The Drainage Plan sheet and supporting documentation, as applicable, shall be submitted with the Preliminary Plat. This sheet shall be prepared on a reproducible copy of the Plat so that the same information shall be repeated together with the following:
A. 
Topographical information of the existing land included within the proposed plat boundaries and extending 200 feet outside the boundaries or covering the limits of adjacent property that will affect or impact stormwater drainage on or across the site, whichever is greater, as shown by contour lines of two-foot (2') intervals. Contour information is available from the Town Engineer. Topography shall be based on the North American Vertical Datum of 1988 (NAVD88).
B. 
A drainage area map at a suitable scale (1"=200' or larger) showing all proposed onsite and existing offsite drainage areas with points of concentration/discharge and contours at two foot intervals identified; the location, dimension, description and flow lines of existing and proposed drainage features and systems; existing and proposed streets and alleys; proposed crests, sags and street intersections with proposed flow arrows; existing and proposed floodplains and floodways on or adjacent to the site; any proposed topographic changes affecting drainage; benchmark information; a bar scale and a north arrow.
C. 
Include a table of runoff calculations with the following headings and subsequent information for each offsite and onsite drainage area and concentration/discharge point.
* Drainage area designation
* Area in acres (A)
* Runoff coefficient (C)
* Frequency factor (Cf)
* Time of concentration (Tc)
* Proposed 100 year intensity (I100)
* Proposed 100 year runoff (Q100)
* Comments indicating to where runoff is proposed to flow
D. 
All drainage must be planned in the best interests of the immediate and adjacent properties.
E. 
Drainage arrows shall be shown for all streets and drainage easements. When the maximum permissible capacity of streets to carry stormwater is exceeded the location of storm sewers, curb inlets and open channels shall be shown.
F. 
Supplemental information showing the preliminary design calculations for drainage shall be furnished on 8-1/2 x 11 inch paper attached to the Preliminary Drainage Plan.
G. 
A general description/narrative indicating how proposed onsite and offsite drainage runoff is to be handled in accordance with drainage criteria and the adequacy of the existing downstream drainage system as it relates to proposed runoff from the site.
H. 
The width of drainage and other easements shall be shown.
I. 
Typical sections of any channels with dimensions and depth of flow and freeboard indicated.
J. 
Finished floor elevations of existing and proposed residential and commercial structures and garages.
K. 
The Town Engineer may reduce the above requirements or request additional information as applicable to the lot(s) associated with the replat or development plat.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
These plans shall be submitted with a copy of the Final Plat to the Town Engineer for review and approval for Major Subdivisions and for Minor Subdivisions with Infrastructure when required.
A. 
GENERAL REQUIREMENTS.
1. 
Prior to the commencement of any construction of public works improvements, the developer or person who intends to construct such project shall present plans, specifications, and projections of probable cost setting forth in detail all elements of construction to the Town Engineer for approval. In the case of public improvements associated with subdivision development, the engineering plans (including descriptions of all necessary off-site easements) must be approved in accordance with all requirements of this Subdivision Ordinance prior to approval of the Final Plat.
2. 
The developer shall retain a registered Civil Engineer, licensed to practice in the State of Texas, for all design in new subdivisions or developments, including streets, storm drains, water and sanitary sewers. Each plan sheet shall show the seal and signature of the registered professional Engineer who prepared the plan, including registration number. Alternately, a note signed by the engineer of record that the plans are preliminary, not intended for construction and were prepared under the authority of the subject engineer including registration number of the engineer may be used. However, prior to bidding the project for construction and before a preconstruction conference is held the construction plans shall be signed and sealed by a professional engineered licensed by the State of Texas.
3. 
These plans shall be submitted on standard 22 x 34 or 24 x 36 inch sheets, and shall include the information required herein. Plan and profile sheets shall be presented with the profile view lines up and placed directly underneath the plan view at a scale of 1" = 40' or larger horizontal and 1"=4' or larger vertical scale. A north arrow, date of preparation and bar scale shall be included on each sheet, as applicable.
4. 
Construction plans greater than one (1) sheet shall contain a cover sheet showing the name of the project; the engineer of record including address, phone number, and Texas Board of Professional Engineers firm registration number; the name of the developer or owner including address and phone number; a location map; an index of drawings; and a signature line for LCMUA approval, as applicable.
5. 
[Reserved.]
B. 
FINAL DRAINAGE PLANS:
Unless otherwise specified herein, drainage requirements shall be based on the City of Denton Drainage Design Criteria Manual. The Hydraulic Manual prepared and compiled by the Texas Department of Transportation Bridge Division, with current revisions, may be used in cases not covered by the City of Denton Drainage Design Criteria Manual.
1. 
DRAINAGE AREA MAP AND TABLES.
a) 
Provide a drainage area map at a suitable scale (1"=200' or larger) showing all proposed onsite and existing offsite drainage areas and sub-areas with points of concentration/discharge and contours at two foot intervals identified; the location, dimension, description and flow lines of existing and proposed drainage features and systems; existing and proposed streets and alleys; proposed crests, sags and street intersections with proposed flow arrows; existing and proposed floodplains and floodways on or adjacent to the site; any proposed topographic changes affecting drainage; benchmark information; a bar scale and a north arrow.
b) 
Include a table of runoff calculations with the following headings and subsequent information for each offsite and onsite drainage area and concentration/discharge point.
* Drainage area designation
* Area in acres (A)
* Runoff coefficient (C)
* Frequency factor (Cf)
* Time of concentration (Tc)
* Proposed 100 year intensity (I100)
* Proposed 100 year runoff (Q100)
* Comments indicating to where runoff is proposed to flow
c) 
Provide open channel calculations.
d) 
Provide street capacity calculations.
e) 
Provide an inlet design table. Inlet designations should match drainage area designations.
f) 
Label proposed storm sewer lines.
g) 
Present pre-developed versus post-developed runoff comparison for all discharge points.
h) 
Provide a general location map of the subdivision showing the entire watershed (a 7-1/2 minute USGS Quadrangle is satisfactory).
2. 
STORM SEWER PLAN & PROFILE.
a) 
Show stationed plan and profile of all storm sewers.
b) 
Tie storm sewer stationing with paving stationing.
c) 
Show and label sized and type of pipe, curb inlets, junction boxes, etc. in plan and profile. Label inlet top of curb elevation, flowline elevation and paving station number on plan view. Label inlets as “Special” when nonstandard depths is used.
d) 
Show hydraulics on each segment of pipe to include Q100,C= Manning’s flowing full flow capacity, S, V, V2/2g.
e) 
Plot and label HGL elevations and friction slope whenever full flow in pipe system is anticipated.
f) 
Show all existing and proposed utilities in plan and profile view.
g) 
Show inlet bypass and flow arrows on plan views.
h) 
Show laterals on trunk profile with stations.
i) 
Provide lateral profiles for all laterals longer than 25 feet or with a utility crossing.
j) 
Show existing and proposed ground line in profile view.
k) 
Indicate flow line elevations of storm sewers on profile on 100-foot stations and at the entrance and exits of manholes and junction boxes, etc. Show pipe slope (percent grade).
l) 
Show water surface at all outfall of storm drain in profile and label elevation.
m) 
Provide scaled and dimensioned cross sections for road, railroad and other ditches and associated hydraulic computations.
n) 
Show construction details of all nonstandard structures and appurtenances including dimensions, reinforcing, and components.
3. 
CHANNELS.
a) 
Provide typical section for channel improvements. Include a section for each location where the channel changes in its dimensions or configuration.
b) 
Provide plan and profile showing existing contours and proposed centerline, top of bank, flow line elevations, stationing and 100-year water surface elevation.
c) 
Provide hydraulic calculations on all sections.
d) 
Provide structural details for channel section that involves concrete, gabions, paving material, etc.
e) 
Show all erosion control measures and concrete rip-rap, as applicable.
4. 
DETENTION PONDS.
a) 
Provide drainage area map and show all computations for runoff affecting the detention basin.
b) 
Provide a plan with existing and proposed contours for the detention pond and plan for structural measures, including outflow structure.
c) 
Show and label maintenance access width, concrete pilot channels, access ramp, slope protection, fencing and emergency spillway with dimensions and type of material, as applicable.
d) 
Provide structural details and calculations for any item that is not a standard detail.
e) 
Provide detention basin volume calculations and elevation versus storage curve.
f) 
Provide hydraulic calculation for outflow structure and elevation versus discharge curve.
g) 
Provide routings or modified rational determination of storage requirements, demonstrating the critical duration is used, as applicable.
h) 
Show all erosion control measures and concrete rip-rap, as applicable.
C. 
WATER AND SEWER PLANS.
1. 
Water and Sewer plans shall comply with the requirements of the Lake Cities Municipal Utility Authority. Property served by pre-existing private water systems may apply for a waiver of this requirement...[sic]
2. 
Water Plans shall include the following:
a) 
An overall plan view of the water system for the entire development.
b) 
Stationed plan view of all water mains and stationed profile for all water mains 12 inches in diameter or larger, including pipe size (according to LCMUA requirements) and type of material.
c) 
When profile views are required, show flow line elevations of proposed water mains in the profile view on 100 foot intervals and at bends and connections to existing systems and include grades of pipe segments.
d) 
Stationed locations of all valves, bends, crosses, tees, fire hydrants, reducers and other fittings and appurtenances in the plan view.
e) 
Stationed location of all valves, fittings and other appurtenances in the profile view, as applicable, along with existing and proposed utilities and storm drains that will cross over or under the water line.
f) 
The location of lot lines, easement lines, right-of-way lines, proposed and existing water mains, sewer mains, storm sewers and other utilities in the plan view.
3. 
Sewer Plans shall include the following:
a) 
An overall plan for the sanitary sewer systems for the entire development.
b) 
Stationed plan and profile views of all sanitary sewers, including the pipe size and type of material.
c) 
Flow line elevations of proposed sanitary sewers in the profile views on 100 foot intervals and at entrances and exits of manholes and tie-ins to existing systems. Existing and proposed ground elevations over the sanitary sewer should be included in the profile view. Grades for each main between manholes shall be included.
d) 
Stationed location of all proposed manholes, cleanouts and service lines in the plan view, along with existing and proposed utilities and storm drains that will cross over or under the sanitary sewer.
e) 
The location of lot lines, easement lines, right-of-way lines, locations of proposed and existing sewer mains, water mains, storm sewers and other utilities in the plan view.
D. 
GRADING PLAN.
1. 
Provide a grading plan showing the existing topography using one-foot contours based on the on-the-ground survey or controlled aerial topographic map (dashed lines and labeled) to extend a minimum of 20 feet from the property line onto adjacent property. Show proposed one-foot contours (solid lines and labeled).
2. 
The grading plan shall also include spot elevations and water directional arrows to define the flow pattern.
3. 
Show proposed minimum finished floor elevations and finished pad elevations.
4. 
Show centerline of roadways and stationing every 100 feet.
5. 
Show existing to remain and proposed sidewalks.
6. 
Show proposed right-of-way, easements and building setback lines.
7. 
Show the 100-year flood limits, if any.
8. 
Show existing inlets scheduled to remain and proposed inlets.
9. 
Show existing storm sewer pipes scheduled to remain and proposed storm sewer pipes.
10. 
Show roadway and alley sags and high points.
11. 
Show top of curb elevations every 50 feet on streets, alleys and parking lots.
12. 
Show proposed retaining walls with top and bottom of wall elevations every 50 feet.
13. 
Provide cross sections of typical swale, berm, channel, etc. as a component of the grading plan.
14. 
Where reclamation of the 100-year floodplain is involved provide a note on the grading plan that states Upon completion of all public improvements, submission of all documents necessary to obtain a Letter of Map Revision (LOMR) from FEMA shall be submitted to the Town of Shady Shores. The LOMR will then be reviewed and sent to FEMA prior to acceptance of the subdivision. The LOMR is necessary to remove any lot within the floodplain from the Flood Insurance Rate Map. All changes or additional data, as requested by FEMA upon its review of the LOMR are the responsibility of the owner and/or developer.
E. 
FINAL STREET PAVING PLANS.
1. 
Provide a plan and profile of all streets showing existing grades at each side of the right-of-way and proposed top of curb grades.
2. 
Provide elevations in profile every 100 feet and at changes in slope for the centerline and/or back of curb on both sides of the street. Provide elevations in profile every 25 feet through a vertical curve. Show percent grades.
3. 
Show typical right-of-way cross-sections of proposed streets showing the width, thickness and type of pavement, base and subgrade; the location within the right-of-way; specific street crown information; and pavement reinforcing steel, as applicable.
4. 
Show horizontal and vertical curve data.
5. 
Show sidewalk, sidewalk ramps, flume entrances and driveway locations when driveways are intended to be constructed with street improvements.
6. 
Show curb return elevations in the plan view on the street and on the intersecting street.
7. 
Show inlets, flumes and other structures in the plan view that may affect the street.
8. 
Show top of inlet elevations.
9. 
Show positive overflow drainage path at sag inlets.
10. 
All other requirements of the current street standards shall be included in the plans.
11. 
Provide anticipated trip generation table as a separate document for review based on proposed land use and Institute of Transportation Engineers (ITE) Trip Generation Manual. For purposes of determining if a Traffic Impact Analysis (TIA) is required, trips are calculated based on the ITE Trip Generation Manual average rates for the proposed use and proposed or expected square footage of buildings or land area as appropriate. The applicant may provide trip generation calculations based on the uses and square footages or land areas using the ITE regression equation or the average. The Town Engineer shall review the information to determine if further analysis is required and may waive the requirement.
F. 
EROSION CONTROL PLAN.
1. 
An erosion control plan shall be included with the construction plans showing all proposed temporary erosion and sedimentation controls, including location, dimensions and details for any required sedimentation ponds. Contour information and proposed inlet locations shall be shown along with any special standard details.
G. 
SIGNING AND LIGHTING PLANS.
1. 
Signing plans shall show the location and type of signs to be installed throughout the development.
2. 
Lighting plans shall show the location of proposed street lights and conduit throughout the development. Lighting standards shall be submitted to the Town for approval prior to construction.
3. 
Signing and lighting plan information can be included on the same plan sheets if the information can be clearly shown.
H. 
SPECIFICATIONS AND COST ESTIMATES.
1. 
The Town has adopted the specifications outlined in the Public Works Construction Standards as published by the North Central Texas Council of Governments (NCTCOG), latest version (See Section 5.5 below). Any alternate or special specifications must be submitted, reviewed and approved by the Town Engineer prior to approval of the construction plans.
2. 
Estimates of probable construction cost shall be prepared using quantities shown on the construction plans and recent unit prices from bids on similar projects. Reasonable contingencies should be included to cover uncertainty in the projection. Actual recent bids supported by bid and performance bonds may be used in lieu of projections of probable cost.
3. 
Upon approval of the construction plans, specifications and estimates of probable construction cost by the Town Engineer, approval of the contract documents, bonds and financial assurance; acquisition of all necessary off-site easements, and upon receipt of the inspection fees, the Town shall issue a permit for the construction of public improvements.
(Ordinance 130 adopted 6/5/00; Ordinance 217-9-2009, sec. 5, adopted 9/14/09; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
The Subdivider must furnish a written statement to the Town designating that the subdivision will be served with gas or will be total electric service. If a gas distribution system is to be installed then all distribution main and service lines shall be installed before street construction is complete.
The Subdivider must furnish a written statement to the Town designating how the subdivision will be served by electrical, natural gas, telephone and cable television. Utility construction shall be coordinated with street construction to avoid unnecessary pavement cuts.
The Subdivider’s choices for public utilities to serve the subdivision are required to be approved, in advance of Final Plat approval by the Town Council.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
A separate document of report entitled “Engineering Report” shall be submitted with final plans and specifications. This report shall summarize calculations and other Engineering information pertaining to the major items of design significance as may be necessary in the Town’s review of the plans and specifications to determine whether the facilities proposed for construction have been designed in accordance with the intent of the Design Standards contained or referenced herein. Calculations should include drainage facilities, water demand, sewage flows, and any others which are considered necessary by the Town.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
The Town of Shady Shores, Texas, does adopt the Public Works Construction Standards as published by the North Central Texas Council Governments (NCTCOG), plus any local amendments adopted by the Town of Shady Shores, for use in public works or facilities construction within the Town of Shady Shores and its Extraterritorial jurisdiction. These specifications are adopted in their entirety. All builders, developers, and contractors are to utilize said specifications in the construction of any public facilities or projects which are anticipated to be dedicated to, accepted by, or utilized by the public within the Town of Shady Shores and its extraterritorial jurisdiction. To the extent that any of the provisions of these standard specifications are in conflict with any other Town ordinances, the most restrictive or exacting standard shall apply.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
A. 
PURPOSE:
The standards and requirements of this section are adopted for the following purposes:
1. 
To protect human life, health and property;
2. 
To provide for the sound use and development of all areas in such a manner as to minimize flood impacts;
3. 
To retain natural floodplains in a condition that minimizes interference with floodwater conveyance, floodwater storage, aquatic and terrestrial ecosystems, and groundwater and surface water;
4. 
To minimize erosion and sedimentation problems and enhance water quality; and
5. 
To minimize future operational and maintenance expenses.
B. 
GENERAL REQUIREMENTS:
General requirements for development of an area shall include the following drainage considerations:
1. 
Drainage study required.
All drainage studies, calculations and designs both off-site and on-site shall be based upon the full development of the drainage basin.
2. 
Drainage improvements required.
All developments shall provide for any new drainage facilities, the improvement of any existing drainage facilities, channel improvement or grading, driveway adjustments, culvert improvements or any other improvements, drainage facility or work which is necessary to provide for the stormwater drainage needs of the development in accordance with the requirements and design standards of this section, including but not limited to any drainage facilities, improvements or other work which is necessary to:
a) 
Adequately protect the development from flooding, including the effects of the one-hundred-year flood;
b) 
Provide for the conveyance of all stormwater from the development when fully developed to an adequate discharge point.
c) 
Provide for the conveyance of existing storm drainage flowing through the development.
d) 
Properly control any increase in the upstream or downstream stage, concentration or water surface elevation caused by the development to a minimum.
3. 
Off-site drainage.
Off-site drainage facilities and improvements shall be provided by the development wherever additional stormwater runoff from the development would adversely affect any off-site property or would overload an existing drainage facility, whether natural or manmade. If the developer cannot obtain the necessary easements to make required off-site drainage improvements, upon the request of the developer after compliance with the provisions contained herein, the Town may bring condemnation proceedings to obtain the off-site drainage easements.
4. 
Detention facilities.
Detention facilities may be used to reduce peak discharges. All detention facilities shall comply with the design criteria of this section. Detailed engineering studies of the entire basin shall be required to ensure that the timing of peak flows has not been altered to create higher peak flow elsewhere in the basin. Detention facilities may be constructed in phases, if phased so as to provide for the timely needs of the development.
5. 
Development in Floodplains.
Development within a floodplain as defined by the base flood is prohibited.
6. 
Floodplain modification and permitting.
When any development desires to redefine the floodplain area as defined by the Federal Emergency Management Agency within the development, the necessary engineering studies shall be submitted. The studies will demonstrate that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood at any point within the community and the limits of the revised floodplain area. The area within the floodplain which will be necessary to provide for the drainage needs of the development shall be dedicated to the public as a drainage easement on the final plat.
7. 
Drainageways and improvements.
a. 
Generally, drainageways which are still functioning primarily in a natural and adequate state shall not be altered or improved to provide for the drainage needs of a development, unless there is no other reasonable means or method to provide for such drainage as determined by the Town Engineer.
b. 
As part of the required improvements, all debris, small brush, vines and other obstructions shall be cleared from that portion of any channel located within or on the perimeter of the development, as directed by the Town Engineer, prior to the connection of any utilities for any building within a development. A development may also be required to provide clearing of off-site floodways to the extent necessary to adequately receive or convey stormwater runoff from the development, based on the roughness coefficient approved during the design process for the final plat.
c. 
Development discharging stormwater runoff into a floodway shall provide supplemental vegetation, on-site and off-site, when necessary to preserve or restore any disruption to the natural state. The vegetation planted shall be as approved by the Town Engineer. The vegetation requirement shall apply to any portion of any floodway, on-site or off-site, which would be affected by runoff from the development.
8. 
Minimum finished floor elevation.
Minimum finished floor elevations for proposed development areas subject to flooding shall be two (2) feet above the one-hundred-year flood elevation based on ultimate watershed development conditions, and shall be substantiated by an elevation certificate, certified by a licensed professional engineer. The elevation certificate must be presented before the issuance of a building permit.
C. 
GENERAL DESIGN STANDARDS:
General design standards shall be as follows:
1. 
Drainage design manual adopted.
The City of Denton Drainage Design Criteria Manual as amended, including associated Water Quality Requirements is adopted. In addition to meeting the requirements expressly set out herein, all drainage systems shall comply with the design requirements contained in the drainage design manual adopted by ordinance. Where there is any conflict between a provision set forth herein this ordinance and a provision of the City of Denton Drainage Design Manual, the provisions herein shall apply.
2. 
Drainage computation data.
Design of drainage facilities and improvements shall be based on hydraulic and hydrologic computations prepared by the developer engineer. Computations and data shall be submitted to the Town Engineer for approval.
3. 
Street access crossing channels.
No development shall be designed to access a public street across a channel without providing adequate clearance for the channel. All bridges crossing channels shall have one (1) foot of freeboard between the 100-year water surface elevation and the lowest beam of the bridge. All culvert crossings shall have two (2) feet of freeboard between the 100-year water surface elevation and lowest top of curb or pavement elevation of the street.
4. 
Channel requirements.
Channel regulations and improvement shall be in accordance with the following:
a) 
Channels which serve as drainageways shall be maintained in a natural state as provided for in this section. Undeveloped branches of natural channels and creeks of local drainage systems should remain in a natural state unless maintenance and hydraulic considerations require improvements.
It shall be the policy of the Town to discourage the destruction of natural drainageways by construction of lined channels and other structural measures, where nonstructural flood control is feasible.
b) 
Open Channel Design:
Open channel capacity shall be calculated by Manning’s Formula and roughness coefficients shall be as follows:
Type of Lining
Roughness Coefficient “N”
Maximum Permissible Mean Velocity
Mowed Grass
0.035
6 ft./sec.
Natural Vegetation
0.030–0.120*
6 ft./sec.
Concrete Lined
0.015
15 ft./sec.
* As applicable
Side slopes of channels shall be no steeper that than 3:1 in earth and 2:1 when lined with concrete.
c) 
The minimum grade allowed on a channel or ditch shall be 0.5% (five-tenths foot per one hundred feet) for a concrete-lined channel or ditch and 1.0% (one foot per one hundred feet) for a grass-lined channel or ditch unless otherwise approved by the Town Engineer.
d) 
Channels shall have one (1) foot of freeboard above the one-hundred-year flood.
e) 
The design for all open channels shall be based on geotechnical investigations, unless determined to be unnecessary by the Town Engineer.
5. 
Lot drainage.
Generally, each lot shall be designed or graded to direct stormwater into an abutting street, alley, channel or inlet. If drainage is provided in the rear of any lot by a channel or closed storm drainage system the facilities shall be designed for the 100-year flood. Where it is not practical to provide abutting drainage facilities for each lot, drainage facilities such as a closed pipe system or drainage ditch shall generally be required whenever the stormwater runoff from one (1) or more lots is directed across a second residential lot, or whenever facilities are necessary to avoid an adverse effect on any other lot. It shall be unlawful for any person to fill, modify or otherwise obstruct any drainage easement designed or used as a drainage channel or structure.
D. 
SPECIFIC DESIGN CRITERIA.
Design criteria. Design criteria shall be as follows:
1. 
Where a subdivision is traversed by a watercourse, drainageway, natural channel or stream, there shall be provided an easement and/or right-of-way conforming substantially to the limit of the one hundred (100) year flood. In the new subdivisions the developer shall provide all the necessary easement and right-of-way required for drainage structures, including storm drain piping and open channels. Easement width for storm sewer pipe shall not be less than twenty (20) feet.
2. 
Drainage structures are to be constructed at all street crossings over the major streams in the Town and shall accommodate the 100-year design discharge.
3. 
In determining the most feasible flood control method, consideration shall be given to nonstructural measures as well as structural measures.
4. 
In developments adjacent to floodplains, all floor elevations shall be at least two (2) feet above the one hundred (100) year flood elevations and shall be substantiated by an elevation certificate, certified by a licensed professional engineer. The elevation certificate must be presented before the issuance of a building permit.
5. 
In areas where the 100-year flood elevation has been previously determined the 100-year flood elevation shall not be increased due to new development.
6. 
Design flood frequencies. The following listed facilities shall be designed to handle the flood frequencies indicated:
Facility
Flood Frequency
(Years)
Street capacity and enclosed pipe system, if needed
100
Driveway culverts and roadside ditches
100*
Street right-of-way
100
Improved and natural channels
100
Culverts
100
Bridges
100
Floodplain
100
* The Town will allow driveway culverts and ditches to be designed for the 25-year storm where physical constraints exist. This determination will be made at the time the permit is issued. This provision does not apply to new development, including residential and nonresidential.
7. 
Street drainage requirements.
a. 
The permissible water spreads for curbed streets are based on the 100-year flood. All streets shall be capable of conveying the 100-year flood flows and shall not exceed the top of curb. The spread limits listed below shall apply to the following streets and facilities:
Permissible Water Spread 100-Year Flood
Street Classification
Permissible Spread
Arterial
One lane open in each direction or one travel lane open, as applicable
Collector
One travel lane open
Local or Residential
Top of curb
Historic
Within the right-of-way
b. 
Curb height on all streets are to be not more than six (6) inches and at least equal to the depth of water at design flow.
c. 
The combined capacity of storm drain pipe, street and surface drainage shall contain the one hundred (100) year design flow within street rights-of-way and/or drainage easements.
d. 
Drainage flows across intersections will be allowed at local or residential street intersections (none allowed across arterial or collector streets) and shall be at valley crossings.
e. 
Street crowns for curbed streets shall be reduced for approximately one hundred (100) feet on each side of valleys[.]
f. 
Concrete valley gutters shall be provided where the gutter flow must be carried across intersections of curbed streets, minimum width of valley gutters shall be eight (8) feet.
8. 
Pipe system requirements.
a. 
Storm drain systems capable of conveying the 100-year frequency flood are required when water spread and intersection cross flow limits are exceeded for curbed streets. Closed pipe systems shall be required for discharges up to and including the equivalent flow of a forty-eight (48) inch pipe, unless the grade of the natural ground is less than 0.5 percent, then an enclosed pipe system shall be required for discharges up to and including one hundred (100) c.f.s.
b. 
The minimum velocity with the pipe flowing full shall be three (3) c.f.s. per second.
c. 
The minimum storm drain pipe diameter shall be eighteen (18) inches.
d. 
Pipe soffits at changes in pipe sizes shall be set at the same elevation.
e. 
Vertical curves in the conduit will not be permitted, and horizontal curves will be permitted only with the approval of the Town Engineer.
f. 
Manufactured “Y” fittings shall be required at all pipe junctions.
g. 
Pipe junction angles shall be a maximum of 60 degrees.
h. 
Manholes shall be placed at the connection of two (2) or more laterals, at bends greater than 30 degrees, at grade changes, and at the beginning/end of the storm drain system when required by the Town Engineer. Maximum manhole spacing shall be as follows:
Pipe Size
(inches)
Maximum Spacing
(feet)
18–36
600
42–60
1,000
Larger than 60
1,000
9. 
Culverts.
All street culverts shall meet the following requirements:
a. 
Culverts shall be designed to carry the expected water flow (based on design flood frequency) within the channel. Culverts shall not be less than 18-inch diameter unless otherwise approved by the Town Engineer.
b. 
For all driveways with open ditch drainage the culvert size will be determined by the Town engineer and sized on a case-by-case basis to meet current standards. Replacing an existing broken pipe or resetting an existing pipe does not require increasing its size to meet current standards. Residential homeowners, builders and developers will set their own culverts within Town right-of-way, subject to inspection by the Town Engineer or Building Official at the following phases:
1. 
After the culverts are set in place to check the proper elevation of the flow line. For concrete driveways forms must be in place (steel reinforcement not required at this inspection phase). For asphalt driveways base material should be in place.
2. 
After application of driveway surface and headwalls.
Each culvert end must be even with the roadway ditch elevation, not below it. In some cases this will require the driveway to have a slight rise or re-grading the entire ditch in front of the property and/or beyond. Permission to excavate along another’s property must be obtained, in writing, by the permittee.
Developments which are required to submit engineering plans shall include culvert sizing as part of those plans, including associated catchment areas and flow calculations based on current drainage criteria.
c. 
Culverts shall be made of approved classes of reinforced concrete pipe (RCP) or corrugated metal pipe (CMP) and shall be joined together properly by materials approved by the Town Engineer.
d. 
The minimum grade allowed for all culverts shall be 0.5% (five-tenths foot per one hundred feet) unless otherwise approved by the Town Engineer.
e. 
Headwalls shall be provided at all culverts.
f. 
Culvert discharge - velocity limitations:
Culvert Discharging On To:
Maximum Allowable Velocity
(F.P.S.)
Native soil
6
Sod Earth
6
Paved or Riprap Apron
15
Rock
15
Outlet protection shall be provided where discharge velocities will cause erosive conditions.
10. 
Detention ponds.
The following requirements and design standards shall apply to detention ponds to the extent they do not conflict with any applicable federal or state laws or regulations, as amended:
a. 
The one hundred year flood shall be used to determine the volume of detention storage required. Detention facilities shall be designed so that any additional runoff generated by the proposed development will not increase the amount of original discharge for storm frequencies from the five-year to the one-hundred-year flood.
b. 
The modified rational method shall be used to construct runoff hydrographs for detention storage design when the contributing drainage area is two hundred (200) acres or less. The procedures outlined in Soil Conservation Service Technical Release No. 20 (TR-20) or in the U.S. Corps of Engineers’ Flood Hydrographs Package (HEC-1) shall be used to determine runoff hydrographs for detention storage design when the contributing drainage area exceeds two hundred (200) acres. The Town Engineer may approve the use of other methods for runoff hydrographs when appropriate.
c. 
The outflow structure of a detention basin discharging water into any natural stream or unlined channel shall discharge at a culvert discharge rate.
d. 
Detention basins resulting from excavation shall provide positive drainage. The side slopes for any excavated detention basin, which is not in rock, shall not exceed 4:1.
e. 
Earthen embankments used for water impoundments must be constructed according to specifications for fill material and be designed based upon geotechnical investigations of the site.
f. 
Detention basins shall be designed with adequate ingress and egress to allow for regular maintenance, including periodic desilting and debris removal.
g. 
An emergency spillway or overflow area shall be provided at the maximum 100-year water level with a minimum capacity for 25-year storm with six inches of freeboard. The spillway shall be constructed of concrete, unless otherwise approved by the Town Engineer. The spillway must also meet all applicable State and Federal criteria.
h. 
All detention ponds shall be stabilized against significant erosion, including at outflow structures and inlets.
i. 
A concrete pilot channel shall be provided with a minimum width of 10 feet and a minimum grade of 0.50% for publicly maintained ponds and a 6 foot width and a minimum grade of 0.50% for privately maintained ponds.
11. 
Easements.
In addition to any other provisions herein relating to easements for improvements, the following requirements for easements for drainage improvements, channels and facilities required for any development by this section shall apply:
a. 
All drainage systems and facilities which are not to be included within an existing or proposed public street right-of-way shall be located within easements to be dedicated to the town and shall have adequate access to a public street. Prior to acceptance of any public drainage facilities, all easements within which the facilities are located shall be cleared of all buildings, structures, or other obstacles that would interfere with access to the easements.
12. 
Positive Overflow.
At all sag inlets positive overflow shall be provided such that the overflow elevation at the low point shall not be higher than 0.5 feet above the top of curb.
(Ordinance 130 adopted 6/5/00; Ordinance 217-9-2009, sec. 6, adopted 9/14/09; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
The boundaries of any subdivision presented for review and filing shall be monumented and such monuments shall be duly noted on said plat and within the accompanying dedication instrument according to Rule 663.11 of the Texas Board of Land Surveying (Certification and Monumentation of Surveys), in no case shall a boundary course of said subdivision to be monumented in intervals greater than 1,300 feet.
Subsequent to installation of utilities and pavements, all lot corners, curve points and changes in course in any line with [within] the subdivision shall be monumented in accordance with said Board of Land Surveying Rule 663.11 by the platting surveyor under the sponsorship of the developer.
A. 
All monuments shall be of materials recognizable as being those property boundary monuments by professional surveying standards, and shall be of sufficient length and girth and placed in locations sufficiently stable to withstand abuse of normal conditions with significant movement.
1. 
Under most circumstances no steel rods smaller than 1/2" in diameter and shorter than 13" in length should be used nor should pipes smaller than 1/2" inside diameter and shorter than 13" in length be used.
2. 
No monument made of a wood material shall be used.
B. 
The point of beginning for land in a subdivision described by metes and bounds should be clearly defined on the plat, and any plat shall be clearly related to the survey, tract, or subdivision of which it is a part.
C. 
All distances shown on the final plat shall be horizontal ground lengths.
D. 
A minimum of three (3) elevation benchmarks shall be installed in all Major subdivision reflecting elevation using North American Vertical Datum of 1988. The Town Engineer may require the installation of additional benchmarks in unusually large or complex site.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)
All construction projects shall include temporary erosion and sedimentation controls in accordance with item 3.12 of the Standard Specifications and Stormwater Quality Best Management Practices for Construction Activities published by the North Central Texas Council of Governments. Stormwater Pollution Prevention Plans shall be submitted for approval by the Town Engineer prior to approval of construction projects.
(Ordinance 130 adopted 6/5/00; Ordinance 300-03-17 adopted 3/13/17; Ordinance 329-12-2019 adopted 12/9/19)