§ 35-210. Low Impact Development and Natural Channel Design Protocol (LID/NCDP).
STATEMENT OF PURPOSE
The purpose of this voluntary section is to provide site design flexibility, development incentives, and strategies to implement low impact development and natural channel design protocols. This section reduces the need for variances that would otherwise be required for applicants that voluntarily desire to implement LID/NCDP approaches within their site. This section also implements existing city policies which call for the use of LID/NCDP techniques, including but not limited to SA2020, Master Plan, and Complete Streets policies.
The LID/NCDP use pattern implements the following policies of the master plan:
Natural Resource Goals
Goal 1 Preserve the unique, rare, and significant features of San Antonio's natural environment
• Sub-Policy 1.a.2. Water. Encourage the conservation of the City's surface and ground water resources through public education programs and information programs and protective regulations.
• Policy 1.b. Develop and implement a management plan for land use activities which include the best management practices, based on scientific study that will protect the recharge and drainage zones of the Edwards Aquifer from pollution.
• Sub-Policy 1.b.3. Support new development designs that incorporate street, drainage and lot layouts which reduce storm runoff, pollutant loading, and the need for landscape irrigation.
• Sub-Policy 1.b.4. Adopt urban drainage standards which reduce nonpoint source pollution and minimize downstream flooding.
• Sub-Policy 1.b.10. Establish standards for vegetation clearing and maintenance.
• Sub-Policy 1.b.11. Maximize open space and minimize impervious cover through all available means.
• Policy 1.c. Work with elected representatives, other governing bodies, and public interest groups to develop a comprehensive management plan for water resources including the development of additional sources of clean water for the San Antonio area.
• Policy 1.d. Encourage retention of the 100-year floodplains as natural drainage ways without permanent construction, unnecessary straightening, bank clearing or channeling.
• Sub-policy 1.d.1. Encourage the ecological management of floodplains and promote their use as open space, such as greenways, parks, wildlife habitat, and pedestrian-friendly linkage corridors.
• Sub-policy 1.d.2. Adopt strong stormwater management practices throughout the drainage area which include site specific measures such as:
- on-site stormwater retention and detention;
- reduction in impervious cover;
- natural bank contouring;
- floodplain preservation and buffering;
- preservation of riparian habitat;
- stormwater harvesting sites for reuse purposes.
Goal 2 Integrate environmental quality protection into all phases of local planning and policy implementation
• Policy 2.a. Establish a strong natural resources protection policy for San Antonio.
• Sub-policy 2.a.1. Support the preservation and improvement of the current quality of San Antonio's air, land, and water resources and revise current City codes, regulations and practices to reflect this policy.
• Policy 2.d. Develop ordinances which preserve integrity of the natural settings of neighborhoods, communities, open spaces and parks, and develop clear procedures for their enforcement.
Goal 3 Achieve a sustainable balance between the conservation, use and development of San Antonio's natural resources.
• Policy 3.a. Develop programs to attract environmentally sensitive industry to San Antonio and to encourage local industry to adopt water conserving and minimal impact technologies in their operations.
• Sub-policy 3.a.4. Provide incentives for companies to reduce water and energy consumption, and to reuse or recycle water.
• Policy 3.c. Develop incentive programs to reduce energy and water consumption.
• Sub-policy 3.c.6. Expand programs to encourage individuals and businesses to replace high water-using vegetation with water saving landscapes.
PREAMBLE
LID/NCDP is a site assessment, site planning, and structural BMP design process that reduces impervious area and its effects. The process works to first identify then protect and preserve environmentally sensitive features; and uses both natural areas and engineered stormwater controls that mimic natural functions, with a goal of replicating the predevelopment hydrology.
The San Antonio River Basin LID Technical Guidance Manual provides site design principles to identify protected areas and minimize impacts to existing vegetation, high value soils, geology, and habitat. For LID/NCDP planning, the team (owner, architect, engineer, etc.) begins the process with a site analysis to determine which protected features exist on the site and the optimal preservation or enhancement.
To encourage the use of LID/NCDP, this section provides a number of bonus credits toward meeting requirements of this chapter, including but not limited to landscaping, parkland, tree canopy, buffering, street trees, density, and stormwater fee credit.
(a)
Applicability. The provisions of this section shall apply to any voluntary application meeting the requirements of subsections (b) through (o) of this section and which is designated as a "Low Impact Development and Natural Channel Design Protocol (LID/NCDP) Plan" by the applicant.
Within the city of San Antonio and its extraterritorial jurisdiction (ETJ), the LID/NCDP plan shall be based on the San Antonio River Basin LID Technical Guidance Manual and/or the Natural Channel Design Protocol - San Antonio, Texas Region as amended.
The Unified Development Code continues to be applicable to issues not covered in this section, except where these would conflict with the LID/NCDP use pattern, in which case the conflict shall be resolved in favor of the LID/NCDP use pattern as long as the LID/NCDP does not create an adverse impact to adjacent property owners or drainage structures or interfere with public safety and emergency response.
(b)
Processing Procedures.
(1)
Generally. A low impact development and natural channel design protocol plan is a voluntary use pattern application and may be processed as part of a plat, tree affidavit, tree permit, building permit, master development plan, or other development review applications.
(2)
Incentives. An LID/NCDP plan shall be eligible for two (2) types of incentives as approved by the director of the development services department for credit/offset incentives or the director of transportation and capital improvements or their respective designee for fee based incentives.
A.
Credit and Offset Incentives. The applicant managing a minimum of sixty (60) percent of the water quality volume shall receive credit and offset incentives for LID/NCDP according to table 210-1.
Applicants using LID and NCDP practices and managing less than sixty (60) percent of the site water quality volume shall be eligible to receive bonus credits/offsets 1 through 4 for individual BMPs.
Table 210-1
Credit/Offset Multiplier 1. Stream Buffer or Stream Restoration to Parkland Acre 1.5 2. Stream Restoration to Tree Canopy 1.25 3. Linear Park to Parkland Acre 1.5 4. LID BMP to Tree Canopy 1.5 5. LID BMP to Streetscape Tree 1 6. LID BMP Landscape Elective Credit Up to 25 points 7. LID BMP Drainage Area to Parkland Acre 1.5 8. Density Bonus 10% 1.
Stream Buffer to Parkland Acre. The applicant shall receive 1.5 parkland area credit acres for meeting the stream network buffering requirement in subsection 35-210(i)(1)A.3., below as long as the buffer area contains trail access; this credit may meet up to fifty (50) percent of the site's parkland requirements. Any stream network buffering area on the site which overlaps with a linear trail area shall receive 1.5 parkland area credit acres (i.e., there shall be no double counting of credits for overlapping areas).
2.
Stream Restoration to Tree Canopy. Streams that are restored and that establish a minimum twenty-five (25) foot riparian vegetated buffer will be credited at 1.25 times the tree canopy and will receive 1.5 credit acres for parkland, up to fifty (50) percent of the site's parkland requirements.
3.
Linear Park to Parkland Acre. LID practices meeting a minimum of sixty (60) percent of the performance standard in subsection 35-210(g)(2) below will receive 1.5 credit acres towards parkland requirements up to twenty (20) percent of the site's parkland requirements.
The parkland dimensional requirements in Table 503-2 of this chapter may be reduced up to ten (10) percent to accommodate use of LID BMPs.
Linear trails may receive 1.5 parkland credit acres up to fifty (50) percent of site's required parkland area, if such trails are connected to a portion of the development's remaining parkland area via a pedestrian way. Such linear trails may deviate up to ten (10) percent from dimension requirements in Table 503-2 of this chapter.
4.
LID BMP to Tree Canopy. A canopy cover offset of 1.5 times the area of the vegetated LID BMP treatment area shall be provided where tree preservation is used in conjunction with LID practices. To receive 1.5 times credit, the landscape LID practice must be approved based on the standards of this section and appendix H of this chapter and must meet a minimum of sixty (60) percent of the performance standard in subsection 35-210(g)(2) below.
5.
LID BMP to Streetscape Tree. Tree preservation in the right-of-way area is encouraged in LID/NCDP developments. As an alternative to the streetscaping requirements for new landscape trees in the right-of-way, up to twenty (20) percent of the new required streetscaping trees may be offset by installing a vegetated LID stormwater BMP if part of an approved LID/NCDP integrated stormwater management plan, except in areas zoned as a corridor overlay district or form-based zoning district. A maintenance plan must be approved for the LID BMPs in the right-of-way.
6.
LID BMP Landscape Elective Credit. For an LID/NCDP plan meeting a minimum of sixty (60) percent of performance standards in subsection 35-210(g)(2) below, areas with LID BMPs will receive up to twenty-five (25) points for elective landscaping criteria of this chapter. Credit will be allocated according to the proportion of trees, small trees, large shrubs, and small to medium shrubs and native grass cover in the LID BMPs.
7.
LID BMP Drainage Area to Parkland Acre. Where LID practices such as bioretention areas, rain gardens, and swales are part of an approved LID/NCDP integrated stormwater plan, the preserved pervious areas which drain to these practices and which serve multiple uses such as trails, open space, and recreation, shall be counted toward the site's required parkland requirements of this section and may be constructed in designated parkland area. This may meet up to sixty (60) percent of the site's parkland requirements.
8.
Density Bonus. For an LID/NCDP plan meeting a minimum of sixty (60) percent of performance standards in subsection 35-210(g)(2) below, the applicant may increase by ten (10) percent the density allowed in Table 310-1 of this chapter.
9.
Allowance for LID BMPs in Table 510-2 Bufferyards. For LID/NCDP vegetated LID BMPs in bufferyard types A, B, and C shall be allowed. In bufferyard types D, E, and F, LID BMPs shall be allowed in the first ten (10) feet as measured from the interior of the site. The minimum plant materials required for each specific bufferyard type as described in Table 510-2 of this chapter shall be installed within the respective bufferyard area.
10.
Allowance for LID BMPs in Public Right-of-Way. For an LID/NCDP plan meeting a minimum of sixty (60) percent of performance standards in subsection 35-210(g)(2), LID/NCDP vegetated LID stormwater management features may be located within the right-of-way medians, planting strips, curb extensions, or other permeable surface within the street right-of-way; permeable pavement may be used for sidewalks per subsection 35-210(f)(6) below. The applicant may construct vegetated LID BMPs in the privately maintained area of the street right-of-way and receive LID performance standards and detention credits for such BMPs. For the latter, a sliding scale based on the cumulative reduction in flow for the water quality storm, 2-year storm, 5-year storm, 25-year storm and 100-year storms will be applied. To receive a credit, the BMPs must be adjacent to the applicant's development property, must be privately maintained, and must have a long-term maintenance agreement.
11.
Irrigation of LID BMPs. Elimination of permanent irrigation systems is a cost-saving incentive available to property owners. LID BMPs that use native plants and meet a minimum of sixty (60) percent of the performance standard in subsection 35-210(g)(2) for the managed drainage area are not required to install a permanent irrigation system; however, an LID/NCDP BMP that does not install a permanent irrigation system shall provide a detailed alternative irrigation plan and schedule for the establishment and maintenance of the BMP vegetation. LID BMPs, with or without permanent irrigation systems, are subject to the general maintenance requirements of subsection 35-511(c)(4) of this chapter. It is recommended that commercial properties direct air conditioning condensate into BMPs for irrigation as needed and to meet the requirements in City Code, chapter 34, section 34-274.
B.
Fee Based Incentives. The applicant managing a minimum of sixty (60) percent of the water quality volume for the project site shall receive credit and offset incentives for LID/NCDP according to Table 210-2.
Future modification or dissolution of an approved LID/NCDP integrated stormwater plan or its associated operation and maintenance schedule may require reimbursement of any fee based incentives provided, and discontinuance of any ongoing fee based incentives per subsection 35-210(l)(2).
1.
Stormwater Fee Discount. The stormwater fee discount available for incorporating the use of LID/NCDP is specified in City Code, chapter 34, section 34-7.07.
2.
Stormwater Fee in Lieu of (FILO) Discount. Per Table 210-2 below, a minimum credit of five (5) percent of the required FILO payment, based on section 35-C109 of this chapter, may be designated for parcels that manage sixty (60) percent of the water quality volume or greater.
3.
Permeable Pavement Impervious Cover Credit. Permeable pavement shall not be counted as impervious cover if designed to store the 2-year, 24-hour storm event as specified by appendix H of this chapter.
Table 210-2
Percent of Water Quality Volume Managed (1) 60% 70% 80% 90% 100% Credit/Offset FILO Fee Discount Meets LID Performance Standard 5% 10% 20% 25% 30% Meets Detention Requirements or Increases Channel Storage through NCDP Cumulative Reduction in Flow Sliding Scale —
see 210(i)(1)(B)(1) Water quality volume is defined as the runoff volume resulting from the first 1.5 inches of rainfall falling in twenty-four (24) hours on the developed portions of the site.
(3)
Variances. Within the incorporated areas of the city and the ETJ, variances shall be processed in accordance with section 35-483 of this chapter.
(4)
Application Requirements.
A.
Minimum Water Quality Volume Requirements. In order to be considered an LID/NCDP plan and be eligible for incentives in Table 210-2 above, a minimum of sixty (60) percent of the required water quality volume resulting from the increase in impervious area for the entire site, including all of the parking and street areas, must be managed to meet the performance standards in subsection 35-210(g)(2) below.
Individual BMPs may receive credit according to Table 210-1 as approved by the director of development services or their designee.
B.
Preliminary Site Design Review Meeting. The San Antonio River Authority is available free of charge to meet with owners or their design team including engineer, architect and landscape architect before, during or after the development services department's preliminary plan review meeting or as needed any time during the development design process. The preliminary LID/NCDP site design review meeting may be conducted with or without City of San Antonio staff.
C.
Requirements of an LID/NCDP Integrated Stormwater Plan. The LID/NCDP integrated stormwater plan required by this section shall contain architectural, landscape architecture and engineering drawings, maps, assumptions, calculations and narrative statements as needed to adequately describe the proposed development or redevelopment of the tract and the measures planned to comply with the LID/NCDP performance standards in subsection 35-210(g)(2) below. Plan content may vary to meet the needs of specific site requirements.
The plan must also meet the requirements of the current stormwater engineering review team checklist.
Guidelines for the LID/NCDP integrated stormwater plan preparation may be obtained from the director of the transportation and capital improvements department or designee or on the transportation and capital improvements department website. One (1) copy of the approved LID/NCDP integrated stormwater plan shall be kept on file at the jobsite.
D.
Construction Standards. All construction of LID and NCDP stormwater management measures addressed by this section should conform to applicable best management practices outlined in two (2) guidance documents: San Antonio River Basin LID Technical Guidance Manual and Natural Channel Design Protocol, San Antonio, Texas Region.
These guidance documents may be updated or revised periodically based on new information and new approved technologies. These sources are recommended for guidance for LID/NCDP applicants. Choice of specific LID and NCDP measures is at the option of the applicant.
E.
Single-Family Lots. A single-family residential lot, not part of a larger development, is eligible to submit a simplified stormwater management plan. The simplified plan must include the following:
1.
A brief project summary including the location, description of existing property, and the proposed development;
2.
Calculations that show the development adheres to the LID performance standards in subsection 35-210(g)(2).
3.
An exhibit showing the site boundary, proposed locations of building, driveway, parking and other impervious area footprints.
4.
The plan must show the proposed locations of stormwater BMPs and the positive overflow pathways for storms exceeding the flow rate and volume managed by the BMPs.
F.
Plat Note. Developments with LID/NCDP shall have the following note placed on the plat (minor variations of this note may be accepted as approved by the director of TCI:
The property owner has elected to provide low impact development (LID) and/or natural channel design (NCD) on lot(s) XX, block XX, NCB XXXXX. Building permits for this property shall be issued only in conjunction with necessary LID/NCDP approved by the City of San Antonio. The property may be eligible for credit and offset incentives and/or fee incentives when approved by the City of San Antonio. If the property owner elects not to provide LID and/or NCDP, the incentives may not be granted and the property shall conform to all applicable development standards of chapter 35, the Unified Development Code.
G.
Restrictions on Property Usage. Conservation areas and open space (floodplains, buffer zones, greenbelts, open space, park dedication, tree save areas, etc.) if applicable to a site, shall be provided according to platting and development requirements and procedures of this chapter. The location of all such designated natural areas, parkland, open space, etc. shall be described and delineated in the integrated stormwater plan. Revisions to these areas after an LID/NCDP plan is approved will be subject to city review. Revisions may increase or decrease incentives, and the property shall conform to all applicable development standards of this chapter.
Land within the rights-of-way of below and above-ground utilities or roads shall not count toward the site's buffer zone, open space, parkland or other conservation area requirements.
H.
Deed Recordation Affidavit. A deed recordation affidavit shall be required when LID/NCDP is proposed with a building or site work permit and the associated plat does not include the plat note from subsection 35-210(b)(4)F. Once an LID/NCDP integrated stormwater plan has been approved for the site, within sixty (60) days the applicant shall submit a deed recordation affidavit referencing the LID/NCDP integrated stormwater plan, including a description of LID/NCDP components and the stormwater plan's operation and maintenance agreement. Building permit approval may be withheld until the affidavit is reviewed and approved by the City of San Antonio. Certificate of occupancy may be withheld until proof of recordation of the affidavit is submitted to and accepted by the City of San Antonio.
The affidavit may be drafted such that modifications or removal of LID/NCDP components does not require revoking or vacating the deed recordation affidavit. However, those modifications to the LID/NCDP integrated stormwater plan must be submitted to the city for review and approval, and may result in nullification or reimbursement of credits and/or incentives. The property shall conform to all applicable development standards of the Unified Development Code.
I.
Improvement Security. LID/NCDP stormwater control measures shall be recognized similar to other site improvements (e.g., drainage infrastructure, streets, etc.). As such, a performance agreement, in the form of a financial security, shall be required and adhere to the procedures and the guarantees of performance specified in section 35-437 of this chapter.
J.
Record Drawings and Final Approval. Upon completion of an LID/NCDP BMP project, and before a temporary certificate of occupancy or field acceptance of public or private infrastructure improvements that are part of LID/NCDP integrated stormwater plan shall be granted, the applicant shall conduct a post-construction site inspection and verify that the completed project is in accordance with the approved stormwater plan and designs. Before a final certificate of occupancy, or release of the performance bond for construction of public or private infrastructure improvements, the designer of record shall submit actual record drawings for all structural stormwater management facilities and flow paths after final construction is completed. See subsection 35-210(k)(1) below, for detailed requirements of the record drawings.
(c)
Density. Except for the density bonus allowed in subsection 35-210(b)(2)A., a LID/NCDP shall comply with the density standards of this chapter.
(d)
Traffic Impact Analysis. An LID/NCDP shall comply with the traffic impact analysis standards of this chapter.
(e)
Lot Layout. An LID/NCDP shall comply with the lot layout standards of this chapter except as follows:
(1)
Setback, Side Yard, and Rear Yard Incentives. In order to accommodate LID BMPs and optimize LID/NCDP site design, required setback, side yards, and rear yards in Table 310-1 of this chapter may be reduced as long as such reductions meet fire code standards. The reductions may not compromise public safety such as the sight distance triangles defined in subsection 35-506(d)(5) of this chapter.
(f)
Transportation. A LID/NCDP shall comply with the transportation standards of this chapter except as follows:
(1)
Minimum Pavement Width and Street Design. Applicants shall adhere to the traditional street design standards in section 35-506, Tables 506-4 and 506-4A of this chapter.
(2)
Credit for LID Practices in the Street Right-of-Way. See credit allowed in subsection 35-210(b)(2)A. Use of swales with curb is allowed by right in the following zoning districts RP, RE, RD, and FR, and allowed with conditional approval in zoning districts R-20, O-1, MI-1, and MI-2.
(3)
Curb and Edge Treatment. Where a portion of a project or public improvement has been designed specifically as a LID stormwater management feature, saw tooth curb edge treatment is encouraged as part of LID/NCDP.
(4)
Separation of LID Practices and Utilities. For LID BMPs installed in the right-of-way, care must be taken to allow the co-placement and separation of utilities in such a way as to avoid utility damage during construction. The applicant may reference the street cross sections in the San Antonio River Basin LID Technical Guidance Manual for appropriate placement and installation of BMPs in the street right-of-way.
(5)
Use of Permeable Pavement for On-Street Parking. The applicant may reference the approved list of permeable pavement materials for on-street parking areas in the San Antonio River Basin LID Technical Guidance Manual, as may be updated periodically. Permeable pavement must meet the requirements of subsection 35-210(b)(2)B.3. above to receive FILO credit.
(6)
Sidewalks. In order to reduce effective impervious area, an approved permeable pavement may be used for sidewalks as long as the materials meet ADA requirements. The applicant shall adhere to the approved list of permeable pavement materials that may be used for sidewalk areas in the San Antonio River Basin LID Technical Guidance Manual as may be updated periodically.
(7)
Special Purpose Medians. Designers may incorporate BMPs into dividers constructed for aesthetic purposes such as at entrances for subdivisions and landscaping features. LID stormwater BMPs shall be designed according to specifications in the San Antonio River Basin LID Guidance Manual. The minimum width for such special purpose dividers with LID BMPs shall be in accordance with subsection 35-506(n)(2) of this chapter. No vegetation shall be placed in the median that will obstruct the drivers' sight distance defined in subsection 35-506(d)(5) of this chapter.
(8)
Traffic Calming Devices. Traffic calming devices approved for use in LID/NCDP developments include curb bump outs with LID/BMPs or curb extensions with LID/BMPs as illustrated in the San Antonio River Basin LID Guidance Manual.
(g)
Stormwater Management. An LID/NCDP application shall comply with the stormwater management standards of appendix H of this chapter, except as follows:
(1)
Integrated Stormwater Management. After accounting for stormwater quality and volume credits from environmentally sensitive site design per subsection (i), natural resource protection and tree preservation, applicants shall use LID structural BMPs or a combination of LID and conventional BMPs to meet the balance of LID performance standards required in subsection 35-210(g)(2) below.
The applicant may choose the appropriate combination of environmentally sensitive site design techniques and LID structural BMPs to meet the LID performance standards. Approved LID structural BMPs, as well as design and maintenance guidance for each BMP, may be found in the San Antonio River Basin LID Technical Guidance Manual.
(2)
LID Performance Standards.
A.
On-site Stormwater Management Framework. Per subsection 35-210(b)(4)A., a minimum of sixty (60) percent of the water quality volume must be managed to be considered an LID/NCDP development. If less than one hundred (100) percent of the water quality volume will be managed, the designer will give first priority to managing the runoff volume from all of the parking and street areas within the development limits. The water quality, volume, and flow rate LID performance standards below are presumed to be met if the stormwater management system is sized and designed to manage a minimum of sixty (60) percent of the WQV using the guidance in the San Antonio River Basin LID Technical Guidance Manual.
B.
On-site Stormwater Management Criteria. For new development, a stormwater management system with LID shall treat the water quality volume (WQV) resulting from the first 1.5 inches (equivalent to the ninetieth (90th) percentile storm calculated using the methodology developed by the EPA in report 841-B-09-001. The daily rainfall total for the period of record at the San Antonio International Airport was used to calculate the ninetieth (90th) and eighty-fifth (85th) percentile storms referenced in this section.) of rainfall falling on the developed portions of the site in a twenty-four (24) hour period.
Compliance with this WQV performance standard through a combination of infiltration, filtering, and settling is presumed to meet the following treatment levels:
1.
Removal of eighty (80) percent of the average annual post development total suspended solids (TSS) load; and
2.
Removal of sixty (60) percent of the annual bacteria load. The applicant shall be eligible for incentives to treat stormwater from the new development according to Tables 210-1 and 210-2.
C.
Definitions. For the purposes of this section, development and redevelopment are as defined in appendix H of this chapter.
D.
Redevelopment Standards. A redevelopment site shall be subject to a reduced LID performance standard: the stormwater management system will be sized and designed based on the runoff volume resulting from the first 1.18 inches (equivalent to the ninetieth (90th) percentile storm calculated using the methodology developed by the EPA in report 841-B-09-001. The daily rainfall total for the period of record at the San Antonio International Airport was used to calculate the ninetieth (90th) and eighty-fifth (85th) percentile storms referenced in this section.) of rainfall in twenty-four (24) hours from rebuilt areas and newly developed areas on the site. The applicant shall be eligible for incentives to treat stormwater from the redevelopment site according to Tables 210-1 and 210-2.
(3)
Special LID Requirements for Karst Areas Outside the Edwards Aquifer Recharge Zone. If applicable, the applicant shall identify and locate karst features and submit a map with the concept plan and stormwater management plan for the proposed development project. The map shall display, according to the best information available, topographic and geologic information and features (including, but not limited to, faults and fractures along waterways and sinkholes), and proposed and existing stream buffer preservation areas.
Any existing karst swales, sinkholes, or solution features should be surveyed and indicated in the integrated stormwater plan. Buffers or reserves for features collecting drainage for watersheds should be set aside as defined by RG-348A (Optional Enhanced Measures for the Protection of Water Quality in the Edwards Aquifer (Revised)) in the integrated stormwater plan so that all future landowners are aware of the presence of solution features or sinkholes on their property.
(4)
Special LID BMP Requirements/Considerations for Historic Areas.
A.
Landscaping. Removal of existing landscaping or sod areas and replacing them with vegetated LID BMPs is allowed where not removing character defining landscaping elements and with historic design review commission approval and a certificate of appropriateness.
B.
Hardscaping. Removal of existing hardscaping and replacing it with pervious pavement treatments is allowed where not removing character defining hardscaping elements.
(5)
Manufactured Products for Stormwater Management. In addition to the BMPs included in the San Antonio River Basin LID Technical Guidance Manual, several proprietary manufactured products have been adopted by the Texas Commission on Environmental Quality (TCEQ) to meet a minimum of eighty (80) percent TSS removal. These devices shall not be accepted to meet the volume reduction requirement of subsection 35-210(g)(2), but will be allowed for pre-treatment, filtering, trash removal and oil and grease removal as the first structural BMP in a treatment train. Devices that have not been approved by TCEQ may be acceptable to the Director of the transportation and capital improvements department or designee only if they meet the Technology Assessment Protocol - Ecology (TAPE) guidelines.
A.
Pre-Treatment and Trash Removal Applications.
B.
Hydrodynamic Separators. Hydrodynamic separators utilize cyclonic motion of stormwater to physically remove sediments and floatable materials. They do not provide volume or rate reduction; therefore, their most appropriate application is upstream of BMP practices that can provide these functions. Hydrodynamic separators are particularly well suited for providing pretreatment in areas of high sediment loading for BMPs whose primary function is filtration or infiltration, as they can reduce maintenance frequency and extend the life of the downstream BMP.
C.
Screens and Trash Racks. Screening devices that capture large floatable debris are recommended for all inlets that drain into preserved/restored streams or BMPs. These devices provide a single point for collection and disposal of trash that would otherwise be dispersed into natural areas.
D.
Enhanced Filtration.
1.
Cartridge Filters. Cartridge filters that rely on structurally enclosed media to filter stormwater and remove pollutants may be used in applications where LID structural BMPs described in the LID Design Manual are determined to be infeasible or not in the best interest of the city according to the director of transportation and capital improvements or designee. Cartridge filters shall not be used in areas with high sediment loading unless hydrodynamic separator pretreatment is installed. Cartridge filters may be used as part of a treatment train but do not retain the volume defined as the performance standard in subsection 35-210(g)(2).
2.
High Rate Filter Media. Customized high rate filter media may be utilized to meet partial water quality performance goals if LID BMPs designed using the San Antonio River Basin LID Technical Guidance Manual are infeasible or not in the best interest of the city according to the director of transportation and capital improvements or designee. High rate filter media applications may include tree boxes, tree filters, or any filter system that treats but does not retain the volume defined as the performance standard in subsection 35-210(g)(2). The WQV defined in subsection 35-210(g)(2) must pass through the high rate filter media and achieve the pollutant removal targets. Treating the WQV using high rate media does not equate to meeting the volume reduction requirement in subsection 35-210(g)(2).
(h)
Utilities. See utilities standards, section 35-507, of this chapter. Also see subsections 35-210(b)(4)D., restrictions on property usage, and 35-210(f)(4), separation of LID practices and utilities, above.
(i)
Natural Resource Protection and Tree Preservation.
(1)
Environmentally Sensitive Site Design.
A.
Site Analysis. For LID/NCDP, the design process begins with a site analysis to determine the degree to which the following features exist on the site and the feasibility of their preservation or enhancement:
1.
High Value Soils. Preservation of high infiltration soils is encouraged. For the purposes of this section, high infiltration soils are defined as all soils with infiltration rates greater than one (1) inch per hour.
2.
Geomorphic Assessment. The applicant shall perform a NCDP geomorphic assessment according to subsection 35-210(i)(2) below.
3.
Stream Network Buffering. The stream buffer to parkland credit incentive is applicable to LID/NCDP plans that preserve the habitat and watershed management functions of riparian buffers. To the extent that any of the following stream network elements exist on a site, at a minimum, the LID/NCDP shall preserve:
i.
A riparian buffer with a minimum average width of twenty-five (25) feet from the top of bank for all Jurisdictional Waters of the U.S. and;
ii.
All of the floodway and flood fringe within the regulatory 100-year floodplain, as shown on official FEMA maps, and any letter of map revision (LOMR);
iii.
A riparian buffer with minimum average width of fifty (50) feet from the edge of the regulatory 100-year floodplain as delineated on the official FEMA maps and any letter of map revision (LOMR). To reduce fragmentation, no more than ten (10) percent of the buffer can be less than thirty-three (33) feet wide;
iv.
A riparian buffer with a minimum average width measured from the top of the bank and determined based on the slope of the streamside area in accordance with the table methodology found in City Code, chapter 34, section 34-913 for all perennial streams or intermittent streams with a drainage area of greater than one hundred (100) acres. In all cases, a twenty-five (25) foot-wide riparian buffer zone must be preserved. To reduce fragmentation, no more than ten (10) percent of the buffer can be less than thirty-three (33) feet wide;
v.
A riparian buffer with minimum average width of fifty (50) feet from the top of bank of any perennial, intermittent streams with a drainage area of less than one hundred (100) acres or ephemeral streams draining more than forty (40) acres. In all cases, a twenty-five (25) foot-wide riparian buffer zone must be preserved. To reduce fragmentation, no more than ten (10) percent of the buffer can be less than thirty-three (33) feet wide;
vi.
All areas within twenty-five (25) feet of the top of bank of any ephemeral stream draining less than forty (40) acres; and
vii.
The applicable stream buffer requirements of this chapter's tree preservation and floodplain requirements, or applicable recharge protection provisions in City Code, chapter 34, section 34-920, recharge feature protection and buffer zone, whichever is most stringent.
4.
Slopes. Slopes greater than fifteen (15) percent should be evaluated for erodibility using the natural resources conservation service erodibility index.
B.
Offsetting Stormwater Detention, Water Quality, and Volume Requirements. Environmentally sensitive site design practices that manage the increased runoff due to development may be evaluated using standard hydrologic approaches required for the LID/NCDP integrated stormwater plan. Environmentally sensitive design site practices shall also be credited toward meeting the site's LID performance standard.
C.
Establish Clearing, Grading and Stockpiling Limits. Grading plans shall clearly identify limits of construction areas and include a ten (10) foot buffer between areas of disturbance and protected areas, BMPs or buildings and any environmentally sensitive area. Allowable stockpile areas shall be identified in areas that will be paved or disturbed during subsequent construction.
(2)
Natural Channel Design Protocol.
A.
Restorative Practices for Natural Channels. All channels draining more than twenty (20) acres within an environmentally sensitive site design plan should be evaluated for:
1.
Protection if the channel is stable and functioning properly, or
2.
Restoration if the channel is unstable.
For the purposes of this section, channels should be evaluated using a geomorphic assessment as defined in the Natural Channel Design Protocol, San Antonio, Texas Region, as amended, to determine the degree of instability. See subsection 35-210(b)(2)A. for bonus tree canopy and parkland credits for stream restoration.
B.
Earthen Engineered Channel Design to Reduce Erosion and Maintenance. Engineered channels that are necessary to convey local and/or off-site flows shall be designed either as vegetated swales or as multi-stage flood control channels (see Natural Channel Design Protocol, San Antonio, Texas Region as amended).
C.
Restoration Credit for Existing Engineered Channels. Existing engineered channels that are armored using either concrete or rock rubble may be redesigned using NCDP. As part of an LID/NCDP integrated stormwater plan, channels will be credited as flow reduction and water quality features based on scientifically based benefits. Such benefits shall be documented in the LID/NCDP integrated stormwater plan.
D.
Design Protocols. Recommended natural channel design protocols may be found in Natural Channel Design Protocol, San Antonio, Texas Region (2013), which may be updated from time to time.
(j)
Parking. An LID/NCDP shall comply with the parking standards of this chapter except as follows:
(1)
Parking Space. To minimize impervious area, use of minimum vehicle spaces allowed in Tables 526-3a and 526-3b of this chapter is encouraged except where preservation of woodlands or significant stands of trees is desired; in such cases, per subsection 35-526(b)(6) of this chapter, the director of the transportation and capital improvements department or designee may waive up to fifty (50) percent of the minimum parking spaces required by Table 526-3. Permeable pavement is encouraged for vehicle spaces above the minimum requirement, and as stipulated in subsection 35-210(l)(3) below. Use of shared off-street parking facilities is encouraged, as practicable, according to subsection 35-526(g) of this chapter.
(2)
Dimensions. To reduce impervious area, an LID/NCDP may reduce parking dimensions using one (1) of the following options.
A.
Alternative Parking Dimensions. Use of the parking space dimensions in Table 210-3 below is allowed as an alternative to the requirements of Table 526-1 of this chapter.
Table 210-3
Angle Width Curb Length 1-way aisle 2-way aisle Stall Depth 30 degrees 8'-6" 17' 12' NA 15' 45 degrees 8'-6" 12' 12' NA 17' 60 degrees 8'-6" 9'-9" 16' 20' 17'-6" 90 degrees 8'-6" 8'-6" 25' 25' 18' B.
Compact Parking Allowance. Up to forty (40) percent of the required parking spaces may be designated for use by compact vehicles with minimum dimensions of eight (8) feet in width and sixteen (16) feet in length. Compact vehicle parking shall be identified by individually marking each parking space surface with lettering a minimum of six (6) inches in size.
(3)
Use of Permeable Pavement. Permeable pavements may be used in low-traffic portions of the off-street parking area, including all marked parking stalls and infrequently used fringe parking areas. The applicant may reference the approved list of permeable pavement materials that may be used for off-street parking areas in the San Antonio River Basin LID Technical Guidance Manual. Permeable pavement must meet the requirements of subsection 35-210(b)(2)B.3. above to receive FILO credit.
(4)
Parking Area Landscaping, Buffering, and Shading. To encourage multifunctional LID BMPs and provide incentives for their use, bioretention areas, vegetated swales, planter boxes, rainwater harvesting systems, NCDP, and other vegetated BMPs may be used to meet parking area landscaping requirements in this chapter and may be constructed in designated landscape areas as part of an approved LID/NCDP integrated stormwater management plan for the site. See subsection 35-210(b)(2) above for allowable credits.
(k)
Construction Activities and Reporting Requirements. A registered design professional in responsible charge (RDPiRC) or certified inspector, retained by the owner of the land, shall provide oversight of construction activities. An inspector (other than the RDPiRC) must be certified through the San Antonio River Basin Construction Inspector Certification program. The inspector and contractor shall work to avoid damage or alterations of the existing site conditions that could deteriorate or compromise the structural and non-structural LID BMPs.
The inspector may reference guidance and checklists from the BRWM Design and Construction Inspection of LID BMPs registration course. The LID/NCDP plan shall adhere to City Code, chapter 34 stormwater compliance for construction activity and reference the San Antonio River Basin LID Technical Guidance Manual for construction practices, including environmentally sensitive construction, construction sequencing, and inspections.
Inspections may also be conducted by city staff. However, those inspections will not waive any owner, contractor, or RDPiRC requirements or responsibilities.
(1)
Record Drawings and Final Agency Acceptance. Upon completion of a project, the applicant shall conduct a post-construction site inspection and verify that the completed project is in accordance with the approved stormwater plan and designs. Before a final certificate of occupancy is issued, the designer of record shall submit the following items to the transportation and capital improvements department for review and acceptance:
A.
Record (as-built) drawings; and
B.
Post-construction inspections certification form which can be obtained from the director of the transportation and capital improvements department or designee or on the transportation and capital improvements department website.
(l)
Maintenance.
(1)
Maintenance Required. Structural stormwater management practices must be privately owned and shall be maintained by the property owner, unless the practices are part of a capital improvement project managed by a public agency. An operation and maintenance schedule shall be submitted to the director of transportation and capital improvements department or designee prior to approval of construction plans.
(2)
Annual Maintenance Inspection Report. The person responsible for maintenance of any structural stormwater management practice installed pursuant to this section shall submit to the director of the transportation and capital improvements department or designee an annual inspection report from a registered design professional licensed by the State of Texas or a certified inspector. A single-family residential lot, not in a subdivision, is not required to submit annual inspection reports.
(3)
Operation and Maintenance Compliance.
A.
LID/NCDP Plan Three-Year Establishment Period. The standard establishment period for an LID/NCDP integrated stormwater plan shall be three (3) years. It is recommended that the owner obtain a registered design professional licensed in the State of Texas or a certified inspector to perform at least quarterly inspections of the structural stormwater management practices during the first year after construction of the LID/NCDP improvements to promote proper establishment.
B.
Dissolution of an LID/NCDP Plan. If the applicant or owner wishes to dissolve the LID/NCDP integrated stormwater plan or operation and maintenance schedule within the establishment period, the following conditions apply:
1.
The applicant or owner must notify the director of transportation and capital improvements department or designee.
2.
The applicant or owner must meet the requirements of appendix H of this chapter.
3.
The applicant or owner must meet the parkland, landscaping, and tree preservation requirements of the ordinance in effect on the date when the city was notified of the desire to dissolve the plan and/or schedule.
4.
The applicant or owner forfeits all ongoing fee-based incentives.
5.
The applicant or owner must reimburse to the city all fee-based incentives accrued to date within thirty (30) days of receiving the assessment of incentives. If such assessment is not paid within thirty (30) days, the matter will be referred to the city attorney's office to enforce compliance.
If the owner fails to provide annual inspection reports during the establishment period, the city may elect to inspect the structural stormwater management practices for proper maintenance and functionality. Failure to provide annual inspection reports and to maintain structural stormwater management practices within the establishment period may result in forfeiture and/or reimbursement of incentives.
C.
Modification of a LID/NCDP Plan. If the owner proposes to modify the LID/NCDP integrated stormwater plan and/or maintenance agreement during or after the establishment period, the revised integrated stormwater plan shall be submitted to and reviewed by the City of San Antonio Transportation and Capital Improvements Department. The revised plan and any associated incentives shall be subject to the requirements of section 35-210, appendix H of this chapter, and other pertinent sections of this chapter.
(m)
Compliance. Compliance with the requirements of this section shall be enforced through sections 35-490 through 35-492 of this chapter.
(Ord. No. 2016-02-18-0107 , § 2, 2-18-16)