BRANDON LAKES AVENUE PRE AND POST CONDITIONS DRAINAGE REPORT

Transcription

1 BRANDON LAKES AVENUE PRE AND POST CONDITIONS DRAINAGE REPORT Hillsborough County Public Works County Center, 22nd Floor 601 E. Kennedy Blvd. Tampa, FL BRANDON LAKES AVENUE DRAINAGE IMPROVEMENTS Capital Improvements Project (CIP) No Submitted by: 3868 Sun City Center Blvd. Sun City Center, FL Phone: Fax: CA# November 22, 2016 Mark Flint, P.E. License #38627 This item has been electronically signed and sealed by Mark Flint, P.E., on November 22, 2016 using an SHA-1 authentication code. Printed copies of this document are not considered signed and sealed, and the SHA-1 authentication code must be verified on any electronic copies.

2 I. PURPOSE The intent of this drainage report is to evaluate the drainage and debris-capture improvement design for the Brandon Lakes Avenue Drainage Improvement project (Hillsborough County CIP No ). There is a reported problem with trash and debris being discharged into Valrico Lake at the existing point of discharge of the stormwater management system servicing the Brandon Lakes Avenue subdivision. The purpose of this project is to partially divert flow from the existing 30-inch outfall pipe (that flows eastward towards the Brandon Lakes Avenue dead end and into Valrico Lake) to the proposed bubbler system (that flows northward along Meadowcrest Drive and discharges into Valrico Lake). The proposed flow-diversion junction box will also serve as a trash/sediment sump. Fiber-reinforced plastic (FRP) screens will also be installed to the top of the existing downstream 42 pipe within the proposed junction box to physically capture any floating debris collected by runoff. It is important to note that stormwater management system at the location of the proposed work is expected to be surcharged at all times due to the tailwater conditions of Valrico Lake. This drainage report provides an assessment of the proposed drainage improvements that satisfy the requirements established by the Southwest Florida Water Management District (SWFWMD) Statewide ERP and Hillsborough County. II. DESCRIPTION The existing stormwater system is located along Brandon Lakes Avenue in Valrico, FL, and consists of a network of pipes, curb inlets, and valley curbs. The project area is located in Section 13, Township 29S, and Range 20E. The community of Valrico lies within the Pemberton Creek-Baker Canal Area (PBA) watershed. The PBA watershed covers approximately 65 square miles in central Hillsborough County and is roughly bound by Knights Griffin Road to the north, Plant City limits & State Highway 39 to the east, Durant Road & Downing Street to the south, and State Road 579 & Parsons Avenue to the south. The watershed is also divided by several large roads, including Interstate 4, Martin Luther King Drive, Forbes Road, and McIntosh Road. The location of the Brandon Lakes Avenue Drainage Improvement project is illustrated in Figure 2 on the following page. Figure 1. Pemberton Creek/Baker Canal Area (PBA) that contains Brandon Lakes Avenue 2

3 Figure 2. General Vicinity Map III. EXISTING CONDITIONS The Brandon Lakes Avenue stormwater system features a network of pipes, curb inlets, and valley curbs. Currently, no form of water quality treatment exists for this system, which was constructed in the 1970s. This has resulted in debris being conveyed by runoff and discharging untreated directly into Valrico Lake. The drainage area served by this project s stormwater system is comprised of residential properties within Valrico, Hillsborough County, FL. These properties total approximately acres. Based on historical data and record drawings provided by Hillsborough County, Brandon Lakes Avenue is subdivided into 9 subbasins 5 south of Brandon Lakes Avenue and 4 north of Brandon Lakes Avenue (see Figure 4 on the following page). Figure 3. Floating Trash and Debris within Curb Inlet at SW Corner of Brandon Lakes Ave. & Meadowcrest Dr. 3

4 Subbasin ID A B C D E F G H I Area (AC) Figure 4. Existing Drainage Map from Historical Data and Record Drawings (Relabeled to Match ICPR Model Basins) and Subbasin Areas (in Acres) Rainfall from each subbasin is conveyed into curb inlets located within each subbasin and also flows overland (when pipe capacity is full) towards the east until it discharges into Valrico Lake. 4

5 Figure 5. Existing Conditions Drainage Map (Flow discharges to the east into Valrico Lake)

6 IV. PROPOSED CONDITIONS A concrete junction box (known as ST-1 in the attached construction plans) is being proposed at the SE corner of Brandon Lakes Avenue & Meadowcrest Drive that will both partially divert flow to the north via 30-inch reinforced concrete pipe (RCP) (see Figure 6) to the new point of discharge (known as ST-3 in the attached construction plans; located within an existing 65-ft. drainage easement as reported by the Winchester Woods Subdivision asbuilts, dated 1984) and capture floating debris and sediment. The historic flow path of runoff will be maintained as is, except for a proposed fiber-reinforced plastic screen to be attached at the top of the pipe opening of the existing downstream (east) 42 pipe within the proposed junction box (see Figures 7 and 8). FRP screens are also proposed for the new 30 RCP along Meadowcrest Drive at the proposed junction box (ST-1) and at the proposed manhole (ST-2). By capturing large floating debris and sediments within the proposed box, this will allow for easier maintenance and disposal of collected pollutants. This proposed work provides a method of water quality treatment that can be retrofitted into the aging system. The new drainage feature (the proposed 30-inch RCP along Meadowcrest Dr.) will act as a bubbler system (see Figure 8). Figure 6. Typical Section of Proposed Work along Meadowcrest Drive

7 Figure 7. Cross Section of Proposed Junction Box/Trash Sump (ST-1) 7

8 Figure 8. Plan and Profile of Proposed Work

9 Figure 9. Proposed Conditions Drainage Map (Flow is partially diverted to the north and discharges into Valrico Lake.) 9

10 V. ICPR MODEL RESULTS The following tables show the ICPR model results for existing and proposed conditions for the subbasins immediately upstream and downstream of the proposed work. For all storm events, predicted flood staging is reduced. Therefore, no adverse impacts to the existing upstream and downstream basins are anticipated with this project. Table yr, 24-hour Storm Event Location Max Stage (NAVD88 ft) Description Node ID Existing Proposed Difference Subbasin at upstream (western) end of Node D C Subbasin at upstream (northern) end of Node D H Subbasin at upstream end of proposed flow-diversion junction box/trash sump D Subbasin at (eastern) downstream end of proposed flow-diversion junction box/trash sump E Table yr, 24-hour Storm Event Location Max Stage (NAVD88 ft) Description Node ID Existing Proposed Difference Subbasin at upstream (western) end of Node D C Subbasin at upstream (northern) end of Node D H Subbasin at upstream end of proposed flow-diversion junction box/trash sump D Subbasin at (eastern) downstream end of proposed flow-diversion junction box/trash sump E

11 Table yr, 24-hour Storm Event Location Max Stage (NAVD88 ft) Description Node ID Existing Proposed Difference Subbasin at upstream (western) end of Node D C Subbasin at upstream (northern) end of Node D H Subbasin at upstream end of proposed flow-diversion junction box/trash sump D Subbasin at (eastern) downstream end of proposed flow-diversion junction box/trash sump E Table 4. 5-yr, 24-hour Storm Event Location Max Stage (NAVD88 ft) Description Node ID Existing Proposed Difference Subbasin at upstream (western) end of Node D C Subbasin at upstream (northern) end of Node D H Subbasin at upstream end of proposed flow-diversion junction box/trash sump D Subbasin at (eastern) downstream end of proposed flow-diversion junction box/trash sump E

12 Table yr, 24-hour Storm Event Location Max Stage (NAVD88 ft) Description Node ID Existing Proposed Difference Subbasin at upstream (western) end of Node D C Subbasin at upstream (northern) end of Node D H Subbasin at upstream end of proposed flow-diversion junction box/trash sump D Subbasin at (eastern) downstream end of proposed flow-diversion junction box/trash sump E VI. OPERATION AND MAINTENANCE INSTRUCTION A. OPERATION The project s drainage system is a gravity system and requires no operational protocols. B. MAINTENANCE i. Inlet Grates: Inlet grates will be checked monthly for damage or blockage. Any damaged grates will be replaced or repaired. Any debris blocking full flow through the gate will removed. ii. iii. Pipes and Inlets: Pipes and inlets will be inspected annually for damage or blockage. Any damaged pipes or inlets will be repaired or replaced. Any damaged pipes or inlets will be repaired or replaced. Any trash or debris will be removed. Trash Sump: The trash sump will be inspected semiannually for damage or blockage and/or as needed after major storm events. Any trash, debris, and sediment collected within the trash sump will be disposed off-site. 12

13 ATTACHMENTS (ICPR Model Results) 13

14 Brandon Lakes Ave Drainage Improvements Nodes A Stage/Area V Stage/Volume T Time/Stage M Manhole Basins O Overland Flow U SCS Unit CN S SBUH CN Y SCS Unit GA Z SBUH GA Links P Pipe W Weir C Channel D Drop Structure B Bridge R Rating Curve H Breach E Percolation F Filter X Exfil Trench M: A U: BASIN A M: F U: BASIN F M: B U: BASIN B W: F-G W: F-B P: F-B EX 15" CMP M: G U: BASIN G P: G-C EX 15" CMP W: G-C M: C U: BASIN C W: G-H M: H U: BASIN H P: H-D EX 18" RCP W: H-D M: D U: BASIN D W: H-I M: I U: BASIN I P: I-E EX 18" PVC W: I-E M: E U: BASIN E W: I-OUTFALL T: VALRICO LAKE W: A-B P: A-B EX 18" CMP P: B-C EX 30" CMP W: B-C P: C-D EX 36" RCP W: C-D P: D-E EX 42" RCP W: D-E P: E-VL EX 30" RCP W: E-OUTFALL Existing Conditions Existing 30" RCP Outfall (East) Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc.

15 Brandon Lakes Ave Drainage Improvements Max Time Max Warning Max Delta Max Surf Max Time Max Max Time Max Name Group Simulation Stage Stage Stage Stage Area Inflow Inflow Outflow Outflow hrs ft ft ft ft2 hrs cfs hrs cfs A BASE 10-YR PRE B BASE 10-YR PRE C BASE 10-YR PRE D BASE 10-YR PRE E BASE 10-YR PRE F BASE 10-YR PRE G BASE 10-YR PRE H BASE 10-YR PRE I BASE 10-YR PRE VALRICO LAKE BASE 10-YR PRE A BASE 100-YR PRE B BASE 100-YR PRE C BASE 100-YR PRE D BASE 100-YR PRE E BASE 100-YR PRE F BASE 100-YR PRE G BASE 100-YR PRE H BASE 100-YR PRE I BASE 100-YR PRE VALRICO LAKE BASE 100-YR PRE A BASE 2.33-YR PRE B BASE 2.33-YR PRE C BASE 2.33-YR PRE D BASE 2.33-YR PRE E BASE 2.33-YR PRE F BASE 2.33-YR PRE G BASE 2.33-YR PRE H BASE 2.33-YR PRE I BASE 2.33-YR PRE VALRICO LAKE BASE 2.33-YR PRE A BASE 25-YR PRE B BASE 25-YR PRE C BASE 25-YR PRE D BASE 25-YR PRE E BASE 25-YR PRE F BASE 25-YR PRE G BASE 25-YR PRE H BASE 25-YR PRE I BASE 25-YR PRE VALRICO LAKE BASE 25-YR PRE A BASE 5-YR PRE B BASE 5-YR PRE C BASE 5-YR PRE D BASE 5-YR PRE E BASE 5-YR PRE F BASE 5-YR PRE G BASE 5-YR PRE H BASE 5-YR PRE I BASE 5-YR PRE VALRICO LAKE BASE 5-YR PRE Existing Conditions Existing 30" RCP Outfall (East) Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc. Page 1 of 2

16 Brandon Lakes Ave Drainage Improvements Max Time Max Warning Max Delta Max Surf Max Time Max Max Time Max Name Group Simulation Stage Stage Stage Stage Area Inflow Inflow Outflow Outflow hrs ft ft ft ft2 hrs cfs hrs cfs Existing Conditions Existing 30" RCP Outfall (East) Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc. Page 2 of 2

17 Brandon Lakes Ave Drainage Improvements Nodes A Stage/Area V Stage/Volume T Time/Stage M Manhole P: ST-2-ST-3 M: ST-2 A: ST-3 W: ST-3 Basins O Overland Flow U SCS Unit CN S SBUH CN Y SCS Unit GA Z SBUH GA Links P Pipe W Weir C Channel D Drop Structure B Bridge R Rating Curve H Breach E Percolation F Filter X Exfil Trench M: A U: BASIN A M: F U: BASIN F W: F-B P: F-B EX 15" CMP M: B U: BASIN B W: F-G M: G U: BASIN G P: G-C EX 15" CMP W: G-C M: C U: BASIN C W: G-H M: H U: BASIN H M: D U: BASIN D W: H-I P: H-D EX 18" RCP W: H-D P: ST-1-ST-2 W: D-E M: I U: BASIN I P: I-E EX 18" PVC W: I-E M: E U: BASIN E W: I-OUTFALL T: VALRICO LAKE A: ST-1 W: A-B P: A-B EX 18" CMP P: B-C EX 30" CMP W: B-C P: C-D EX 36" RCP W: C-D P: D-ST-1 42" RCP P: ST-1-E 42" RCP P: E-VL EX 30" RCP W: E-LAKE Proposed Conditions w/ 21" Top Clip on Exist. 42" Pipe, 9" Top Clips on Prop. 30" Pipes Existing 30" RCP Outfall + Proposed 30" RCP Bubbler Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc.

18 Brandon Lakes Ave Drainage Improvements Max Time Max Warning Max Delta Max Surf Max Time Max Max Time Max Name Group Simulation Stage Stage Stage Stage Area Inflow Inflow Outflow Outflow hrs ft ft ft ft2 hrs cfs hrs cfs A BASE 10-YR POST B BASE 10-YR POST C BASE 10-YR POST D BASE 10-YR POST E BASE 10-YR POST F BASE 10-YR POST G BASE 10-YR POST H BASE 10-YR POST I BASE 10-YR POST ST-1 BASE 10-YR POST ST-2 BASE 10-YR POST ST-3 BASE 10-YR POST VALRICO LAKE BASE 10-YR POST A BASE 100-YR POST B BASE 100-YR POST C BASE 100-YR POST D BASE 100-YR POST E BASE 100-YR POST F BASE 100-YR POST G BASE 100-YR POST H BASE 100-YR POST I BASE 100-YR POST ST-1 BASE 100-YR POST ST-2 BASE 100-YR POST ST-3 BASE 100-YR POST VALRICO LAKE BASE 100-YR POST A BASE 2.33-YR POST B BASE 2.33-YR POST C BASE 2.33-YR POST D BASE 2.33-YR POST E BASE 2.33-YR POST F BASE 2.33-YR POST G BASE 2.33-YR POST H BASE 2.33-YR POST I BASE 2.33-YR POST ST-1 BASE 2.33-YR POST ST-2 BASE 2.33-YR POST ST-3 BASE 2.33-YR POST VALRICO LAKE BASE 2.33-YR POST A BASE 25-YR POST B BASE 25-YR POST C BASE 25-YR POST D BASE 25-YR POST E BASE 25-YR POST F BASE 25-YR POST G BASE 25-YR POST H BASE 25-YR POST I BASE 25-YR POST ST-1 BASE 25-YR POST ST-2 BASE 25-YR POST Proposed Conditions w/ 21" Top Clip on Exist. 42" Pipe, 9" Top Clips on Prop. 30" Pipes Existing 30" RCP Outfall + Proposed 30" RCP Bubbler Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc. Page 1 of 2

19 Brandon Lakes Ave Drainage Improvements Max Time Max Warning Max Delta Max Surf Max Time Max Max Time Max Name Group Simulation Stage Stage Stage Stage Area Inflow Inflow Outflow Outflow hrs ft ft ft ft2 hrs cfs hrs cfs ST-3 BASE 25-YR POST VALRICO LAKE BASE 25-YR POST A BASE 5-YR POST B BASE 5-YR POST C BASE 5-YR POST D BASE 5-YR POST E BASE 5-YR POST F BASE 5-YR POST G BASE 5-YR POST H BASE 5-YR POST I BASE 5-YR POST ST-1 BASE 5-YR POST ST-2 BASE 5-YR POST ST-3 BASE 5-YR POST VALRICO LAKE BASE 5-YR POST Proposed Conditions w/ 21" Top Clip on Exist. 42" Pipe, 9" Top Clips on Prop. 30" Pipes Existing 30" RCP Outfall + Proposed 30" RCP Bubbler Tailwater Derived from SWMM Interconnected Channel and Pond Routing Model (ICPR) 2002 Streamline Technologies, Inc. Page 2 of 2