Table of Contents Agenda 2 Wastewater Treatment Plant (WWTP) Hydraulic Capacity Update Staff Report 3 WWTP Capacity Outline 5 WWTP Capacity Charts 6 Drainage Concerns on Oak Hill Drive and Quail Drive Staff Report to Council 9 23 11 11 Budget Amendment BA-2011-18 14 Drainage Map and Pipe System 15 Photos June 2010 Rain Event 16 1
CITY OF MONROE CITY COUNCIL STRATEGIC PLANNING MEETING 300 WEST CROWELL STREET MONROE, NORTH CAROLINA 28112 OCTOBER 4, 2011-4:30 PM AGENDA www.monroenc.org 1. Wastewater Treatment Plant (WWTP) Hydraulic Capacity Update 2. Drainage Concerns on Oak Hill Drive and Quail Drive 3. Strategic Plan 2010 Accomplishments AS A COURTESY, PLEASE TURN OFF CELL PHONES AND PAGERS WHILE MEETING IS IN PROGRESS. This Agenda is tentative and is subject to change up to and including the time of the meeting. 2
CITY OF MONROE STAFF REPORT TO: VIA: Mayor Kilgore and City Council Members H. Wayne Herron, City Manager DATE: October 4, 2011 FROM: SUBJECT: Russell Colbath, Water Resources Director Wastewater Treatment Plant (WWTP) Hydraulic Capacity Update SUMMARY STATEMENT City council is requested to receive information regarding current WWTP capacity and future strategic planning. REVIEW Current WWTP Capacity and Expansion Triggers The WWTP is currently permitted to discharge 10.4 MGD, calculated using the monthly average of daily flows. The NCDENR rules that will drive a possible future expansion (the 80/90 Rule) will require an expansion to begin when the annual average of daily flows reaches 90% of capacity, or 9.36 MGD. WWTP Flow Trends The 12-Month average daily flow rates for the past ten (10) years are as follows: Year Flow MGD 2000 7.11 2001 6.15 2002 6.63 2003 8.03 (Yearly Rainfall = 70 inches) 2004 7.02 2005 7.11 2006 6.89 2007 6.51 2008 6.41 2009 6.41 2010 6.42 For calendar 2010 the average daily flow represents a capacity utilization of 61%. The average daily flow has decreased 9.7% since the year 2000. This decrease is primarily due to loss of industrial customers, but also due to the success of our inflow and infiltration elimination program and rehabilitation of aging sewer mains. Wet weather years can play a factor as seen in 2003, but will become less important as additional sewer rehabilitation is completed. 3
On Paper Commitments Future Growth The attached Table shows residential and non-residential project commitments made to date and the allocated capacities that have not yet come on-line. Considering the extensive list of on-paper commitments previously made, the City still maintains 1.92 MGD of additional WWTP capacity to accommodate additional economic development (See page 3 of spreadsheet). The rate at which future sewer flows will be realized is a function of economic conditions. It is important to note that the 2,275 residential lots being held in reserve capacity represents over 40 years of future growth at the current single family permit growth rate. Legislative actions, like the Annexation Reform Act of 2011, could further limit potential for future flow increases. The attached graph provides a sensitivity analysis for flow growth rates of 1.0%, 1.5% and 2.0%. Strategic Plan and Expansion Timing The current Strategic Plan related to WWTP capacity and potential future expansion is attached. The current plan calls for design to begin in FY 2016 and construction to begin in 2019. Given the historical decrease in flow and continued success of our sewer rehabilitation program, staff will be reconsidering all Strategic Plan items and timing as part of the FY 2013 budget preparation. It is likely that staff will recommend the deferral of the WWTP Strategic Plan items to mitigate the impacts of rate increases and maximize the efficient utilization of existing WWTP capacity. If an average growth rate assumption of 1.5 % is used for the next 25 years, the WWTP design and expansion timing would be deferred until 2028 and 2036 respectively. It is also possible that the 25 year growth rate may be less than 1.5%. RECOMMENDATION City Council is requested to receive information regarding current WWTP capacity and future strategic plan actions. 4
City Council Strategic Planning Meeting October 4, 2011 Water Resources Department Agenda Outline WWTP Capacity Update 1. Current WWTP Capacity and Expansion Triggers 2. WWTP Flow Trends 3. On Paper Commitments Future Growth 4. Strategic Plan and Expansion Timing 5. Discussion and Questions 5
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STAFF REPORT TO: VIA: Mayor Kilgore and City Council Member Wayne Herron, City Manager DATE: September 23, 2011 FROM: SUBJECT: James N. Loyd, Jr., P.E., Engineering Director Drainage Concerns on Oak Hill Drive and Quail Drive SUMMARY STATEMENT City Council is requested to 1) consider information pertaining to drainage concerns within the Oak Hill Drive and Quail Drive neighborhoods and 2) approve a budget amendment from the Stormwater Utility Fund in the amount of $30,000 for a detail drainage study of the area. REVIEW Since 1999, the Engineering Department has received several stormwater complaints from residents within the Oak Hill Drive and Quail Drive area regarding flooding within their neighborhood. The properties at 1104, 1106, 1107 and 1108 Oak Hill Drive have experienced yard flooding as a result of the back water effects from the existing pond at 1305 Quail Drive. Pictures are attached showing a flooding event that occurred last summer (June 2010). The previous property owner at 1107 Oak Hill Drive constructed a one foot high stone wall in the front yard in an attempt to divert runoff around the house. Some of the property owners in the area have expressed to Staff that they feel Central Academy of Technology and Arts (CATA) is the cause of the flooding of Oak Hill Drive. CATA has a wet pond in front of the school that appears to be constructed for water quality purposes. The Engineering Department could not find any records pertaining to the review of the wet pond; however, there is a memo for the Conditional Use Permit review in 2003 indicating that the property was within the Lake Lee Watershed and subject to a 24 percent impervious limitation without stormwater management. The Union County Schools engineer was to provide calculations that indicated the peak runoff for the 2 and 10-year storm event did not increase the peak runoff downstream. Since there were already existing impervious surfaces on-site and the property does not exceed 24 percent impervious, the Engineering Department suspects the current pond is a previous sediment control basin that was not removed. Based on Staff s review, flooding along Oak Hill Drive is primarily related to an undersized drainage system whose outfall is controlled by a pond located downstream on Quail Drive. Approximately 162 acres of runoff drains to a single 30 reinforced concrete pipe (RCP) under Oak Hill Drive and then discharges downstream to the pond. In addition, Oak Hill Drive is a curb and gutter street with a single catch basin on either side of the street located in front of 1107 and 1108 11
Oak Hill Drive. By today s standards, the system would be designed for a 25-year storm event requiring at least four (4) 36-inch diameter pipes and additional basins along the street to collect stormwater runoff. As indicated by the attached map, the drainage basin above Oak Hill Drive consists of various land uses including residential, wooded, open space, cemetery and educational. The existing 30 RCP drains into a small pond at 1305 Quail Drive. Runoff from the pond then drains into a drainage ditch that runs along Quail Drive to a 72 corrugated metal pipe (CMP) under Griffith Road. In addition to the162 acres from the Oak Hill Drive area, an additional 21 acres drains into the existing pond from the Lakewood Drive area. The existing pond has about an acre of surface area that is controlled by three (3) 24 corrugated metal pipes under the driveway for 1305 and 1303 Quail Drive. The pond has about 2.5 feet of storage for excess runoff before overtopping the driveway at 1305 and 1303 Quail Drive. The storage provided is not considered significant for the drainage area. The ditch below the existing pond is an irregular shaped, vegetated ditch that is in stable condition. In October 2010, the stormwater maintenance crew replaced the existing pipe under Oak Hill Drive due to its condition with the same size pipe and material. The City of Monroe has an obligation to maintain its drainage system and under the current project parameters, the pipe size could not be upgraded to a larger size due to utility conflicts and road elevation. The project replaced the catch basin in front of 1107 and 1108 Oak Hill Drive with standard catch basins and added a concrete headwall on the upstream end to help improve flow into the drainage system. In addition, sinkholes were repaired at 1106 and 1108 Oak Hill Drive. As previously stated, there are a number of factors that contribute to the flooding in the Oak Hill Drive and Quail Drive neighborhoods. They include: The pipe under Oak Hill Drive is undersized based on the size of the drainage basin and current buildout condition; Age of the drainage system in the Oak Hill Drive and Quail Drive area. Oak Hill Drive was constructed in the late 1960s, requiring less stringent design guidelines; The existing pond at 1305 Quail Drive controls the water surface level for the Oak Hill Drive drainage system during larger storm events; and, The backwater effect from the culvert under Griffith Road could be having an impact to the drainage ditch along Quail Drive. It should be noted that the FEMA flood map study area stops at Griffith Road. Based on these factors, Engineering Staff recommends a detail study of this area to determine what, if any, improvements can be made within the basin to improve the drainage system. Primary concerns are impacts downstream of Quail Drive if any improvements are made to Oak Hill Drive and to the pond on Quail Drive which may need to be modified or eliminated to enhance drainage flows. It should be noted that the ditch that flows from Oak Hill Drive to Griffith Road is a jurisdictional stream. A permit from the US Army Corps of Engineers and the North Carolina Department of Environmental and Natural Resources Division of Water Quality will be required for improvements made to the existing pond at 1305 Quail Drive and the drainage ditch that flows from Oak Hill Drive to Griffith Road. Any improvements to the drainage ditch below Griffith Road may require a permit from the North Carolina Floodplain Mapping Program. C:\Users\brobinso\AppData\Local\Temp\Staff Report to Council 9 23 11.doc 12
The cost to have an engineering consultant perform the initial analysis is estimated at $30,000 which would necessitate a budget amendment from the Stormwater Utility Fund if the desire is to move forward this fiscal year. As provided for in the Strategic Plan update, additional areas of small watershed basins requiring additional study include: Area Oak Hill Drive/Quail Drive Neighborhood Downtown west side of Hayne Street Downtown east side of Hayne Street Ann Street/Walter Street Area Fiscal Year FY13 FY13 FY14 FY14 The drainage studies are proposed to be funded through the Stormwater Utility Program. The drainage concerns were reviewed by the Environment and Water Resources Committee at their meeting on September 20, 2011. The Committee recommended that Staff move forward during the current Fiscal Year with the study of the Oak Hill/Quail Drive Neighborhoods and take to City Council a budget amendment from the Stormwater Utility Fund for the work by an engineering consultant. RECOMMENDATION The Environment and Water Resources Committee and Staff recommend that City Council approve the Budget Amendment (BA-2011-18) from the Stormwater Utility Fund for the detail drainage study of the Oak Hill Drive/Quail Drive neighborhoods. Attachments: Drainage Map and Pipe System on Oak Hill Drive Photos June 2010 Rain Event BA-2011-18 C:\Users\brobinso\AppData\Local\Temp\Staff Report to Council 9 23 11.doc 13
CITY OF MONROE BUDGET AMENDMENT BA-2011-18 1. Amendment necessary to appropriate funds for Stormwater Drainage Study. Stormwater Fund: Revenues: Appropriation from Fund Balance $30,000 Expenditures: Stormwater Operations $30,000 Adopted this 4 th day of October, 2011. Bobby G. Kilgore, Mayor Attest: Bridgette H. Robinson, City Clerk C:\Users\brobinso\AppData\Local\Temp\Budget Amendment BA-2011-18.doc 14
Drainage Basin Map Pipe System on Oak Hill Drive 15
June 2010 rain event Yard flooding at 1108 Oak Hill Drive (05/31/10) Road flooding in front of 1106 Oak Hill Drive Backyard of 1107 Oak Hill Drive (06/30/10) Front yard of 1107 Oak Hill Drive (06/30/10) Looking across lower end of pond (06/30/10) Back of pond at 1305 Quail Drive (06/30/10) (driveway for 1305 Quail Drive) (backyard of 1107 Oak Hill Drive) 16