Chapter 15.50
STORM DRAINS
Sections:
15.50.040 Cleaning and testing (APWA 33 08 00).
15.50.060 Retention/detention basins.
15.50.070 Storm water pollution prevention plan.
15.50.010 General.
The installation specifications for storm drain systems shall conform to the APWA Standard Specifications unless noted otherwise in this chapter.
All development projects which will increase the storm runoff above what would be expected for an undisturbed site shall be required to provide on-site retention or detention. Such runoff shall be accommodated on site to match the intensity for a eightieth percentile storm event or as otherwise directed by the city’s UPDES permit or by state code. Storm events larger than that are allowed to release at a rate consistent with the predeveloped conditions of the site. On-site retention may be provided throughout the development or in one specific location. All storm drain pipes shall have a minimum cover of two feet. Minimum size of storm drains is 12-inch diameter for tie-ins and 15-inch diameter for main lines.
No person shall discharge or cause to be discharged any storm water, surface water, ground water, roof runoff, subsurface drainage, cooling water, or unpolluted industrial process waters to any sanitary sewer. Storm water and all other unpolluted drainage shall be discharged to such sewers as are specifically designated as combined sewers or storm sewers, or to a natural outlet approved by the director. Industrial cooling water or unpolluted process waters may be discharged, on approval of the director, to a storm sewer, combined sewer or natural outlet.
Storm drain manholes and sumps shall meet confined space requirements, and shall be equipped with ladder rungs and other such devices as required to ensure public safety. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.010)].
15.50.020 Pipe.
Piping used for storm water conveyance includes concrete and HP ADS piping or approved equal. All pipe shall conform to the material and installation specifications included in this chapter. Storm drain bedding materials shall consist of three-quarter-inch gravel and extend six inches below and to the sides of the pipe and 12 inches above the top of the pipe. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-21-2022 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.020)].
15.50.030 Minimum slopes.
Minimum slopes for different size pipes are as follows:
|
Pipe Diameter |
Minimum Slope |
|---|---|
|
12 inches |
0.194% |
|
14 inches |
0.158% |
|
15 inches |
0.144% |
|
16 inches |
0.132% |
|
18 inches |
0.113% |
|
21 inches |
0.092% |
|
24 inches |
0.077% |
|
27 inches |
0.066% |
|
30 inches |
0.057% |
|
36 inches |
0.045% |
[Ord. O-09-2024 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.030)].
15.50.040 Cleaning and testing (APWA 33 08 00).
After the storm drain lines have been laid and the trench backfilled, they shall be thoroughly cleaned and tested for leakage and alignment in the presence of the city engineer or his/her designee before acceptance by the owner. Cleaning shall be done using a high pressure jet cleaning machine, producing a minimum of 800 psi. Wastewater and debris shall not be permitted to enter storm drain lines in service, but shall be removed at the lowest manhole of the extension. Such cleaning shall be done by private crews at the expense of the owner.
Storm drain lines will be required to have a TV test prior to acceptance and prior to the release of the warranty bond. Storm drain boxes or manholes shall be air tested under the general observation of the city inspector. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-21-2022 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.040)].
15.50.050 Sumps.
Sumps shall not be used in Eagle Mountain City unless approved by the city engineer. If approved, all sumps must be constructed with a grease trap.
Additionally, sumps shall only be located as staked in the field and indicated on the plans. They shall be to the grade indicated by the cutsheets and as staked in the field. Excavation and backfill shall conform to Chapter 15.30 EMMC. If the sump is located in an area where the earth is stratified with gravel layers, care shall be taken during backfill to be sure that these layers are not sealed off from the sump beginning three feet below the bottom of the sump up to the top of the subgrade. One- to three-inch diameter drain rock shall be used. The original material shall be removed and the total backfill done with imported drain rock. After backfilling is completed, the entire excavation shall be thoroughly flooded to ensure that settlement is complete. Grates shall be set in place and adjusted for final elevation and alignment. The city requires a fabric barrier between the drain rock and road base (or other backfill).
Sumps may only be constructed of reinforced concrete, precast sections, and shall meet the requirements of ASTM C478-73 in accordance with standard detail drawings S-15, S-16, and S-17. Sumps shall have eccentric lids to ensure adjustments in alignment. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.050)].
15.50.060 Retention/detention basins.
A. Retention Basins. All retention basins shall be constructed with a maximum water depth of four feet. All retention basins shall have a series of interconnected sumps connected to curb inlet boxes or storm drain main lines. All retention basins shall be landscaped in accordance with city standards. All retention basins shall be constructed with a minimum slope of 5:1.
All retention basins shall be constructed for drainage areas designated in the general plan. Basins for smaller areas may be allowed only with prior written approval of the city engineer or his/her designee.
B. Detention Basins. All detention basins shall be constructed with a maximum water depth of 18 inches, with that depth remaining for no longer than a six-hour period. Detention basins must be landscaped and they may be located in park and recreational areas. Each detention basin shall have a manually controlled outlet to a storm drain main line. Detention ponds greater than 18 inches must have a minimum side slope of 5:1. Fencing around detention ponds may be required as determined by the city engineer or his/her designee.
C. All ponds must be certified prior to acceptance. Ponds must be constructed as they are required for the detention of the proposed improvements. If the ultimate design of a subdivision has located the detention basin in a future phase of the subdivision, either a temporary detention basin must be constructed, or an easement for the approved detention must be given to the city and the detention basin must be constructed with the required phase. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A); Ord. O-03-2010 § 1 (Exh. A § 10.060)].
15.50.070 Storm water pollution prevention plan.
A storm water pollution prevention plan meeting all requirements as mandated by the state of Utah Department of Environmental Quality shall be required and maintained for all construction within a subdivision. Elements of this SWPPP shall include BMPs to protect the existing and natural storm drainage systems from incurring increased sedimentation. BMPs will include at a minimum silt fences, inlet protection, and stabilized construction entrance. All inlet protection to meet or exceed ASTM D8057 inlet protection standard. Additional BMPs may be required as needed and determined by a certified storm water plans reviewer. The SWPPP is to be approved by the city engineer or his/her designee. The approved SWPPP plan is to be maintained while any construction activities are occurring within a subdivision. Modifications may be made to the SWPPP during the construction process if it becomes evident that additional modifications are needed to protect storm drainage structures or adjacent properties. The SWPPP and all accompanying documentation are to be available electronically at the project site at the time of an on-site inspection or upon request by the DWQ, EPA, or the MS4. The Storm Water Phase II Final Rule, construction rainfall erosivity waiver, is not offered.
On sites disturbing greater than one acre of land and all commercial sites, the SWPPP sign must be a minimum of four feet wide and three feet tall, bottom of sign placed two feet minimum off the ground, white background with red and black lettering. Pertinent information shall be located at the bottom of the SWPPP sign and shall include the following: authorization to discharge letter/notice of intent (NOI), electronic SWPPP access link, site notice, and the public notice sheet.
Redevelopment projects disturbing greater than one acre, including projects part of a common plan of development or sale which disturbed an acre or greater must provide a site-specific plan for net gain to onsite storm water retention or a reduction to impervious surfaces. Redevelopment projects increasing impervious surfaces by greater than 10 percent must prevent off-site discharge of the net increase in storm water volume associated with precipitation from all rainfall events less than or equal to the eightieth percentile rainfall event.
Single-lot residential home SWPPP signs to be 24 inches wide and 18 inches tall (realtor size) with the bottom of the sign placed a minimum of 12 inches off the ground, front of sign to face toward street and have white background with “SWPPP” in black or red lettering, along with UPDES number. Back of sign to have authorization to discharge letter/NOI and electronic SWPPP access link.
An appeals process shall allow a construction operator to appeal an enforcement option. The appeal process will be included as part of the city’s procedures and will be posted in a publicly available location. [Ord. O-09-2024 § 2 (Exh. A); Ord. O-44-2023 § 2 (Exh. A); Ord. O-21-2022 § 2 (Exh. A); Ord. O-02-2020 § 2 (Exh. A); Ord. O-21-2016 § 2 (Exh. A); Ord. O-13-2015 § 1 (Exh. A)].