any. b. Development Criteria Reference and Constraints. Discussion of previous drainage studies (i.e., project master plans) for the subject property that influence or are influenced by the proposed drainage design and how the studies and plans will affect drainage design for the site. i. Discussion of site constraints such as slopes, streets, utilities, existing structures, and the proposed development or site plan impacts on the proposed drainage plan. c. Hydrological Criteria. 7 6/29/2006 i. Identify design rainfall (source of design storm depth i. ii'. information NOAH Atlas, UD&FCD maps, etc.). Identify design storm recurrence intervals. Identify runoff calculation method(s) and any computer models. i. Identify detention discharge and storage calculation 1 method(s) and computer models. Discussion and justification of other criteria or calculation methods used that are not presented in or referenced by the WCSDC. d. Hydraulic Criteria. Identify capacity references and any computer models. ii. Identify detention outlet type. iii. Identify check/drop structure criteria used. vi) Discussion of other drainage facility design criteria used that are presented in the WCSDC. 4. Drainage Facility Design. a. General Concept. Discussion of concept and typical drainage patterns for historical conditions. i. Discussion of compliance with off-site runoff considerations and constraints. i. Discussion of the content of all tables, charts, figures, or drawings presented in the report. 10. Discussion of anticipated and proposed drainage patterns. 1 b. Specific Details. Discussion of compliance with drainage criteria (street, inlet, and pipe capacities, etc). 8 6/29/2006 i . Discussion of drainage problems encountered and solutions at specific design points. i' . Discussion of detention storage and outlet design. v . Discussion of maintenance access and aspects of the design. Provide copies of Draft CDPHE or State Engineer's permit applications (where applicable). 5. Conclusions. a. Compliance with the WCSDC. b. Drainage Concept. Effectiveness of drainage design to control damage from storm runoff. i . Influence of proposed development on any applicable Weld County Master Drainage Plan recommendations. ii. i Identification of and written approval of affected irrigation company or other property owner(s). Weld County may require that the applicant provide evidence that offsite impacted jurisdictions have been notified of the proposed drainage plans and potential impacts. 6. References. a. Reference all criteria and technical information used. 7. Appendices. a. Hydrology Computations. Land use assumptions regarding adjacent properties. ii.i Initial and major storm runoff computations at specific design points. Iii. Historic and fully developed runoff computations at specific design points. vi) Computer model input and output. 9 6/29/2006 b. Hydraulic Computations. Culvert sizing. i. Storm sewer sizing. i Street capacity evaluation. iv Storm inlet sizing. v Swale sizing. Open channel sizing. i. Check dam and/or drop structure sizing. viii. Detention pond area/volume capacity and outlet sizing. �1 ix Changes to Calculation Methods - If applicant / design engineer modifies any portion of UD&FCD spreadsheets used for hydrologic or hydraulic calculations, the applicant/design engineer shall identify all changes to calculation assumptions or computer programs as to type of change and specific factors that were modified. ; Computer model input and output. C'Q. Change of Zone Drainage Report Drawing Contents. I.A General Location (vicinity) Map shall be provided at a scale of 1" _= 2000' or larger in sufficient detail to identify upstream off-site drainage areas flowing into the development, downstream areas receiving site flows, and general drainage patterns in the project area. Z•A ISfainage Plan of the proposed development shall be provided at a scale from 1" = 100' or 1" = 200' on a 24" x 36" drawing. The plan shall show the following information: 1+ I\ Existing contours at 2-feet maximum intervals, contours should extend at least 200 feet from all project boundaries or further if necessary to show upstream and downstream drainage relationships impacting the development. S X. Property lines, lot lines, utility crossings and easements. CI. Streets with names. 10 6/29/2006 Existing drainage facilities, pipes, structures, irrigation facilities, and sizes. 5. Overall drainage area boundary and sub-area boundaries. 6. Proposed contours and flow directions indicated with arrows. 7. Location oft proposed storm sewers, swales, open channels, culverts, cross- pans, and other appurtenances. 8.,, Proposed outfall point(s) for runoff from the development area and facilities to convey flows to the final outfall point without damage to downstream 1 properties. 9. Location and elevations of all defined 100-year floodplains and floodways affecting the property. 104 Location and types of proposed permanent erosion control features. Section 8-11-130. Final Drainage Plan Report. The purpose of the Final Drainage Report is to update the preliminary design concepts, and to present the design details for the drainage facilities discussed in the Change of Zone Drainage Report. Also, any change to the preliminary concept shall be presented. The Final Drainage Report shall identify all approved requests for variance from Weld County Storm Drainage Criteria. All Fin Reports shall be typed on 8-1/2" x 11" paper and bound. Drawings 24" x 36" shall be included. The Final Drawings shall be bound within the report or included within a pocket attached inside the back cover of the report. The Final Report needs to stand-alone and therefore all calculations, computer outputs, plans, supporting documents and important reference material should be copied and included within the report appendix. The report shall include a cover letter presenting the final design for review and shall be prepared by or supervised by an engineer licensed in Colorado. Only original documents sealed in ink will be accepted. The sealed report shall contain a certification sheet as follows: ' . "I hereby certifit at this report for the final drainage design of (Name of Development) was prepared by me (or under my direct supervision) in accordance with the provisions of the Weld County storm drainage criteria for the owners thereof" Registered Professional Engineer State of Colorado No. (Affix Seal) I 1 6/29/2006 f3`A Final Drainage Plan Report Contents. The final drainage report shall be prepared in accordance with the outline shown above under Change of Zone Drainage Report. In addition to including all of the items required for the report and plans submitted with the Change of Zone described above under Change of Zone Drainage Report and Drawings, the Final Drainage Report and Drawings should include: 1. Proposed location and sizing of all storm sewers, swales, open channels, culverts, cross-pans, and other appurtenances, including cross-sections of swales and open channels. 2. Routing and accumulation of flows at various critical points for the minor storm runoff. 3. Routing and accumulation of flows at various critical points for the major storm runoff. 4. Detention storage facilities and outlet works, including proposed 100-year water surface elevations. 5. Location of all existing and proposed utilities. 6. Routing of off-site drainage flows through the development. 7. Minimum lowest opening elevations of residential and commercial buildings above the 100-year water surface in streets, open channels, ditches, swales, or other drainage facilities, as illustrated by the preliminary grading plans. 8. Proposed on-site private and public drainage easements. 9. Proposed off-site private and public drainage easements. 10. Elevations of manhole and inlet inverts in relation to project datum. 11. Proposed water surface elevations for street encroachments for the minor and major storm. 12. Critical hydraulic structure dimensions. 13. Orifice plate sizes. 14. Detention pond volumes. 15. All other critical hydraulic elevations. 12 6/29/2006 16. Operations and Maintenance instructions for the proposed stormwater drainage facilities. 17. Construction-Phase Erosion and Sediment control calculations. 18. Permanent Erosion and Sediment control calculations. C.The Final Drainage Report design hydraulic calculations shall be provided for each of the proposed elements of the final drainage design. Section 8-11-140. Construction Drawings and Specifications. Where drainage improvements are to be constructed in accordance with the accepted Final Drainage Report, the signed and sealed construction plans (on 24" x 36" mylar) and specifications shall be submitted in conformance with the Final Plat for review and acceptance prior to construction. The sealed plans and specifications for the drainage improvements shall include all drainage components designed within the Final Drainage Report. The info oration required for the drawings and specifications shall be in accordance with sound engineering principles, the WCSDC and the Weld County requirements for development and subdivision design. Construction documents shall include geometric, dimensional, structural, foundation, bedding, hydraulic, landscaping, erosion control and other details as needed to construct the storm drainage facilities. The accepted Final Drainage Plan shall be included as part of the construction documents for all facilities affected by the drainage plan. Submittal of digital format final plans and As-built drawings may also be required by Weld County Public Works Department. Weld County requires a minimum of three sets of paper construction plans for use by Weld County Inspectors. Where rtsion control and sediment control improvements are to be constructed in accordance with the accepted Final Drainage Report, the erosion control and sediment control construction plans (on 24" x 36" mylar) and specifications shall be submitted in conformance with the Final Plat for review and acceptance prior to construction. The plans and specifications for the erosion control and sediment control improvements shall include all erosion control and sediment control components designed within the Final Drainage Report. Both con ction-phase and post-construction (permanent) erosion control and sediment control construction drawings shall be submitted. The construction-phase erosion control and sediment control construction drawings shall be submitted separately from post-construction (permanent) erosion control and sediment control drawings. The construction-phase and post-construction phase erosion control and sediment control construction drawings shall be the basis of compliance evaluations by Weld County inspectors. 13 6/29/2006 Section 8-11-150. As-built drawings. A. Recording of Drawings. 1. The project record drawings shall be submitted to and accepted by Weld County. Drawings will be submitted in appropriate digital form when requested by the County. 2. Each drawing shall be labeled "DRAWINGS OF RECORD" in neat large printed letters. 3. Construction information shall be recorded concurrently with construction progress by the Contractor. 4. Project Record Drawings shall be marked legibly and with an indelible pen. 5. Project Record Drawings shall record actual construction and contain, but not limited to, the following: a. Field dimensions, elevations, and details. b. Field changes which are made by minor deviations to the design drawings. c. Details, which are not on the original Construction Drawings. d. Elevations of manhole and inlet inverts in relation to project datum. e. Critical hydraulic structure dimensions. f. Orifice plate sizes. g. Detention pond volumes. h. All other critical hydraulic elevations. g. Floodplain and floodway delineations and BFEs where applicable. h. Dimensions of erosion control installations. 6. Payment of permit fees must precede final acceptance. 14 6/29/2006 B. Submission. The project record drawings shall be submitted to and accepted by the Weld County Inspectors with a transmittal letter containing the following: a. Date. b. Project Title. c. Design Engineer's name, address, and telephone number. d. Title and number of each Record Document. e. The signature of the Design Engineer, and their Professional Engineering stamp. 2. The initial acceptance of the storm drainage improvements will not be made until all Weld County installation requirements are satisfied and the Project Record Drawings are received and accepted by Weld County. 3. Acceptance of storm drainage improvements will not be made until all onsite drainage easements have been recorded. Acceptance of storm drainage improvements will not be made until all offsite drainage easement agreements have been signed and notarized. 4. The final drawings of the storm drainage improvements will not be made until the Project Record Drawings are received and accepted by Weld County. 5. Weld County requires that the Project Record Drawings first be submitted in blueline form for preliminary acceptance before final mylars are submitted. Submittal of digital format final plans and digital format as-built drawings may also be required by Weld County Public Works Department. 15 6/29/2006 APPENDIX 8-L Weld County Addendum to the Text of the Urban Storm Drainage Criteria Manuals UD&FCD STORM DRAINAGE CRITERIA MANUAL VOLUME 1 DRAINAGE POLICY 1.4 Planning Change...watershed in the Denver region. To ...watersheds in the Weld County area. Change ...can be stored in detention and retention reservoirs. To ...can be stored in detention reservoirs. 1.5 Technical Issues Change ...(CUHP),or... To ...(CUHP),HEC-1,HEC-HMS,or... Change ...of stormwater detention and retention basins... To ...of stormwater detention basins... Change ...the many detention and retention facilities in the Denver region. To ...the many detention facilities in the Weld County area. Change....The various governmental agencies within the Denver region have adopted and need to maintain their floodplain management programs. To....Weld County has adopted and needs to maintain its floodplain management program. 1.6 Flood Insurance Change ...The Denver region should encourage continued participation... To ...The Weld County area continues to participate... A Deleted:6/192006 1 629/204 2.1 Drainage is a Regional Phenomenon That Does Not Respect the Boundaries Between Government Jurisdictions or Between Properties Add....Weld County may from time to time enter into Agreements with adjacent counties to cooperate on regional planning. The Policy of the Weld County shall be to pursue a jurisdictionally unified drainage effort to assure an integrated drainage system and to cooperate with other regional and local planning agencies on drainage matters. 3.1.2 Rainfall-Runoff Relationships Change ...of the Denver region. To ...of the Weld County area. 3.1.4 Library Change ...The District should... To ... Weld County should... Change ...of the District's educational... To ...of Weld County's educational... 3.1.5 Runoff Magnitudes Change ...for Denver region... To ...for the Weld County area... 3.2 Floodplain Data Delete...:"the District's Flood Hazard area Delineation Studies," 3.2.2 Data Inventory Change ...in a central District depository... To ...in a Weld County Public Works file... .(Deleted:6/19/2006 • 2 6/29/20% 3.2.4 Priority for Data Acquisition Change The District will... To Weld County will... 3.3.1 Master Plan Change ...in the District. To ...in Weld County. 4.1 Total Urban System Change ...for most of the watersheds in the Denver region. To ...for the Weld County area. Change....An effort to complete the coverage of master plans for yet unplanned areas of the District should be continued until full coverage is achieved. To....An effort to complete coverage of drainage master plans for yet unplanned areas of Weld County should be continued until full coverage is achieved. 4.1.2 Master Plan Delete....Entire first paragraph of this section. Change....The District has... To....Weld County has... Add....the Policy of Weld County shall be to enforce and implement adopted Master Drainage Plans.These Master Drainage Plans may be amended from time to time in the future. 4.1.3 Planning Process Ingredients Delete...."to 10"within item 2. ,.{Deleted:6/19/2006 _ J 3 6/29/2004 _ 4.1.6 WaterOuality Change....in the Denver region. To ...in the Weld County area. 4.5 Detention and Retention Storage Add....the Policy of Weld County shall be to require regional and/or on-site detention for all future developments. Temporary or interim detention/retention may be required if the downstream regional facilities have not yet been constructed per the applicable Master Plan. Stormwater retention facilities are normally not allowed in the Weld County area, but will be considered for special circumstances. It is Weld County policy to require detention of runoff from the 100-year storm falling on the developed site and release of the detained water at the rate of the runoff of the 5-year storm falling on the undeveloped site. Detention releases based on soil types are not approved for Weld County. Proposed development must provide for safe conveyance of offsite flows through the proposed development site. Offsite flows may be routed through or around the proposed detention facilities. Positive drainage must be provided. 4.5.4 Reliance on Non-Flood-Control Reservoirs Delete....the entire paragraph. Add....Jurisdictional dams are classified by the State Engineer as either low, moderate, or high hazard structures depending on conditions downstream. Dams are classified as high hazard structures when,in the event of failure,there is a potential loss of life. Dams presently rated as low or moderate hazard structures may be changed to high hazard rating if development occurs within the potential path of flooding due to a dam breach. In this case, the reservoir owners would be liable for the cost of upgrading the structure to meet the higher hazard classification. The Policy of the Weld County shall be to: 1. Restrict upstream development to areas outside of the jurisdictional dam water surface elevation created by a 100-year storm plus freeboard. 2. Restrict downstream development to areas outside of the jurisdictional dam 100- year floodplain.The jurisdictional dam 100-year floodplain is defined as either: a. The 100-year floodplain downstream of the emergency spillway assuming the dam is full to the elevation of the emergency spillway at the beginning of the 100-year storm and the 100-year storm is routed through the dam and out the emergency spillway, {Deleted:6/192006 4 6/29/200(y b. Or the path that the basin's 100-year floodplain would form through the downstream development if the dam were removed by the owner. 4.5.5 Reliance on Embankments Change....by the District. To ...by Weld County. 5.1 Design Criteria Change ...by the District. To ...by Weld County. 5.1.1 Design Criteria Change...in the Denver region... To ...in the Weld County area... Add....the Weld County Public Works Department may grant variances from the design criteria of this Manual by acceptance of the Final Drainage Report in which the variance request is well documented. 5.2.1 Design Storm Return Periods Delete....the entire second paragraph. 5.2.2 Initial Storm Provisions Delete...."2-to"and"depending on local criteria" 5.4 Streets Change....as summarized in Table DP-1. To....as summarized in Table DP-1 and in the Streets/Inlets/Storm Sewers chapter of this Manual. Deleted:6/192006 7 • 5 6/29/2006, Change....summarized in Table DP-2. To....summarized in Table DP-2 and in the Streets/Inlets/Storm Sewers chapter of this Manual. Change....presented in Table DP-3. To ...presented in Table DP-3 and in the Streets/Inlets/Storm Sewers chapter of this Manual. Change ...in the Denver region... To ...in the Weld County area... 5.5 Irrigation Ditches Add....it is the Policy of Weld County to prohibit the discharge of stormwater runoff from developed areas into irrigation ditches and facilities except as required by water rights or where such discharges are in conformance with approved Master Drainage plans. Further, wherever new development will alter patterns of drainage into irrigation ditches by increasing flow rates or volumes, or will change the historic concentration points of runoff, the County shall require each new development to obtain written consent of the appropriate ditch company before approving the drainage design and development. 5.5.1 Use of Roadside Ditches Change....Landplanners downhill from a ditch should plan... To....Landplanners and engineers with a proposed development downhill from a ditch shall plan... Add....For new development, it shall be the policy of Weld County to prohibit undetained discharges to roadside ditches located in the County right-of-way. In the event a proposed development wishes to design stormwater discharge to a County right-of-way,the developer, at the request of the County,shall have the requirement to design and construct drainage improvements to the right-of-way at the developers' own expense. Such improvements shall include, but not be limited to: detention ponds, armored channels,culverts, and other drainage facilities. Cost-sharing of such needed improvements may be borne by adjacent developments, such cost sharing to be negotiated by the developer. Weld County may require written agreements and construction bonding of such offsite drainage improvements. 5.5.3 Conformance With Master Plan Change ...in a District's master plan... To .....in the Weld County master plans... ,.{Deleted:6/19/2006 6 6/29/2004 • Change ...by the District and... To ...by Weld County and... 5.6 Detention and Retention Facilities Maintenance Change ...in the Denver region. To ...in the Weld County area. 6.1 Purpose Delete...."various governmental agencies within the Denver region should initiate floodplain management programs." 6.2 Goals Change ...of Denver region... To ...of Weld County area... 6.3.2 New Development Add....The Policy of Weld County shall be to outsource engineering review of all CLOMR and LOMR submittals received with a development application. The Developers shall reimburse the Weld County Public Works for all outsourced engineering review costs. Upon FEMA approval of a CLOMR or LOMR, payment of all outsourced engineering review costs is due and payable to Weld County. Developers are welcome to contract directly with our outsourced Consultant(s) for the preparation of CLOMR's and LOMR's,if they so desire. 7.1 Adoption of Drainage Master Plans Change ...within the District. To ...within the Weld County area. 7.3 Amendments Change ...by any governmental agency should be reviewed by the District to... To ...by anyone should be reviewed by the Weld County to... {Deleted:6/19/2006 7 6/29/2004 Change...The District should continually review the needs of the Denver region in regard... To ... Weld County should continually review the needs of the community in regard... 7.5 Drainage Improvements Add....entire new section as follows: Weld County Master Drainage Plans set forth improvements required for existing and future growth areas. There are areas of Weld County for which no Master Drainage plans yet exist. Weld County may require a Master Drainage study in support of proposed development. The policy of Weld County regarding the design and construction of improvements within the Master Drainage Plan areas shall be as set forth below,subject to Weld County budget and appropriation approvals. 1. Weld County shall identify needed design and construction of improvements as set forth in adopted Master Drainage Plans for existing and future growth areas. 2. The drainage systems for future development and redevelopment shall be designed and constructed by the Developer(s). 3. The Developers shall be responsible for design and construction of temporary or interim storm drainage systems required due to the lack of adequate storm drainage facilities downstream of new development. 4. The Developers may be responsible for design and construction of permanent storm drainage systems required due to the lack of adequate storm drainage facilities downstream of new development. DRAINAGE LAW No changes. PLANNING 7.1 Initial Drainage Change....The initial storm has been defined by the District to have a return frequency ranging from once in 2 years to once in 10 years. To....The initial (minor) storm has been defined by Weld County to have a return frequency of . petered:5 yema(dm&yearral are ror q y pert 5 yea and a S-ye r sto alias, once in 10 years(the 10-year storm)for all}tses. once - {Deleted:otter Deleted:6/19/2006 • 8 6129/2004 __ 9.1 Storm Sewers Change....storm runoff expected to occur once every two to ten years. To....storm runoff expected to occur once every J0 0 years(the 10-year storm)for all pses. Deleted:5 years(the 5-year stone)for rural, ural residential,and agricultural areas, once m 9.4 System Sizing Deleted:other Change....The suggested design return periods to be used by local jurisdictions in the Denver region for storm sewer design for all land uses is 2—to 10—years. To....The design return period to be used for storm sewer design in Weld County i;;he 10-year c„.--t Deleted:by the Weld County storm for all And uses. Storm sewers passing flow under County roads shall have a minimum N- -f Deleted:for I design capacity for the 10-year storm and a minimum diameter of 15 inches or equivalent open\ Deleted:mural,residential,and l area. System sizing design shall adhere to Weld County street inundation riteria of 6 inches for ' ,, agricultural areas is the 5-year storm; f the minor storm,18 inches for the major storm even(. \:t Deleted:is to be used for designs RAINFALL `,, f Deleted:other fDeleted:ceteris Deleted:as summarized in Tables DP- I,DP-2,and DP-3 and in the 1.0 Rainfall streets/Wets/storm sewers chapter of this Manual Add....For proposed Weld County development drainage design, the Rainfall Depth-Duration- Frequency maps presented in the USDCM may be utilized only for those areas of Weld County shown on the Figures in that manual (Figures RA-1 through RA-12). Drainage designs proposed for locations outside of the areas of Weld County covered by Figures RA-1 through RA-12 should utilize the depth-duration-frequency information provided in the Precipitation-Frequency Atlas of the Western United States, Volume II — Colorado published by the National Oceanic and Atmospheric Administration (NOAA). The NOAA Atlas may be accessed at: http://www.nws.noaa.gov/oh/hdsc/noaaatlas2.htm. Where development is proposed in larger watersheds, design hydrology should utilize longer storm durations appropriate for the size of the entire watershed. See Tables RA-1 and RA-3 in the USDCM for storm duration and area adjustments. RUNOFF 3.3.1 Rainfall Add....See Tables RA-1 and RA-2 within the USDCM Rainfall Chapter for 1-hour and 2-hour rainfall area adjustments and distributions. For locations outside of the areas of Weld County {Deleted:6/19(2006 J • 9 6/292005 covered by USDCM Figures RA-1 through RA-12, utilize the depth-duration-frequency information provided in the Precipitation-Frequency Atlas of the Western United States,Volume II. 5.1 Published Hydrologic Information Change....The word"District" To....The words"Weld County"throughout the paragraph. Change....for the majority of the major... To....for the major... Change....library. To....Weld County Public Works office. STREETS/INLETS/STORM SEWERS 1.3 Components of Urban Stormwater Collection and Conveyance Systems Change....within the District are... To....within the Weld County are... 2.2 Design Considerations Change....,the District has... To....,Weld County has... Change....These standards were given in the POLICY Chapter and are repeated in Table ST-2 for convenience. To....These standards are provided in Chapter 3,Planning Section 9A of the WCSI) manual. -- Deleted:Table ST-2 of the uD&FCD -- Stormwater Criteria Change....The District has... To....Weld County has... Change....These standards were given in the POLICY Chapter and are repeated in Table ST-3 and Table ST-4 for convenience. To....These standards are provided in Chapter 3,Planning,Section 9.4 of the WCSDC jnanual. _ Deleted:Tables ST-3 and ST-4 of the UD&FCD Stonnwater Criteria (Deleted:6/192006 10 0/29/2000 _ Notes: Allowable flow depth is measured vertically from the gutter flowline at the curb face. 2.3.1 Curb and Gutter No changes. 2.3.1.3 Allowable Gutter Hydraulic Capacity Weld County Change....There are two sets of reduction factors developed for Denver metropolitan areas (GUO 20006). To....There are two sets of reduction factors developed for Denver metropolitan areas (GUO 2000b)and they shall also be utilized for the Weld County area. 3.1 Inlet Functions,Types and Appropriate Applications Add....The standard inlets permitted for use in Weld County streets are: INLET TYPE PERMITTED USE Curb Opening Inlet Type R All street types with 6" vertical curb Grated Inlet Type C All streets with a roadside ditch or swale Grated Inlet Type 13 Alleys or private drives with a valley gutter Combination Inlet Type 13 All street types with 6"vertical curb 3.3.6 Inlet Clogging Add....To account for effects which decrease the capacity of the various types of inlets, such as debris plugging,pavement overlaying and variations in design assumptions,the theoretical capacity calculated for the inlets is to be reduced by the factors presented below for the standard inlets permitted for use in Weld County. {Deleted:6/19/2006 • • I 6/29/2006, WELD COUNTY ALLOWABLE INLET CAPACITY CONDITION INLET TYPE PERCENT OF THEORETICAL CAPACITY ALLOWED Sump or Continuous Grade CDOT Type R 5' length 88 10' length 92 15' length 95 Continuous Grade Combination Type 13 66 Sump Grated Type C 50 Grated Type 13 50 Sump Combination Type 13 65 3.4.2 Design Considerations Delete....Table ST-2 lists pavement encroachment standards for minor stones in the Denver metropolitan area. 4.2 Design Process,Considerations,and Constraints Change....Pipe sizes smaller than 15 inches are not recommended for storm sewers. To....The minimum size storm sewer pipe within a Public Right-of-Way or Public Drainage Easement shall be 15 inches in diameter or equivalent open area. Refer to the "Weld County Development Standards and Specifications Governing the Construction of Public Improvements", latest edition,for allowable storm sewer pipe materials. 4.4.1 Flow Equations and Storm Sewer Sizing Add....The Manning's roughness coefficient "n" for all storm sewer pipe capacity Weld County calculations shall be 0.013 regardless of pipe material (ie. Concrete, PVC, or HDPE) with the exception of corrugated metal pipes which shall have a coefficient of 0.025. 4.5 Hydraulic and Energy Grade Line Calculations Add....The hydraulic grade line and energy grade line shall be calculated for each storm sewer system and included in the Final Drainage Report. Each storm sewer system shall be profiled on the Final Construction Drawings and shall include the design flow hydraulic grade line (HGL). The energy grade line(EGL) for the design flow shall be at least 6 inches below the final finished elevation of the manhole rims and inlet flowlines. ( _ l Deleted:6/19/2006 • • 12 0/29/2014 MAJOR DRAINAGE 3.2.3.2 Side Slopes Paragraph 1 Add....For constructed or natural channels with sideslopes steeper than 2:1, appropriate construction setbacks from the channel edge may be required to allow potential future channel meandering. Access for maintenance may require easement. 3.2.7 Summary of Preliminary Design Guidance Add....to Table MD-2 the following: Grass lined open channels conveying < 50 cfs may reduce the minimum 1.0 foot freeboard requirement to the freeboard required to conveying 1.33 times the 100-year design flow. The reduced freeboard may only occur if a 1.0-foot minimum freeboard is not physically or reasonably possible and a variance request is submitted. 3.2.8 Maintenance Eligibility Delete first paragraph. Add....Weld County will only maintain eligible major drainage ways by special agreement. The requirements below must be satisfied as of(adoption date) for a major drainage channel to be eligible for Weld County maintenance. Note that the Weld County "Maintenance Eligibility Guidelines"may change with time. 3.2.8.3 Grass-Lined Channel Design Change....he design for a grass-lined channel must meet the following criteria to be eligible for District maintenance: To....The design for a grass-lined channel must meet the following criteria to be eligible for Weld County maintenance. 3.3.4 Maintenance Change....A maintenance access mad with a minimum passage width of 12 feet shall be provided along the entire length of all major drainageways.The local government may require the road to be surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete slab. To....Weld County and the design engineer shall work together to provide access to all major drainageways as determined appropriate at the time of preliminary and final design. {Deleted:6/19/2006 • • • 13 6/29/2004 Add....Weld County encourages volunteers to assist the Weld County in performing routine maintenance of all the drainage ways within the County through an Adoption program and will assist these groups in a variety of ways. 3.5 Choice of Channel Lining Change....Manufactured channel linings such as gabions, interlocked concrete blocks, synthetic linings,etc.,are not recommended for new developments. To....Manufactured channel linings such as gabions, interlocked concrete blocks, synthetic linings, etc., are not recommended for new developments, but will be considered by Weld County on a case-by-case basis. 4.1.5 Trickle and Low-Flow Channels Add....Under drain pipes shall not be used in lieu of trickle channels within Weld County but will be considered by Weld County on a case-by-case basis. 4.1.7 Water Surface Profile Change....Water surface profiles should be computed for all channels,typically for the 10-year and 100-year events. To....Water surface profiles shall be computed for all open channels conveying > 50 cfs within Weld County. Add....Hydraulic grade lines shall be shown on the Final Construction Drawing profiles of open channels conveying> 50 cfs within Weld County. It is not necessary to show energy grade lines on Final Construction Drawing profiles,but encouraged. The energy grade line for the design flow shall be at or below the final finished top of channel bank elevation. Hydraulic grade lines on Final Construction Drawings are encouraged and will ease assessment and review of compliance with street inundation criteria. 4.1.8 Maintenance Change....A stable maintenance access road with a minimum passage width of 12 feet shall be provided along the entire length of all major drainageways. The local government may require the road to be surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete slab. To....Weld County and the design engineer shall work together to provide access to all major drainageways as determined appropriate at the time of preliminary and final design. :l Deleted:6/19/2006 • • 14 6/29/20c! 4.2.2 Design Procedure Change....Water surface profiles must be computed,typically for the 10-and 100-year events. To....Water surface profiles shall be computed for all open channels conveying>50 cfs within the Weld County. Add....Hydraulic grade lines shall be shown on the final drawing profiles of open channels conveying > 50 cfs within the Weld County. Energy grade lines on final drawing profiles are encouraged. Hydraulic grade lines on Final Construction Drawings are encouraged to' ease assessment and review of compliance with street inundation criteria. 4.2.3 Life Expectancy and Maintenance Change....A maintenance access road with a minimum passage width of 12 feet shall be provided along the entire length of all major drainageways. The Local government may require the road to be surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete slab. To....Weld County and the design engineer shall work together to provide access to all major drainageways as determined appropriate at the time of preliminary and final design. 4.3 Concrete-Lined Channels Change....Vegetated channels are normally preferable in the Denver region... To....Vegetated channels are normally preferable in the Weld County area... Change....In the Denver region,all channels carrying supercritical flow... To....In Weld County,all channels carrying supercritical flow... 4.3.6 Maintenance Change....A maintenance access road with a minimum passage width of 12 feet shall be provided along the entire length of all major drainageways. The local government may require the road to be surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete slab. To....Weld County and the design engineer shall work together to provide access to all major drainageways as determined appropriate at the time of preliminary and final design. A Deleted:6/192006 15 6/29/2006, 4.4.1.3 Wire-Enclosed Rock(Gabions) Change....For these reasons,the District discourages... To....For these reasons,Weld County discourages... 4.4.7 Maintenance Change....A maintenance access mad with a minimum passage width of 12 feet shall be provided along the entire length of all major drainageways. The local government may require the road to be surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete slab. To....Weld County and the design engineer shall work together to provide access to all major drainageways as determined appropriate at the time of preliminary and final design. 4.5 Bioengineered Channels Change....The District advocates.....District's policies... To...Meld County advocates Weld County's policies... 4.5.3 Bioengineering Resources Change....within the District. To....within Weld County. 4.5.4 Characteristics of Bioengineered Channels Change....1. of the Denver area,... To.... 1. of the Weld County area,... Change....2. grade controls,most bioengineered channels require... To....2. grade controls,bioengineered channels may require... Add.....Weld County is open to review and accept alternate bioengineering methods that provide protection to toe of bank slopes(i.e.jacks and lunkers,etc.). {Deleted:6/19/2006 16 6/29/2006, _-- 7.0 rotection Downstream Of Culverts Change. ...wl ' the District. To....within Weld Co UD&FCD STORM DRAINAE CRITERIA MANUAL VOLUME 2 HYDRAULIC STRUCTURES 4.1.2 Bridge Opening Freeboard Add....The bridge low chord elevation shall be a minimum of 1-foot above the 100-year water course energy grade line. CULVERTS 1.1.2 Headwater Delete....The headwater elevation for the design discharge should be consistent with the freeboard and overtopping criteria in the POLICY chapter........ Add.... The maximum culvert headwater to diameter ratios are: STORM FREQUENCY HEADWATER TO DIAMETER 10-Year HW/D< 1.0 100-Year HW/D< 1.5 The minimum culvert capacities are: STREET MINIMUM CAPACITY CLASSIFICATION (RECURRENCE INTERVAL) Local 10-Year Collector 10-Year Arterial 10-Year When the flow in a roadside ditch exceeds the capacity of the culvert and overtops the cross street, the flow over the street crown shall not exceed the minor storm and major storm depth limits presented in Chapter 3, Planning, Section 9.4 of the WCSDC manual, Weld County may require „,-- Deleted:Tables ST-2,ST-3,and ST-4 additional culvert capacity in order to prevent flooding of adjacent properties. Mme Urban Drainage uoscm Streets/Inlets/Storm Sewers chapter {Deleted:6/192006 J IS 6/29/2004_ 2.1.1 Energy and Hydraulic Grade Lines Add....The hydraulic grade line and energy grade line shall be determined for each culvert system and included in the Final Drainage Report. Each culvert system shall be profiled on the Final Construction Drawings and shall include the design flow hydraulic grade line. 3.5.3 Culvert Diameter Add....It is the policy of Weld County to require a minimum culvert diameter of 15 inches. Weld County may require additional culvert capacity in order to prevent flooding of adjacent properties. Delete....Since the pipe roughness influences the culvert diameter, both concrete and corrugated metal pipe should be considered in design,if both will satisfy the headwater requirements. Add....Refer to the "Weld County Design and Construction Standards and Specifications", latest edition,for allowable culvert pipe materials. Add....The Manning's roughness coefficient "n" for all culvert pipe sizing calculations shall be 0.013 regardless of pipe material (Concrete, PVC, or HDPE) with the exception of corrugated metal pipes which shall have a coefficient of 0.025. 4.1 Projecting Inlets Add....At a minimum, a culvert entrance and outlet shall include a flared end section. Erosion protection(riprap,etc.)may be required. 8.0 Trash/Safety Racks Change....The District strongly... To....Weld County strongly... 8.1 Collapsible Gratings Change....The District does not... To....Weld County does not... ,.{Deleted:6/19/2006 j 19 /5_29/2006, STORAGE 2.0 Application Of Different Types Of Storage Add....6. Above ground parking lot detention ponds may be utilized when land area for a grassed lined detention pond is not available. To prevent damage to and floatation of automobiles,parking lot detention ponds shall not exceed 12 inches in depth at any point. Parking lot detention ponds shall have signage to inform the general public about the potential for flooding. The 100-year water surface elevation of a parking lot detention pond shall not encroach into a public street. 3.1.2 Use of Regional(i.e.,Hvdrograph Routing)Detention Sizing Procedure Change....the District recommends... To....Weld County recommends or may require ... Add....Sizing of detention storage volumes shall utilize outflow hydrographs that have been properly calculated to account for variable head discharge rates. 3.1.3 Water Quality Capture Volume in Sizing Detention Storage Add....Within Weld County, the water quality capture volume shall be considered a portion of the total 100-year detention pond volume. 3.2.1 Maximum Allowable Unit Release Rates for On-Site Facilities Change....in a District-approved... To....in a Weld County-approved... 3.2.2 Empirical Equations for the Sizing of On-Site Detention Storage Volumes Change....for areas within the District. To....for areas within Weld County. Change....If the District has a master plan... To....Where Weld County has a master drainage plan... {Deleted:6/19/2006 20 6/29/2006, 3.2.4 Multi-Level Control Change....The District recommends... To....Weld County recommends... Delete the 5 -or 3.3 Design Storms for Sizing Storage Volumes Add....The 10-year and 100-year storms shall be the design storms for all water quality and detention pond designs,respectively,within Weld County. -{Deleted: 3.3.2 Drainage and Flood Control Change....Thus,whenever a District-approved... To....Thus,whenever a Weld County-approved... 3.3.3 Spillway Sizing Add....Each detention pond shall contain an emergency spillway capable of conveying the peak 100-year storm discharge draining into the detention pond. The invert of the emergency spillway shall be set equal to or above the 100-year water surface elevation. The depth of flow out the emergency spillway shall be<6 inches and the spillway shall have effective erosion protection. 3.3.4 Retention Facilities Change....problem,the District recommends... • To....problem,Weld County recommends... 3.4 Reservoir Routing of Storm Hydrographs for Sizing of Storage Volumes Change....2. Determine Hydrology: The hydrograph may be available in published district outfall system planning or a major drainageway master plan report. To....2. Determine Hydrology: .....The hydrograph may be available in Weld County Master Drainage Plans or Updates. Change....spelled out in a District-approved... {Deleted:6/19/2006 21 6/29/2004 To....spelled out in a Weld County-approved... 3.4.1 Initial Sizing Change 3....from a District Master Plan,... To 3....from a Weld County Master Plan,... 3.4.2 Initial Shaving Change....The District does... To....Weld County does... Change....the District encourages... To....Weld County encourages... 4.0 Final Design Considerations Change....The District urges... To....Weld County urges... 4.3 Geometry of Storage Facilities Change....within the District... To....within Weld County... Delete....(e) ...or fortification of the embankment to prevent catastrophic failure when overtopped. Add....(e) emergency spillway with erosion protection designed to safely convey the 100-year overtopping flows. 4.4 Embankments and Cut Slopes Change....2.Freeboard—The elevation of the top of the embankment shall be a minimum of 1 foot above the water surface elevation when the emergency spillway is conveying the maximum design or emergency flow. To....2. Freeboard — The elevation of the top of the embankment shall be a minimum of 1 foot above the 100-year water surface elevation in the detention pond. ,.(Deleted:6/19/2006 22 6/29/2006, Add....5. Emergency Spillway Downstream Protection — In order to protect the emergency spillway from catastrophic erosion failure, buried riprap shall be placed from the emergency spillway downhill to the embankment toe of slope and covered with 6 inches of topsoil. The riprap shall be sized at the time of final engineering design. Grouting of the riprap may be required. Add....6. Concrete Cutoff Wall—A concrete cutoff wall, 8 inches thick, 3 foot deep, extending 5 feet into the embankment beyond the emergency spillway opening, is encouraged on all private detention ponds and required on all publicly-owned regional detention ponds. A concrete cutoff wall will permanently define the emergency spillway opening. The emergency spillway elevation shall be tied back into the top of embankment using a maximum slope of 4:1. 4.7 Outlet Works Add....The outlet pipe of regional detention ponds shall contain a minimum of two (2) concrete cutoff walls embedded a minimum of 18"into undisturbed earthen soil. The cutoff walls shall be a minimum of 8 inches thick. The outlet pipe bedding material shall consist of native earthen soil and not granular bedding material to at least the first downstream manhole or daylight point. 4.8 Trash Racks Add....For safety reasons, trash rack angles are to be 3 horizontal to 1 vertical (3:1) or flatter per Urban Drainage research(Nelson&Kroeger,2005). 4.9 Operation and Maintenance Add....15. An operations maintenance manual for each water quality pond, detention pond, and outlet structure facility shall be developed and provided to Weld County Public Works and the development Home Owners Association at the time of final submittal. 4.11 Access Add....Drivable access applies only to Regional Detention facilities within Weld County. Each regional detention pond will be considered on a case-by-case basis at the time of final design. 5.0 Criteria For District Maintenance Eligibility Add....Regional Master Planned detention ponds, designed and constructed by or on behalf of Weld County, shall be owned and maintained by County as specified in the applicable Development Agreement(s). All other detention ponds shall be considered privately owned and privately maintained. .(Deleted:6/19)2006 23 (/29/2004 • FLOOD PROOFING 1.2.1 Classification of Flood Proofing Change....In the Denver metropolitan area, To....In the Weld County area, 4.1.1 Determine Flood Hazards Change....is available from the District and local officials. To....is available from Weld County officials or directly from FEMA at: http://www.msc.fema.gov/hardcopv.shtml. 4.1.3 Contact Local Officials Change....The District and local officials have... To....Weld County officials have... Change....District or community officials can... To....Weld County officials can... REVEGETATION 1.0 Introduction Change....within the Urban Drainage and Flood Control District(District). To....within Weld County. Change....in the District virtually... To....in Weld County virtually... Deleted:6/19/2006 • 24 6/29/20M, • 2.0 Scope of This Chapter and Relation of Other Relevant Documents To last paragraph Add.... See revisions to RV tables included in this chapter for Weld County-specific seed mix recommendations. 3.2 Site Preparation Add....Before revegetation work is started,an inventory of vegetation should be taken. If noxious weeds,as listed in Weld County Code,Chapter 15,exist on-site,appropriate steps need to be taken before, during, and after work is completed, to control their spread. Contact the Weld County Public Works Weed Division Supervisor at 970-304-6496 for additional information if needed. 3.3 Seeding and Planting Add....Seed mixtures should be coated with Mycorrhiza at the rate of 2 pounds per acre at the time of seeding. If mulching with straw,be sure the straw is seed free and weed free. 3.4 Maintenance Change....becoming established(normally the first year). To....becoming established(for 1 to 2 years at least). Change....Weed infestations should be managed using appropriate physical, chemical, or biological methods ..... To....Weed infestations should be managed using appropriate physical or chemical methods..... Delete....(See the other.....options). Add....The project owners/developer, not Weld County, will be responsible for site maintenance until vegetative establishment. 4.2 Soil Amendments Change....within the District,amendments... To....within Weld County,amendments... ,.(Deleted:6/19/2006 25 6/29/2006, Change....Consideration should be given to importing topsoil,instead.... To....Consideration should be given to importing topsoil,from the vicinity,instead.... Change....work in the District. To....work in Weld County. 4.3 Recommended Seed Mixes Change....within the District are... To....within the Weld County are... Add....The inclusion of wild flowers in the seed mix is optional in Weld County. Areas seeded along Weld County roads may be spot sprayed by the county to control the spread of noxious weeds. This spraying may affect some wild flower species. Do not plant frees or shrubs in the County right-of-way. Delete....the row containing Redtop(Agrostis alba)from Table RV-1 Delete....the row containing Nuttall's sunflower(Holianthus nuttallii)from Table RV-1 Delete....the row containing Canadian bluegrass(Ruebens)(Poa compressa)from Table RV-2 Delete....the row containing Flax*(Linum lewisii)from Table RV-2 Delete....the row containing Blue Flax(Linum lewisii)from Table RV-3 Delete....the row containing Canby bluegrass(Poa canbyi)from Table RV-4 Delete....the row containing Flax(Linum lewisii)from Table RV-4 Change....2.1 to....0.3 in Table RV-5 Change....0.3 to....2.1 in Table RV-5 Delete....the row containing Flax(Linum lewisii)from Table RV-5 Delete....the row containing Blue Flax(Linum lewisii)from Table RV-7 Delete....the row containing California poppy(Eschscholtzia califomica)from Table RV-7 Delete....the row containing Blackeyed Susan(Rudbeckia hirta)from Table RV-7 Deleted:6/19/2006 1 • • • • 26 _629/2006,_ Delete....the row containing Rubber rabbitbrush(Chrysothamnus nauseosus)from Table RV-8 Delete....the row containing Spanish bayonet(Yucca glauca)from Table RV-8 Delete....the row containing Smart weed(Polygonum persicaria)from Table RV-9 Delete....the row containing Foxtail barley(Hordeum jubatum)from Table RV-9 rnNeted:6/192006 27 6/29/200 GRASS SEEDING RECOMMENDATIONS FOR WELD COUNTY Add....GRASS SEEING RECOMMENDATIONS FOR WELD COUNTY GENERAL INFORMATION 1. If a species is listed as"15%to 30%" in mixture,please use a percentage within the given parameters to arrive at the amount used in the seed mix. 2. The numbers listed in the"Seeding Rate—Dryland" column is to be used for most dryland sites in this area. The amounts listed in"Seeding Rate—Irrigated"are to be used for those areas that will be irrigated,or sites that are highly erodible. 3. A seed mix is complete when a combination of the species chosen totals 100%. 4. The recommended varieties column lists the preferred varieties that are known to do well in this area. If this column is blank, refer to a local seed dealer for recommendations on varieties. TO OBTAIN DESIRED SEED MIX 1. Refer to the appropriate range site,defined in the local soil survey. 2. Chose the species within each range site. Names in bold italics represent the preferred species for each site. 3. If the range of percentage in the mix column lists"up to 45%"then chose an amount of the species to use in the mix that correlates within this range. 4. Take the percentage of each species used in the mix and multiple by the seeding rate. a. Example: i. Site is a dryland site. ii. Sand bluestem at 8.0 pounds of PLS/Acre is used at 25% in the see mix. iii. Take 25%x 8.0=2.0 pounds of Sand bluestem to use in the mix per acre. iv. Multiple the 2.0 pounds by the number of acres to get the total amount of pounds of the species to use for the mix. b. NOTE: The seeding rates are listed in Pounds of Pure Live Seed(PLS)per acre,and not in bulk pounds. ,.{Deleted:6119/2006 28 6/29/204 • Refer to the following tables for grass seeding recommendations. Deleted:6/192006 29 6/29/2004__ Table RV-10 GRASS SEEDING TABLES BASED ON RANGE SITES Species indicated in bold italics indicates the preferred species RANGE SITE: Deep Sands,Choppy Sands,Sandy Bottomland,Sandy Meadow, Sandy Foothills,Sandy Divide RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Sand Bluestem Elida,Woodward,Garden 20 to 35 8.0 16.0 Yellow Indiangrass Llano,Holt,Cheyenne,Oto 10 to 30 5.0 10.0 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder 10 to 30 2.5 4.5 Prairie sandreed Goshen 10 to 30 _ 3.5 6.5 Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell up to 15 4.5 9.0 Little bluestem Pastura,Cimmarron up to 10 _ 3.5 7.0 Blue grama Hachital,Lovington up to 10 1.5 3.0 Western wheatgrass Arriba,Barton,Rosana up to 10 8.0 16.0 Needleandthread up to 15 7.5 15.0 Thickspike wheatgrass Critana up to 10 5.5 11.0 Indian ricegrass Paloma up to 10 6.0 12.5 RANGE SITE: Sandy Plains RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Sand Bluestem Elida,Woodward,Garden 15 to 30 8.0 16.0 Prairie sandreed Goshen 10 to 25 3.5 6.5 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder 10 to 30 2.5 4.5 Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell 5 to 20 4.5 9.0 Yellow Indiangrass Llano,Holt,Cheyenne,Oto 5 to 20 5.0 10.0 Western wheatgrass Arriba,Barton,Rosana up to 20 8.0 16.0 Blue grama Hachital,Lovington up to 15 1.5 3.0 Little bluestem Pastura,Cimmarron up to 10 3.5 7.0 Needleandthread up to 15 7.5 15.0 Thickspike wheatgrass Critana up to 10 5.5 11.0 Indian ricegrass Paloma up to 10 6.0 12.5 {Deleted:6/192006 J 30 6/292000_ RANGE SITE: Loamy Plains Clayey Plains,Loamy Slopes RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Western wheatgrass Arriba,Barton,Rosana 20 to 45 8.0 16.0 Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell 20 to 40 4.5 9.0 Blue grama Hachital,Lovington 10 to 25 1.5 3.0 Green Needlegrass Up to 30 5.0 10.0 Needleandthread up to 15 7.5 15.0 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder up to 20 2.5 4.5 Big bluestem Kaw up to 10 5.5 11.0 Little bluestem Pastura,Cimmarron up to 10 3.5 7.0 Bur: 8.0 Bur: 16.5 Buffalograss Texoka,Sharps Improved up to 10 Floret: 3.0 Floret: 6.0 Yellow Indiangrass Llano,Holt,Cheyenne,Oto up to 10 5.0 10.0 RANGE SITE: Gravel Breaks,Loess Breaks,Sandstone Breaks RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell 20 to 45 4.5 9.0 Little bluestem Pastura,Cimmarron 10 to 35 3.5 7.0 Western wheatgrass Arriba,Barton,Rosana 10 to 20 8.0 16.0 Blue grama Hachital,Lovington 5 to 15 1.5 3.0 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder up to 20 2.5 4.5 Prairie sandreed Goshen up to 20 3.5 6.5 Yellow Indiangrass Llano,Holt,Cheyenne,Oto up to 20 5.0 10.0 Big bluestem Kaw up to 20 5.5 11.0 Needleandthread up to 15 7.5 15.0 Indian ricegrass Paloma up to 10 6.0 12.5 RANGE SITE: Shaly Plains,Alkaline Plains,Salt Flat,Salt Meadow,Saline Overflow RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Western wheatgrass Arriba,Barton,Rosana 30 to 45 8.0 16.0 Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell 20 to 40 4.5 9.0 Alkali sacaton Salado 10 to 35 1.0 1.5 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder up to 20 2.5 4.5 Blue grama Hachital,Lovington up to 15 1.5 3.0 Yellow Indiangrass Llano,Holt,Cheyenne,Oto up to 10 5.0 10.0 Big bluestem Kaw up to 10 5.5 11., peieted;6/192006 • 31 6/29/2006, ___ RANGE SITE: Overflow RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Western wheatgrass Arriba,Barton,Rosana 30 to 45 8.0 16.0 Green Needlegrass Vaughn,Butte,Niner,El Reno,Haskell 10 to 30 5.0 10.0 Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder 10 to 20 2.5 4.5 Big bluestem Kaw 5 to 20 5.5 11.0 Yellow Indiangrass Llano,Holt,Cheyenne,Oto 5 to 20 5.0 10.0 Blue grama Hachital,Lovington up to 10 1.5 3.0 {Deleted:6/192006• J • 32 6/29/2000 • RANGE SITE: Wet Meadow RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Grenville,Nebraska 28,Blackwell, Switchgrass Pathfinder 15 to 30 2.5 4.5 Yellow Indiangrass Llano,Holt,Cheyenne,Oto 15 to 30 5.0 10.0 Big bluestem Kaw 15 to 30 5.5 11.0 Prairie Cordgrass 15 to 30 Little Bluestem Pastura,Cimmarron up to 10 3.5 7.0 Western wheatgrass Arriba,Barton,Rosana 10 to 20 8.0 16.0 Slender wheatgrass San Luis up to 10 5.5 11.0 RANGE SITE: North of Highway 14 RECOMMENDED %IN SEEDING RATE COMMON NAME VARIETIES MIX DRYLAND IRRIGATED Western wheatgrass Arriba,Barton,Rosana 30% 8.0 16.0 Blue grama Hachita,Lovington 30% 1.5 3.0 Sideoats grama Vaughn,Butte,Niner,El Reno,Haskell 30% 4.5 9.0 Bur: 8.0 Bur: 16.5 Buffalograss Texoka, Sharps Improved 10% Floret: 3.0 Floret: 6.0 4.5 Mulching Add.... • At least 70 percent(%)of the mulch by weight shall be 10 inches or more in length. • The appropriate use of fabric blankets under trees and shrubs is suggested. 5.0 Post-Construction Monitoring Delete....several years... Add....three to five years.... Delete....first two growing Add....first two to three growing Delete....at least once a year.... Add....at least twice a year... {Deleted:6/192006 33 6/29/2000, Design Examples Add....Weld County does not have specific values to use for the CI,C2,and C3 coefficients within the"Detention Volume by Modified FAA Method"spreadsheet. Please use the UD&FCD(Denver area)values. UD&FCD STORM DRAINAE CRITERIA MANUAL VOLUME 3 STORMWATER QUALITY MANAGEMENT No changes to the Stormwater Quality Management chapter are currently proposed. NEW DEVELOPMENT PLANNING 1.2 Four-Step Process Within Step 3,paragraph 2: Change....The Urban Drainage and Flood Control District does not... To....Weld County does not... 1.3 Other BMPs Add....Weld County will consider and allow use of new, innovative BMP technologies upon review of the proposed BMP(s)on a case by case basis. 1.5.4 Guidance for Selecting and locating WOCV Facilities Paragraph 2- Change....by local jurisdictions and the District. To....by Weld County. 1.5.5 Incorporating WOCV into Stormwater Quantity Detention Basins Add....to the last paragraph: Weld County requires that the 100-year detention volume be provided for a given site and allows the WQCV to be incorporated within the 100-year volume. Deleted:6/19/2006 34 6/29/2006, STRUCTURAL BMP'S 6.4 Design Considerations Change....paragraph 3...are approved in advance by the District. To....are accepted in advance by Weld County. 9.0 Retention Pond(RP)—Sedimentation Facility Add....Retention facilities are normally not allowed in Weld County, but will be considered by Weld County for special circumstances. Retention facilities shall be sized to contain a volume equal to twice the 100-year storm runoff volume plus one foot of freeboard. Water within a retention facility shall be mechanically removed and disposed of off-site by the property owner within 48 hours after a storm event. TYPICAL STRUCTURAL BMP DETAILS Typical Outlet Structure General Notes Note#8 Change....The underdrain, including a shutoff valve, from the perimeter of the pond is required (SQJ aknej j for.... 1L-Atm..) c.. CQlvt,i ti„ ) To....The underdrain, including a shutoff valve accessible from the perimeter of the pond is required for... Fiu�re1 Delete....Figure 1 in its entirety. Figure 2 Delete...Overtopping Spillway Option. Change....Outlet Pipe= 120%of 100-YR Capacity within the Drop Box Outlet Option To....Outlet Pipe= 100%of 100-YR Capacity within the Drop Box Outlet Option :l Deleted:6/19/2006 35 6/29/2004 Figure 2-a Delete....Overtopping Spillway Option. Change....Outlet Pipe= 120%of 100-YR Capacity within the Drop Box Outlet Option To....Outlet Pipe= 100%of 100-YR Capacity within the Drop Box Outlet Option MAINTENANCE RECOMMENDATIONS Add the following introductory paragraph: Weld County will require that all submittals include an Operations and Maintenance manual for all water quality and detention pond facilities. The operations and maintenance manuals shall also be distributed to the applicable Home Owners Association and/or business park association (or equivalent). The operations manuals will include instructions on safe and correct operations, repair, and maintenance of all installed equipment and facilities and recommended inspection schedules. INDUSTRIAL AND COMMERCIAL BEST MANAGEMENT PRACTICES Add the following introductory paragraph: Weld County will require that all submittals include an Operations and Maintenance manual for all industrial and commercial water quality and detention pond facilities. The operations and maintenance manuals shall also be distributed to the applicable business park association or equivalent). The operations manuals will include instructions on safe and correct procedures for the operation, repair, and maintenance of all installed equipment and facilities. The manuals shall provide recommended inspection schedules. 5.0 Structural Controls In Table IC-1 Delete....Retention Pond Add....Spill Containment Area {Deleted:6/19/2006 36 6/29/2006, NONSTRUCTURAL BEST MANAGEMENT PRACTICES No changes to the Stormwater Quality Nonstructural Best Management Practices chapter are currently proposed. CONSTRUCTION BEST MANAGEMENT PRACTICES 1.1 General Change....and submitted to the local jurisdiction to obtain a construction or site grading permit. To....and submitted to Weld County to obtain a grading permit or a building permit. 1.3 Erosion and Sediment Control Plan Change....must be submitted to the appropriate local government for review and approval. To....must be submitted to the Weld County for review and acceptance. Add....The written narrative report can be a subsection within the drainage report. The erosion and sediment control plan must include specific inspection and repair/maintenance requirements. 1.3.1 Narrative Report Change Item 16 as follows: ....in the (insert name of local jurisdiction) file for this project. The plan appears to fulfill the Urban Drainage and Flood Control District's technical criteria and the criteria for erosion control and requirements of(insert name of local jurisdiction). To....in the Weld County file for this project. The plan appears to fulfill Weld County criteria for erosion control. 1.3.2 Site Plan Change Item"m"as follows: ...placed in the(insert name of local jurisdiction)file for... To....placed in the Weld County file for... Deleted:6/19/2006 37 6/29/2004 1.3.3 Approval of Erosion and Sediment Control Plan Delete....The entire paragraph. Add....An Erosion and Sediment Control Plan must be accepted prior to issuance of a grading permit or a building permit. The final Erosion and Sediment Control Plan must be consistent with the Drainage Report. Approval of the Erosion and Sediment Control Plan does not imply acceptance or approval of Drainage Plans, Utility Plans, Street or Road Plans, or any other aspect of site development. 1.3.4 Exemptions and Variances Change....may be provided by a city or county. To....may be provided by Weld County. Change Item"lb"as follows: ...or other structures on plots zoned R1-R3 of less than five(5)acres in size... To....or other structures where the disturbed area will be less than one(1)acre in size... Change Item 1.d as follows: ...less than five(5)acres... To....less than one(1)acre... Change Item 1.d as follows: ...locally-approved Erosion... To....locally-accepted Erosion... Change Item 1.h as follows: ...local jurisdiction... To....Weld County... Delete....Item 2 Variances in its entirety Add....Item 2 Variances as follows: {Deleted:6/192006 • • • 38 6129/20% • The Weld County Engineer may grant variances from the criteria of the Construction Best Management Practices chapter by his/her acceptance of the Final Drainage Report in which the variance request is well documented. 2.2 Summary of Criteria Revegetation Change....opinion of the District or county of jurisdiction,is... To....opinion of Weld County,is... Disposition of Temporary Measures Change....or as authorized by the District or county of local jurisdiction. To....or as authorized by Weld County. 2.4.2 Stormwater Quality Plans Second paragraph: Delete....Where local regulations have not been developed, 3.3.2 Temporary Revegetation Change....suitable for the Denver metropolitan area... To....suitable for the Weld County area... 4.1 Vehicle Tracking Change....deemed necessary by the District or county of jurisdiction, To....deemed necessary by Weld County, 4.3.3 Sediment Basins Change....in the Denver region shall be... To....in the Weld County area shall be... ,.{Deleted:6/19/2006 • 39 6/29!7006 5.1 Working Within or Crossing a Waterway Change....2. ...The city or county of jurisdiction should also To....2. ...Weld County should... 5.3 Outlet Protection Change....temporary total retention of the runoff form a 24-hour, 100-year storm may be provided. Written approval by the local city or county must be obtained for total retention of stormwater. To....temporary total retention of the runoff may be considered on a case by case basis upon acceptance from Weld County. 8.0 Disposition of Temporary Measures Change....or as authorized by the city or county jurisdiction. To....or as authorized by Weld County and applicable coordinating agencies(CDOT,CDPHE). Delete....the entire second paragraph Add.....The Professional Engineer preparing the construction phase erosion and sediment control plan shall obtain the approval of Weld County before removal of any temporary measures. 9.0 Maintenance Delete....the entire second paragraph Add....The Professional Engineer preparing the permanent erosion and sediment control plan shall submit a schedule of planned inspection and instructions for operations and maintenance for all installed permanent erosion and sediment control measures. The plan shall include identification and specifications (size, materials, etc.) of parts and equipment potentially needing repair or replacement over the life of the installed measures. A copy of the inspection schedule and instructions for operations and maintenance shall be provided to the applicable Home Owners Association or Business Park management(or equivalent). 10.0 Erosion and Sediment Control Warranty Prior to acceptance and approval of all installed permanent erosion and sediment control measures, Weld County will require that the owner shall warrant the measures shown on the approved erosion {Deleted:6/19/2006 no 6/29/2094 and sediment control plan are properly constructed, installed, and are free from defective materials and/or defective workmanship. {Deleted:6/192006 41 6/29/2004 Page 1 of 2 Esther Gesick From: David Bauer Sent: Tuesday,August 22, 2006 1:35 PM To: Esther Gesick Subject: RE: Weld County Code Ordinance#2006-7.1st Esther, I looked at the hard copy I had of the Volume 3, Urban Drainage Manual. The notes there are different than what is included in the current download pdf on the Urban Drainage website -- hence the confusion on wording for Note #8. The current download-able note #8 is: Underdrains along the perimeter of the permanent pool, including a shutoff valve, are recommended for Constructed Wetland Basins and a Retention Ponds to help dewater the pool for rehabilitative maintenance. Note # 8 in our Addendum should state: Underdrains, accessible from the perimeter of the permanent pool, including a shutoff valve, are recommended for Constructed Wetland Basins and a Retention Ponds to help dewater the pool for rehabilitative maintenance. I show our change shown in red italics. It's really really minor but clarifies that the maintenance can occur even if the pond has water in it. I don't know why Urban Drainage has not caught this one yet. Thank you for all you efforts on this — it's been a year in the making and I can see the finish line, David Bauer Weld County Public Works From: Esther Gesick Sent: Friday, August 18, 2006 10:15 AM To: Bruce Barker; David Bauer Cc: Jennifer Luna Subject: Weld County Code Ordinance #2006-7.1st Bruce and David, Please review the attached document and let me know of any necessary changes. I did take some liberty to rearrange the order for Code consistency purposes. It is attached in Word and WordPerfect versions(Word did not convert the tables very well, but you'll get the idea.) I will be back from vacation on 8/30 and I slated first reading for 9/11, which will give me a week to do any changes you may have by then. Thanks! 8/31/2006 Hello