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A. All subdivisions shall be connected to a sewage collection and disposal system approved by the City Engineer at the expense of the subdivider.
B. If a separate sanitary sewage disposal system is proposed, it must be approved, in writing, by the Texas Commission on Environmental Quality (TCEQ) prior to approval of the final plat. These written approvals shall be presented to the City and City Engineer.
C. The City Engineer may prohibit installation of sewage disposal facilities requiring soil absorption systems where such systems will not function due to high ground water, flooding or unsuitable soil characteristics. Such action by the City Engineer shall be based on the review and finding of the City and/or County Health Officer. The City may require that the subdivider note on the face of the plat and in any deed of conveyance that soil absorption fields are prohibited in designated areas. No designs shall be approved by the City for installation of septic tank systems on lots less than one-half (½) acre. If the subdivider wishes to develop a subdivision using septic tanks, a plat note must be placed on the plat and the deed restrictions stating that the future owners understand that they are purchasing a lot without sanitary sewer lines and that the City is not required to provide such services to such lots.
D. If a sanitary sewer system is located on or within one thousand three hundred twenty feet (1,320') near the proposed subdivision, the City shall require the subdivider to provide sewage facilities to connect to the system and shall prescribe the procedures to be followed by the subdivider in connecting to the system. All developments bordering planned extensions of major transmission/distribution lines shall install such lines to and through the development at the cost of the subdivider subject to the City’s standard reimbursement policies.
E. The minimum size of sanitary sewer shall be eight inches (8") in diameter. Sewer service stub outs shall be four inches (4") for residential uses and six inches (6") for commercial, industrial, multi-family, and institutional uses. In order to facilitate sewer cleaning, the City of Alamo will require manhole spacing of no more than four hundred feet (400') apart, unless otherwise approved by the Public Works Director.
F. Pipe shall be polyvinyl chloride (PVC) pipe (SDR 26) all of which having the proper wall thickness and bedding required for the specific application or as specified by the City. (Ord. 16-07-17, 7-18-2017; amd. Ord. 81-11-22, 11-1-2022)
A. Installation: All utility lines that pass under a street or alley shall be installed before the street or alley is paved. Where it is necessary that utility lines pass under the street or alley pavement, they shall be extended to a point at least three feet (3') beyond the edge of the pavement.
B. Minimum Utility Line Height: Overhead utility lines crossing alleys shall be a minimum of eighteen feet (18') high.
C. Easements: Except where alleys of not less than twenty feet (20') in width are required, easements not less than fifteen feet (15') in width shall be retained (71/2 feet on each side of rear lot lines). Where necessary, easements not less than ten feet (10') in width on each side, lot lines shall be retained for poles, wires, conduits, storm sewers, sanitary sewers, water lines, open drains, gas lines or other utilities. Such easements may be required across parts of lots other than as described above upon recommendation of the City Engineer. Where the proposed platted area adjoins area, the full alley easement width may be required along the lots adjoining the platted or unplatted areas.
D. Street Lighting And Electrical Services: All electrical and communication lines shall be installed underground. Streetlights shall be placed on residential streets at each intersection and in each cul-de-sac. The spacing of the streetlights shall not be less than two hundred fifty feet (250') or greater than three hundred feet (300'). If the distance between intersections is greater than three hundred feet (300'), intermediate light may be required. Subdividers are responsible for placing streetlights in all subdivisions.
1. Streetlight fixtures for arterial roadways are to consist of four hundred (400) watt, high pressure sodium, cobra type fixtures with six feet (6') to fourteen feet (14') extensions mounted on a thirty five foot (35') concrete standard pole. If wood poles are present they may be utilized as long as height and spacing comply with standard.
2. The streetlight fixtures for residential roadways are to consist of two hundred fifty (250) watt high pressure sodium, cobra type fixtures with six foot (6') extensions mounted on thirty five foot (35') concrete standard poles. Spacing preferred at three hundred foot (300') intervals.
3. Streetlight approval is required on all subdivisions.
E. Streetlights Required: The requirement of the placement of streetlights in extraterritorial jurisdiction subdivisions shall be applicable as per Hidalgo County minimum requirements. In lieu thereof, the subdivider may be responsible for placement of money in escrow with the City or the County, in an amount equal to the cost for the placement of such streetlights as estimated by the applicable electric company providing for the same and upon annexation by the City, if funds were placed with the City, the City shall provide for the placement of streetlights using such escrow funds. (Ord. 16-07-17, 7-18-2017)
A. All block corners, angle points and points of curves and all corners of boundary lines of subdivisions shall be marked with a one-half inch (1/2") steel rod two feet (2') in length, set in the center of a concrete monument six inches (6") in diameter and thirty six inches (36") deep with the top flush with the finished ground surface.
B. Where, due to topographic conditions, permanent structures or other conditions, the view is obstructed between any two (2) adjacent monuments, intermediate monuments shall be so set as to assure a clear view between adjacent monuments.
C. Intermediate corner property corner markers, consisting of one-half inch (1/2") steel rod or three-quarter inch (3/4") pipe, three feet (3') in length, shall be driven flush with the ground surface to mark the corners of all lots. (Ord. 16-07-17, 7-18-2017)
A. General. The purpose of this section is to outline the general parameters for proper design considerations of drainage requirements in Alamo, Texas. By establishing guidelines for the orderly presentation of the design, a storm drainage system compatible with needs of Alamo can be achieved. As with any design, all requirements, limitations and procedures for every storm situation cannot be identified; therefore, the responsibility of using sound engineering judgment must be prudently assessed and consistently practiced.
B. Master Drainage Plan And Policy. All drainage design must be coordinated with the. City of Alamo, and with the latest approved Master Drainage Plans, which may exist and be available, If applicable, the design must identify the current floodway and flood boundary map prepared by the. Federal Emergency Management Agency and comply with all their requirements.
1. General Policy.
a. This Drainage Policy shall apply to all drainage improvements within the City limits of Alamo, Texas, and its immediate Extraterritorial Jurisdiction (ETJ); though county drainage policies may also be considered to ETJ plats. When a conflict in design arises with applicable criteria (Hidalgo County Drainage District No. 1, Texas Department of Transportation, etc.) the more restrictive criteria shall generally govern, as recommended by the city’s consulting engineer.
b. All drainage reports and plans shall be prepared by a Licensed Professional Engineer holding a valid license to practice in the State of Texas.
c. All proposed development within the City and its ETJ shall require a storm sewer outfall designated in accordance with the prevailing Master Drainage Plan; or in its absence, pursuant to responsible engineering analysis of the drainage basin.
d. In instances where proposed drainage infrastructure improvements require conveyance to an outfall, the developer shall be responsible for design of the conveyance to accommodate storm water runoff from fully developed conditions within the entire subject drainage basin and all reasonable interconnects. The City may consider a cost share or reimbursement program for (oversized) costs associated with the construction of the offsite conveyance; but such participation by the City is not a mandatory consideration. The City shall have the final decision as to what the drainage infrastructure shall be.
e. All storm sewer conduit and related appurtenances maintained by the City of Alamo shall be located within City right-of-way and/or dedicated drainage easements. Where a subdivision is traversed by a watercourse, drainageway, natural channel or stream, there shall be provided an easement or right-of-way conforming substantially to the limit of such watercourse, plus additional width to accommodate maintenance and future needs.
f. All drainage facilities including street gutters, inlets, pipes, and related appurtenances to the drainage outfall system shall be designed to intercept and convey runoff from a 10-year frequency storm event and checked for a 25-year frequency storm event.
g. The drainage outfall system (channels and ditches) shall be designed to convey and/or detain storm water runoff from a 50-year frequency storm, The developer must comply with regulations to attain approval for connection to a drainage outfall system through a jurisdictional entity.
h. Improvements which will increase the frequency of flooding or the depth of inundation of unprotected structures in the 100-year flood plain or areas of flooding shall not be permitted for construction. The developer must comply with any prevailing City drainage regulations that would strictly govern this policy.
i. Off-site discharge for post development conditions shall not exceed the pre-development peak discharge for all storm events up to and including the 10-year storm event.
j. Stormwater runoff generated from developed improvements shall be detained onsite for a 50-year frequency storm event and released into the receiving system at the pre-developed, peak discharge rate for a 10-year frequency storm event.
k. For redevelopments that have no existing detention, the pre-developed peak discharge rate shall include land cover prior to any development on site.
l. For master planned developments, stormwater detention requirements shall be reassessed, as needed, if land use is substantially changed such that engineered calculations show an increase in runoff when compared to its original approval.
m. Residential lots shall have a post-development finished grade of 0.25% prior to a certificate of occupancy being issued; said 0.25% grade intended to provide perpetual positive drainage toward the front of the lot and toward the street’s storm system. The general contractor shall be responsible for such compliance. The 0.25% slope is in accord to the Hidalgo County’s development policies (3.1.4.1).
n. In no instance shall site grading of the building site adversely affect neighboring properties.
o. In the event of a difference in grade between adjacent properties, each property shall be graded to drain away from the deviation. Grade differentials in excess of 1-foot shall require an engineered retaining structure,
p. Construction activity shall not interfere with the normal operation of existing drainage systems.
q. Storm drainage designs shall account for off-site drainage patterns affected by any proposed drainage improvements,
r. Variances from procedures described in this policy shall require advisory action by the Planning and Zoning Commission during the plats* examination wherein the City’s engineer and/or consulting engineer shall provide his/her professional opinion as to the merits of the variance being requested. Thereafter, the variance shall be presented to the Board of Commissioners, along with the action to the accompanying plat, where said Board shall consider the variance request, staffs position, and the recommendation of the Planning & Zoning Commission, where after said Board shall tender its final action on the matter. A variance request to the drainage policies shall incur a $200 administrative filing fee to off-set engineer’s time to evaluate calculations, storm models, communications with various agencies/departments, etc.
s. All formulas and factors appearing in this policy are presented in English units unless noted otherwise.
t. Acceptable methods of regulation of peak flow achieved by on-site or off-site include parking lots, recreational areas, swales, ponds, reservoirs, channels, and yard areas below top of curb, provided Water does not escape through curb openings, driveways. However, the design is not limited to those methods listed above. Bermed yards are not acceptable. Rear swales in a series of residential lots are also not acceptable.
C. Design Storm Frequencies. Storm drainage planning requires establishment of standards to accomplish design objectives. Storm frequency is a basic criterion necessary in storm drainage design and refers to the magnitude of a storm. Therefore, the selected design frequency establishes the degree of protection desired. Initial storms, as referred to in this manual designate a storm frequency within a 10-year reoccurrence cycle. Run-off from an initial storm is normally intercepted and conveyed by a conveyance system consisting of inlets and a pipe system, A major storm refers to a rainfall having the probability of reoccurrence once every 100 years. Major storms are controlled and conveyed in open drainage systems. Design storm frequencies are as follows:
TABLE II-1: DESIGN STORM FREQUENCIES
| |
Area or Facility | Design Frequency (Developed) |
TABLE II-1: DESIGN STORM FREQUENCIES
| |
Area or Facility | Design Frequency (Developed) |
Enclosed Pipe System (Internal Subdivision) | 10 years |
Enclosed Pipe System (Outfall Master Drainage Plan) | 10 years |
Channels and Ditches (1) | 50 years |
Culverts and Bridges | 50 years |
Floodways Between Building Lines | 100 years |
(1) Channels and ditches shall have one (1') foot of freeboard Note: Storm drainage designed to convey the indicated frequency storm and detain the difference between the 10-year pre-developed runoff and the developed design frequency. | |
D. Drainage Considerations. Drainage design is an integral part of any new development. Proper planning and coordination of the drainage scheme, along with the development plans, is required to achieve an operational and economical storm drainage system. Lack of drainage consideration during the initial planning phase may lead to unnecessary inundation, and added cost due to extension of the drainage system into areas not properly considered. Existing sites and redevelopment areas shall require appropriate detention measures to be designed and constructed.
1. Responsibility in Development.
a. Developers must provide acceptable conveyance for storm waters from the development to the outfall at their expense. All drainage facilities shall be designed to provide capacity for fully developed conditions within the entire subject drainage basin. Please view division B.1.d. of this section for further comprehensive cross-referencing.
b. A seven (7) year Developer’s Reimbursement Contract may be entered into with the City for the costs of over sizing the offsite system for future development. Future development that connects to the system is ultimately responsible for reimbursement. After the 7 year tenure, the proceeds of applicable reimbursement by tying-in developers shall be provided to the City of Alamo (for their monitoring and perpetual maintenance costs of said infrastructure). Reimbursement by subdividing developers shall always be required prior to plat recordation.
c. All on-site drainage construction development is the responsibility of the Developer.
d. All on-site detention facilities must be designed by a professional engineer in accordance with City’s standards specified herein and placed within easements. Access easements to the facility shall be provided with paved or with an all-weather surface, dependent on maintenance circumstances.
e. Internal enclosed pipe drainage systems shall be designed by a professional engineer for a 10-year storm return frequency. Offsite outfall and detention design shall be based on Table II-1.
f. Drainage requirements not considered through the subdivision process will be addressed during the building permit process. At any rate, all new construction shall meet the city’s drainage requirements, including but not limited to, reimbursement fees, buffer fencing, possible dedication of related drainage easements, etc.
E. Water Spread Limit. Streets function primarily to serve traffic, and for that reason, must be expected to have some degree of usability during periods of rainfall Water spread limits are an effective way of defining the protection required to achieve that usability. The following water spread limits are established:
TABLE II- 2: WATER SPREAD LIMITS | |
Street Classification | Permissible Water Spread |
Major Thoroughfare (Divided) | 10-year storm -1 traffic lane must stay open in each direction |
Minor Streets | 10-year storm -1 traffic lane must stay open |
Residential Streets | 10-year storm |
The permissible water spreads are based upon the initial storm frequencies (10-year), but consideration must be given to street conveyance of the major storm (100 year) and possible flooding. All streets shall be capable of conveying a major storm without water encroaching into adjacent buildings. Therefore, the maximum spread limits in streets for a major .storm shall generally., be the building lines. This requirement of utilizing the streets to convey the major storm run-off may require increasing the capacity of the enclosed drainage system.
F. Drainage System Requirements.
The complete drainage in an urban area is composed of: (1) The Conveyance System, consisting of inlets, storm drains, and the associated appurtenances to convey the initial storm run-off (10- year); and (2) The Major System for the major run-off (25-year to 100-year), which consists of swales, ditches, channels, floodways, and emergency overflows to prevent water encroachment into residential and commercial facilities.
The initial storm drain system shall be required when the run-off exceeds the limitations established in divisions A. through E. of this section. Inlets and storm drains shall be designed in accordance with applicable portions of this section. All pipe systems maintained as a public facility shall be constructed with reinforced concrete pipe or other materials approved by the City Engineer or the City-s consulting engineer. The drainage design shall include a plan and profile of storm drainage improvements and shall include a plot of the design hydraulic grade line.
Reinforced concrete lined channels shall have a maximum side slope of 1.5:1 (horizontal to vertical). Unlined ditches shall be no steeper than 2:1 for stability and maintenance purposes. All channels, lined and unlined, shall have a 1-inch per foot traverse bottom slope to the centerline.
Unlined ditches will be considered for quantities larger than the equivalent flow of a 72- inch pipe. These channels shall provide one (1) foot of freeboard minimum. Additional freeboard shall be considered where wave action is anticipated. All drainage ditches shall also provide detention for the difference between the 10-year pre-developed flow and the developed frequency.
All culverts crossing under streets shall extend from property line to property line, plus sufficient length on each end to permit a 3:1 slope to extend from the street property line to a point six (6) inches beneath the top of the headwall. All culverts shall have adequate reinforced concrete headwalls and/or wing walls for 3:1 fill slope with aprons at each end, see detail. Culvert ends shall be protected in accordance with Texas Department of Transportation, drainage facility placement. All culverts shall be designed by a professional engineer to provide sufficient clear zone to ensure vehicular safety.
Additional storm drain criteria follow:
1. Minimum velocity with the pipe flowing full shall be three (3) feet per second.
2. Minimum storm drainpipe shall be constructed of reinforced concrete pipe (RCP), and the minimum diameter shall be 24 inches; however, 18" RCPs may be used should there be a ground cover consideration
3. Pipe diameters shall not decrease downstream.
4. Pipe crowns at change sizes shall be set at the same elevation.
5. The City Engineer and/or consulting engineer will permit minimum vertical and horizontal curves in the conduit only upon review and approval.
6. Street crowns shall be reduced for approximately 100 feet on each side of valley gutters.
7. A maximum of two valley gutter crossings may be used at intersections and shall not be placed at through streets.
8. Utilization of on-site detention is required and must be approved by the City of Alamo, Texas; especially for subdivisions inside the city’s corporate limits: for plats in Alamo’s ETJ, this will be assessed bn a case-by-case basis depending on county policies, precedence, and other logistical circumstances that may be germane to a sound drainage solution regarding detention.
9. At streets with culverts or bridges, an emergency overflow shall be provided to contain the 100-year channel flow within the building lines.
10. Streets should be graded to avoid sumps and utilize the natural existing flow patterns.
11. The maximum length of gutter flow before run-off is intercepted by an underground storm sewer system is 300 feet from the high point to an inlet measured along the gutter (or a length meeting capacity). Maximum separation of 600 feet between inlets is also required. Water spread limits must also be achieved, as per Texas Department of Transportation manual.
12. Erosion and sediment control during construction shall be coordinated with the storm drainage design and in accordance with the current Texas pollution discharge elimination system.
13. Discharge and outfall by use of agriculture field drains shall not be permitted.
14. Valley gutters may be allowed if approved by the City of Alamo, Texas. Minimum size shall be 6-feet wide.
15. Storm sewer systems shall be predominantly constructed within the street right- of- ways only.
16. A maximum 8-inch bleeder line connection will be allowed to any existing city storm sewer system. For connections bigger than this, detailed engineering calculations, indicating minimum downstream and upstream areas are affected, shall be submitted for approval.
G. Fees.
1. Off-site Outfall Drainage Costs.
In areas where the City or another Developer has installed the Off-site Outfall Drainage Systems and a reimbursement policy and contract has been executed, all proposed developments shall be required to pay their pro-rata share of those costs as per the contract prior to the recordation of the subject/connecting subdivision plat.
In areas where the Outfall Drainage System is not installed, the proposed development may:
a. Install the required improvements identified on the latest approved Master Drainage Plan (state/county/city) or as required by the City of Alamo, Texas to the furthest upstream end of the development to a point of outfall discharge and submit for a Reimbursement Contract.
b. Install drainage facilities sized as per the drainage policy for the proposed development to the nearest existing outfall that has sufficient capacity. The City may, at its option, oversize the facilities for future growth in accordance with the latest approved Master Drainage Plan (state/county/city) and initiate a Reimbursement Contract.
c. Propose alternate methods of drainage and conveyance which will be submitted to the City for approval. Detain on-site all run-offs in excess of the pre-development run-off (10 year) rate and quantity. All detention areas must provide a method of drainage within a 48-hour period after the storm passes.
2. Detention Costs. The Developer is responsible for all on-site detention costs. Off-site detention proposals shall be subject to a case-by-case review by the City Engineer and/or the City’s consulting engineer.
3. Over-sizing On-site Drainage and Detention Facilities. On-site drainage and detention facilities will be the sole responsibility and cost of the developer. Any oversizing will be borne by the developer, although it will remain a city option on whether to partner share the oversized cost; however, this option is clearly and unilaterally at the city’s sole discretion on whether to participate or not. At no time will such oversizing may cause additional flooding and/or overload the existing drainage system.
H. Design Parameters.
1. Hydrology.
a. The primary consideration in any drainage study must begin with determination of rainfall in terms of intensity, duration, and frequency. The data to be used for calculating the amount of rainfall and the determination of run-off shall be that found in the Hydraulic Manual prepared and compiled by the Texas Department of Transportation Bridge Division - latest Edition.
b. The Rational Method will be used due to its general simplicity and acceptance. The Rational Method is based on the principal that if rain persists at a uniform rate, the run-off will equal the rate of rainfall. This solution method is applicable to small areas and shall not be applied to areas exceeding 200 acres.
The method is expressed by the formula:
Q = CiA
Where:
Q = Discharge in cfs. (cubic feet per second)
C = By land, use determination. Graph No. GR-1 may be used as allowed by the City.
I = Rainfall intensity is inches per hour at the time of concentration or average run-off Velocity in feet per minute of flow divided into the distance in feet along the course. (I is determined from the I-D-F curves of the TXDOT Hydraulic Manual.)
A= Area in acres of drainage basin
I = b
(tc+d)e for Hidalgo County:
— | E | B | d |
10 yr. | 0,778 | 87 | 9,2 |
25 yr. | 0.771 | 98 | 9,2 |
50 yr. | 0.749 | 99 | 9.2 |
100 yr. | 0.740 | 103 | 9.6 |
c. The Tables II-3 and II-4 show the adopted average velocities to be used to calculate minimum times of concentration, percentage of impervious area, street velocities and capacities to be used in the City of Alamo, Texas. Graph No. GR-1 shows the adopted method for Ross miller’s Nomograph Estimation of C (run-off coefficient).
TABLE II - 3: AVERAGE VELOCITIES FOR TIME OF CONCENTRATION CALCULATIONS | |||
Areas
| Slope in Percent %
| ||
.1 - .5 | .6 - 3 | 4 - 7 | |
Woodlands | 0.10 | 0.10 - 1.5 | 1.5 - 2.5 |
Lawns/Pastures, Residential | 0.15 | 0.20 - 2.5 | 2.5 - 3.5 |
Cultivated | 0.25 | 0.30 - 3.0 | 3.0 - 4.0 |
Storm Sewer/Outlet Channels | Determine velocity with Manning’s Formula | ||
TABLE II - 4: PERCENTAGE OF IMPERVIOUS AREA | ||
Description | Plot Size (sq. ft.) | **Average Impervious Area % |
TABLE II - 4: PERCENTAGE OF IMPERVIOUS AREA | ||
Description | Plot Size (sq. ft.) | **Average Impervious Area % |
Residential Estate | >43,560 | 9 |
Residential Dwelling | 43,560 | 17 |
Residential Dwelling | 21,780 | 38 |
Residential Dwelling | 16,000 | 43 |
Residential Dwelling | 10,000 | 46 |
Residential Dwelling R-2 | 7,500 | 46 |
Residential Dwelling R-1 | 6,230 | 50 |
Multiple-family Dwelling | Variable | 72 |
Schools | Variable | 35 |
Churches | Variable | 85 |
Commercial District | Variable | 85 |
Shopping Center District | Variable | 85 |
Industrial District | Variable | 72 |
Freeway | Variable | 85 |
Open Land* | Variable | 1 |
* Open land in rural areas and public parks increased to 1.0 percent to account for roads, drives, and scattered buildings.
2. Hydraulics. Storm water is conveyed usually on the upper end of a drainage basin by inlets and storm sewers (closed conduit systems) to channels and through culverts and bridges. All calculations and design procedures for this hydraulic work shall follow the Hydraulic Manual prepared and compiled by the Texas Department of Transportation Bridge Division - latest Edition. Tables II-6, II-7, and H-8 show adopted Manning’s Coefficients, minimum pipe slopes, maximum channel velocities and roughness coefficients for channels to be used in Alamo, Texas.
3. Complex and large drainage basins. For drainage areas larger than 200 acres use TR-55, HEC-1, HEC-HMS, or other hydrologic methods as approved by the City Engineer.
TABLE II-6: MANNING’S COEFFICIENT OF ROUGHNESS FOR PIPE
| ||
Material | Value of n | Adopted n Value |
Concrete Monolithic Conduit | 0.012- 0.017 | 0.015 |
Concrete Pipe | 0.011-0.015 | 0.013 |
25% Paved | 0.021 -0.023 | 0.022 |
Fully Paved | 0.012-0.015 | 0.013 |
Plastic Pipe (Smooth) | 0.011 -0.015 | 0.013 |
Note: V = 1.486/n R2/3 s1/2 (Value where V= 3fps)
TABLE 11-7: RECOMMENDED MAXIMUM CHANNEL VELOCITIES
| |
Channel Material | Maximum Channel Velocity (fps) |
TABLE 11-7: RECOMMENDED MAXIMUM CHANNEL VELOCITIES
| |
Channel Material | Maximum Channel Velocity (fps) |
Fine Sand | 2.0 |
Coarse Sand | 4.0 |
Fine Gravel | 6.0 |
Earth | |
Sandy Silt Silt Clay Clay | 2.00 3.50 6.00 |
Grass Lined Earth | |
Bermuda Grass - Sandy Silt Silt Clay | 6.00 8.00 |
Reinforced Concrete Lining | 15.0 |
TABLE II-8: MANNING’S COEFFICIENT OF ROUGHNESS FOR CHANNELS | ||
Channel Type | n Values* | |
Minimum | Maximum | |
TABLE II-8: MANNING’S COEFFICIENT OF ROUGHNESS FOR CHANNELS | ||
Channel Type | n Values* | |
Minimum | Maximum | |
Concrete | 0.012 | 0.018 |
Cement rubble | 0.017 | 0.030 |
Concrete gutter | 0.015 | 0.020 |
Rock rip-rap | 0.030 | 0.045 |
Unlined Channel | ||
Poor grass growth | 0.025 | 0.035 |
Average grass growth | 0.035 | 0.045 |
Dense grass growth | 0,040 | 0.050 |
Stony beds, weedy bank | 0.025 | 0.040 |
Rock cuts, smooth & uniform | 0.025 | 0.035 |
Rock cuts, rugged & irregular | 0.035 | 0.045 |
Natural Stream Channel | ||
Some grass & weeds; little or no brush | 0.030 | 0.035 |
Dense growth of weeds, depth of flow materially greater than weed height | 0,035 | 0.050 |
Some weeds, fight brush on banks | 0.035 | 0.050 |
Some weeds, heavy brush on banks | 0.050 | 0.070 |
For trees within channels with branches submerged at high stage, increase all values above by: | 0.010 | 0.020 |
Pasture, no brush | ||
Short grass | 0.030 | 0.035 |
Tall grass | 0.035 | 0.050 |
Cultivated Areas | ||
No Crop | 0.030 | 0.040 |
Mature row crops | 0,035 | 0.045 |
Mature Field crops | 0.040 | 0.050 |
Heavy weeds, scattered brush | 0.050 | 0.070 |
Wooded | 0.120 | 0.160 |
*Maximum and minimum “n” values adopted from the Texas Department of Transportation | ||
I. Detention.
Continuous development that has occurred throughout the City of Alamo has resulted in an increase both in the peak rates arid the total volumes of Storm water run-off Therefore, land previously not subject to flooding has become flood-prone as a result of unregulated run-off from the subsequent development. Concurrently, land that was already flood-prone has experienced an increase in the frequency and severity of flooding. The use of detention ponds (basins that temporarily store storm water run-off) to reduce peak rates of run-off is an effort by the City of Alamo, Texas and the County to reduce or eliminate these changes, as well as to help maintain the traditional character of the watershed.
The City’s adopted methodology for small urban detention ponds centers around the Rational Method, which is essentially a simple equation used to calculate the peak flow rate of storm water run-off for a particular storm and a particular watershed. The equation is expressed as Q = CiA. “Q” is the peak flow rate. “C” is the run-off coefficient representing the ratio of peak flow rainfall intensity, “i” is the peak rainfall intensity which has a duration equal to the time required for run-off to collect from all points in the watershed (this time is referred to as the “time of concentration”). “A” is the area of the contributing watershed. Since this method yields only one piece of information (the peak flow rate), various modifications have been created in order to generate more information and thus simulate or more closely approximate real-life conditions, Two of these modifications are currently being used and accepted by the City of Alamo, Texas and are called the Variable Rainfall Intensity Method (VRIM) and the Modified Rational Method (MRM).
Both the VRIM and MRM are attempts to produce workable models of desired storm water run off patterns. These patterns, called hydrographs, are graphical representations of the changing flow rate of storm water run-off past a specified point over a prescribed period of time. The VRIM (See Graph No. GR-2, Figure I-iii) more closely resembles actual storm run-off hydrographs in shape and in total volume, due to its curvilinear shape and its run-off distribution with respect to time. Its peak flow rate is the same as that calculated by the basic Rational Method. The VRIM can be used for watersheds up to several hundred acres. However, it involves many more calculations (with corresponding time and effort) than the MRM, if not done with the aid of pre- programmed routines on a computer or programmable calculator. By contrast, the MRM (See Graph No. GR-2, Figure I-iv) is a series of straight-line hydrographs that are crude approximations of run-off hydrographs for storms of various durations.
1. Calculation of Detention Outlet Size. Detention pond discharges into an existing storm sewer line or existing ditch. The outlet size should be calculated to release the pre-developed rate (9.5 agricultural) only.
a. Maximum pool elevation at or below the design hydraulic grade line of the outfall. The discharge line shall be sized for the design storm within the outfall pipe flowing full.
b. Maximum pool elevation at or above the hydraulic grade line at the outfall. Provide a reducer or restrictor to be constructed inside the discharge line. The discharge line shall be sized for the design storm with the outfall pipe flowing full.
c. Reducer or restrictor pipes shall be sized as follows:
(1) Use the orifice equation to calculate the required orifice size:
Q = CA2g h
D = Q1/2 /(2.25h 1/4)
Where: Q = Outflow discharge (pre-developed rate)
C = 0.8 (Coefficient of discharge)
A = Orifice area (SF)
G = Gravity (32.2 ft/sec.2)
H = Head (ft.)
D = Orifice diameter (ft.)
(2) Restrictor shall be either of the calculated required diameter or of the equivalent cross-sectional area. The orifice diameter D shall be a minimum of 0.5 feet.
For each storm duration, the peak flow rate is calculated by the basic Rational Method; except that the intensity used is that for the time of storm duration rather than the time of concentration of the watershed.
The rising limb is a straight line from zero to the peak flow rate extending over a period of the “proposed” or “post-development” time of concentration, A straight line then continues across the graph at the peak flow rate until the storm duration time has been reached. The falling limb is a mirror image of the rising limb. This type of hydrograph is easy to produce, both mathematically and graphically, and is usually applicable for watersheds up to 25 acres.
The City of Alamo, Texas has accepted various methods for determining detention pond storage volumes. All of the methods establish a “lower limit” line to approximate the assumed release rate of water from the pond. This line is applied to the inflow hydrograph for each storm duration. The enclosed area below the inflow hydrograph line and above release rate line constitutes the required storage volume for that particular storm. A range of storm duration that yields the absolute peak for all possible storm durations is used. This peak storage volume is the value that determines the final storage requirement.
The method currently endorsed by the City of Alamo, Texas assumes a horizontal release rate line that extends across the entire graph and is equal to the maximum allowable release rate called “Peak Shaving”. The outflow structure must take into account the early outflows in the storm and keep them at or below the corresponding values in the “existing” or “predevelopment” hydrograph.
Storm water run-off from a particular watershed that does not flow through the detention pond yet must be addressed in the design is called “by-pass” flows. The maximum allowable release rate must be reduced by the peak flows generated from areas that bypass the pond. The peak flows shall be calculated from the basic Rational Formula, using the time of concentration for the given area and the corresponding rainfall intensity for the specific return period of the storm. When multiple-pond systems are involved, the “Peak Shaving” method is not considered to be applicable for cascaded ponds, where the outflow from one pond flows into another pond. Cascaded ponds will require the application of a dynamic model. Multiple-pond systems that do not have cascaded ponds may be designed by this method, in which each subarea to a given pond is treated as a separated design.
For detention/retention areas, side slopes shall be designed at a minimum 3:1 (H:V) slope, or as proposed by the project engineer and approved by the City Engineer and/or consulting engineer.
J. Required Submittals. The following submittals shall be required as part of the drainage and engineering report on all improvements:
1. Preliminary Approval Phase. In order to properly review and consider projects and grant preliminary approval, the following items must be addressed and shown on the submittal.
a. A reproduction of that portion of the latest approved City’s Master Drainage Plan (state/county/city), if available, showing the relationship of the area to be improved and the proposed improvements to the City’s outfall system.
b. Calculations for time of concentration; Q (peak allowable run-off or peak existing run-off prior to development); storage required, and pipe, channel or ditch sizing,
c. A site drainage plan at 1" = 50' showing:
(1) Lot grading with minimum finished floor elevations;
(2) Street flow with preliminary elevations, grades, and flow;
(3) Proposed drainage improvements;
(4) Proposed method of detention;
(5) Existing and proposed one foot (or 0.50 foot if required) contour intervals to 150 feet outside of the subdivision boundaries, referenced to the latest National Geodetic Vertical Datum and to the City Benchmark Datum;
(6) Drainage sub-areas;
(7) 100-year flood elevation and direction of overflow.
d. Certified statement by design Engineer stating FEMA’s designated flood zone, anticipated high water elevation in a 100-year flood, and statement describing drainage pattern in the subdivision and the adequacy of the proposed plan for drainage. When required, a Conditional Letter of Map Revision (CLOMR) shall be submitted to FEMA, prior to preliminary approval.
Any substantial changes to the plat after approval has been granted by both the Planning and Zoning Commission and the Board of Commissioners shall require resubmittal to the P&Z and Board of Commissioners for re-consideration and formal action.
2. Construction Phase. After preliminary approval has been granted by the City of Alamo’s Planning and Zoning Commission and the Board of Commissioners, the City will accept construction plans and specification for review, The submittal should include the following:
a. Seven (7) complete sets of plans, profiles, and specifications for all drainage improvements showing:
(1) Street widths, grades, existing and proposed profiles;
(2) Drainage pipes, ditches, channels with grades and existing and proposed profiles;
(3) Cross-sections;
(4) Complete construction details;
(5) All plans signed and sealed by a Registered Professional Engineer;
(6) TCEQ rules and regulations, as it relates to storm water management shall be followed. A copy of the Notice of Intent (NOI) shall be submitted prior to approval. The approved copy shall be forwarded as soon as possible;
(7) An approved CLOMR shall be presented to the City of Alamo, Texas prior to Final approval.
b. Cost Estimate for all drainage improvements signed and sealed by a Registered Professional Engineer and approved by the City Engineer.
c. After the City reviews the submittals, a meeting with the project engineer will be conducted to go over any comments. The engineer is responsible for making any adjustments/corrections to the plans and resubmitting for approval.
d. Upon approval of the construction documents, the City will schedule a Pre-Construction Conference (PCC). The PCC will be held at the City Hall or a designated location with the Developer, the Project Engineer, the Contractor and the City of Alamo (Public Works Department, Utilities Department, Fire Department, Planning Department, and the City’s consulting engineer), and all other parties as designated by the City. The seven (7) sets of plans submitted shall be reviewed and, if in order and upon approval, will be signed by the responsible parties. The signed plans shall be the “Official Construction Plans” for the project and will be distributed among the attendees.
e. A Notice to Proceed (NTP) horn the City of Alamo shall be issued, delineating the proposed project and its required conditions; once payment of the PCC fee and any required geo-tech lab escrow fees are made.
f. Any changes, revisions and/or deletions from the approved sets of plans including change orders, shall be submitted to the City of Alamo through the City’s Planning Department (3 copies) for consideration. The Public Works Department and/or the City’s engineering staff shall consider the submittal and issue the response thru the Planning Department. The City is not obligated to accept any improvements deviating from the approved construction plans or approved changes.
g. Three (3) certified copies of the as-built (copies on Mylar and on AutoCAD 2004 Compact Disk format), shall be furnished to the City upon completion of the improvements and verification by the project engineer; and shall reflect his/her engineer’s seal and signature on said as-builts.
h. After construction is complete where new paved street systems were accepted, should there be severe erosion predominantly onto the streets’ curb and gutter areas, the Developer and/or the General Contractor shall continue to be responsible to remove said erosion of soil from the street system for a reasonable period post-construction. The removal of eroded soil from the curb and gutters is necessary to minimize/avoid silt infiltration into the storm system.
3. Final Approval Phase. Final approval from the P&Z and Board of Commissioners is subject to review and approval by the Public Works Department. The following is required before final approval is granted.
a. Finalized versions of all the required submittals in the Preliminary Approval Phase.
b. Approved construction plans are required for final approval.
c. An approved CLOMR shall be presented to the City prior to final approval.
The City of Alamo, Texas, its Board of Commissioners are ultimately responsible for final subdivision plat approval. A subdivision plat will not be forwarded to the Board of Commissioners for consideration until all the requirements have been met.
K. Approved Materials.
1. Reinforced Concrete Pipe.
Comply with requirements of ASTM C 76, Class III, minimum installed with flexible plastic (Bitumen) at all joints, tongue and groove joints.
Gaskets shall comply with AASHTO M-198 751, Type B, and shall be installed in strict accordance with pipe manufacturer’s recommendations.
2. Polyvinyl Chloride (PVC) Pipe. PVC pipe is only permitted when specifically approved by the City Engineer. Pipe and fittings shall comply with ASTM D 3034, rated SDR 26. Pipe shall be continually marked with manufacturer’s name, a pipe size, cell classification, SDR rating, and ASTM D 3034 classification. Pipe joints shall be integrally molded bell ends in accordance with ASTM D 3034, Table 2, with factory supplied elastomeric gaskets and lubricant. PVC pipe is not permitted under streets.
3. Manholes.
a. Cast-in-place and pre-cast Manholes.
(1) Cast-in-place Manholes shall be constructed of 3000 PSI concrete.
(2) In accordance with ASTM C-478.
4. Inlets.
a. Type A.
b. Type C-C.
c. Type C.
d. Type F.
5. Cast Iron Frames, Covets, and Grates.
a. As approved by specifications,
6. Specification for Construction and Utility Castings.
Manhole Frames and Covers/Grates
Catch Basin Inlets
Curb and Gutter Inlets
Ditch and Median Inlets
Trench Drainage Inlets
a. Applicable Codes
(1) Whenever reference is made to the furnishing of materials or testing thereof to conform to the Standards of any technical society, organization or body, it shall be constructed to mean the latest standard, code specification or tentative specifications adopted and published at the time of advertisement for bids, even though reference has been made to an earlier standard. Such standards are made a part hereof to the extent, which is indicated or intended.
(2) The following are names and abbreviations of such groups:
AASHTO | for American Association of State Highway and Transportation Officials |
ACI | for American Concrete Institute |
AlSC | for American Institute of Steel Construction |
ANSI | for American National Standards Institute |
API | for American Pipe Institute |
ASA | for American Standards Association |
ASCE | for American Society of Civil Engineers |
ASTM | for American Society of Testing Materials |
AWSC | for American Welding Society Code |
AWWA | for American Water Works Association |
CIPRA | for Cast Iron Pipe Research Association |
Fed. Spec. | for Federal Specification |
NCPI | for National Clay Pipe Institute |
SDHPT | for State Department of Highways and Public Transportation |
UL Inc. | for Underwriter’s Laboratories, Inc. |
UPPA | for Uni-Bell Plastic Pipe Association |
(3) Where no reference is made to a code, standard or specification, the Standard Specification of ASTM, AWWA, or ANSI, as appropriate, shall govern.
(4) If the specifications and drawings show requirements that are in excess of codes and ordinances, then the specifications and drawings shall be followed. Should there be any conflicts between the specifications and drawings, and the codes and ordinances having jurisdiction, the Bidder shall report these in his bid.
b. General: This specification is applicable for gray and ductile iron castings or frames, gates, rings, and covers that are for use by the City of Alamo, Texas, Castings shall be manufactured by East Jordan Iron Works, or other approved USA manufacturer. All manufacturers shall be approved suppliers to the City of Alamo. The approved manufacturer shall be able to demonstrate that there is an acceptable quality control program at the producing foundry, prior to supplying castings.
c. Materials: Gray iron castings shall be manufactured from iron conforming to ASTM A48 Class 35B, as noted in section 3.1 of AASHTO M306. Ductile iron castings shall be manufactured from iron conforming to ASTM A536. The iron material used in products provided shall have a minimum recycled material content of 75%. The recycled materials shall consist of post-consumer material.
d. Manufacture: Castings shall be of uniform qualify, free from sand holes, gas holes, shrinkage, cracks and other surface defects, Castings shall be reasonably smooth and well cleaned by shot blasting. For traffic service castings, bearing surfaces between manhole rings and covers or grates and frames shall be ground or machined with such precision to prevent rocking. As-cast dimensions may vary within accepted foundry tolerances as outlined in the Iron Castings Handbook published by the American Foundry men’s Society, Inc. nominally, casting dimensional tolerances shall be +/- 1/16" per foot. All published casting weights are average and approximate values and shall vary +/- 5%. Castings shall be furnished painted or unpainted as specified by the purchaser.
e. Workmanship: Castings shall show careful finished workmanship in all particulars, Castings which have been damaged either during manufacture or shipping may be rejected. Defects which would constitute poor workmanship include pinholes, shrink, crack, dirt, scab and slag.
f. Sampling: Random checks on the castings may be conducted by the purchaser. These random checks shall be conducted in accordance with the AASHTO M306 Section 6.0 guidelines.
g. Proof Load Testing: Traffic service castings shall have a first article proof load test conducted and the results of that proof load shall be made available to the purchaser upon request. The proof load shall be conducted in accordance with the method and procedure that is outlined in AASHTO M306 Section 7.0, proof load testing. The casting shall be tested on a suitable and calibrated load testing machine and the casting shall hold a 40,000-pound proof load for one minute without experiencing any cracks or detrimental permanent deformation.
h. Inspection: Inspections shall be in accordance with 9.1.1 (refer to #7 above- Proof Load Testing) or 9.1.2 of AASHTO M306. Results of these tests shall be furnished to the purchaser upon request, The heat or production date and product numbers, as cast on the casting shall be the basis of trace-ability and recording of the tests.
i. Certification: A foundry (a workshop or factory for casting metal) certification shall be furnished to the purchaser stating that samples representing each lot have been tested, inspected, and arc in accordance with this specification.
j. Marking: Each casting shall be identifiable and show, at a minimum, the following: name of the producing foundry, country of manufacture (such as “Made in USA”), ASTM material designation, recycle symbol, individual part number, cast or heat date. Castings shall also include all lettering as shown on the specification drawings.
k. Records: Test results for each lot of castings shall be maintained by the foundry for a minimum of seven years and shall be available to the purchaser upon request.
L. Warranty:
Test results for each lot of castings shall be maintained by the foundry for a minimum of seven years and shall be available to the purchaser upon request.
All materials, products, and workmanship shall be guaranteed for a period of 1-year from the written Date of Acceptance by the City and the date approved As-built drawings are submitted.
M. Standard Details. The following list of Standard Details (see Appendix A) show the adopted standards required by the City:
1. Standard Detail DR-1 Type “A” Inlet
2. RESERVED
3. Standard Detail DR-3 Type “F” Inlet
4. Standard Detail DR-4 Type “C” Inlet
5. Standard Detail DR-5 Type “C-C” Inlet
6. Standard Detail DR-6 Pre-Cast Storm Concrete Manhole
7. RESERVED
8. Standard Detail DR-8 Trench Bedding Circular Pipe Storm Detail
9. Standard Detail DR-9 Valley Gutter Detail
10. RESERVED
11. RESERVED
12. Standard Detail DR-12 Concrete Safety End Treatment Detail
13. Standard Detail DR-13 Storm Sewer Manhole Cover Details
14. RESERVED
15. RESERVED
16. Standard Detail DR-16 Pilot Channel Detail
17. Discharge Structure Detail
(RESERVED slots may be filled-in as subsequent storm templates are adopted)
N. Supplemental Requirements.
1. Property Owners or Homeowner’s Associations.
a. When a Subdivision contains either common private property or other private improvements which are not intended to be dedicated to the City of Alamo for public use, such as private streets, detention ponds, a private recreation facility or open space, or other private amenities, a Homeowner’s Association shall be established for the purpose of maintaining the areas. The Homeowner’s Association shall be created consistent with State and other appropriate laws. Copies of the Homeowner’s Association Agreement must be submitted with the Preliminary Plat Application and reviewed by the City Attorney and/or other city officials.
b. In the case of an individual one-lot subdivision, the Property Owner shall dedicate, by plat, a swale/detention pond in the form of a private easement. Single lot subdivisions do not require submission of a Homeowner’s Agreement or Conditions, Covenants and Restrictions (“CCRs”).
c. For Homeowner’s Associations, the Conditions, Covenants and Restrictions (CCRs) and the Homeowner’s Association documents, such as the Articles of Incorporation and Homeowners Association by-laws, shall be submitted to the City for review and possible amendment, along with the Preliminary Plat Application, and shall be recorded, with the Final Subdivision Plat, in the deed records of Hidalgo County in order to ensure that there is an entity in place for long-term maintenance of these improvements. No plat shall be recorded until the CCRs, as may need to be amended, are satisfactory to the City of Alamo assuring perpetual maintenance of any and all private drainage improvements.
d. The City, its agents, and employees, shall have the right of immediate access to the common elements, private property and private improvements, at all times, if necessary, for the preservation of public health, safety and welfare. Should the Property Owners or Homeowner’s Association fail to maintain the common elements to City specifications for an unreasonable time, the City may elect to activate ordained due process protocols to remedy the nuisance or maintenance matter: and thereafter levy any assessment on the Property Owners and/or Homeowner’s Association to cover the cost of maintenance or repairs plus any administrative costs incurred.
e. The Property Owners or Homeowner’s Association must register a contact person with the Community Planning and Development Department. The City shall be notified within ten (10) working days of any change in said contact person. Such contact person must be authorized to receive and distribute information to the Property Owner or Board of Directors of the Homeowner’s Association.
f. If for any reason there is any change or dissolution of the Homeowner’s Association, notice shall be given to the City’s Community Planning and Development Department within ten (10) days of the date of any change or dissolution. The City shall also be provided with an updated CCRs and Homeowner’s Association documentation within the ten (10) days. It is clearly understood that all property owners of the subdivision shall be owners of common properties and, as such, are jointly and legally responsible for said properties’ maintenance costs and upkeep to retain said private improvements in a functional condition.
g. Should there be private drainage improvements reflected on a subdivision plat as common areas wherein such induce perpetual private maintenance, plat notes indicating this shall be required: once the plat is recorded, this is a legal instrument which shall further indicate the legal and high duty to perpetually maintain such common areas.
2. Drainage Design.
a. The difference between the 50-year storm post development runoff and the 10-year pre-development runoff shall be detained on-site. Engineered detention calculations shall be submitted to the City Engineer and/or City’s consulting engineer.
b. On-site detention methods shall include ponds or engineered sub-surface systems. Alternative methods of detention shall be reviewed and approved by the City Engineer and/or city’s consulting engineer.
c. Where the outfall facilities are located more than 300 feet outside the development boundaries, an alternative method of drainage and conveyance may be submitted to the City Engineering staff for approval. Any on-site retention areas must contain the 50-year storm runoff volume for the development and dissipate it into the subsurface within a 48-hour period. A signed geotechnical report, in accordance with the requirements of the detention/retention ponds established in the subsequent sections, must be submitted by a bona fide geo tech firm.
3. Detention Design.
a. Design Considerations.
(1) On-site detention facilities shall be situated in privately dedicated areas. Existing drainage facilities (i.e., City of Alamo’s Drainage Ditches, Regional Stormwater Detention Facilities, etc.) shall not take the place of dedicated facilities unless previously included in the City of Alamo’s Master Drainage Plan if available. Detention areas may be incorporated into landscape and greenbelt areas if vegetation does not adversely affect required design volumes or impede hydraulic efficiency.
(2) Storm water runoff shall be conveyed to detention areas via storm sewer networks, flumes and curb cuts within dedicated right-of-way or flowage easements.
(3) Side slopes shall not exceed 3:1 (H: V). In areas with a potential for vehicular or pedestrian activity, detention pond depths exceeding 3.0 feet shall require a safety buffer in the form of benching or fencing around the perimeter of the pond, (NOTE: cross reference Sec. 11-3-16 Fence Buffering, if needed). The bottom of the basin shall be graded to drain towards the outlet structure. A pilot channel shall be placed along the flow line from inlet to outlet to ensure positive flow. Trash racks shall be incorporated into outlet structure design. A minimum of 10 feet shall be maintained around the perimeter of the entire pond to allow for routine maintenance and/or repair; however, should the ponds’ depth be substantial, a wider perimeter maintenance road shall be required by the City of Alamo.
(4) Detention area design shall consider proximity and elevation of adjacent building structures. Bank areas shall be graded to drain away from such structures. A minimum of 1-foot of freeboard above design pool elevation shall be required. The design of detention areas shall incorporate diversion of overflows into street right-of-way or drainage/flowage easements in the event of an extreme event or outlet structure failure.
(5) Detention pond areas shall be vegetated to prevent erosion and deposition of silts. Common Bermuda, Winter Rye or a combination of the grasses may be used. Vegetated areas shall include provisions for irrigation systems. Ultimately, Landscaping regulations involving landscaping improvements to drainage ponds, inclusive of Section 9-6-10 (A)(9), shall be complied with.
4. Detention Pond Details.
a. Refer to details DR-10 thru DR-16A
5. Detention Pond Operation and Maintenance.
a. Detention ponds shall be maintained by foe owner(s) of record for commercial, institutional, and multi-family developments. For single-family residential developments, Property Owners and/or Homeowner’s Association shall maintain the detention pond(s).
(1) The Property Owners or the Homeowner’s Association, or then’ designated representative, shall be responsible for routinely inspecting ponds to ensure that all components of the pond are maintained and are in good working condition.
(2) Failure to adequately maintain the detention pond(s) in reasonable order and condition, constitutes a violation of this section. The City is hereby authorized to give notice, by personal service or by United States mail, to the Homeowners Association, Property Owners or occupant, as the case may be, of any violation, directing foe Homeowners Association or Property Owners to remedy the same within ten (10) calendar days. The Property Owners or the Homeowners Association will also be subject to a fine of $2,000.00 per day if not remedied by the tenth (10th) day of such notice. Each day of violation shall constitute a separate offense.
6. Parkland Dedication.
a. Land dedicated to the City under this section may be utilized for park and recreation uses, contingent on approval of design requirements, size, flood zone designation, existing parks in general vicinity, advisory action by the Planning & Zoning Commission and the Parks and Recreation Board: and ultimately the Board of Commissioners. The final decision on whether to accept any park land, inclusive of a dual used tract (parks and drainage pond), shall rest with the Board of Commissioners. There is no obligation by the City to accept any park land by any developer - - the ultimate discretion shall rest with the City on this matter and there shall be no appeal.
O. Penalty Clause. Any person, firm or corporation who violates, disobeys, omits, neglects or refuses to comply with or who resists the enforcement of any of the provisions of the Drainage Policy adopted herein shall be fined not more than Two Thousand Dollars ($2,000.00) for each offense. Each day that a violation is permitted to exist shall constitute a separate offense. (Ord. 02-01-22, 1-4-2022; amd. Ord. 65-09-22, 9-6-2022; Ord. 70-10-22, 10-4-2022)
All lots shall abut on an approved street for a distance of at least fifty feet (50') and shall provide safe and convenient pedestrian and vehicular access from the lot onto the street. On cul-de-sacs the fifty foot (50') frontage will be measured at the minimum setback line. Such setback line shall be no less than twenty five feet (25') from the front property line to the face of the building and shall be required on all lots. Lots on cul- de-sacs shall also have a thirty five foot (35') (minimum) frontage at the property line. Lots shall have a minimum area of six thousand two hundred fifty (6,250) square feet and a minimum depth of not less than one hundred feet (100'). (Ord. 16-07-17, 7-18-2017)
A. Crosswalk rights-of-way, six feet (6') in width, shall be dedicated where deemed necessary by the Governing Body to provide pedestrian circulation or access to schools, playgrounds, shopping centers and transportation to other community facilities or to provide pedestrian circulation within the subdivision.
B. Crosswalk ways shall be provided with a concrete sidewalk at least four feet (4') wide. (Ord. 16-07-17, 7-18-2017)
A. Requirements For Payments Toward Park Improvements:
1. Community parks are those parks providing for a variety of outdoor recreational opportunities and within convenient distances from a majority of the residences to be served thereby. The ultimate residential property owners who, by reason of the proximity of their property to such parks, shall be the primary beneficiaries of such facilities. Therefore, the following general requirements shall apply:
a. Whenever a final plat is filed for approval in accordance with the zoning and subdivision regulations of the City, the developer of such plat shall pay an amount equal to five hundred dollars ($500.00) per proposed residential lot or housing unit equivalent (for apartments) to the City of Alamo to be used toward improvements at existing parks or the acquisition of property for new parks.
b. The final plat of the subdivision shall not be processed unless the developer has fully complied with this chapter.
c. Funding received from a subdivision developer shall be used toward park improvements or for the acquisition of property for a park within the area from which funding was received.
d. All funds collected must be expended by the City within ten (10) years from the date received for park improvements or acquisition of property for park development. Such funds shall be considered to be spent on a first in, first out basis. If not so expended, the property owners of the subdivision(s) on the last day of such period, shall be entitled to a refund of such sum after the owners submit the request in writing to the City Manager and after giving the City a six (6) month opportunity to spend the funds towards park improvements or towards the purchase of property for a park anywhere within the City of Alamo.
e. The owners of such property must request such refund within one (1) year or the entitlement of such right shall be forever barred.
f. These requirements shall apply to residential subdivisions within the City limits or residential subdivisions outside the City limits that will be annexed into the City limits within five (5) years or that will benefit from or use the City’s parks.
g. On NON-residentially zoned subdivision plats or non-residentially zoned lots where (residential) park fees were not received by the City of Alamo prior to said plats’ recording, the City’s prevailing park fee per dwelling unit shall be required to be paid during the building permit process for residential units built on such properties as either a permitted or conditional use; or if said non-res lots are later residentially rezoned or if an existing Lot is ‘approved’ by the City to increase the number of residential units not previously factored-in during the original subdivision process. The above circumstances shall be imposed only if they are evident on plats that were recorded after the original ‘approval date’ of the City’s park dedication code (being 6-5-1990). On future non-residential plats, the following plat note may be required: Should any non-residentially zoned lot on this plat be later used for a residential effect, it shall comply with the terms of Section 11-3-15 (A)(1)(g) of Alamo’s Code of Ordinances.” Regardless if the plat note is included or not on the plat, this will not preclude, prevent, or impede the city from enforcing the merits of this provision. Furthermore, on any
B. Special Conditions:
1. Play areas within an apartment complex shall not be credited toward public land use as a park unless each is in excess of one (1) acre in area, is approved by and dedicated to the City, and is made open for public use.
2. Drainage easements may be classified as part of a park if the channel is constructed in accordance with City engineering standards and there is park land not less than two hundred feet (200') in width adjacent to and outside of the channel.
3. Each park must be located adjacent to a public street.
C. Reserved Land: Land shown as reserved on the Comprehensive General Plan for a major recreational center, reservation, school site, park or other public use shall be reserved for a period of one (1) year from the date the plat is filed for record for purchase by the interested governmental authority at land appraisal value at the time of purchase.
(Ord. 16-07-17, 7-18-2017; amd. Ord. 36-06-22, 6- 7-2022; Ord. 66-11-23, 11-6-2023)
A. In all subdivisions, a minimum six foot (6') fence buffer shall be required along any natural and/or manmade hazard such as an open canal, open ditch, caliche pit, detention pond, and holding pond which, in the opinion of the City, is necessary for the lot's occupants to be protected from. Such installed buffer fences shall be a minimum of chain link fence. Six foot (6') opaque fence buffering may also be required along collector streets, minor arterial streets, and major arterial streets as defined by the Hidalgo County Thoroughfare Plan. Such installed buffer fences shall be a minimum of cedar fence construction. (Ord. 16-07-17, 7-18-2017)
In cases where the developer of a subdivision extends utilities from an off-site location into their subdivision, the City of Alamo may enter into a reimbursement contract with a developer.
The developer who seeks the extension of water, sewer, drainage, or streets from an off-site location to their property must advance the cost of construction thereof. Any future developments that occur within seven (7) years of the approval of the construction who wish to utilize the improvements installed by the original developer must participate in the original cost by reimbursing either the developer within seven (7) years of the completion of those lines, or the City of Alamo after that date to offset book keeping costs and maintenance of the improvements by the City.
After entering into a reimbursement contract with the developer, the City will be the fiscal agent regarding the pro-rata shares submitted by future developers wishing to utilize the improvements installed by the original developer. The City shall reimburse to the developer, according to a schedule breakdown of pro-rata shares per parcel of land for the improvements, which shall be submitted by the project engineer for approval by the City. Such breakdown costs are to be made a part of the reimbursement contract. (Ord. 16-07-17, 7-18-2017)
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