Storm Water Flow Rate Calculations from a North Carolina Licensed Engineer
Budget: $1,500 – $3,000 USD
Storm Water Project Scope of Work for City of Asheville North Carolina
Provide stormwater calculations as required by the city of Asheville North Carolina for the proposed 24” HDPE culvert on the attached site plan and the As-Built stamped drawing. 75% will be paid upon receipt of the stormwater calculations and stamped plans, and 20% will be paid upon receipt of the stamped As-Built record drawing.
These plans will have to have the engineering firm's information and seal, stamp along with the calculations that conform to the following guidelines:
The existing conceptual site plan that has been attached will need to be recreated from the .pdf that you have received. A .dwg file may or may not be available. In any case, all of the owner’s information will need to be updated because the information on the .pdf provided shows incorrect ownership information.
Public and private storm drain systems shall be designed on the basis of the 10-year storm for inlet spacing, the 25-year storm for drainage pipe sizing, the 50-year storm for cross-street drainage, and the 100 year storm for flood plain areas. Pipes shall be designed at full flow with a maximum allowable capacity 7/8 full.
• Runoff rates shall be calculated by the Rational Method, Natural Resource Conservation Service (NRCS) Method, or other acceptable procedure. Runoff computations shall be based on rainfall data published by the North Carolina Department of Environment and Natural Resources (NCDENR) “Erosion and Sediment Control Planning and Design Manual” (hereafter referred to as “NCDENR Erosion Control Manual”).
• For drainage areas of 20 acres or less, the Rational Method is recommended to calculate runoff. For drainage areas greater than 20 acres use the NRCS Method.
• Time of concentration (Tc) shall be determined by a method that is approved by NCDENR.
• Storm duration shall equal the time of concentration (Tc).
• Storm drain pipe shall be sized in accordance with the Manning Equation.
• Storm drains shall be designed to provide a velocity of at least 2 feet per second at design flow and no more than 15 feet per second.
• The minimum pipe diameter shall be 15 inches for private structures and 18 inches within the public right of way.
All other detailed parameters for the City of Asheville can be found at this link:
https://codelibrary.amlegal.com/codes/ashevillenc/latest/ashevilledesign/0-0-0-1031
Along with the initial stamped design and calculations, stamped As-Built calculations that are performed after the actual installation from a licensed North Carolina engineer are also required within this scope of work. The As-Built Stamped Record Drawing shall conform to the city of Asheville North Carolina’s requirements:
9E Appendix E: Storm Drainage and Stormwater As-built Record Drawing Specification
Per the final release requirements outlined in the Code of Ordinances; All stormwater management BMPs, facilities and related improvements, and all storm drainage structures and conveyances shall be field surveyed and represented on an as-built record drawing per the following specifications;
• 1 copy of a digital electronic file of the as-built record drawing shall be delivered on CD-ROM in
• AutoCAD .dwg format (Version 14 or newer).
• 2 hardcopies of each as-built record drawing sheet are required upon delivery.
• All digital as-built record drawing entities shall be referenced using the North Carolina State Plane Coordinate System, U.S. Survey Feet as Units of Measure (grid coordinates, carried to two or more decimal places), NAVD 88’ Vertical Datum, NAD 83’ Horizontal Datum (epoch specified). This spatial reference shall be clearly noted on the drawing. All drawing entities shall be referenced to a monument grid tie associated with at least one storm drainage structure located on the subject property. The relative horizontal and vertical accuracy of field surveyed data should be equal to or less than 0.10 feet.
• The as-built record drawing shall include a North arrow indicating Grid North.
• The as-built record drawing shall include the City of Asheville issued permit number related to the storm drainage and/or stormwater project.
• The as-built record drawing shall include a vicinity map depicting the general location of the site.
• The general feature type, northing, easting, and top elevation of all storm drainage structures, stormwater BMPs, facilities, and related improvements shall be clearly labeled on the drawing, adjacent to the feature to which they correspond OR the labels may be configured using a cross- referenced table system that utilizes unique identifiers.
• All pipes and like conveyances shall be represented on the drawing and associated with text or labels indicating slope, distance, diameter (or dimensions), material type, inverts (in & out), and dissipation pad sizes. Text and labels should be clearly legible and placed next to the features to which they correspond OR they may be configured using a cross-referenced labeling and table system that utilizes unique identifiers.
• All above-ground detention or retention facilities, BMPs, or similar facilities shall be represented on the drawing using 1’ contours enclosed by outer breakline(s). Labels or text indicating the maximum storage volume (for a 50-year storm event) and associated elevation should be placed inside the feature or adjacent to the feature with which it corresponds. Perimeter fencing associated with storage facilities must be represented on the drawing per as-built conditions. A field surveyed as-built detail of any outlet control structures or associated features must be included.
• All accessible structures and conveyances associated with underground storage systems shall be represented within the drawing. Labels or text indicating the maximum storage volume (for a 50- year storm event) and associated elevation should be placed inside the feature or adjacent to the feature with which it corresponds. A field surveyed as-built detail of any outlet control structures or associated features must be included.
• The outline of the 100-Year (1% annual chance) floodplain boundary and any associated floodway or non-encroachment areas shall be represented on the drawing per the approved site plans.
• The as-built record drawing shall include the boundary of the subject property by courses and distances with references.
• Storm drainage structures and conveyances, and stormwater BMPs, facilities, and related features shall be included in one or more separate CAD drawing layers, where the keyword “Stormwater” shall be included in the title or name for all such layers.
• Impervious features and facilities, including but not limited to; driveways, parking areas, walkways, building footprints & utility pads shall be represented on the drawing per the approved site plans. These features shall be included in one or more separate CAD drawing layers, where the keyword “Impervious” shall be included in the title or name for all such layers.
• The as-built record drawing shall be certified, signed, dated, and sealed by a registered design professional certified to sign and seal such documents. The text “As-Built Record Drawing” shall be clearly marked on each page.
A link to the above requirements is below:
https://codelibrary.amlegal.com/codes/ashevillenc/latest/ashevilledesign/0-0-0-1371
Provide stormwater calculations as required by the city of Asheville North Carolina for the proposed 24” HDPE culvert on the attached site plan and the As-Built stamped drawing. 75% will be paid upon receipt of the stormwater calculations and stamped plans, and 20% will be paid upon receipt of the stamped As-Built record drawing.
These plans will have to have the engineering firm's information and seal, stamp along with the calculations that conform to the following guidelines:
The existing conceptual site plan that has been attached will need to be recreated from the .pdf that you have received. A .dwg file may or may not be available. In any case, all of the owner’s information will need to be updated because the information on the .pdf provided shows incorrect ownership information.
Public and private storm drain systems shall be designed on the basis of the 10-year storm for inlet spacing, the 25-year storm for drainage pipe sizing, the 50-year storm for cross-street drainage, and the 100 year storm for flood plain areas. Pipes shall be designed at full flow with a maximum allowable capacity 7/8 full.
• Runoff rates shall be calculated by the Rational Method, Natural Resource Conservation Service (NRCS) Method, or other acceptable procedure. Runoff computations shall be based on rainfall data published by the North Carolina Department of Environment and Natural Resources (NCDENR) “Erosion and Sediment Control Planning and Design Manual” (hereafter referred to as “NCDENR Erosion Control Manual”).
• For drainage areas of 20 acres or less, the Rational Method is recommended to calculate runoff. For drainage areas greater than 20 acres use the NRCS Method.
• Time of concentration (Tc) shall be determined by a method that is approved by NCDENR.
• Storm duration shall equal the time of concentration (Tc).
• Storm drain pipe shall be sized in accordance with the Manning Equation.
• Storm drains shall be designed to provide a velocity of at least 2 feet per second at design flow and no more than 15 feet per second.
• The minimum pipe diameter shall be 15 inches for private structures and 18 inches within the public right of way.
All other detailed parameters for the City of Asheville can be found at this link:
https://codelibrary.amlegal.com/codes/ashevillenc/latest/ashevilledesign/0-0-0-1031
Along with the initial stamped design and calculations, stamped As-Built calculations that are performed after the actual installation from a licensed North Carolina engineer are also required within this scope of work. The As-Built Stamped Record Drawing shall conform to the city of Asheville North Carolina’s requirements:
9E Appendix E: Storm Drainage and Stormwater As-built Record Drawing Specification
Per the final release requirements outlined in the Code of Ordinances; All stormwater management BMPs, facilities and related improvements, and all storm drainage structures and conveyances shall be field surveyed and represented on an as-built record drawing per the following specifications;
• 1 copy of a digital electronic file of the as-built record drawing shall be delivered on CD-ROM in
• AutoCAD .dwg format (Version 14 or newer).
• 2 hardcopies of each as-built record drawing sheet are required upon delivery.
• All digital as-built record drawing entities shall be referenced using the North Carolina State Plane Coordinate System, U.S. Survey Feet as Units of Measure (grid coordinates, carried to two or more decimal places), NAVD 88’ Vertical Datum, NAD 83’ Horizontal Datum (epoch specified). This spatial reference shall be clearly noted on the drawing. All drawing entities shall be referenced to a monument grid tie associated with at least one storm drainage structure located on the subject property. The relative horizontal and vertical accuracy of field surveyed data should be equal to or less than 0.10 feet.
• The as-built record drawing shall include a North arrow indicating Grid North.
• The as-built record drawing shall include the City of Asheville issued permit number related to the storm drainage and/or stormwater project.
• The as-built record drawing shall include a vicinity map depicting the general location of the site.
• The general feature type, northing, easting, and top elevation of all storm drainage structures, stormwater BMPs, facilities, and related improvements shall be clearly labeled on the drawing, adjacent to the feature to which they correspond OR the labels may be configured using a cross- referenced table system that utilizes unique identifiers.
• All pipes and like conveyances shall be represented on the drawing and associated with text or labels indicating slope, distance, diameter (or dimensions), material type, inverts (in & out), and dissipation pad sizes. Text and labels should be clearly legible and placed next to the features to which they correspond OR they may be configured using a cross-referenced labeling and table system that utilizes unique identifiers.
• All above-ground detention or retention facilities, BMPs, or similar facilities shall be represented on the drawing using 1’ contours enclosed by outer breakline(s). Labels or text indicating the maximum storage volume (for a 50-year storm event) and associated elevation should be placed inside the feature or adjacent to the feature with which it corresponds. Perimeter fencing associated with storage facilities must be represented on the drawing per as-built conditions. A field surveyed as-built detail of any outlet control structures or associated features must be included.
• All accessible structures and conveyances associated with underground storage systems shall be represented within the drawing. Labels or text indicating the maximum storage volume (for a 50- year storm event) and associated elevation should be placed inside the feature or adjacent to the feature with which it corresponds. A field surveyed as-built detail of any outlet control structures or associated features must be included.
• The outline of the 100-Year (1% annual chance) floodplain boundary and any associated floodway or non-encroachment areas shall be represented on the drawing per the approved site plans.
• The as-built record drawing shall include the boundary of the subject property by courses and distances with references.
• Storm drainage structures and conveyances, and stormwater BMPs, facilities, and related features shall be included in one or more separate CAD drawing layers, where the keyword “Stormwater” shall be included in the title or name for all such layers.
• Impervious features and facilities, including but not limited to; driveways, parking areas, walkways, building footprints & utility pads shall be represented on the drawing per the approved site plans. These features shall be included in one or more separate CAD drawing layers, where the keyword “Impervious” shall be included in the title or name for all such layers.
• The as-built record drawing shall be certified, signed, dated, and sealed by a registered design professional certified to sign and seal such documents. The text “As-Built Record Drawing” shall be clearly marked on each page.
A link to the above requirements is below:
https://codelibrary.amlegal.com/codes/ashevillenc/latest/ashevilledesign/0-0-0-1371