§ 19.9. Drainage and Flood Hazards

A.

Specific Intent

a.

Protect human life and health;

b.

Minimize expenditure of public money for costly flood control projects;

c.

Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;

d.

Minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in flood plains;

e.

Help maintain a stable tax base by providing for the sound use and development of all areas in such a manner as to minimize future flood blight areas;

f.

Insure that potential buyers are notified that property is in a flood area;

g.

Secure review and approval of the method for handling and disposing of stormwater runoff in the City and its ETJ, and securing review, analysis, and approval by the appropriate authority of the design, construction, and maintenance of drainage way facilities in conformance with the Cibolo Design and Construction Manual;

h.

Impose standards and conditions upon the excavating, grading, filling, and berming of the land within the City in conformance with the Cibolo Design and Construction Manual;

i.

Minimize the danger that materials may be swept onto other lands causing injury to others;

j.

Insure the safety of access to property in time of flood for ordinary and emergency vehicles;

k.

Minimize prolonged business interruptions.

l.

Preserve and protect sensitive natural areas that serve an ecological function in minimizing flood damage.

m.

Create a priority for maintaining natural drainage systems wherever possible, and emphasize the design and arrangement of stormwater facilities as community amenities, appropriate to the planning context.

n.

Minimize the amount of impervious surfaces directly connected to stormwater systems, and reduce the amount of flow, speed of flow and level of contaminants entering both natural and manmade stormwater systems.

o.

Allow flexibility in site designs and cooperation among adjacent development sites, to allow the most efficient development of sites and encourage individual designs that support a more regional or watershed-based stormwater solutions.

p.

Integrate high-performance flood protection and stormwater systems into the open space system.

q.

Encourage creative design solutions that allow areas to perform multiple functions in terms of stormwater management, flood protection, open space and recreation, landscape and urban design, or other site development support functions.

r.

Create physical stream buffers to minimize the risk potential pollutants from entering streams, protected wetlands and other environmental sensitive area. Where practical and feasible, future park amenities should be incorporated into these buffers to further the City's park and recreation goals.

s.

Minimize negative environmental impacts of site development on the air and water by developing technical criteria requiring responsible construction sequencing, criteria for silt fences and rock dams, dust control, construction site waste management, concrete washout systems and designated vehicle maintenance and washing, requirements for re-seeding/re-vegetation, using geotextile matting and/or sodding; where appropriate, criteria for storm drain inlet protection and stabilized construction entrances and requirements for spoils and staging areas.

t.

On a case by case basis, accepted professional engineering and geotechnical design considerations shall be applied to the specific characteristics of the property being developed to develop a stormwater management designs that limit stormwater discharge and excessive grading in order to create nonerosive drainage patterns and to provide development incentives to preserve existing high-value vegetation and provide vegetative filter strips in stormwater designs.

u.

It is the policy of the City to reserve appropriate spaces that may be interconnected into a linear park network. The City Council may require that any drainage easement that provides a connection or connections to adjoining neighborhoods or an existing or proposed linear park network also be designated as a public access easement for the purpose of providing pedestrian and bicycle access and may request parkland dedication for this purpose in accordance with this UDC. Linear parks, where required or proposed, must be designed in accordance with the Cibolo Design and Construction Manual.

B.

Methods for Reducing Flood Losses and Negative Environmental Impacts

a.

Limit runoff from development to a level not to exceed that runoff that would exist under natural, undeveloped conditions unless provided for in a regional detention facility;

b.

Restrict or prohibit uses that are dangerous to health, safety, or property in times of flood, or cause increases in flood heights or velocities;

c.

Require that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;

d.

Control the alteration of natural flood plains, stream channels, and natural protective barriers, which are involved in the accommodation of flood waters;

e.

Control filling, grading, dredging and other development which may increase flood damage;

f.

Prevent or regulate the construction of flood barriers which will unnaturally divert flood waters or which may increase flood hazards to other lands.

g.

Minimize the installation of impervious surfaces that result in greater stormwater volumes and higher, erosive velocities by allowing parking lots, service roads, and other suitable areas normally covered with concrete and asphalt, such as outdoor storage areas, to utilize porous pavement, pavers, and other "green" design solutions provided that such alternatives designs that are properly designed with highly durable materials in accordance with accepted engineering standards.

h.

Limit stormwater discharges to less than 5 feet per second in natural waterways, provide landscaping and parkland dedication incentives to include vegetative filter strips, or ponds, to enable an integrated means of sediment removal and preserve existing high-value vegetation, particularly hardwoods and the surrounding vegetation for soil stability and natural filtration.

i.

Require that construction plans include plan details or a narration that describes construction sequencing details.

j.

Develop Include design details for silt fence, rock dams, and other erosion control devices and storm inlet protection.

k.

Construction plans shall include a dust control plan, details showing where and how construction site waste management will be provided by the City's franchised solid waste collection provider, details for the storage of fuel or any other hazardous material(s), and details for concrete washout systems.

l.

Construction plans shall show plans for re-seeding/re-vegetation; geotextile matting; or sodding; as appropriate

m.

Construction plans shall show details of all storm drain inlet protection systems.

n.

Stabilized construction entrances shall be required for all developments and shall be shown on the construction plan set.

o.

Construction plans shall show protected spoils and staging areas and the methods proposed to contain the materials in these areas.

p.

Discharge from fueling/vehicle washing areas. The purpose of this section to discourage the practice of discharging contaminated water or waste into the MS4 and reduce discharges of pollutants, such as detergents, sediments, oil, grease, heavy metals and oxygen demanding substances, from fueling and vehicle washing areas. No persons shall:

1.

Introduce into the MS4 and/or water bodies of any contaminated water or waste from a commercial car wash facility, from any vehicle washing, cleaning, or maintenance area at any new or used automobile or other vehicle dealership, rental agency, body shop, repair shop, maintenance facility, or from any washing, cleaning, or maintenance area of any commercial or public service vehicle, including any truck, bus, or piece of heavy equipment, by any business or public entity;

2.

Introduce into the MS4 and/or water bodies any wash water from the washing, cleaning, deicing or other maintenance of aircraft; or

3.

Discharge into the MS4 and/or water bodies any contaminated water or waste from commercial establishments including but not limited to gas stations, service stations, and auto repair shops with areas exposed to weather conditions.

q.

Construction, development, redevelopment and land disturbance run-off. The purpose of this section to reduce the pollutants such as sediments, heavy metals, toxic material, and nutrients in the stormwater discharges from construction, development, redevelopment and land disturbance activities/sites. No persons shall:

1.

Discharge from a construction site flow having a pH value lower than 6.0 or higher than 10.5;

2.

Discharge any type of industrial waste from construction sites to the MS4 and/or water bodies;

3.

Introduce any garbage, rubbish, or yard waste into the MS4 and/or water bodies;

4.

Discharge, including, but not limited to, paint or paint brush cleaning water or solvents or thinners or turpentine or any other combination from single family dwelling or any construction;

5.

Leave unused construction materials or used construction materials or debris on the construction, development, redevelopment, and land disturbance sites. All on site debris shall be properly disposed of in the landfill within thirty (30) days from the occupancy of the structures; or

6.

Wash any type of trucks, including, but not limited to, ready mix trucks or material supply trucks on or around the construction site.

r.

Ready mix concrete truck washing. The purpose of this section to reduce pollutants such as sediments, concrete, altered pH, and oxygen demanding substances in the wash water discharges from ready mix concrete trucks. No person shall wash residual ready mix concrete from concrete mixing trucks regardless of its location, in an area where discharges might enter the MS4 and/or water bodies.

C.

General Provisions

a.

Lands to Which This Section Applies . These requirements shall apply to all areas within the City and its extraterritorial jurisdiction.

b.

Proper Drainage, Plans, Approval. All subdivisions shall be designed to convey the flow of stormwater without damage to persons or property. The subdivision shall be designed to ensure drainage at all points along streets and provide positive drainage away from building sites while, simultaneously, preventing discharge of runoff onto adjacent properties.

c.

Responsibility . All drainage facilities required in accordance with this chapter shall be installed and paid for by the subdivider in accordance with applicable standards and specifications of the City, including those specified in City Code of Ordinances Part 2, Chapter 30 (Floods).

d.

Additional Standards and Requirements . All plans for drainage control shall be consistent with requirements of this Article and all local and regional drainage plans. All plans for drainage control shall also be subject to approval by the City Engineer or his duly-authorized representative.

e.

Basis for Establishing the Areas of Special Flood Hazard . The areas of special flood hazard identified by the Federal Emergency Management Agency, with accompanying Flood Insurance Rate Maps and Flood Hazard Boundary-Floodway Maps and any revision thereto are hereby adopted by reference and declared to be a part of this UDC.

f.

Drainage Standards. The Floodplain Administrator shall apply standards, where applicable, for drainageway facilities and stormwater detention facilities which shall be adopted in the Cibolo Design and Construction Manual. Said standards shall be followed by every person, firm, corporation in the construction, installation, and maintenance of drainageway facilities and stormwater detention facilities and shall regulate the design, installation, utilization and maintenance of all detention and drainage facilities and structures; the design, installation, utilization and maintenance of sedimentation and erosion control procedures, facilities and structures; and shall establish acceptable methods for controlling soil sedimentation and erosion.

g.

Compliance . No structure or land shall hereafter be located, altered, or have its use changed without full compliance with the terms of this Division and other applicable regulations. The provisions of this Section shall apply to and be binding upon every person, firm, or corporation who seeks to develop, redevelop, grade, excavate, fill, berm, or dike land within the City.

h.

Abrogation and Greater Restrictions . The requirements of this UDC are not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this ordinance and another conflict or overlap, whichever imposes the more stringent restrictions shall prevail.

i.

Interpretation . In the interpretation and application of all provisions shall be:

(1)

Considered as minimum requirements;

(2)

Liberally construed in favor of the purpose of this Article to minimize flooding; and,

(3)

Deemed neither to limit nor repeal any other powers granted under State or Federal statutes.

j.

Warning and Disclaimer of Liability. The degree of flood protection required by this UDC is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. On rare occasions, greater floods can and will occur and flood heights may be increased by man-made or natural causes. These regulations do not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. The requirements of this Division shall not create liability on the part of the City or any official or employee thereof for any flood damages that result from reliance on the UDC or any administrative decision lawfully made there under.

k.

Localized Flooding Areas . Flood Insurance Rate Maps (FIRM), as amended, defines drainage areas subject to general flooding problems. The City Council has the right to adopt a map that defines any known areas subject to "Localized Flooding". A Localized Flooding Map, if adopted by City Council, may be amended by City Council. Localized Flooding Maps and the FIRM maps shall collectively serve as the basis for application for the stormwater management criteria to individual developments.

D.

Facilities Required

The subdivider shall provide an adequate storm drainage system to protect each lot throughout the subdivision from flooding. These drainage facilities may consist of a combination of natural features, swales, watercourse improvements, bridges and culverts, enclosed storm sewers and other man-made improvements to carry off stormwater within the subdivision. The drainage system shall use detention ponds, retention ponds and siltation ponds, individually or in concert, to control runoff and to protect downstream properties from any increase in flooding originating from the subdivision. The system shall be integrated with the overall drainage system of the city, and the design of the system must be approved by the City Engineer in accordance with the requirements of this UDC and the Cibolo Design and Construction Manual.

E.

Standards for Subdivision Plats

a.

Consistency Required . Subdivision plats shall be consistent with all provisions of this UDC.3

b.

Requirements . All plats shall meet Floodway Development Permit requirements, when applicable, and the provisions of the Cibolo Design and Construction Manual.

c.

Base Flood Elevation Data . Base flood elevation data shall be provided for all subdivision plats and other proposed development, if applicable.

d.

Provisions Prior to Final Approval of Plats . Prior to final approval of a Final Plat, the developer shall provide either actual construction of all approved drainage and detention facilities required by the City or sufficient surety bond, trust agreement, performance bond, or an irrevocable letter of credit; approved by the Floodplain Administrator and City Attorney guaranteeing the developer's pro-rata share of construction of all required drainageway and detention facilities in accordance with an approved Drainage Plan (in conjunction with approved Construction Plans) and Cibolo Design and Construction Manual.

F.

Stormwater Management

Stormwater management facilities shall be provided prior to site construction or clearing, where design is required at the time of platting.

a.

Stormwater management shall be designed and constructed to prevent adverse conditions from arising on property adjoining and downstream of the subdivision site. Adverse conditions include increases in peak flows, water surface elevations and flow velocity. The drainage report shall show that mitigation of the impacts of development on the drainage system will be provided as part of the development. Mitigation may include detention, retention, infiltration, channel improvements, and other means acceptable to the City Engineer. Stormwater Management facilities shall be designed to reduce post-development peak flow rates of discharge to pre-development rates for the 10, 25, and 100 year storm events at all points of discharge. The drainage report shall also include an evaluation of downstream conditions.

b.

The City Council, after considering a recommendation from the City Engineer and staff, may waive the Stormwater Management requirements as outlined herein and approve subdivisions of land that have fewer than seven (7) residential lots with a density of two (2.0) dwelling units or less per acre.

G.

Detention and Drainage Facilities

a.

Requirements and Standards . On-site stormwater detention shall be required for all new developments to offset increased runoff resulting from new developments except for those developments for which approved regional detention facilities have been established or for which alternate plans have been approved by the City Engineer. Design standards for all stormwater detention and drainage facilities shall be established by adopted in the Cibolo Construction and Design Manual.

b.

Title Ownership and Maintenance . Detention and drainage facilities herein provided for shall be dedicated to the public and maintained by the public unless such facilities are an integral, usable part of the development, in which case the ownership and maintenance of said facilities may remain with the private sector. These systems, when retained by the owner shall be maintained by the current and subsequent owners in a manner that will allow them to function as designed. The owner must execute a written maintenance agreement with the City before this option is used and such agreement shall be filed with the Guadalupe County Recorder. These agreements shall be as encumbrances upon the land.

1.

Major drainage systems not retained by the owner shall be conveyed by title, easement or through the acceptance processes of this UDC to the City as required by the City Engineer and City Attorney.

2.

The dedication of a detention facility shall provide that, in the event that the City Council determines that the detention facility is unneeded or unnecessary as a result of drainageway improvements, the same may revert to the party making such dedication, or the abutting owners, or their respective heirs, successors, or assigns.

3.

The City shall only maintain concrete drainage structures that were either constructed by the City or which were formally accepted by the City, per Section 20.3.6 of this UDC.

c.

Private Drainage Facilities . Roof drains, building drains, and parking lot drainageways may be located outside dedicated drainageways.

H.

Alternative Design Standards

a.

Purpose . It is the purpose of this section to provide for the consideration of detention and drainage facility designs which differ from the conventional design standards as outlined within this UDC, but which are based upon sound engineering judgment. Such alternative(s) shall meet the purpose and intent of the standard being varied. In this context, detention and drainage facilities shall mean physical improvements such as detention ponds, retention ponds, drainage swales, as well as any other infrastructure element of a proposed development. Land Development Code Chapter 3: Subdivision Regulations Article 2: Subdivision Standards

b.

Approval Based on Engineering . Decisions regarding design of such physical improvements in a subdivision should be based on engineering studies. Thus, while this UDC provides standards for design, the regulations are not a substitute for sound engineering judgment. Therefore, a licensed engineer may submit alternative designs to be reviewed and considered by the City Engineer, including the option of providing a downstream assessment.

c.

Relationship to UDC/Cibolo Design and Construction Manual . If the proposed alternative design is approved by the City Engineer, then the all other applicable provisions of this UDC and the Cibolo Design and Construction Manual shall be deemed to have been met. If the proposed alternative design standards are not approved by the City Engineer, then the standards contained this UDC and the Cibolo Design and Construction Manual shall apply.

d.

Appeals to the Planning and Zoning Commission . If a proposed alternative design is rejected by the City Engineer, the subdivider may appeal the decision to the Planning and Zoning Commission.

I.

Construction Sequencing and Erosion Controls

Construction Plans required by this UDC shall be accompanied by a comprehensive and detailed report and plan for the control of erosion and sedimentation. The report shall include a construction sequencing plan which details the proposed placement, maintenance and removal of temporary erosion controls, the slope stabilization techniques which are to be employed and the restoration measures, including vegetative types, which are to be employed as part of the process of subdivision development. The plan shall list and show the location of temporary erosion controls, show the physical details of the controls, and include a construction sequencing list which will govern the timing of the use of various controls in relation to distinct steps in subdivision construction.

J.

Land Clearing Restrictions

No clear-cutting or rough-cutting of land shall be permitted unless approved by a construction sequencing and erosion control plan as required by this UDC and the issuance of a Site Development Permit, except for limited clearing and rough-cutting necessary for soil testing and surveying as required by this UDC. No other clearing or rough-cutting shall be permitted except as necessary for construction of temporary erosion and sedimentation controls until these controls are in place and approved by the City Engineer. Areas to be cleared for temporary storage of spoil or construction equipment, or for the permanent disposal of fill material or spoils, shall be shown on preliminary plat.

K.

Enforcement of Erosion Controls and Clearing Restrictions

If a subdivider does not comply fully with an approved erosion control and construction sequencing plan, or violates the restrictions on land clearance in the preceding subsection, the City Manager shall notify the subdivider in writing that the City may correct the violation and revegetate the disturbed area at the subdivider's expense unless, within 30 days after the date of the notice, the subdivider complies, corrects the violation, provides the required erosion and sedimentation controls and provides continuing maintenance thereof acceptable to the City Manager.

L.

Required Drainage Study

1.

General

a.

Drainage Plans shall be prepared by a registered professional engineer licensed by the State of Texas.

b.

Drainage Plans submitted for final approval shall bear the signature of the submitting engineer and the following certification:

"I hereby certify that I am familiar with the adopted ordinances and regulations of the City governing detention and drainage facilities; that these plans have been prepared under my direct engineering supervision; and that the above and foregoing Drainage Plan complies with all governing ordinances and the adopted drainage standards of the City pertaining to detention and drainage facilities to the best of my knowledge, information and belief."

c.

Upon completion of a required drainage facility improvement, a certification from a contractor or registered professional engineer shall be provided similar to the following certification:

"I hereby certify that the detention improvements were constructed and completed in accordance with the approved Drainage Plans."

d.

Plan Elements . A Drainage Plan shall consist of engineering drawings, contour maps, and all supporting engineering calculations, as applicable to the land area covered by the Plan, as detailed in Section H below, which are required to demonstrate full compliance with the requirements of this UDC and the Cibolo Design and Construction Manual.

e.

Requirements in Areas of Special Flood Hazards . Drainage Plans for developments in areas of special flood hazard shall adhere to all requirements of this UDC, the Cibolo Design and Construction Manual and the Special Flood Hazard requirements in the City Code of Ordinances Part 2, Chapter 30 (Floods).

f.

Administration of Drainage Plans .

1.

Processing of Drainage Plans. All Drainage Plans as required by this section shall be submitted to and received by the Floodplain Administrator. A conference to discuss the Drainage Plan may be held with the Floodplain Administrator, but only after Construction Plans have been officially submitted.

2.

Within twenty (20) working days after receipt of a properly completed Drainage Plan, the Floodplain Administrator shall either approve or deny the submitted plan.

3.

Approval of a submitted Drainage Plan shall only constitute acceptance by the Floodplain Administrator of the certification of the submitting engineer and such acceptance shall not operate to remove any requirement of Cibolo's adopted Drainage Standards which are not specifically considered in the approved plan.

4.

Drainage Plans which meet the requirements of this ordinance and which conform to all requirements of the UDC and the Cibolo Design and Construction Manual shall be approved.

5.

If the required findings cannot be made based upon the information contained in the submitted plan, such additional information as is required by the Floodplain Administrator to make such determination will be identified; in the event that the information deficiency is of a technical nature, the Floodplain Administrator may request an engineering conference with the submitting engineer.

6.

If a submitted Drainage Plan is denied, the certifying engineer or applicant, as applicable, shall be advised in writing of the disapproval.

g.

Drainage Study Contents . The subdivider shall submit a drainage study with the final construction plans for residential subdivisions, and wherever stormwater flow management facilities shall be regional and dedicated to the public. The required drainage studies in commercial subdivisions where facilities are site-specific and privately maintained may be submitted with building permit construction documents for each lot. The drainage study shall provide the following information, for both existing and fully developed conditions, for the entire watershed drainage area upstream of the lowest point(s) in the subdivision.

1.

The entire watershed drainage area(s) depicted on a 7.5 minute series U.S.G.S. map.

2.

The drainage area(s) within the subdivision, depicted on a topographic map with two-foot contour intervals.

3.

Composite runoff factors.

4.

Times of concentration.

5.

Related rainfall intensity factors.

6.

10-, 25- and 100-year flood flow quantities with the 10-, 25- and 100-year flood plain limits for the existing and fully developed watershed shown on the preliminary plat.

7.

Preliminary street grades sufficient to determine high points, low points, and direction of runoff flows.

8.

Proposed locations of inlets, storm sewers and culverts.

9.

Proposed routing of drainage ways.

10.

All proposed drainage easements, including width of easement and configuration of channel.

11.

The calculations to determine the volume of proposed detention/retention/sedimentation ponds.

12.

Roads, measured curb to curb, shall be designed for 10-year storm event, and right-of-way to right-of-way for a 25-year storm event. Underground drainage facilities and all above ground channels shall be designed to a full-flow 25-year storm event. Regional stormwater pond and the 100-year floodplain shall be designed to 100-year storm events. Stormwater designs shall ensure proper conveyance of the 1% annual storm event.

The above information shall be supplemented with narrative text describing the watershed and the subdivision, including their general soil conditions, downstream channel conditions, all weather access, and the presence of special flood hazard areas within the subdivision. The study shall be prepared by a professional engineer registered in the State of Texas. The drainage study shall be submitted along with the preliminary plat. The City Engineer shall review the submission and verify that all UDC requirements have been met.

h.

Downstream Drainage Assessment . Downstream drainage assessment shall extend from the outfall of the subdivision to a point downstream, determined by one of two methods:

•  Zone of Influence - Point downstream where the discharge from a proposed development no longer has a significant impact upon the receiving stream or storm drainage system

•  Adequate Outfall - Location of acceptable outfall that does not create adverse flooding or erosion conditions downstream

These methods recognize the fact that a structural control providing detention has a "zone of influence" downstream where its effectiveness can be felt. Beyond this zone of influence the stormwater effects of a structural control become relatively small and insignificant compared to the runoff from the total drainage area at that point. Based on studies and master planning results for a large number of sites, a general rule of thumb is that the zone of influence can be considered to be the point where the drainage area controlled by the detention or storage facility comprises 10% of the total drainage area. This is known as the 10% Rule. As an example, if a structural control drains 10 acres, the zone of influence ends at the point where the total drainage area is 100 acres or greater.

The downstream assessment shall include the following steps:

1.

Determine the outfall location of the site and the pre- and post-development site conditions.

2.

Using a topographic map, determine a preliminary lower limit of the zone of influence using the 10% Rule.

3.

Using a hydrologic model determine the pre-development peak flows and velocities at each junction beginning at the development outfall and ending at the next junction beyond the preliminary lower limit of the zone of influence (10% point). Model all undeveloped off-site areas as "fully built-out" for both the pre- and post-development analyses. Use the City Future Land Use Map to determine future land uses for the model. Evaluate discharges and velocities for the 10-year, 25-year and 100-year storm events. Use storm durations equal to 24-hours and two times the time of concentration calculated for the outfall of the subdivision.

4.

Change the land use on the subdivision site to post-development conditions and rerun the model.

5.

Compare the pre- and post-development peak discharges and velocities at the downstream end of the model. If the post-developed flows are higher than the pre-developed flows for the same frequency event, or the post-developed velocities are higher than the allowable velocity of the downstream receiving system, extend the model downstream. Repeat steps 3 and 4 until the post-development flows are less than the pre-developed flows, and the post-developed velocities are below the allowable velocity. Allowable velocities are provided in the Cibolo Design and Construction Manual.

6.

Add proposed stormwater management facilities to the model designed so that the model shows that adverse effects are mitigated. Adverse effects can be shown to be mitigated if flooding is not increased, velocities do not exceed the greater of allowable maximum velocities or pre-development velocities, and that the peak flow at the downstream limit of the zone of influence is not increased.

M.

Drainage Easements

1.

General Requirements

Natural waterways and channels should be used wherever practical to carry runoff. Any modifications to existing waterways and channels must be approved by the City Engineer. Where a subdivision is traversed by a watercourse, drainageway, natural channel or stream, an easement or right-of-way shall be provided conforming substantially to the 100-year floodway or channel limits of such watercourse, plus additional width to accommodate future needs.

2.

Enclosed Systems

Storm drainage easements shall be provided for existing and proposed enclosed drainage systems. Easements shall be centered on the systems. The easement width shall have a minimum width of ten feet. Additional drainage easement width may be required based on the formula: W = 5' + 2H + D

(W = Easement Width; H = Depth of Soil Over Pipe/Box; D = Diameter/Width of Pipe/Box)

3.

Open Channels

Storm drainage easements along proposed or existing open channels shall provide sufficient width for the required channel and such additional width as may be required to provide ingress and egress of maintenance equipment; to provide clearance from fences and space for utility poles; to allow maintenance of the channel bank; and to provide adequate slopes necessary along the bank.

The minimum easement width shall be the width of the channel plus 15 feet on one side (20 feet with utilities) and 2 feet on the opposite side unless approved by the City. The channel top width is determined by the locations where the channel side slopes intersect with adjacent grade with cross slopes less than 10 percent.

4.

Overflow Drainage

Storm drainage easements shall be provided for emergency overflow drainage ways of sufficient width to contain within the easement stormwater resulting from a 100-year frequency storm less the amount of stormwater carried in an enclosed system.

N.

Flood Hazards

1.

General Policy.

All subdivisions shall conform to the "Flood Disaster Protection Act of 1973," Public Law 93-234, and the latest revisions thereof. Development shall adhere to all policies and requirements of the Federal Emergency Management Agency and Chapter 30 "Flooding" of the City Code of Ordinances.

2.

Flood Plain Designations and General Restrictions.

Federal flood plains are based on a 1% annual occurrence frequency discharge, and apply only in those areas where official Federal Emergency Management Agency maps have been prepared, or where a 1% annual occurrence water and surface profile studies are available for the City and its extraterritorial jurisdiction. Until a regulatory floodway is designated, no new construction, substantial improvements, or other development (including fill) shall be permitted in an area having special flood hazards as defined by Chapter 30 of the City Code of Ordinances, this UDC and the Cibolo Drainage and Construction Manual unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not substantially increase the water surface elevation of the a 1% annual occurrence flood at any point within the City's subdivision jurisdiction.

3.

Flood Hazards to Water and Wastewater Systems.

New or replacement water supply systems and/or wastewater systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters. On-site waste disposal systems shall be located so as to avoid impairment of them or contamination from them during flooding.

O.

Green Space Preservation

1.

Purpose and Definitions

The purpose of this section is to establish minimal acceptable requirements for the design of buffers to protect the streams, wetlands and floodplains of Cibolo, Texas; to protect the water courses, reservoirs, lakes and other significant water resources in Cibolo; to protect Cibolo's riparian and aquatic ecosystems; and to provide for the environmentally sound land use.

The following definitions shall be used to define the terminology described in this "Green Space Preservation" section:

Best Management Practices or BMP - refers to schedules of activities, prohibitions of practices, maintenance procedures, and other management practices to prevent or reduce the pollution of waters of the United States. BMP's also include treatment requirements, operating procedures, and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.

Environmentally Sensitive Area - Any area wherein plant or animal life, listed in the Texas Endangered Species Act and/or the Federal Endangered Species Act, exists or there is evidence of their inhabitance.

Erosion - refers to the wearing away of land by the action of wind, water, gravity, ice or any combination of these forces.

First Order Stream - No defined tributaries drain into this stream and it normally originates from springs, seeps or rain runoff from the higher elevations in a watershed and conducts water into a higher order stream. First order streams appear on a USGS 1:24,000 Topographical Map.

Fourth Order Stream - is a stream formed by the confluence of two third order streams.

Ordinary High Water Mark (OHWM) - shall mean "that line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas," as defined in 33 CFR Part 328 Definition of Waters of the United States- Section 328.3 e.

Second Order Stream - is a stream formed by the confluence of two first order streams.

Stream Order - is a classification system for streams based on stream hierarchy, with the smallest stream having the lowest numerical classification.

Streams - are identified on U.S. Geological Survey (1:24,000) maps.

Stream System - means a stream channel of a given order together with one or more of the following: 1) 100-year floodplain; 2) Hydrologically related wetland; 3) Reservoir receiving water from one or more streams.

Third Order Stream - is a stream formed by the confluence of two second order streams.

Vegetative Buffer - A vegetated area, including trees, shrubs, and herbaceous vegetation, that exists or is established to protect a stream system. A vegetative buffer for a stream system generally consists of a strip of land, with native vegetation, along both sides of a stream system.

2.

Applicability

a.

This section shall apply to development subject to the UDC. A development is exempt from this ordinance if it does not contain a stream system.

b.

This ordinance shall apply to surface mining operations except that the design standards shall not apply to active surface mining operations that are operating in compliance with an approved U.S. Department of the Interior surface mining permit.

c.

This ordinance shall apply to the City, a municipal corporation, and its lawful ETJ.

d.

This section applies to all development except for activities initiated prior to the effective date of this UDC and meeting any of the following criteria:

• Valid, unexpired permit in accordance with development regulations;

• A current, executed public works agreement;

• A valid, unexpired building permit;

• A complete, unexpired plat application;

• An approved and unexpired Master Plan;

• Platted property.

3.

Preservation and Buffering Requirements

a.

All third order and higher stream systems are required to be preserved and buffered in accordance with this section.

b.

First and Second order stream systems, which include any of the following criteria, are required to be preserved and buffered in accordance with this section unless the "Conservation Plan Requirements" described in this section are satisfied:

• An environmentally sensitive area.

• Wetlands and Waters of the U.S. according to the Wetland Map.

• Existing trees with a caliper equal to or greater than 8 inches DBH within the stream channel or potential stream buffer, excluding the undesirable trees referenced in Article 17 of this UDC.

4.

Design Standards for Stream Buffers

a.

The width for vegetative buffers shall depend on the order of the stream being developed.

b.

First and Second order streams that are to be protected shall have a buffer originating from OHWM extending 50 feet on either side of the stream.

c.

The required width of a buffer for a third order stream will be 50 feet on both sides measured from the OHWM, with 25 feet of buffer added for each level of increase in stream order. For example, a fourth order stream shall have a 75 foot buffer. A fifth order stream should have a 100 foot buffer.

d.

Permanent boundary signs approved by the Planning and Development Services Director (CDS Director hereafter) shall be installed after construction is completed.

e.

The following are permitted exceptions:

1.

Regardless of the stream order, the maximum width of the buffer is 100 feet from the OHWM.

2.

All development shall comply with the City Code of Ordinances Chapter 30 (Floods), this UDC and the Cibolo Design and Construction Manual.

3.

The width of the buffer on each side of the stream maybe adjusted (both width and length) as long as the total square footage of the buffer remains the same for the stream order but in no event shall the buffer be less than 25 feet on any side.

4.

The 25 feet of buffer immediately adjacent to the OHWM, containing undisturbed native vegetation, is restricted to permitted road, utility crossings, stormwater management facilities and recreational facilities approved by the City. The remainder of the buffer, also containing native vegetation, is restricted to utility rights-of-way, designated biking/hiking paths, stormwater management facilities, and recreational facilities by the City.

5.

Design Standards for Existing Ponds and Buffers

a.

Existing ponds may be used as stormwater management facilities, in accordance with City Code of Ordinances Chapter 30 (Floods), the UDC and the Cibolo Design and Construction Manual if a conservation plan is submitted in accordance with this section. Existing ponds, to be used as a stormwater management facility, shall have a buffer width of 20 feet.

b.

The area of the 20 foot buffer may include the embankment as long as the total square footage is maintained.

6.

Green Space Plan Requirements

a.

Stream systems and buffers shall be shown on site-specific drainage maps.

b.

Prior to construction, signs shall be placed every 100 feet on orange construction border fencing at the edge of the buffer zone to inform workers that the placing of construction materials in the buffer zones during the construction phase is prohibited.

7.

Conservation Plan Requirements

Where disturbance of protected first or second order stream systems are proposed, the following shall be submitted:

a.

A Green Space Plan.

b.

A location or vicinity map of areas outlined in the section.

c.

A summary of disturbance activities, and an in-depth detailed description of disturbances that affect or may affect areas outlined in this section.

d.

A detailed description of mitigation activities, as outlined below:

1.

If Wetlands and/or Waters of the U.S. are affected:

a.

Section 404 Permit

b.

Wetland Mitigation Plan.

2.

If trees are removed:

a.

All 4 inch DBH caliper or greater trees removed must be replaced by an equal caliper sized tree of the same species, excluding the undesirable treed identified in this UDC; or smaller trees of the same tree species that equal the caliper of the removed tree (i.e.: four one-inch DBH trees to replace a 4 inch DBH caliper tree).

b.

This/these tree(s) must be located within the stream system or buffer on the property where the removed tree was located.

c.

Twenty-five percent (25%) of the original tree species must be replaced with the same species. The remaining 75% of original tree species may be replaced with "approved tree" species listed in this UDC.

8.

Buffer Management and Maintenance

a.

Protected stream systems and vegetative buffers shall be managed to enhance and maximize the unique value of these resources. Management includes specific limitations on alteration of the natural conditions of these resources. The following practices and activities are restricted within the vegetative buffer:

1.

Clearing of any existing vegetation;

2.

Soil disturbance by grading, stripping, or other practices;

3.

Filling or dumping;

4.

Use, storage, or application of herbicides.

b.

The following structures, practices, and activities are permitted in the vegetative buffer, with specific design or maintenance features:

1.

Roads, bridges, sidewalks, and utilities

a.

These facilities may be constructed if such are required by the City; access to the property would be hindered or compromised because of the property's location; or if conditions specific to the land require it. In any of these instances, the P&E Director or his/her designee may administratively grant approval or deny the request for the construction of said structure(s). In the event of denial by the Planning and Engineering Director or his/her designee, the issue may be appealed to the Planning and Zoning Commission, whose decision shall be final.

b.

The right-of-way should be the minimum width needed to allow for maintenance access and installation.

c.

The angle of the crossing shall be as near to perpendicular as allowed by the P&E Director or his/her designee. In the event of denial by the P&E Director the issue may be appealed to the Planning and Zoning Commission and City Council, whose decision shall be final.

d.

Every effort shall be made to minimize the number of road crossings within each subdivision and no more than one road crossing is allowed for every 1,200 feet of buffer.

2.

Stormwater Management

a.

These facilities may be constructed, if such are required by the City for flood control or to improve water quality or habitat in the stream. In any of these instances, an applicant may request a waiver of the standards for Planning and Zoning review and City Council approval. A waiver may only be granted if the proposed "alternate stormwater design solution" is consistent the spirit and intent of this UDC and consistent with generally accepted engineering practices.

b.

When constructing stormwater management facilities, "best management practices" shall be observed. The area cleared will be limited to the area required for construction and adequate maintenance access as required in this UDC and the Cibolo Design and Construction Manual.

c.

Material dredged or otherwise removed during construction or subsequent maintenance from a stormwater management facility shall be stored outside the buffer.

3.

Stream restoration projects approved by the P&E Director or his/her designee are permitted within the vegetative buffer.

4.

Water quality monitoring and stream gauging are permitted within the vegetative buffer as approved by the P&E Director or his/her designee.

5.

Individual trees within the buffer that are in danger of falling, causing damage to dwellings or other structures, or causing blockage of the stream, may be removed. Other tree cutting techniques approved by the P&E Director or his/her designee may be undertaken within the vegetative buffer under the advice and guidance of the Planning and Zoning Commission, if necessary to preserve the riparian forest from extensive pest infestation and disease infestation.

6.

Selective clearing for health and safety purposes is allowed as determined by P&E Director or his/her designee.

c.

The Final Plat and all right-of-way plans shall clearly show the extent of any vegetative buffer on the subject property.

d.

All protected vegetative buffer areas and stream systems shall run with the land and continue in perpetuity. Protected vegetative buffer areas and stream systems may be dedicated to the public by separate instrument, which must be submitted to the City Engineer and P&E Director or his/her designee for approval and recorded in the land records, or by a Final Plat. If the owner property desires to keep the stream system and buffer as an amenity, there shall be a covenant, to be submitted to the City Engineer and CDS Director, for approval and recorded in the land records, that restricts the use of the stream system and buffer to uses set forth herein, and specifies that the owner, or an owner designee, must ensure that the stream system and buffer is maintained by the owner, his heirs successors and assigns for so long as the stream system and buffer remains in private ownership.

e.

The P&E Director or his/her designee and City Engineer shall inspect the buffer annually and immediately following severe storms for evidence of sediment deposition, erosion, or concentrated flow channels. Corrective actions shall be taken to ensure the integrity and functions of the vegetative buffer.

f.

The City will maintain all vegetative buffer and stream systems that are created pursuant to this section which have been dedicated to the public.

g.

Weeds and grass shall be maintained by the property owner, HOA, or Property Owner Association on which the easement is located in accordance the City Code of Ordinances provisions for high weeds and grass.

9.

Linear Parks

It is the policy of the City to reserve appropriate spaces that may be interconnected into a linear park network. The City Council may require that any drainage or utility easement that provides a connection or connections to adjoining neighborhoods or an existing or proposed linear park network also be designated as a public access easement for the purpose of providing pedestrian and bicycle access and may request parkland dedication for this purpose in accordance with this UDC. Linear parks, when provided, must be designed in accordance with the Cibolo Design and Construction Manual.

10.

Incentives

a.

If buffer widths on first and second order streams are strictly adhered to, the conservation plan requirement shall be waived.

b.

Credit shall be given as determined by the P&E Director or his/her designee for the development of Linear Parks around natural drainage and wooded areas that provide potential recreational uses. Criteria for flood plain areas (based upon a hundred-year flood plain) that is dedicated as parkland, will be given credit as determined by the P&E Director or his/her designee by meeting the following requirements:

1.

Flood plain and natural drainage area shall generally not exceed 60% of total park site.

2.

At least 50% of required dedicated parkland shall have slopes in the range of 2% and not to exceed 5%, well-drained and suitable for active use.

3.

Additional flood plain acreage over 75% of required parkland may be dedicated at a (3:1) ratio in acres in lieu of non flood plain property and any such consideration of acreage shall be at the discretion of the Planning Director in compliance with the Parks and Open Space Comprehensive Master Plan.

4.

The P&E Director or his/her designee shall determine whether land offered for dedication complies with the standards for dedication as provided in the Cibolo Master Parks Plan and Comprehensive Master Plan.

c.

Stormwater discharges into large creeks

1.

For development adjacent to the main stem of Cibolo, Dietz, Town Creek East, Town Creek West, Town Creek or Santa Clara Creeks, stormwater discharge may not require detention facilities, provided that the engineer is able to demonstrate that the increased direct discharge will not result in any adverse impacts to any downstream or adjacent property, and provided that there is compliance with the City Code of Ordinances Chapter 30 (Floods) and all other aspects of this UDC and Cibolo Design and Construction Manual.

d.

On-site detention within the plat boundaries of a residential subdivision

1.

For detention ponds in residential developments voluntarily created to enhance the protection of 1 ^st and 2 _nd order streams, the required private maintenance shall extend to the warranty period as provided by other ordinances.

2.

When a first or second order stream within development is voluntarily protected, a R.O.W. section may be similarly modified as provided herein.

e.

Commercial subdivisions distributed detention

1.

Distributed detention on commercial subdivisions where streams are to be voluntarily protected shall be allowed, deferring the construction of required stormwater detention facilities to the building permit (construction) phase, so long as the deferral is approved at final platting and covered by a note on the face of the plat.

2.

In cases where a development includes a protected stream system, the required detention volume may be distributed over the site provided the plat is annotated with a note indicating the "Q" (volumetric discharge) of each lot.

3.

The required private maintenance period for off-line detention facilities shall extend to the warranty period. Warranties shall remain in effect as provided by this UDC.

4.

For developments where all lots are at least one acre in area, minimum storage requirements for detention and the maximum discharge rate requirement shall be included on the plat for each lot, specifying the requirement for each lot to individually meet the requirements of this UDC and the Cibolo Design and Construction Manual during the building permit process. A General Note approved by the P&E Director or his/her designee that specifies these requirements shall be included on the face of the plat. Calculations for said lot storage volumes and discharge rates shall be approved by the City Engineer in conjunction with their review of the improvement plans for the development during the platting process.

f.

Park credit transferability

1.

Voluntary protection of first and second order streams entitle the owner to a park credit for the stream system protected and its surrounding buffer on an equivalent square footage basis. If the following criteria are met:

a.

Flood plain and natural drainage area shall generally not exceed 75% of the site;

b.

At least 50% of the buffer shall have slopes in the range of 2% and not to exceed 5%, be well drained and suitable for active use;

c.

Additional park requirements, if any, shall be incorporated (be adjacent) to any buffer.

d.

The buffer and the park space shall be reviewed by the P&E Director or his/her designee to ensure that the buffer and park space requirement comply with the City Standards for Dedication as a park and buffer.

e.

If the buffer and park meet the requirements set forth herein the P&E Director or his/her designee shall make a recommendation to the City Council regarding the acceptance of said buffer and park.

2.

Mandatory protected third order streams and higher qualify for a park credit for the surrounding buffer on an equivalent square footage basis. If the following criteria are met:

a.

Flood plain and natural drainage area shall generally not exceed 75% of the site;

b.

At least 50% of the buffer shall have slopes in the range of 2% and not to exceed 5%, well drained and suitable for active use;

c.

Additional park requirement, if any, shall be incorporated, or be adjacent to, any buffer.

d.

The buffer and the park space shall be reviewed by the P&E Director or his/her designee to insure that the proposed buffer and park space complies with the City standards.

e.

If the buffer and park meet the requirements set forth herein, the P&E Director or his/her designee shall make a recommendation to the City Council regarding the acceptance of said buffer and park.

3.

Park credits obtained pursuant to this provision shall be transferable but may only be used for projects identified on the current City 5-Year CIP.

4.

In the event there is first or second order stream systems located on a tract ten acres or smaller and the owner of said tract wishes to voluntarily preserve the stream system he shall be entitled to a park credit.

5.

Any decision by the P&E Director or his/her designee which does not favor the acceptance of park and buffer may be appealed to the Planning and Zoning Commission for a recommendation regarding the acceptance of the park and buffer to the City Council.

11.

Waiver/Credit

a.

The City Council, in consultation with the City Engineer, may grant a waiver for projects or activities for which it can be demonstrated that strict compliance with the ordinance would result in a practical difficulty or for those projects or activities serving a public need where no feasible alternative is available

b.

The City may, as deemed appropriate by the P&E Director or his/her designee, give credit towards the average buffer width on the platted property for the restoration of riparian habitat and/or installation of a wetlands area within the property boundaries if such installations are ecologically integrated with the riparian system. The square footage of the restored area or wetlands area shall be credited toward the square footage required for the buffer zone.

c.

The applicant shall submit a written request for any waiver to the P&E Director or his/her designee. The application shall include specific reasons justifying the waiver and any other information necessary to evaluate the request. The applicant shall demonstrate how strict application of the UDC results in a hardship. In consideration for a waiver, the P&E Director or his/her designee may recommend site design, landscape planting, fencing, and the like to compensate for a waiver. The Director shall formulate a recommendation for the Planning and Zoning Commission and Council to consider in their review and approval of the proposed waiver.

12.

Connection to Cibolo Lineal Park System

The Planning and Zoning Commission and City may require the Green Space Preservation areas described herein to be dedicated or incorporated by some other appropriate legal instrument or plat reservation into the City Linear Park System described in this UDC.