MIDAS CREEK PROJECT. FINAL DESIGN REPORT SKR Hydrotech 4/11/2012

Transcription

1 2012 MIDAS CREEK PROJECT FINAL DESIGN REPORT SKR Hydrotech 4/11/2012

2 Executive Summary... 1 Section 1 Introduction... 1 Background Information... 1 Purpose of Study... 1 Scope of Work... 1 Section 2 Description of Study Area... 2 Location... 2 Existing Canal Crossings... 2 Existing Butterfield Creek... 3 Existing Midas Creek... 3 Section 3 Previous Drainage Study... 3 Section 4 Current Drainage Study... 3 Section 5 Field Investigation and Drainage Facility Inventory... 4 Culvert Survey... 4 Section 6 Hydrologic Analysis... 5 Introduction... 5 Drainage Basin Delineation... 5 Precipitation... 6 Modeling Methodology... 7 Model Calibration... 8 Future Development Conditions... 8 Hydrologic Modeling Results... 9 References Section 7 Hydraulic Analysis Existing Culvert Hydraulic Modeling Results Existing Bridge Culvert Section 8 Recommended Storm Drainage System Improvements Storm Drainage Deficiencies and Recommended Improvements Proposed Bridge Culvert Section 9 Estimate of Probable Construction Cost Estimate of Probable Construction Cost Midas Creek Project i SKR Hydrotech

3 Section 10 Engineering Design Fees Engineering Design Fees Midas Creek Project ii SKR Hydrotech

4 Executive Summary The southwest quadrant of Salt Lake County is currently one of the fastest developing areas in the State of Utah. The ongoing urbanization in the southwest quadrant of Salt Lake County has created flood control problems in the area. The Southwest Canal and Creek Study (SWCC) was completed by Bowen Collins and Associates, Inc. for the Salt Lake County Public Works Department in The study concluded that most of the hydraulic structures in the southwest quadrant of Salt Lake County needed improvements in order to facilitate the 100 year flood. The existing bridge culvert MC 19 has been analyzed based on a revised existing watershed model that includes the future developments mentioned in the SWCC study, including the exclusion of the Daybreak Development. The calculated 100 year peak discharge is 650 cfs. The existing bridge culvert MC 19 would be overtopped at flows in excess of 440cfs based on the existing conditions of the culvert outlet. A redesigned 15 X 6 culvert would have the capacity to facilitate the 100 yr. discharge of 650cfs while maintaining a one foot freeboard below the finished floor of a residence southwest of the structure. Section 1 Introduction Background Information Midas Creek is one of the streams in the southwest quadrant of Salt Lake County. The creek flows through commercial and residential areas of South Jordan City. Many of the hydraulic structures identified in the Southwest Canal and Creek study (SWCC) have been reconstructed and improved. However, recommended improvements to Midas Creek culvert number 19 (MC 19) haven t been made as of this report to facilitate the 100 year flood. Purpose of Study The purpose of this study is to calculate the 100 year storm peak discharge flow and determine any deficiencies of the MC 19 bridge culvert in handling the 100 year storm peak discharge flow. A hydraulic analysis will be conducted of the existing culvert and a proposed new box culvert to facilitate the 100 year flow while maintaining a one foot freeboard from the top of the road or from the top of the bank, whichever is most critical. Scope of Work a) Hydrologic modeling of the watershed and basin feeding into MC 19 along with calculation of hydrologic parameters such as the 100 yr discharge at MC 19. b) Hydrologic modeling of flooding that would occur due to a 100 yr discharge at the existing MC 19 and determination of the return period of the largest storm MC 19 can facilitate. c) Conduct a hydraulic analysis and design of a new culvert to facilitate the predicted 100 yr discharge. Midas Creek Project 1 SKR Hydrotech

5 Section 2 Description of Study Area Location MC 19 culvert is located right next to the intersection of Jordan Hills Dr. (11500S) and 1300W in South Jordan City. Midas Creek flows from West to East, passes through MC 19,, and eventually discharges into the Jordan River. Jordan Hills Drive is the roadway on top of the MC 19 and appear to be in the flood plain created by the 100 year storm. culvert. There are two residences that are located northwest and southwest of the culvert The watersheds that deliver run offf to MC 19 are Butterfield Creek and Midas Creek. The approximate boundary of those watersheds are from the top of the Oquirrh Mountainss to the Jordan River and from South to South, containing approximately 27 square miles see Figure 1: Midas Creek Watershed Boundary. DAYBREAK DEVELOPMENT Figure 1: Midas Creek Watershed Boundary Existing Canal Crossings There are five canals which flow from south to north across Midas Creek. Four of the canals collect runoff from urbanized areas and convey the flow to the next downstream overflow structure and release into the corresponding natural stream or major storm drain pipeline. The Welby Jacobs Canal has no storm water capacity and is not utilized as a county flood control facility. The existing canal crossings were not included in our analysis for the 100 year storm peak discharge. Midas Creek Project Final Design Report 2 SKR Hydrotech April 11, 2012

6 Existing Butterfield Creek The Butterfield Creek drainage originates in the Oquirrh Mountains just south of the main Kennecott Copper Pit. The drainage channel runs along Butterfield Canyon Road. From the canyon mouth, drainage is conveyed east via a ditch along approximately South. Near the City of Herriman, the channel originally became less and less defined and eventually disappeared in the fields north of Herriman and west of 6000 West. The future development identified in the 2003 SWCC study has taken place and infrastructure improvements have been made. For the purposes of this project, direction by South Jordan City was to include this drainage basin in the watershed boundary. Existing Midas Creek The Midas Creek drainage basin begins in the Oquirrh Mountains on the east side of the Kennecott Copper Pit. Runoff from the mountains collects in several natural channels that continue west of Oquirrh Boulevard (an Extension of U 111). The channel continues east from this point along the natural channel to approximately 4800 West. From this point east to the Jordan River, Midas Creek is routed through multiple highway crossings, canal crossings, and residential developments. The channel turns to the northeast near 1300 West and South before traversing to the east again near the River Front Parkway and discharging into the Jordan River at about South. Section 3 Previous Drainage Study The previous drainage studies done in this are the 1998 Storm Drain Collection System Master Plan prepared by EWP Engineering and the 1996 Storm Drainage Master Plan for Herriman Area/Butterfield Drainage prepared by EWP Engineering. These studies were not evaluated for this project as they were evaluated in the current drainage study. Section 4 Current Drainage Study The current drainage study done in this area is the before mentioned 2003 SWCC prepared by Bowen Collins and Associates, Inc. Midas Creek Project 3 SKR Hydrotech

7 Section 5 Field Investigation and Drainage Facility Inventory Culvert Survey On February 6, 2012 we surveyed the existing bridge culvert and water depths. The bridge culvert was constructed of concrete with a natural terrain for the channel bottom. There is a concrete headwall and wing walls with square edges at the openings. The inlet side of the culvert is naturally vegetated and is shaped like a trapezoid. The survey inverts actually are lower at the inlet then at the outlet due to some kind of hydraulic jump. The outlet side of the bridge culvert was shaped very much rectangular and only about 13.5 feet wide by 2 feet high. The Figure 2 Inlet View MC study reports the depth to be 2.5 feet deep. The difference is most likely due to the accumulation of sediment over the nine years between studies. The headwall structure is approximately 11 feet high and for the purposes of this report has a top elevation of 4390 above MSL. There is a residence just southwest of the MC 19 structure that has a walk out basement that has an estimated basement finish floor elevation of Downstream structure MC 20 was recently improved and replaced with a 17 x 6 box culvert. Figure 3 Outlet view MC 19 Midas Creek Project 4 SKR Hydrotech

8 Section 6 Hydrologic Analysis Introduction A hydrologic analysis was conducted of the Midas creek watershed in order to determine the peak flow that would occur at culvert MC 19 during a storm with a 100 year return period. Runoff calculations were performed for existing conditions, including the future retention of all storm runoff from the daybreak development. The results of the hydrologic analysis were compared with the results of the hydraulic analysis of culvert MC 19 to identify deficiencies, determine the return period of the storm MC 19 could handle, and improvements to MC 19 in order to facilitate the runoff of a storm with a 100 year return period. Drainage Basin Delineation The Midas creek drainage basin was delineated in Watershed Modeling Solutions (WMS) using a Digital Elevation Model (DEM) of the South Jordan area. Some manual corrections were made to the delineation of Midas creek to reflect the actual stream path as can be seen using aerial photographs. Further corrections were made to reflect the connecting of Butterfield creek to Midas creek by 8,500 linear feet of 60 inch Reinforced Concrete Pipe (RCP). These corrections significantly increased the area of the Midas Creek drainage basin. The Daybreak Development currently retains 100 percent of its runoff and subsequently excluded from the Midas Creek drainage basin therefore reducing the overall area of potential runoff. This area was previously included in the current drainage study. There are four canals running south to north across the Midas creek drainage basin. A significant portion of storm water in the urban areas of the drainage basin is discharged into these irrigation canals. It is assumed that all storm water within the drainage basin that discharges into the four canals would be routed to the next downstream overflow structure and released into Midas creek. Therefore, the drainage basin was delineated as if the four canals were nonexistent. Another improvement since the current drainage study was performed is the detention pond constructed near the intersection of South and Midas creek. Two sub basins were delineated having areas of square miles and 2.9 square miles. The storage discharge parameters of the detention pond (provided by South Jordan city) can be seen in Table 1 and were accounted for within the model. Midas Creek Project 5 SKR Hydrotech

9 Table 1: Detention Basin Parameters Storage (ac-ft) Discharge (cfs) Precipitation The temporal distribution of rainfall for the 100 year design storms used was developed using a Farmer Fletcher distribution modified by Salt Lake County. The 100 year 3 hour design storm distributions and rainfall depths for the mountain and valley gages can be seen in Table 2. Due to the variance in terrain of the Midas creek basin, an average rainfall distribution and depth of 1.83 in was used. Since intense summer cloudbursts events are rarely equally distributed over a large area, precipitation depth reduction factors were applied to the upper sub basin with an area of sq. miles. The Salt Lake City Hydrology Manual (1983) recommends the following precipitation depth area relationship for a storm of 3 hour duration: Reduction Factor=.01*( *Area^0.46) An areal reduction factor of 0.70 was applied to the precipitation depth of the upper basin resulting in a final precipitation depth of 1.28 inches. After the 3 hour 100 year storm analysis was completed a separate analysis was conducted using a Type II 24 hour distribution with a rainfall depth of 2.4 inches over the lower basin and 1.68 inches over the upper basin. Precipitation depths for the 24 hour duration 100 year storm were provided by the NOAA Atlas 14, Volume 1, Version 5 and multiplied by an areal reduction factor of 0.70 where appropriate. The Type II 24 hour distribution was used as an alternative storm due to its common occurrence in the state of Utah. Midas Creek Project 6 SKR Hydrotech

10 Table 2: 3 Hour Mountain and Valley Gages 3-Hour Mountain Gage 3-Hour Valley Gage Time Incremental Rainfall (in) Time Incremental Rainfall (in) 1:00 0 1:00 0 1:15 0 1:15 0 1: : : : : : : : : : : : : : : : : : : : : : : : :30 0 4: Hour Storm Depth (in) Hour Storm Depth (in) 1.68 Modeling Methodology The hydrologic analysis of the Midas creek drainage basin was performed by the HEC HMS hydrologic modeling program. The model s input parameters were assembled by WMS and included drainage basin delineations using DEMs and aerial photography, soil surveys and land use maps. The SCS curve number method was used to model the amount of precipitation lost to infiltration and abstraction. Curve numbers were assigned to selected terrain using land use maps, aerial photography, and soil surveys. A weighted average curve number of 80 was calculated for the lower basin of Midas Creek and a curve number of 70 for the upper basin. These curve numbers were assigned using values found in SCS TR 55 (1986). Hydrologic soil types for the Midas creek drainage basin were determined based on the SCS Soil Survey of the Salt Lake Area (1974). The Clark Transform method along with the Kerby method for overland flow was used to calculate drainage basin time of concentration and storage coefficients (Table 3). In order to include the effects of the detention basin, all runoff from the upper Midas Creek Project 7 SKR Hydrotech

11 basin accumulated at the detention basin of Midas creek and South and routed to the culvert MC 19 using the Muskingum Cunge routing method. A Manning s channel roughness value of was used for common natural channels along with a trapezoidal channel with a bottom width of 15 ft. Initial abstraction of the Midas Creek drainage basin was calculated using the following equation: Ia=.05*S; S =(1000/CN) 10 An Initial abstraction of inches was determined for the upper basin and a value of inches was calculated for the lower basin of the Midas creek drainage basin. The equation Ia=.05*S was determined from the Runoff Curve Number Method: Examination of the Initial Abstraction Ratio (2001) report. Table 3: Hydrologic Parameters for 100 yr. 3 hr. storm PARAMETER Upper Basin Lower Basin Area (mi^2) Curve Number Initial Abstraction (in) Time of Concentration (hr) Storage Coefficient (hr) Areal Reduction Factor Rainfall Depth (in) Model Calibration No model calibration was performed due to the lack of historical stream flow records of which to reference. Input parameters could therefore not be optimized as to reflect natural and existing conditions. Future Development Conditions Future development conditions were not accounted for except for the exclusion of the Daybreak development due to their 100 percent retainage storm drainage design. It should be noted that all Midas Creek Project 8 SKR Hydrotech

12 results from the hydrologic analysis pertain to present day land use and hydrologic conditions. With Daybreak excluded from the drainage basin, the drainage basin measured square miles. Hydrologic Modeling Results With the Daybreak development retaining all of its runoff, HEC HMS calculated a peak runoff of 650 cfs occurring at Culvert MC 19 for a 3 hour 100 year storm. When a Type II 24 hour storm distribution with a rainfall depth of 2.4 inches was implemented, HEC HMS calculated a peak runoff of 830 cfs (see Figure 4: Outflow Hydrograph for 100 yr. Storm). Currently for both the three hour and Type II 24 hour distributions, the detention basin proved to be ineffective in regulating the flow downstream. The capacity of the detention basin at South exceeded the amount of flow coming in from the upper basin; therefore reducing the release rate of the detention basin outlet would further decrease the flow experienced at culvert MC 19. The results of the hydrologic modeling were compared with hydraulic modeling results of the existing culvert MC 19. Deficiencies and recommendations will be discussed later in this report. Flow (cfs) cfs 830 cfs Time (min) 3 hr. Farmer/Fletcher Design Storm Type II 24hr Design Storm Figure 4: Outflow Hydrograph for 100 yr. Storm Midas Creek Project 9 SKR Hydrotech

13 References Bowen Collins & associates, Inc Southwest Canal and Creek Study, Volume 1 of 2, prepared for Salt Lake County Engineering Division, April 2003 Donald E. Woodward, USDA, NRCS, Derwood Maryland Runoff Curve Number Method: Examination of the Initial Abstraction Ratio John H. Humphrey, CH2Hill, 1983, Salt Lake City Hydrology Manual, prepared for the Salt Lake City Department of Public Utilities, Project no. BOI34284.A0.ST. TRC North American weather Consultants, September 1999, Rainfall Intensity Duration Analysis, Salt Lake County, Utah, prepared for Salt Lake County. U.S. Department of Agriculture, Soil Conservation Service, June 1986, Urban Hydrology for Small Watersheds, Technical Release 55. U.S. Department of Agriculture, Soil Conservation Service, April 1974, Soil Survey of Salt Lake Area, Utah Section 7 Hydraulic Analysis Existing Culvert Hydraulic Modeling Results Existing Bridge Culvert The existing bridge culvert MC 19 varies from the culverts inlet to the outlet. Using the shape of the inlet which has an area of approximately 34 square feet and is shaped like a trapezoid, the maximum discharge without overtopping the headwall and roadway is approximately 577 cfs see Figure 5 Inlet Dimensions used for Existing Discharge Capacity. However, the shape of the outlet is rectangular and only has an area of 27 square feet. Using those attributes in the calculation the existing bridge culvert can only handle approximately 440 cfs see Figure 6 Outlet Dimensions used for Existing Discharge Capacity. Assuming that the existing culvert is outlet control with a maximum capacity of 440 cfs, MC 19 can only facilitate the 50 year storm without having the headwater rise above the headwall. Midas Creek Project 10 SKR Hydrotech

14 Figure 5 Inlet Dimensions used for Existing Discharge Capacity Figure 6 Outlet Dimensions used for Existing Discharge Capacity Midas Creek Project 11 SKR Hydrotech

15 Section 8 Recommended Storm Drainage System Improvements Storm Drainage Deficiencies and Recommended Improvements As can be seen in Figure 7 Existing 100 Year Flood (Blue shade), the house just southwest of the MC 19 bridge culvert is inside the 100 year floodplain. Salt Lake County requires any improvements to the bridge culvert to provide one foot freeboard in order to not flood this residence. The only way this criteria can be met is to remove the existing bridge culvert and construct a new one that is sized properly to provide the freeboard. Figure 7 Existing 100 Year Flood (Blue shade) Proposed Bridge Culvert Per Salt Lake County Replacement and new bridges and culverts Design criteria, the new box culvert needs to be designed for the 100 year storm flow and provide a freeboard of one foot below the bank of the natural channel or roadway. The existing floodplain is due to the undersized bridge culvert and the height of the roadway or culvert headwall. The top of the headwall is four feet higher than the finish floor elevation in the walk out basement of the residence. Since the roadway can t be lowered below the elevation of the walk out basement, the proposed box culvert must be sized to keep the flow in the channel. Midas Creek Project 12 SKR Hydrotech

16 Unfortunately the proposed culvert would have to be sized at 28 x 6 in order to keep the headwater depth to four feet (one foot below the top of bank). This isn t feasible due to the downstream side of the culvert where there is a residence even closer to the creek (see Figure 8 Downstream Residence). Figure 8 Downstream Residence The next best solution was to provide one foot freeboard below the nearby residence s walk out basement finish floor elevation. Using this criteria the proposed box culvert design results in a size of 15 feet by 6 feet and has a capacity of 650 cfs for the 100 year storm peak discharge (see Figure 9 Longitudinal View of Proposed Structure). Note that the headwater elevation of 4385 is one foot below the surveyed finish floor elevation of the walk out basement of Midas Creek Project 13 SKR Hydrotech

17 Figure 9 Longitudinal View of Proposed Structure Section 9 Estimate of Probable Construction Cost Estimate of Probable Construction Cost Table 4: Estimate of Probable Construction Cost MIDAS CREEK PROJECT ESTIMATE OF PROBABLE CONSTRUCTION COST ITEM NO DESCRIPTION OF ITEM UNIT QTY UNIT COST TOTAL COST 1 UNCLASSIFED EXCAVATION CY 650 $ 15 $ 9,750 2 DEMOLITION SY 250 $ 30 $ 7,500 3 HAND RAILS LF 84 $ 20 $ 1, 'X6' CULVERT LF 50 $ 775 $ 38,750 5 NEW BOX CULVERT INSTALLATION LF 50 $ 400 $ 20,000 6 NEW WING WALL EA 2 $ 5,000 $ 10,000 7 EXIST BOX CULVERT REMOVAL LF 50 $ 200 $ 10,000 8 NEW PCC PAVEMENT SECTION SY 250 $ 100 $ 25,000 9 DEWATERING LS 1 $ 5,000 $ 5, UTILITY CONFLICTS LS 1 $ 10,000 $ 10,000 CONTINGENCY (20%) $ 27,536 GRAND TOTAL $ 165,216 Midas Creek Project 14 SKR Hydrotech

18 Section 10 Engineering Design Fees Engineering Design Fees Table 5: Engineering Design Services Cost ENGINEERING DESIGN SERVICES CIVIL DESIGN CIVIL CIVIL LEADER ENGINEERING ENGINEERING TOTAL J. SNEED G. RILEY K. KIM MEETING SITE SURVEY HYDROLOGICAL MODELING (WMS) CULVERT DESIGN (HY 8) REPORTS AND POSTER TOTAL LABOR HOURS HOURLY RATE $ $ $ MULTIPLIER $ $ $ TOTAL $ 10, $ 8, $ 4, $ 23, Midas Creek Project 15 SKR Hydrotech