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Permit Review Detail
Review Status: Completed
Review Details: FLOODPLAIN
Permit Number - T11OT01953
Review Name: FLOODPLAIN
Review Status: Completed
| Review Date | Reviewer's Name | Type of Review | Description | Status | Comments |
|---|---|---|---|---|---|
| 11/10/2011 | ELIZABETH LEIBOLD | ENGINEERING | REVIEW | Denied | DATE: November 9, 2011 TO: Kent McRae, P.E., PSOMAS REVIEWER: Elizabeth Leibold, P.E. ACTIVITY NUMBER: T11OT01953 SUBJECT: Pantano at Harrison Road Interceptor Sewerline PDSD Floodplain Engineering Review SUMMARY: The submittal was received and reviewed by Engineering Division. Engineering does not recommend approval of the project until the following comments are addressed. In early discussions with the consultant, the assumption was made that the existing soil cement was constructed to 100-year erosion/scour protection. After further research, TDOT stated that the existing roadway crossing may have artificially stabilized the upstream reach (for lesser events such as 25-year and less) but would likely fail during a significant event or over the long term. The proposed sewer design must be able to resist the 100-year event based on a failed condition at the existing low-flow crossing, and specifically: 1. The proposed new sewer line must be designed to withstand scour, including local and long term scour; and, 2. The supporting scour analysis/design for the sewer line must not assume that the existing low-flow roadway crossing will provide long term channel stabilization. The existing low flow crossing was designed to provide, at best, a 25-year roadway crossing. Please address the following comments. COMMENTS: 1) TC Sec. 26-8(a)(2)b: All public utilities, such as sewer systems, shall be located and constructed to minimize or eliminate flood and erosion damage. Address the following comments: a. On sheet 2/34 of 5 of the plans, address the following: i. Delineate the top of bank on planview sheets. ii. Delineate the FEMA SFHA area floodplain on planview sheets. iii. Tucson Code Sec.26-11.2(b)(1): Label pile depths. iv. DS Sec. 10-02.2.3.2.C: Delineate 100-year floodplain limits, label FEMA floodway, and provide note for FIRM panel. v. Check scale on plan sheets; grid does not appear to match scale. vi. Show MH to be reconstructed at STA 12+60.67 on sheet 3 plan view. b. Tucson Code Sec.26-11.2: Address following comments specifically for the drainage statement: i. Provide an additional drainage exhibit showing the FEMA SFHA area floodplain and Pantano top of bank. ii. Tucson Code Sec.26-11.2(b)(4): Include additional cross sectional detail in drainage statement that shows the downstream structure at the Pantano crossing for the existing Harrison Road prism with existing erosion protection depth labeled. Include further discussion of the existing structure and how scour and erosion protection is to be provided by piles and/or existing or proposed structures. iii. The HEC-RAS profile indicates approximately 5 and half feet of cover, whereas the plans shows over 7 feet of cover at lowest point. Explain or correct discrepancy. iv. The Drainage Statement states that the MH's are designed to be located outside of the sandy wash bottom; however there are at least 4 proposed MH's within the floodplain. Revise the statement to explain number of MH's within the top of banks and within the FEMA floodplain limits and how the MH's are designed to prevent sewerline failure. v. Address the following scour comments: 1. Tucson Code Sec.26-11.2: State whether there is MH shaft design provided to minimize sewerline pipe failure during hundred year scour conditions, such as a break away joint at scour depth on the shaft or other design consideration. 2. DS Sec.10-02.6.6.1: Regional watercourse general scour shall be established using a detailed sediment transport study. 3. DS Sec.10-02.6.6.3: Provide revised scour calculation that includes the 2-ft minimum low flow thalweg for regional watercourses. 4. Tucson Code Sec.26-11.2(b)(1): After revising scour calculation, add discussion of the result with regards to compliance of additional 2-ft cover beyond scour depth per state statute requirements. Also include discussion of how proposed scour protection design is provided from the extents of Erosion Hazard Limits, since this portion of the Pantano is not bank protected. 5. Tucson Code Sec.26-11.2: Long term scour can be determined by looking at historical records, inspecting as-built data or channel survey data. This would provide an estimate if the channel has stabilized or a trend of how much the channel is dropping or moving laterally. vi. Provide signature & seal for drainage statement. c. DS Sec.10-02.2.3.1.2.E.1: In the drainage statement, state maintenance responsibility of the sewerline and the erosion protection for the sewer infrastructure. d. DS Sec.10-02.2.3.1.5.G: TDOT approval will be needed for placement of the new sewer in the right-of way. 2) Tucson Code Sec.26-11.2(f): Tucson Code Sec. 26-5.2(15): Address the following soils report comments: a. Provide a copy of the Ninyo & Moore Geotechnical evaluation that includes piling design recommendations, backfill recommendations, and other design considerations for this sewerline within the floodplain. b. Bedding, shading, backfill, and other geotechnical engineering recommendations for this project shall be added to the construction plans. 3) Tucson Code Sec.26-11.2(b)(1): Please acknowledge the following: a. Once the Floodplain Use Permit is approved, right of-way use permit may be required by TDOT. b. As-builts, geotechnical testing & inspection reports, and PDSD Engineering Inspection(s) may be required for final floodplain inspection approval. If you have any questions, I can be reached at 837-4934/ elizabeth.leibold@tucsonaz.gov Elizabeth Leibold, P.E., CPM, CFM Civil Engineer Engineering Division Planning & Development Services Dept |
Final Status
| Task End Date | Reviewer's Name | Type of Review | Description |
|---|---|---|---|
| 02/06/2012 | GERARDO BONILLA | OUT TO CUSTOMER | Completed |
| 02/06/2012 | SUE REEVES | REJECT SHELF | Completed |