A.1 - Storm Water Management Plan Checklist

To standardize the review process and minimize the time for approval by the city during review of the plat and construction drawings for a subdivision, a complete submittal regarding the analysis of existing drainage conditions and the design of modifications or new drainage facilities is necessary. The owner of the property to be developed is required by the Director of TCI to provide, at the owner's expense and as a condition of construction plan approval, a storm water management report for the total development area to be ultimately constructed. The storm water management report shall contain all of the necessary support data, methodologies used in calculations, and conclusions. The checklist below will be used by the city reviewer as a guide during the evaluation of all storm water management reports submitted to the city. The purpose of the checklist is to expedite the review process for both the engineer and the city, and to aid the engineer in the preparation of reports for the city's review. The storm water management report shall be submitted to the Director of TCI through the director of planning and development services prior to approval of any construction plans.

			STAFF USE ONLY
I. Storm Water Management Plan (SWMP)	N/A	Included	Complete	Incomplete	Comments
A. GENERAL
1. Signed, sealed & bound Storm Water Management Plan (SWMP) (one (1) hard copy and one (1) digital copy)
2.  Introduction & Executive Summary of existing conditions, proposed project, and methods used for analysis
3. Adverse Impact Statement: "The increased runoff resulting from proposed development will not produce a significant adverse impact to other properties, habitable structures or drainage infrastructure systems to a point 2,000 feet downstream. Downstream conditions (including actual curb depth) in this reach have been field verified by myself or members of my staff. Therefore, the owner requests to participate in the Regional Storm Water Management Program by paying a fee- in-lieu-of onsite detention."
4.  Regional Storm Water Management Program Participation Form
5.  Project Location Map
6.  Digital Flood Insurance Rate Map (DFIRM) with site superimposed
7.  Grading Plan (Also required in construction plans)
•  Lots grading properly according to FHA Lot Grading Type (A, B, C)
•  Driveway Detail, reference to critical Type "C" lots
• Check T-intersections, cul-de-sacs, and knuckles to make sure runoff is contained in streets
• Interceptor channels are required when:
◦ Offsite drainage area flowing onto site is greater than 3 acres, or
◦ Offsite drainage area flowing onto site is greater than 2 average residential lot depths
8.  Aerial map
•  To expedite review, delineate site boundaries, point 2,000 ft downstream, all downstream storm water facilities and other pertinent physiographic information.
9.  Onsite Drainage Area Map(s) (to scale) for Existing, Proposed, and Ultimate Conditions :
•  Show Time of Concentration (Tc) pathways
•  Show individual and overall drainage areas for the site. Indicate area of each watershed
•  Show computation points and points of discharge; Table of hydrologic calculations for each individual and cumulative drainage area and points of discharge. Include acreage, runoff coefficients, Tc values, and rainfall intensities for the 5, 25, & 100-yr storm events, as applicable.
10.  Overall Drainage Area Map(s) (to scale) for Existing, Proposed , and Ultimate Conditions:
•  Include point 2,000 ft downstream (For lots less than three (3) acres in size adverse impact analysis need only extend to where tributary drainage areas equal to 100 acres)
•  Show Time of Concentration (Tc) pathways
•  Show individual and overall drainage areas for the site. Indicate area of each watershed
•  Show computation points and points of discharge
•  Table of hydrologic calculations for each individual and cumulative drainage area and points of discharge. Include acreage, runoff coefficients, Tc values, and rainfall intensities for the 5, 25, & 100-yr storm events, as applicable
11.  Impervious Cover Exhibit(s) : Indicate existing and proposed impervious cover
12.  Floodplain Submittal is required if property is within, abutting, or adjacent to a floodplain, see Floodplain Section below.
13. Verify if site is in a Mandatory Detention Area
B. HYDROLOGY
1.  Description of Method for Hydrologic Analysis Detailed runoff calculations include:
• Hydrologic Calculation Methods (Reference Chapter 5, Hydrology):
◦ Rational Method: Drainage area ≤ 200 acres
• Detailed Time of Concentration (Tc) calculations;
• Weighted runoff coefficients; Rainfall intensities;
• Peak flow for Q5, Q25, Q100
◦ SCS or other Hydrograph Method allowed for drainage areas > 20 acres and required for drainage areas > 200 acres
• Typical SCS programs used: HEC-HMS, Pond Pack, Hydraflow, XPStorm, etc.
• Provide all electronic files
• Detailed Time of Concentration/Lag Time calculations
• SCS curve number (CN) value: provide detailed calculations & Soil Survey Map or Geotechnical Report to support
◦ Soil Survey Map of area (site delineated, soil type & acreage of each soil group)
• % Impervious Cover detailed calculations and exhibit
• Verify rainfall depths
• Routing Values: Provide detailed calculations (types of routing are Modified Puls or Muskingam Cunge)
◦ Verify Reach lengths for routing and velocities
2.  Table comparing the Existing, Proposed, & Ultimate Condition Peak Flows (5, 25 and 100yr)
C. HYDRAULICS
1.  General:
• Storm water infrastructure for drainage areas < 100 ac, design for the Q25
• For all storm water facilities with drainage area ≥ 100ac, design for Q100
2.  Street Capacity:
• Local 'A': Q5 contained within top of curb, Q25 contained within ROW
• Collector/Local 'B': Q25 contained within top of curb
• Primary/Secondary Arterial: Q25 contained within top of curb & one lane in each direction shall remain passable with a flow depth not to exceed 0.3 ft
• For drainage area > 100 acres, Q100 contained within top of curb. Use actual curb heights in calculations for existing streets (non-standard curbs, street overlays, etc.)
3.  Dead end street draining to unpaved surface:
• Runoff velocity < 6 fps.
• Ensure runoff will flow into drainage easement
4.  Storm Drain:
• Inlets designed for 25 yr capacity
• HGL/EGL: provide detailed calcs (including junction losses). Show on S.D. profiles
• EGL: below top of curb and top of junction box or, if approved by City, specify bolted manhole covers.
• HGL: below gutter
• Min easement: 15 ft min or 6 ft from pipe limits
• Minimum Pipe Slope: 0.3%
• Minimum Cleaning Velocity: 3 fps for 5-yr (20% ac) storm
• Maximum Permissible Velocity:
◦ Maximum Velocity for Trunk lines: 15 fps
◦ Maximum Velocity for Laterals: No limit
• Slopes or velocities outside the allowable range may require additional certifications at permitting or final inspection and/or additional warranties.
• Reinforce Concrete Pipe required under public streets
• Pipe Diameter
◦ Trunk Lines: Minimum 24 in diameter
◦ Laterals and driveway crossings: < 24 in diameter may be allowed on a case-by-case basis
5.  Channels: (provide detailed calculations)
• If Drainage area < 100ac : Contain W.S. for Q25 plus freeboard (see Table 9.3.14)
• If Drainage area ≥ 100ac : Contain W.S. for Q100 or Q25 plus freeboard, whichever is greater
• Channel bend freeboard calculations (if centerline radius is < 3 times the bottom width)
• Verify if the channel has adequate drainage easement
• Include a channel maintenance schedule for new channels
• Verify Manning's Roughness Coefficient (n) (Reference Table 9.2.4.1)
• Earthen channel:
◦ Verify 15 ft access easement on one side
◦ Max 6 fps except as shown in Table 9.3.8
◦ Pilot channel required if slope < 0.5%
◦ Maximum 3:1 side slopes
• Concrete channel:
◦ Verify 15 ft access easement on one side, 2 ft easement on the other
◦ Minimum longitudinal slope: 0.4% or 0.1% with minimum cleaning velocity of 3 fps for existing Q5
◦ For trapezoidal channels, maximum 1.5:1 side slope without geotech design
◦ Handrails or fencing required for channels with vertical walls or side slopes > 2:1 when wall height exceeds 2 ft
◦ Check outfall velocities
• Side-Lot Flumes:
◦ Public Easements: verify 10 ft access easement on one side, 2 ft easement on the other
◦ Private Easements: verify 2 ft easement on either side
◦ Slope and velocity requirements are the same as for concrete channels.
• Turf Reinforcement Matting: 6 fps < V < 12 fps. If > 12 fps, engineer's report should certify that material is appropriate for velocity. Include manufacturer specs & installation instructions. Engineer to certify at final inspection that material was installed correctly.
• Interceptor channel: Drainage easement shall extend a min of 2 ft on both sides of the channel
• Handrails or fencing required on vertical headwalls greater than 2 ft in height and wing walls with slopes steeper than 2:1
6.  Outfalls / Outlets / Transitions
• When one channel discharges into another channel verify that storm water will be contained within the receiving channel. Verify that the outfall velocity into the receiving channel will not result in runoff jumping out of the receiving channel.
• Concrete rip rap or other velocity control/erosion protection measures may be required at pipe/channel and channel/channel intersections and transitions.
• If outfall velocity exceeds 6 fps at transition to earthen channel or other non-paved surface, provide energy dissipators or other velocity control measures
◦ Verify that the proposed energy dissipator type is appropriate for the outfall conditions (Reference Chapter 10, Table 10.4.3)
◦ Detailed calculations are required when energy dissipators are proposed
◦ Provide retard spacing and concrete transition length where applicable
• Hydrograph timing & analysis of backwater may affect outfall and dissipator calculations
D. ADVERSE IMPACT ANALYSIS
1.  Narrative
• Provide an Adverse Impact Analysis and an Adverse Impact Statement
• Discuss in detail the downstream conditions
• Discuss if drainage patterns have changed from the previously approved MDP, if applicable
2.  If site work permit ONLY with no increase in impervious cover - Demonstrate that drainage patterns are not obstructed. Grading plan required. Detailed adverse impact analysis may be required.
3.  Provide detailed hydrologic & hydraulic calculations from proposed development to 2,000 ft downstream
• Verify hydrologic calculation method
• Compare existing, proposed, and ultimate peak flows
• Reference Checklist Section B
4.  Street Capacity:
• Local 'A': Q5 contained within top of curb, Q25 contained within ROW
• Collector/Local 'B': Q25 contained within top of curb
• Primary/Secondary Arterial: Q25 contained within top of curb & one lane in each direction shall remain passable with a flow depth not to exceed 0.3 ft
• For drainage area > 100 acres, Q100 contained within top of curb. Use actual curb heights in calculations for existing streets (non-standard curbs, street overlays, etc.)
• Velocity < 10 fps
5.  Curb Inlets:
• Opening capacity detailed calculations for Q25
• HGL/EGL: provide detailed calcs (including junction losses).
• EGL: below top of curb
• HGL: below gutter line
6.  Storm Drain:
• HGL/EGL: provide detailed calcs (show losses). Show on storm drain profiles.
• EGL: should be below junction box lid/manhole
7.  Channels: (provide detailed calculations for Ultimate Q & Channel Capacity):
• Contain ultimate Q25 plus freeboard or ultimate Q100, whichever is greater, within drainage easement/ROW & does not flood habitable structures.
8.  Culvert:
• Runoff should not overtop an existing structure under the roadway for the existing, proposed, and ultimate of the 5, 25, & 100 yr condition OR &hellip
• A new culvert should be designed for the 25 yr ultimate for drainage areas ≤ 100 acres or 100-year for drainage areas greater than 100 acres
9.  Low Water Crossings (Provide detailed calculations and discuss):
• Low Water Crossing must not be classified as "Dangerous" during regulatory (5, 25, or 100 yr frequency) storm events
• If the WSE exceeds this criterion the crossing may be improved in lieu of providing onsite mitigation measures or paying a fee-in-lieu of detention. This is to be considered on a case-by-case basis and may require a developer agreement.
10.  Underground Utilities in Floodplain:
• Provide buoyancy and scour calculations for the 5, 25, and 100 yr storm events
• Show any required concrete capping or encasement in construction plans
E. DETENTION
1.  Provide Drainage Area Map(s) (to scale) for Existing and Proposed Conditions:
• Also include ultimate conditions, if applicable (phased construction, basin serving multiple lows, etc.)
• Include Time of Concentration/Lag time flow paths
• Modified Rational Method may be used for drainage areas up to 20 acres
• SCS Method to be used for drainage areas > 20 acres (i.e. HEC-HMS, Pond Pak, Hydraflow, etc.)
• SCS Method to be used for modeling multiple ponds, regardless of drainage area
2.  Provide results in tabular format with detailed calculations for allowable/existing, proposed, and ultimate discharges from the structure
3.  Post-development discharges from the pond for the 5, 25, and 100 yr must be equal to or less than existing conditions
4. Provide inflow and outflow hydrographs for 5, 25, and 100 yr (proposed, ultimate)
5. Providerequired storagefor the 5, 25, and 100 yr (proposed, ultimate)
6.  Include stage vs. discharge and stage vs. storage tables
7.  Provide outlet rating curve
8.  Provide Pondpack, Hydraflow Hydrographs, or other applicable calculation files on CD
9.  Verify if pond qualifies as a TCEQ dam. (Reference Chapter 13 for dam requirements)
10.  Verify basin side slopes:
• Maximum 3:1 for earthen berm/side slopes
• Concrete side slopes/walls may require structural details or geotech analysis depending on slope and height (see concrete channel wall requirements)
11.  Check hydraulics of outlet structure:
• Verify weir and orifice size(s) and elevation(s)
• Check effect of tail water elevation on outfall hydraulics
• Outfall velocity: maximum 6 fps (sandy soils may require a discharge velocity less than 6 fps)
• Provide energy dissipation if needed (include calculations and construction details)
12.  Verify design water surface elevations are below the top of pond:
• 100 yr proposed/ultimate or 25 yr proposed/ultimate plus freeboard
• If TCEQ dam, provide auxiliary spillway
13.  Restrictor plates may be required for ponds with phased development
14.  Provide pond grading on subdivision plat
15.  Provide detention pond construction plans (signed & sealed), including but not limited to:
• Pond grading
• Notes for establishing vegetation
• Pond details, including cross-sections with design water surface elevations
• Outfall structure (pipe, weir, etc.) details
• Restrictor plate details, as applicable
16.  Deferred Detention:
• Detailed detention analysis and construction of ponds may be allowed on a case by case basis
• Preliminary detention calculations are still required at platting
17.  Regional Storm Water Detention Facilities :
• Provide 15 ft easement around top of bank and/or 100 yr flood inundation pool for maintenance [and public safety] purposes
18.  Public Detention Facilities:
• Provide access ramps with a maximum slope of 7:1 for access to the flow line of the facility (also recommended for private facilities)
19.  Provide a signed Maintenance Agreement
20.  Drainage Easements for Detention Ponds:
• Show detention pond easements on the plat when the detention is being designed and constructed as part of the plat
• Detention pond easements generally shall not be provided on the plat when detention is deferred
21.  Detention Pond Conformance Letter:
• Submit letter to TCI after pond is constructed
• Plat recordation, building permit approval, or certificate of occupancy may be withheld until letter is submitted by applicant and accepted by TCI
• Plat recordation will not be withheld when deferring detention
F. OTHER

 

			STAFF USE ONLY
II. CONSTRUCTION PLANS Refer to Standard Details and Design Guidance Manual	N/A	Included	Complete	Incomplete	Comments
A. STREET PLANS
1.  Signed and sealed Construction Plans
• Submit one (1) hard copy and one (1) digital copy with original submittal and resubmittals;
• Once the plans are approved, additional hard copies of the plans may be requested for distribution to the City inspectors.
2.  Slope to inlet: min = 0.5% ; max = 4%
• Positive drainage provided to all inlets, including those located at the low point of (i.e. in the sag of) a vertical curve
3.  Provide flow arrow for washout crowns
4.  Provide flow arrows and detailed grading at T-intersections, cul-de-sacs, and knuckles as needed to make sure runoff is contained in streets
B. DRAINAGE PLANS
1.  Signed and sealed Construction Plans
• Submit one (1) hard copy and one (1) digital copy with original submittal and resubmittals;
• Once the plans are approved, additional hard copies of the plans may be requested for distribution to the City inspectors.
2.  Standard notes:
• Improved earthen channels and detention ponds will be vegetated by seeding or siding. Eighty five percent (85%) of the channel surface area must have established vegetation before the City of San Antonio will accept the channel for maintenance
• All concrete lining shall develop a min. compressive strength of 3,000 psi in 28 days
• For normal conditions, the concrete lining shall be a minimum of five (5) inches thick and reinforced with No. 4 round bars @ 18 inches on center each way or welded wire fabric of 6" x 6" - W/D6 x W/D6. Where surcharge, nature of ground, height and steepness of slope, etc. become critical, design shall be in accordance with latest structural standards. All concrete lining shall develop a minimum compressive strength of not less than three thousand (3,000) pounds per square inch in twenty eight (28) days. The depth of all toe downs shall be 36 inches upstream, 24 inches downstream, and 18 inches for side slopes. The City's Construction Inspector may permit an 18" toe down in rock sub grade in lieu of the above toe down requirements. The horizontal dimensions of toe downs shall not be less than six (6) inches.
3.  Storm Drain:
• Minimum easement required (15 ft) or 6 ft from extreme limits of pipe
• Minimum 2' vertical/horizontal clearance between storm drain pipes and other utilities, or provide concrete encasement
4.  Junction box:
• Minimum 6 in clearance from O.D. of pipe to inside of junction box wall
• Invert of junction box to be shaped with concrete fill (2,500 psi min) to ensure drainage to outlet pipe
C. STANDARD DETAIL SHEETS
1.  Junction Box:
• Check for standard junction box detail
• If proposed span larger than standard, reinforcement and concrete wall thickness calculations and a signed and sealed detail must be provided
2.  Curb inlets shall be per City standard details. Inlet extensions are acceptable as follows:
• Maximum of one (1) extension allowed for inlets on grade
• Inlet extensions are typically not allowed for sump inlets
• If proposing multiple extensions on grade or extensions for sump inlets, additional capacity calculations or non-standard detailed drawings may be required
3.  Pipe Bedding and Backfill Details (See special detail)
• Note on 2nd layer (Rocks not larger than 1 in)
4.  Provide concrete collars at all tie-ins
5.  Grout should be added to spring line
6.  Weep Holes :
• Required in rip rap and on headwalls 5 ft and higher
• Place weep holes 6" above the toe at 10 ft o.c.
• Geo-fabric is to be placed behind the riprap to hold the gravel (1 cubic foot per weep hole)
D. UTILITY LAYOUT
1.  Lateral tie-ins from properties to public storm drain systems
• Laterals < 24 in may be approved on a case by case basis
2.  Utilities in the Floodplain :
• Check if any proposed underground utility lines are in floodplain
• Buoyancy and scour calculations may be required
• Concrete capping or encasement may be required
E. GRADING PLAN
1.  Grading Plan:
• Lots grading properly according to FHA Lot Grading Type (A, B, C)
• Driveway Detail, reference to critical Type "C" lots
• Check T-intersections, cul-de-sacs, and knuckles to make sure runoff is contained in streets
• Interceptor channels are required when:
◦ Offsite drainage area flowing onto site is greater than 3 acres, or
◦ Offsite drainage area flowing onto site is greater than 2 average residential lot depths
F. OTHER

 

			STAFF USE ONLY
III. PLAT	N/A	Included	Complete	Incomplete	Comments
A. GENERAL
1. Provide one (1) hard copy and one (1) digital copy of the Subdivision Plat
2.  Existing Contours
3.  Finished/proposed Contours:
• Street only if no significant site grading
• Provide detention pond contours on plat, unless detention is deferred
3.  Label & dimension all drainage easements
• Public easements: ≥ 100 acre drainage area or conveying runoff from public ROW or facilities; and/or containing FEMA floodplain
• Private easements: <100 acre drainage area and/or not conveying runoff from public ROW or facilities, except for some side-lot flumes
• Side-lot flumes: 10 ft access required for public easements; minimum 2 ft either side of channel for private easements
4.  Verify continuation of Streets & Channels
5.  Delineate DFIRM 100 Yr Floodplain
• Provide drainage easement to include the worst case of the FEMA 100 yr and the lesser of the Ultimate 100 yr or the Ultimate 25 yr plus freeboard floodplain or a combination thereof
6.  NOTE: Temporary easement to expire upon incorporation into platted public street ROW.
7.  NOTE: No structures, fences, walls, or other obstructions that impede drainage shall be placed within the limits of the drainage easements shown on this plat. No landscaping or other type of modifications, which alter the cross-sections of the drainage easements, as approved, shall be allowed without the approval of the Director of TCI. The City of San Antonio and Bexar County shall have the right of ingress and egress over grantor's adjacent property to remove any impeding obstructions placed within the limits of said drainage easement and to make any modifications or improvements within said drainage easements.
8.  NOTE : Finish floor elevations must be a minimum of (8) inches above final adjacent grade (for residential lots only).
9.  NOTE: Minimum finished floor elevations for residential and commercial lots shall be elevated at least one (1) foot higher than the computed water surface elevation for the 100 year ultimate development.
10.  NOTE : The maintenance of the detention pond and outlet structure shall be the responsibility of the lot owners or home owners association their successors or assignees and not the responsibility of the City of San Antonio and or Bexar County.
11. To expedite the review of elevation certificates, indicate the specific minimum finish floor elevation for all lots adjacent to FEMA floodplains.
12.  Deferred Detention : Areas within the City Limits.
• Provide NOTE: Storm water detention is required for this property. Building permits for this property shall be issued only in conjunction with necessary storm water detention approved by the City of San Antonio. The property may be eligible to post a fee-in-lieu-of onsite detention (FILO) if offsite drainage conditions allow but only when approved by the City of San Antonio. Maintenance of onsite storm water detention shall be the sole responsibility of the lot owners and/or property owners association and their successors or assignees.
• Provide preliminary calculations of estimated detention basin size.
13.  Easement Requirements:
• Easements will be required for all detention facilities accepting runoff from properties other than the lot on which the detention pond exists or will be constructed. When detention is deferred, in lieu of providing an easement on the plat, TCI may require that a note be placed on the plat specifying which lot(s) will provide detention for other lots. TCI may require that an easement be established by separate instrument at building permit.
• For regional detention facilities the easement shall extend to a minimum of fifteen feet outside both the 100 yr pool and the structural improvements to facilitate maintenance as well as public safety.
B. OTHER

 

			STAFF USE ONLY
IV. FLOODPLAIN SUBMITTAL	N/A	Included	Complete	Incomplete	Comments
A. COSA FLOODPLAIN STUDY
1.  Provide one (1) hard copy and one (1) digital copy of signed and sealed floodplain study.
2.  Narrative:
• Table of Contents and abstract or executive summary
• Introduction that includes project description and history, location, scope and objective of analysis, previous and related studies that may affect this analysis
• Summary, conclusions, and recommendations. Include the impact on the floodplain's Q, WSEL & velocity.
3.  Provide analysis of the following:
• 25 yr existing and ultimate development plus required freeboard condition hydrologic and hydraulic analyses
• 100 yr existing and ultimate development condition hydrologic and hydraulic analyses
4.  Vicinity map
5.  Overall Aerial Drainage Area Map(s) (signed and sealed):
• Show Time of Concentration (Tc) pathways
• Show individual and overall drainage areas. Indicate area of each watershed
• Show computation points and points of discharge
• Show runoff coefficients and impervious cover percentage
6.  Topographic Work Map(s) (signed and sealed):
• ?Existing conditions work map; showing existing contours, plan view of project limits, effective/existing cross sections, effective floodplain limits, property lines, etc.
• Proposed conditions work map; showing the existing and proposed contours where necessary, proposed cross sections, project limits, property lines, revised floodplain limits with drainage easements, etc.
7.  Grading Plan (existing and finished contours) signed and sealed
8.  Channel Cross Sections (existing superimposed on proposed) show the drainage easement, Manning's coefficients, property lines, structures, etc.)
9.  Plotted water surface profiles for the ultimate flows (if applicable)
10.  Easement for Floodplain
• Provide drainage easement to include the worst case of the FEMA 100 yr (1% annual chance) and the lesser of the Ultimate 100 yr or the Ultimate 25 yr plus freeboard floodplain or a combination thereof
• Drainage easements that include FEMA floodplain shall be noted as public easements on plats and other easement documents
11.  Provide detailed Hydrology calculations , see checklist Section I.B.
12.  Channel outfalls perpendicular to the floodplain:
• Channel outfall must be taken to the invert of the floodplain or show the velocity to be less than 6 fps going down the side slope.
• 36 in toe-down required.
• Floodplain development permit is required if within the city limits
13.  Provide a summary table (or tables) of the hydraulic model
14.  CD of all HEC-HMS, HEC-RAS, XP-SWMM, and/or other models used in analyses
15. Is this development over the Edwards Aquifer Recharge Zone?
16.  Flood plain Development Permit Application (1 copy)
17.  Elevation Certificates (if applicable)
18.  Unflooded vehicular access must be available to the development from a public street.
19.  If site is in ETJ, Bexar County is the Floodplain administrator
• COSA Floodplain Development Permit is not required
• Coordinate necessary forms and submittal requirements with the County
• Bexar County signs the FEMA forms
• Verify drainage easement for ultimate conditions
20.  Contour Data:
• If using agency provided 2 ft aerial contours or 1 ft Lidar contours, field verification is required
21.  Floodplain Reclamation:
• Account for storage volume lost (with comparable excavation within the same creek floodplain) when reclamation of ineffective flow OR shallow flooding (overbank) areas is proposed
• If more than 320 acres drain to site, improvements to site may require an administrative exception
22.  Master Development Plans (MDP):
• Provide hydraulic analysis of floodplains that are adjacent to this MDP or if no hydraulic study is being done provide the following note on the MDP with signatures of the Owner and Engineer: "The Floodplain limits on this Master Development Plan are estimated and subject to change. Approval of subdivision plats associated with this Master Development Plan is subject to the review and approval of a Storm Water Management Plan in accordance with the City of San Antonio Unified Development Code."
•  Note that MDPs are conceptual in nature and ONLY conditional approvals shall be given. One condition is that at the time of platting, more detailed downstream analysis will be provided by the engineer.
B. FEMA CLOMR / LOMR
1.  Provide the applicable items listed in the COSA Floodplain Study above
2.  MT-2 Form 1, Sec D:
• Provide Owners and Engineer's original signature
3.  MT-2 Form 2, Sec A:
• Provide an attached explanation if sediment transport is not considered
4.  MT-2 Form 2, Sec B.4:
• Model names in this section must match the models listed in the CD
5.  Detailed Map Revision Study:
• Include 10, 50, 100 and 500 yr analyses
6. If applicable, provide As-Built Grading Plan with engineer's seal and signature.
7. Recommend providing Check-RAS output
8.  Provide models for effective, corrected effective, proposed, and ultimate (future) conditions
9.  Provide existing and proposed FEMA DFIRM Maps with the following:
• Existing - Label Map "Effective" and show the site boundaries
• Proposed - Label Map "Revised/ Proposed", show site boundaries, show only the proposed floodplain limits, floodplain must tie in with the existing floodplain upstream and downstream, show the proposed streets centerline only and label, show the upstream and downstream limits of study
10. Verify that Environmental Site Assessment (ESA) has been submitted (COSA will not review)
C. OTHER

 

			STAFF USE ONLY
V. OTHER COMMENTS	N/A	Included	Complete	Incomplete	Comments