Except as otherwise provided in sec.
12.17.002 of this article, all development subject to this article shall achieve the following performance standards:
(1) Total suspended solids, total phosphorus, oil and grease.
(A) Total suspended solids.
For development on slopes between zero percent (0%) and ten percent (10%), seventy percent (70%) of the annual pollutant load in the stormwater runoff for total suspended solids shall be removed. For development on slopes greater than ten percent (10%) but less than twenty percent (20%), eighty percent (80%) of the annual pollutant load in the stormwater runoff of total suspended solids shall be removed. For development on slopes greater than twenty percent (20%), ninety percent (90%) of the annual pollutant load in the stormwater runoff of total suspended solids shall be removed. All development located within 500 feet of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes between zero percent (0%) and ten percent (10%), must have seventy-five percent (75%) of total suspended solids removed after development is complete. All development located within 500 feet of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes over ten percent (10%), must have ninety percent (90%) of the total suspended solids removed after development is complete.
(B) Total phosphorous.
For development on slopes between zero percent (0%) and ten percent (10%), seventy percent (70%) of the annual pollutant load in the stormwater runoff for total phosphorous shall be removed. For development on slopes greater than ten percent (10%) but less than twenty percent (20%), seventy-five percent (75%) of the annual pollutant load in the stormwater runoff for total phosphorous shall be removed. For development on slopes greater than twenty percent (20%), eighty-five percent (85%) of the annual pollutant load in the stormwater runoff of total phosphorous shall be removed. All development located within five hundred feet (500') of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes between zero percent (0%) and ten percent (10%), must have seventy-five percent (75%) of total phosphorous removed after development is complete. All development located within five hundred feet (500') of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes over ten percent (10%), must have eighty-five percent (85%) of total phosphorous removed after development is complete.
(C) Oil and grease.
For development other than single-family residences, on slopes between zero percent (0%) and ten percent (10%), seventy percent (70%) of the annual pollutant load for oil and grease shall be removed. For development other than single-family residences, on slopes greater than ten percent (10%) but less than twenty percent (20%), seventy-five percent (75%) of the annual pollutant load for oil and grease shall be removed. For development other than single-family residences, on slopes over twenty percent (20%), eighty-five percent (85%) of the annual pollutant load in the stormwater runoff of oil and grease shall be removed. All development other than single-family residences located within 500 feet of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes between zero percent (0%) and ten percent (10%), must have seventy-five percent (75%) of oil and grease removed after development is complete. All development other than single-family residences located within 500 feet of the 691 msl contour line (measured perpendicular to the contour line toward the shore) and on slopes over ten percent (10%), must have eighty-five percent (85%) of oil and grease removed after development is complete.
Table 1 Summary of LCRA Performance Standards for Pollutant Removal Levels Incremental Pollutant Removal Requirements |
|---|
| Total Suspended Solids | Total Phosphorus | Oil & Grease |
|---|
Flatter property (0–10% slope) | | | |
General | 70% | 70% | 70% |
Shoreline (within 500' of 691 MSL) | 75% | 75% | 75% |
Moderately sloped property (10–20% slope) | | | |
General | 80% | 75% | 75% |
Shoreline (within 500' of 691 MSL) | 90% | 85% | 85% |
(2) Streambank erosion.
Streambank erosion shall be controlled by designing the drainage system so that the amount of erosion and siltation occurring in the receiving streams is not increased. Specifically, the magnitude and frequency of the predevelopment one-year design storm shall remain the same. The one-year design storm shall be that storm as defined in the LCRA NPS pollution control technical manual.
(3) Erosion and sedimentation control.
Erosion and sedimentation shall be controlled throughout the development process in accordance with the LCRA NPS pollution control technical manual.
(4) Alternative performance standards for single-family subdivisions.
Development of single-family subdivisions that meets all of the following criteria need not comply with subsections
(1) and
(2) of this section:
(A) Minimum lot size of one (1) acre; and
(B) Street and drainage network is designed without curbs or gutters, or some other suitable design, so that runoff is treated using over-land flow methods to a vegetated buffer. The vegetated buffer must meet the slope and vegetative area cover criteria described in the LCRA NPS pollution control technical manual.
(C) Landowners or land users developing single-family subdivisions shall, at the time of application for building permits from the city, demonstrate the erosion and sedimentation control measures that will be used in accordance with the LCRA NPS pollution control technical manual.
(5) Sub-basin averaging.
It is the intent of this section to have a project, as a whole, meet the performance standards of this section. Each phase of a project shall also meet the performance standard when such performance standard is averaged with phases previously built or under construction. As such, averaging of performance standards between sub-basins is allowed under the following conditions:
(A) Performance standards shall be met or exceeded where drainage impacts an adjacent land owner or environmentally sensitive area.
(B) No off-site sub-basin discharge shall fall below the performance standard by more than ten percent (10%).
(6) Monitoring and reporting.
If a project proposes innovative BMPs, the city may require as a condition of issuing a permit, water quality performance monitoring of certain BMPs. Water quality monitoring shall last a period of at least three (3) years. The cost of monitoring, borne by the applicant, shall not exceed ten percent (10%) of the construction cost of all BMPs serving a project. During the monitoring period, the applicant shall submit annual reports showing the results of the monitoring efforts. The pollutant parameters to be monitored shall be determined at the time of permit issuance. The monitoring and reporting must be satisfactory prior to issuance of the BMP Maintenance permit.
(Ordinance CO42-07-07-12-3I adopted 7/12/07)