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Request for Major Variance: Stevens Creek Trunk Sewer

Mecklenburg County requests a major variance from the Goose Creek Riparian Area Protection Rules for the Stevens Creek Trunk Sewer Phase 1 project. The proposal includes utilizing PVC pipe as an equivalent to ductile iron pipe and implementing stream restoration projects as mitigation.

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Request for Major Variance: Stevens Creek Trunk Sewer

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  1. Request for a Major Variance from the Goose Creek Riparian Area Protection Rules Mecklenburg County Stevens Creek Trunk Sewer – Phase 1 July 11, 2018

  2. Mecklenburg County Soil Survey • 20180307

  3. USGS Topographic Map

  4. Wastewater Collection System Utility Lines • Non-perpendicular crossings • “Allowable with Mitigation” if collection systems are made of ductile iron and 50% of the collection system is cleaned annually • 15A NCAC 02T .0305 • Requires ductile iron within • 10 feet of Class C streams • 50 feet of wetlands • Other materials must meet water main standards (15A NCAC 18C)

  5. Wastewater Collection System Utility Lines • In areas outside of 02T requirements, proposing PVC, AWWA C900, Pressure Class 165 psi, DR25 • PVC pipe produced under AWWA and ASTM standards consider equivalent to DI • Gasket materials are same/similar to provide equal protection for leak free system • All pipe must pass a zero leakage test to ensure watertight system • PVC is inert to corrosion caused by hydrogen sulfide gas

  6. Wastewater Collection System Utility Lines

  7. Wastewater Collection System Utility Lines • Perpendicular crossings • “Allowable” if • both gravity and force main collection systems are made of ductile iron and 50% of the collection system is cleaned annually AND • use underground directional boring methods, bore-and-jack techniques or another appropriate microtunnelling method

  8. Stream Restoration

  9. Proposed Impacts & Mitigation Mitigation Proposal: Permittee Responsible Mitigation

  10. Mitigation Proposal • Decommissioning existing package plant (0.075 MGD) • Sending flow to WWTP outside Goose Creek watershed • Providing capability to replace aging septic • TMDL for fecal coliform for Goose Creek (2005) • Replacing/reducing existing pump stations by constructing a regional pump station to send sewer outside Goose Creek watershed Oxford Glenn Package WWTP

  11. Mitigation Proposal • Stream restoration • Reconnecting floodplain • More stable channel • Buffer Enhancement Plant photos from Maryland DNR

  12. Findings of Fact (9)(a)(i) • Practical difficulties or unnecessary hardships are present: • Charlotte Water is proposing PVC, AWWA C900, Pressure Class 165 psi, DR25 as an equivalent to ductile iron pipe (DIP) for areas not within 10 feet of streams or 50 feet of wetlands. Charlotte water is also proposing to simultaneously complete a stream restoration project such that requiring trenchless stream crossings would not provide any water quality or buffer protection • The hardship results from application of this Rule. Project will comply with the DIP requirements set forth in 15A NCAC 02T .0305. • Hardship is due to the physical nature of the property and is unique. • Charlotte Water has not violated this Rule. • Charlotte Water does not own the property; obtained easements after the effective date of the buffer rule.

  13. Findings of Fact –9(a)(ii) & (iii) • The variance is in harmony with the general purpose and intent of the State’s riparian buffer protection requirements and preserves its spirit • In granting the variance, the public safety and welfare have been assured, water quality has been protected, and substantial justice has been done • Propose to provide watershed improvements including: • Decommissioning an existing package plant • Providing the capability to replace aging septic • Replacing/reducing existing pump stations by constructing a regional pump station to send sewer outside the Goose Creek watershed • Completing a stream restoration project along Stevens Creek and a tributary to Stevens Creek

  14. DWR Recommendation • DWR recommends the Water Quality Committee grant this major variance request • If the Water Quality Committee approves this request, the Division recommends approval with the following conditions or stipulations: • Mitigation • The applicant shall complete the decommissioning of the existing package plant, replace existing pump stations with a regional pump station and complete the proposed stream restoration project. If these activities are not completed, the applicant shall purchase mitigation credits from the Division of Mitigation Services to offset buffer impacts. • Leakage Testing • In the specifications for leakage tests, the allowable leakage is 0 gallons for both pipe and manholes. In addition to passing the air test, there shall be no visible leakage or moving water observed in the pipe and invert. Infiltration testing or additional air testing and repairs will be required if these situations occur. • This major variance shall only apply if the USACE and NCDEQ approve impacts to the stream associated with the subject buffer for the sewer line.

  15. Questions? Carolina heelsplitter

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