CHAPTER 4 - STORM DRAINAGE ANALYSIS

The West Jordan Storm Drain System was analyzed using the model, observations from City staff and best management practices for the industry.

DEFICIENCIES

Deficiencies were identified based on input from City staff and on results from the model. Locations where the City had experienced flooding were analyzed in the model to determine the cause of the flooding. For example, a cul-de-sac that frequently floods could have issues with inlet capacity, pipe capacity, backwater effects, runoff from areas not directly tributary to the cul- de-sac, or the curb and gutter configuration.

Generally, storm drain systems are designed to carry the peak 10-year runoff event, with the 100- year runoff event being conveyed in the storm drain and in the roadway to and through natural channels to the discharge point (in the City's case, the Jordan River). It was determined that for the existing West Jordan Storm Drainage system, full pipe flow is acceptable with minor surcharging being contained in the curb and gutter system.

Tables 4-1, 4-2, and 4-3 and Figures 4-1, 4-2 and 4-3 summarize the drainage deficiencies identified in this study. Table 4-1 and Figure 4-1 describe the 10-year storm drain deficiencies, Table 4-2 and Figure 4-2 describe the 100-year storage deficiencies, and Table 4-3 and Figure 4-3 describe the 100-year conveyance deficiencies. Each deficiency has a Deficiency ID (used in this study), a location description, and problem definition. The Deficiency ID naming convention for Table 4-1 indicates what the type of deficiency is whether capacity related (C) or replacement (age, condition, etc) related (R). The storage deficiencies use the name of the detention basin which is deficient and the 100-year conveyance deficiencies use the name of the model element.

Not all deficiencies necessitate capital improvements. Because storm drain systems are designed to convey the minor (in this case the 10-year) event, a 10-year event will produce flows at or near the pipe capacity of the system. Some nodes in the model identified areas of surcharging which were determined to not be a deficiency because the surcharging is contained in the curb and gutter system. A pipe at capacity or a surcharged node in the model was only added to the deficiency list if flooding was significant in the model and/or City staff had identified previous flooding at the location. After identifying the deficiencies, the project team and City staff met in a series of workshops to discuss which deficiencies warranted action. Deficiencies identified as not warranting action will be monitored by City staff for flooding. Figure 4-4 shows the location of modeled and City identified maintenance deficiencies that were deemed as not requiring action at this time. These locations should be monitored by City personnel to determine if any of these projects need to be added to future Capital Improvement Plans.

Figure 4-1   10-Year Storm Drainage Deficiencies

Figure 4-2   Detention Basins Requiring Additional Volume for the 100-Yr Event

Figure 4-3   100-Year Conveyances

Figure 4-4   Areas to Watch

Table 4-1
10-Year Storm Drainage Deficiencies

Deficiency ID	Location	Problem Description
C1	6200 South from Airport Rd through Fairwind Dr	West Jordan has expressed concerns regarding flooding and the age of this line. They share 6200 S with Taylorsville; however, the only runoff to this line from West Jordan is from the road. West Jordan City is responsible for approximately 10% of the runoff in this line.
C2	Approximately 6600 South from Gold Medal Dr through USL Canal	This line receives all the outside-City runoff from the north up through 6200 South. The City has experienced significant flooding in the backyards of homes. West Jordan flows are approximately 10 cfs, Taylorsville flows are unknown but approximately 300 acres drain to this line from Taylorsville.
C3	6337 South Dixie Drive to Dixie Valley Park	Pipeline is in the easement and is corrugated metal pipe (CMP). Flooding occurs in Dixie Dr.
C4	From Skyview Park to 7200 South along Utah Lake Distributing Canal	Pipe has insufficient capacity during design event.
C5	Harvest Ridge Drive between 7400 South and Jordan Meadows Lane	Some flooding along Harvest Ridge Dr including where it intersects Jordan Meadows Ln. City has identified flooding issues here in the past. The existing storm drain has low slopes and the required head to spill into the Jordan Meadows detention basin creates backwater effects. The area also has a rolling curb and gutter system and needs high back curb installed. When the pond is full, backwater will flood this line out and cause issues for homeowners on Harvest Ridge Dr.
C6	2200 West and approx. 6645 South	Piped storm drain daylights to an open ditch which is frequently clogged with weeds, debris, and leaves.
C7	Camelot Way and Executive Drive	City has identified flooding in a low spot of curb and gutter. The inlets tie into irrigation/storm drain lines in backyards and lack access to manholes. City has identified flooding issues here in the past. The existing storm drain has low slopes. Modeling reveals that 10-year flows are over pipe capacity. The area is a low spot in the curb and gutter system, and ponding flows flood downhill driveways on the east side of the road. There are also connection issues between dual irrigation and storm drain lines.
C8	Between Redwood Dr and Heather Way (behind commercial district)	City has stated that flooding occurs behind businesses.
C9	Near 7800 South Wetland Ponds	Discharge into the Jordan River off 7800S; pipe network nearing capacity. Easement line and corrugated pipe. Maintenance staff has noted excessive sediment collection between the 2nd and 3rd ponds. Ponds do not have an effective access to remove sediment.
C10	2200 West from 7970 South to 7850 South	Several small diameter drain pipes open flow into the Veterans Memorial Park and are frequently clogged causing road flooding.
C11	3200 West from ~7900 to 8100 South	Many small surface losses along 3200S between 7800S and Joel P. Jensen Middle School; losses occur at T junctions as well as inability of inlets to collect peak discharge; pipes may also be undersized. Combination system and easement line.
C12	South of Joel P Jensen Middle School from 3200 West to U&SL Canal	This 36" diameter pipe bottlenecks the flow coming from above. To solve C11 and C14, an upsize is required to lower the outlet HGL for projects C11 and C14.
C13	Old Bingham Hwy from 8395 South through Starlite Dr	Inlet and lines near between Terra Linda Elementary School are insufficient to capture and carry flow. Flooding occurs as it turns onto Old Bingham Hwy and at several laterals in Old Bingham Hwy.
C14	3200 West from 8525 South through approx. Starlite Dr	Pipe capacity in 3200 West is exceeded. Flooding issues have been confirmed by City.
C15	Approx 8135 South from Lynn Ln to Utah Lake Distributing Canal	Pipeline is in the easement and is CMP. Flooding Area.
C16	Teton Estates Dr from Uinta Hills Dr through 4000 West	Some flooding occurring along Teton Estates Dr particularly next to Old Bingham Hwy directly west of Teton Estates Dr.
C17	Wasatch Meadows Dr from Bingham Park Dr through Welby Hills Dr	Pipe is at capacity and experiences minor surface losses along Wasatch Meadows Dr.
C18	Dorilee Park	The City has identified Dorilee Park as an area which has flooded in the past. This is likely due to insufficient storage volume which both lets the pond spill to downstream properties and increases the HGL for upstream properties.
C19	4950 West from Park Vale Drive to 7670 South	Insufficient grade and pipe capacities on 4950 W prevent flows in 4950 West south of Wood Spring Drive from flowing north. This line has flooded several times and has easement line and valley inlet issues. Low slopes and pipe capacities in 4950 W Drive
C20	Dannon Way, Bagley Park Rd, and Leo Park Rd	Many surface losses along Bagley Park Rd. Road flooding occurs.
C21	From 7000 South to approx. Thrush Hill Dr and from approx. Brittany Town Dr to Orion Hill Dr	Lots of small surface losses, surface collection path, flood prone, 70th S approaching 4800 W and Beargrass Rd south of 70th.
C22	Clay Hollow Wash Trail, approx. 5650 West and approx. 8060 South	Emergency overflow pipe has insufficient capacity during the 100-year design event.
C23	Between Hayden Peak Elementary and Barney's Creek Trail	Culvert has insufficient capacity during the 100-year design event.
C24	Redwood Road crossing at Drake Lane, approx 7250 South, and Deseret Industries	City has identified that ADS pipes crossing Redwood Road are damaged and need to be replaced. Additionally, the capacity of the lines in Redwood is insufficient to carry the design flows. The inverts at JCT-5190 and JCT-2972 cause the lines south of them to back up and create flooding on the west side of Redwood Rd..
C25	1300 West from 9000 to 8600 South	Line along 1300S between 8600 and 9000 S is at capacity.
C26	4800 West and Hayden Peak Drive	Culvert has insufficient capacity during the 100-year design event.
C27	8380 South from Stratford Lane to 1300 West	Many small surface losses along 8380 S near 1300 W. This is the line leaving Plum Creek Wetland and ADS pipe.
C28	Excaliber Way from Bandana Circle to South Jordan Canal	The system here has corrugated metal pipes.
C29	Approx. Long Dr (2070 West) from 8770 South to Gardner Lane (8660 South)	Minor flooding at Long Dr and Eagle Court intersection. Easement lines and ADS pipe.
C30	2975 West and Green Meadow Park near 8565 South	Meadow Green Farms Park relieves Utah and Salt Lake Canal under peak flows. Easement line, Corrugated Pipe and Basin work.
C31	4660 West and Hayden Peak Drive	Culvert has insufficient capacity during the 100-year design event.
C32	Approx. 8140 South and Approx. 1250 West	Culvert has insufficient capacity during the 100-year design event.
R33	Approx. 7500 South and 2700 West	Corrugated pipe, combination system and easement lines.
R34	Drake Lane and Redwood Road	City has identified that ADS pipe crossing Redwood Road are damaged and need to be replaced.
R35	7600 South and Redwood Road	City has identified that ADS pipes crossing Redwood Road are damaged and need replaced.
R36	Bora Bora Dr from 1300 West to approx 1600 West	Easement Lines. Combination system and Corrugated Pipe.
R37	9000 South and approx. 1075 West	Separate combination system and easement line.
R38	9000 South Detention Basin	The basin always has water in it and sediment issues because of the elevation of the outlet structure in relation to the South Jordan Canal.
R39	Jaguar Drive from north of WJHS to Bueno Vista Dr to South Jordan Canal	Line is near or at capacity with minor losses throughout collection main until discharge into South Jordan Canal. Easement lines Corrugated pipe and combination system.
R40	9000 South and approx. 2585 West	Pipe running along 9000 S reaches capacity prior to discharge into detention basin (north end of Browns Meadow Park). Basin, corrugated pipe and Easement line.
R41	9000 South and 4400 West Barrington Drive	Vehicular access to the basin is challenging. The system becomes pressurized here.
R42	Cougar Park (west of Cougar Ln at 6400 South)	Water from Kearns comes through this basin. Corrugated pipe exists on north side of basin and easement line. Sediment is filling the detention pond, and the low flow piping system.
R43	U-111 and approx 8100 South	This is a corrugated pipe under U-111 which needs to be replaced.
R44	Southwest corner of Discovery Drive and 5820 West	This basin is dangerous to maintain with a Vactor truck. Inlet box cracks and box grate bends under too much pressure

 

Models were created from the existing models which contain dramatically upsized detention basins; the basins were upsized by adding a large amount of storage at the top of the existing storage curve. The results of these models represent the volume recommended for City design as they report how much water the existing basins would capture in a 100-year design event if they were large enough. The results from those models were compared against the existing physical capacity of the basins and deficiencies are listed in Table 4-2.

Table 4-2
100-Year Existing Storage Deficiencies (values in Acre-Feet)

Basin Name	Current Storage	Required
Additional Storage
RR Park 2	6.1	8.6
Jordan Meadows	1.7	4.6
Shadow Mountain	1.5	2.5
Naylor Farms	1.2	1.9
RR Park 1	15.3	1.3
Old Bingham Hwy	11.6	1.0
RR Park 3	3.8	1.0
Purple Hills/Skyview	50.4	0.6

 

Costs per detention volume were developed using a hypothetical three-acre-foot detention basin assuming the following: the basin is 3 feet deep, $250,000 per acre of land, excavation costs of $20,000 per acre-foot, mobilization/demobilization costs of $5,000 per acre-foot, revegetation (native, non-irrigated) costs of $0.50/square foot. A basin holding 3 acres at 3 feet deep will have an area of approximately one acre. Therefore, the equation is as follows:

$250k/acre * 1 acre + ($20k (exc)+ $5k (mob))/AF * 3 AF + $0.50/sq ft * 43,560 sq ft = $346,780

for the hypothetical three-acre-foot basin. The cost for one acre-foot is therefore $115,593 and including 30% engineering and contingency brings this cost to $150,271 per acre-foot of detention storage. For simplicity, this cost estimate was rounded to $150k/AF.

The 100-year conveyances were also modeled by applying the 100-year design event to the existing model and evaluating where spill was occurring. These segments were identified as 100- year conveyance deficiencies and can be seen in Table 4-3. Appendix A shows the restrictions in the existing conditions and the improved capacity with the Master Plan Projects.

Table 4-3
100-Year Conveyance Deficiencies

Model ID	Problem Description
CDTS-2543	Barney's Creek experiences major backwater in Airport Road causing capacity issues for dual 42" culverts.
CDTS-2543
CDTS-8037	Culvert has inadequate capacity to carry unrestricted 100-year flow of 140 cfs.
CDTS-1846	Culvert has inadequate capacity to carry unrestricted 100-year flow of 200 cfs.
CDTS-1842	Culvert has inadequate capacity to carry unrestricted 100-year flow of 202 cfs.
CDTS-8025	Culvert has inadequate capacity to carry unrestricted 100-year flow of 84 cfs.
CDTS-8050	Culvert has inadequate capacity to carry unrestricted 100-year flow of 214 cfs.
CDTS-8574	Culvert has inadequate capacity to carry unrestricted 100-year flow. The FEMA flow for this culvert is 480 cfs.
CDTS-8347	Culvert has inadequate capacity to carry unrestricted 100-year flow. The FEMA flow for this culvert is 480 cfs.
CDTS-8354	Culvert has inadequate capacity to carry unrestricted 100-year flow. The FEMA flowfor this culvert is 480 cfs.
CDTS-8353	Culvert has inadequate capacity to carry unrestricted 100-year flow. The FEMA flow for this culvert is 480 cfs.
CDTS-7897	Culvert has inadequate capacity to carry unrestricted 100-year flow of 93 cfs.
CDTS-7911	Culvert has inadequate capacity to carry unrestricted 100-year flow of 200 cfs.