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Grand Communities, LLC/Jason M. Wisniwski
LL 975, 976, 1022, 1023,1024,1049,1050 Springbrooke Estates Subdivision located along Lewis Road
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PETITION: The applicant, Grand Communities is requesting a Flood Protection Variance to vary from the following:
1) Section 10.11 (b) - prohibits an increase in the floodway depth and a decrease in the floodway width.
2) Section 10.16 (b) - requires compensation for any fills.
3) Section 10.16 (a) - requires no reduction of flood storage capacity and prohibits changes to the flow characteristics as to the depth and velocity of the waters of the base flood or future-conditions flood.
The subject site is located at Land Lot 975, 976, 1022, 1023,1024,1049,1050, 19th District, 2nd Section, Cobb County, GA.
Recommendation:
Approval to vary from Section 10.11 (b), Section 10.16 (a) and Section 10.16 (b) of the Unified Development Code (UDC) for the purposes on constructing an aerial sewer to serve the residence of the undeveloped portion of the Silverbrooke Estates with conditions:
1. Staff will continue to review the application regarding waiving certain floodplain management stormwater requirements with professional consulting staff. For successful approval the applicant must provide technical data to demonstrate that there is a “no-rise” between the existing conditions and future conditions.
2. Any modification or alterations relating to the design or modifications that results in further impact to the floodplain will be done administratively in collaboration with the City professional consulting staff.
Flood Protection Variance - To waive the sections identified above (Section 10.11 (b), Section 10.16 (b), Section 10.16 (a)) in an effort to construct an aerial sewer to serve the undeveloped portion of Springbrooke Estate with an understanding that certain sections of Chapter 10 of the UDC will be waived.
Location Plan Profile
Background:
The proposed request is for a flood protection variance to vary from the following sections outlined in Article 10 of the Unified Development Code:
1) Section 10.11 (b) - prohibits an increase in the floodway depth and a decrease in the floodway width
2) Section 10.16 (b) - requires compensation for any fills
3) Section 10.16 (a) - requires no reduction of flood storage capacity and prohibits changes to the flow characteristics as to the depth and velocity of the waters of the base flood or future-conditions flood.
The purpose of the request is to facilitate an aerial sewer to provide sewer services to the undeveloped portion of Springbrooke subdivision. The proposed aerial sewer will be located along the eastern section of Lewis Road and will be approximately 129.1 feet long. The aerial sewer is proposed to be an 8-inch diameter pipe which is anticipated to serve up to 458 residential homes. The Springbrooke Estate subdivision consists of Unit 1 and Unit II and was originally approved for a total of 210 lots (number of lots has been modified over the years). Currently there are 106 lots remaining to be built in Unit 1, Phase 2 (undeveloped portion highlighted in orange above). According to the information submitted by the applicant the aerial sewer is the most viable option for providing services to the undeveloped portion of the subdivision. The subject site located is the Medium Density Residential (MDR) zoning district. The site is surrounded by various zoning districts and is developed with single family residences to the west and northwest of the site. Unit II of Springbrooke Estate located to the south of the site is also developed with single family residences. The zoning district that surrounds the site includes single-family residential districts R15C to the west, R30, and R15 to the north. Business Park (BP) zoning district is located to the east of the subject site. The Springbrooke Estate subdivision has had several rezoning and modifications such as variances, plat approval, and architectural design review as listed in the table below (See Table 1: List of Modifications).
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Mayor and Council Approval Date |
Request |
Details |
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February 21, 2005 |
Rezone approximately 119 acres with approximately 108 acres to be Medium Density Residential 5-6 acres to be Low Rise Office |
210 homes 5.79 acres: office space and daycare facility |
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February 6, 2006 |
Rezoning and preliminary Plat approval |
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May 7, 2007 |
Architectural Design Review |
58 elevations were approved |
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May 7, 2007 |
2. Plat Approval for Springbrooke Estate Unit Plate dates April 13, 2007 |
Plat approval for Unit II Phase 1 Plat approval for Unit II Phase 2 |
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May 7, 2007 |
Stream Buffer Variance Side setback Variance Reduction in lot size |
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November 3, 2008 |
Architectural Design Review For Inverness Model B for Lot 86 |
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March 4, 2013 |
Variance to allow less than 50% of homes to have full brick fronts and to allow models to be repeated and to allow 3 story houses |
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November 16, 2015 |
Hardship Variance request to allow clearing of greater than 5 acres |
Approved to clear and grade in phases up to 8 acres |
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April 16, 2018 |
Hardship Variance: The applicant is requesting to clear and grade the right-of-ways and up to ten acres by phase. Hardship Variance: Waive water detention requirements |
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April 16, 2018 |
Rezoning MDR Conditional to MDR Conditional to change stipulations |
All prior stipulations have been replaced |
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May 7, 2018 |
PZ 18-008 Architectural Design Review Fischer Homes Request to approve 6 model |
Request to approve 6 model |
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Table 1: List of Modifications |
Analysis:
Fiscal Impact:
The aerial sewer will be funded by private developers and will aid in reducing the financial burden of the City in extending sewer services to this area. Approval of the request will allow the undeveloped portion of Springbrooke Estates to be developed. Increase in residential development will increase the City’s revenue and will also aid in maintenance of the proposed aerial sewer and other infrastructure that may be impacted.
Analysis by the City Consulting Team
Approval of the request for a Hardship Variance with conditions:
1. The applicant provides hydrologic and hydraulic analyses and supporting technical data, certified by a State of Georgia licensed professional engineer and performed in accordance with standard engineering practices, demonstrating that the encroachment:
a. Will not result in increases of 0.01-foot or greater to the pre-project base and future flood elevations;
b. Will not result in increases of 0.01-foot or greater to floodway elevations during the base flood discharge;
c. Will not result in any increase to the floodway width during the base flood discharge, and;
d. Will not create hazardous or erosion-producing velocities or result in excessive sedimentation.
Analysis:
Variance Request #1 - Encroachment in the regulatory floodway
Section 10-11 (b) of the UDC states: “Encroachments within the regulatory floodway, including earthen fill, new construction, substantial improvements or other development are prohibited, except for activities authorized by variance in accordance with the requirements of this article; provided, however, that encroachments within the regulatory floodway may be permitted for bridges, culverts, roadways, and utilities, if a licensed professional engineer provides and certifies hydrologic and hydraulic analyses and supporting technical data, performed in accordance with standard engineering practice, demonstrating that the encroachment will not result in any increase to the pre-project base flood elevations, floodway elevations, or floodway widths during the base flood discharge.”
The proposed project is a gravity outfall sanitary sewer with aerial crossing over Powder Springs Creek immediately downstream of the Lewis Road Bridge. The sanitary sewer meets the qualifications of a utility which qualifies as a permitted encroachment in Section 10-11 (b) of the UDC. If the applicant can demonstrate with hydrologic and hydraulic analyses, as outlined in the conditions, that the encroachment will not result in increases of 0.01-foot or greater to the base flood and floodway elevations during the base flood discharge and will not result in any increase to the floodway width during the base flood discharge, this condition will be met.
Variance Request #2 -Reduction in flood storage capacity
Section 10.16 (a) Parts 1 and 2 of the UDC states that “No development shall be authorized, and no variance shall be granted within any area of special flood hazard or area of future-conditions flood hazard that could result in development or condition that (1) raises the base flood elevation or future conditions flood elevation equal to more than 0.01-foot and (2) reduces the base flood or future-conditions flood storage capacity.”
The horizontal and vertical alignment of the proposed gravity outfall sanitary sewer requires that fill be placed in the floodplain and no compensatory cut for fill is proposed. Section 10-32 of the UDC outlines 5 criteria for granting flood hazard area variances. Section 10-32 (d) allows the granting of a variance if the variance “will not result in increased flood heights, additional threats to public safety, extraordinary public expense, or creation of a nuisance.” If the applicant can demonstrate with hydrologic and hydraulic analyses, as outlined in the conditions, that the encroachment will not result in increases of 0.01-foot or greater to the pre-project base and future flood elevations, the condition of Section 10-32 (d) will be met and we recommend that Sec. 10.16 (a) Part 2, which requires no reduction of flood storage, be waived.
Variance Request #3 -Changes in flow characteristics as to the depth and velocity
Section 10.16 (a) Parts 3 and 4 of the UDC states that “No development shall be authorized, and no variance shall be granted within any area of special flood hazard or area of future-conditions flood hazard that could result in development or condition that (3) changes the flow characteristics as to the depth and velocity of the waters of the base flood or future-conditions flood as they pass both the upstream and the downstream boundaries of the development area and (4) creates hazardous or erosion-producing velocities, or results in excessive sedimentation.”
Section 10-32 of the UDC outlines 5 criteria for granting flood hazard area variances. Section 10-32 (d) allows the granting of a variance if the variance “will not result in increased flood heights, additional threats to public safety, extraordinary public expense, or creation of a nuisance.” If the applicant can demonstrate with hydrologic and hydraulic analyses, as outlined in the conditions, that the encroachment will not result in increases of 0.01-foot or greater to the pre-project base and future flood elevations, the conditions of Section 10.16 (a) Part 3, in regards to the depth of waters of the base flood or future conditions, and Section 10-32 (d) will be met.
If the applicant can demonstrate with hydrologic and hydraulic analyses, as outlined in the conditions, that the encroachment will not create hazardous or erosion-producing velocities or result in excessive sedimentation, we recommend that Sec. 10.16 (a) Part 3, in regards to changes to the velocity of the waters of the base flood or future-conditions flood, be waived.
Variance Request #4 -Compensation for storage capacity
Section 10.16 (b) of the UDC states that “Compensation for storage capacity shall occur between the average ground water table elevation and the base flood elevation for the base flood, and between the average ground water table elevation and the future-condition flood elevation for the future-conditions flood, and lie either within the boundaries of ownership of the property being developed and shall be within the immediate vicinity of the location of the encroachment. Acceptable means of providing required compensation include lowering of natural ground elevations within the floodplain, or lowering of adjoining land areas to create additional floodplain storage. In no case shall any required compensation be provided via bottom storage or by excavating below the elevation of the natural (pre-development) stream channel unless such excavation results from the widening or relocation of the stream channel.”
The horizontal and vertical alignment of the proposed gravity outfall sanitary sewer requires that fill be placed in the floodplain and no compensatory cut for fill is proposed. As stated previously, Section 10-32 (d) allows the granting of a variance if the variance “will not result in increased flood heights, additional threats to public safety, extraordinary public expense, or creation of a nuisance.” If the applicant can demonstrate with hydrologic and hydraulic analyses, as outlined in the conditions, that the encroachment will not result in increases of 0.01-foot or greater to the pre-project base and future flood elevations, the condition of Section 10-32 (d) will be met and we recommend that Sec. 10.16 (b), which requires compensation for storage capacity, be waived.
Recommendation:
Approval of the request for a Flood Protection Variance with conditions:
1. Staff will continue to review the application regarding waiving certain floodplain management stormwater requirements with professional consulting staff. For successful approval the applicant must provide technical data to demonstrate that there is a “no-rise” between the existing conditions and future conditions.
2. Any modification or alterations relating to the design or modifications that results in further impact to the floodplain will be done administratively in collaboration with the City professional consulting staff.