Wisconsin Legislature: SPS 382.36(5)(c)

1. Covers for all tank openings larger than 8 inches in diameter shall be provided with a permanent warning label indicating the dangers of entering the tank, in accordance with this paragraph.

2. The warning label shall be securely attached and made of a noncorrosive metal or plastic bearing the legend “DO NOT ENTER WITHOUT PROPER EQUIPMENT” or “DANGEROUS GASES EXIST IN TANK” or similar language.

3. The label shall be rectangular in shape with minimum dimensions of 4 by 5 inches.

4. The wording on the label shall be a minimum of 1/2 inch in height and be either indented or raised.

Note: For a listing of best management practices (BMPs) refer to ch. SPS 382 Appendix A-382.36 (3)-1.

Note: Where local discharge requirements are more stringent, stormwater plumbing systems may provide detention and treatment to comply with the local stormwater management plan.

(4) Discharge and connections.

(a) Discharge points. The discharge points for stormwater and clearwater shall be as specified in Table 382.38-1.

(b) Segregation of wastewater.

1. Except as provided in subd. 2., stormwater or clearwater piping may not connect to a sanitary drain system.

2. Where a combined sanitary-storm sewer system is available, stormwater, clearwater and sanitary wastewater may be combined in the building sewer.

3. Stormwater gravity drains shall not be combined with clearwater drains prior to discharging to the storm building drain except where approved by the department.

Note: See also Table SPS 382.38-1 which limits clearwater discharges to sanitary sewer at 50 gpd.

Note: For the use of stormwater or reuse of clearwater, refer to the appropriate requirements in ss. SPS 382.30, 382.34, 382.40, 382.41, 382.70 and this section.

Note: For further explanatory material regarding the rational method, other methods and runoff co-efficients, see ch. SPS 382 Appendix A-382.36 (4).

(5) Input calculations.

(a) Peak flow. The peak flow of stormwater influent to a plumbing system shall be calculated using any of the following methods:

1. ‘Area method.’ For sizing of conveyance piping, when calculating stormwater peak flow based on the tributary area, the area in square feet shall be divided by the following applicable divisors:

a. For roofs the divisor is 26 square feet/gpm.

b. For paved or graveled ground surfaces the divisor is 32.5 square feet/gpm.

c. For lawns, parks and similar land surfaces the divisor is 104 square feet/gpm.

Note: For example, 10,000 square feet of roof area/26 square feet/gpm = 385 gpm or 0.85 cubic feet/second.

2. ‘Rational method.’ For calculating peak flow, the intensity shall be determined using the time of concentration for the tributary area.

Note: For the equation procedure for runoff coefficients for use with the rational method, refer to ch. SPS 382 Appendix A-382.36 (5)-1.

3. ‘Engineering analysis method.’ An engineering analysis shall be based on an analysis provided by a Wisconsin registered architect, registered professional engineer, or permitted designer of engineering systems - plumbing, or an approved alternate standard per s. SPS 381.20 (2) based on the peak flow calculated in accordance with sub. (3) (a).

Note: A model that calculates peak flow such as SWMM, TR-20, TR-55, P8 or an equivalent methodology may be used.

(b) Volume. The volume of stormwater influent to a plumbing system shall be based on an analysis provided by a Wisconsin registered architect, registered professional engineer, or permitted designer of engineering systems – plumbing, or an approved alternate standard per s. SPS 381.20 (2) and a minimum of a two-year, 24-hour storm event and designed so that no property damage occurs at 100-year, 24-hour storm event with a Type II distribution.

Note: For runoff coefficients and use of other methods or models, refer to ch. SPS 382 Appendix A-382.36 (5)-2 and A-382.36 (5)-3.

Note: The intensity of rainfall varies considerably during a storm as well as geographic regions. To represent various regions of the United States, the U.S. Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) developed four synthetic 24-hour rainfall distribution types from available National Weather Service (NWS) duration-frequency data (Hershfield 1961; Frederick et al., 1977) or local storm data. Type IA is the least intense and type II is the most intense short duration rainfall. Types I and IA represent the Pacific maritime climate with wet winters and dry summers. Type III represents Gulf of Mexico and Atlantic coastal areas where tropical storms bring large 24-hour rainfall amounts. Type II represents the rest of the country, including Wisconsin. For more information, see the USDA-NRCS webpage: http://www.nrcs.usda.gov/.

(c) Additional inputs to stormwater systems. Additional inputs to stormwater systems shall be estimated based on anticipated flows and volumes.

(6) Conveyance and detention systems.

(a) Design. The design of stormwater and clearwater conveyance systems shall conform to all of the following:

1. Horizontal stormwater conveyance piping shall be sized using either of the following:

a. An engineering analysis, based on full flow capacity, acceptable to the department.

b. Tables 382.36-1 to 382.36-5 based on pipe type, diameter and pitch.

a. A vertical conductor for stormwater may not be smaller than the largest horizontal branch discharging into the conductor.

b. Vertical conductors shall be sized in accordance with Tables 382.36-1 and 382.36-3 or by an engineering analysis acceptable to the department.

Note: For the use of Baird’s equation, refer to ch. SPS 382 Appendix A-382.36 (6)-1.

3. Clearwater conveyance systems shall be sized in accordance with s. SPS 382.30 (3) and (4).

4. Underground, gravity-flow storm building sewers shall have a minimum 3-inch inside diameter.

(b) Velocity in stormwater conveyance system piping. The pitch of stormwater conveyance system piping shall be designed to create a minimum velocity of one foot per second when flowing full.

1. Except as provided in subd. 2., fittings and connections for stormwater and clearwater conveyance systems shall comply with s. SPS 382.30 (8) and (9).

2. The minimum radius for the first 90° fitting located downstream of a roof drain shall comply with the horizontal to vertical requirements in Table 382.30-4.

(d) Stack offsets. Stack offsets for piping of a clearwater conveyance system piping shall comply with s. SPS 382.30 (6).

(e) Pitch of clearwater gravity conveyance system piping.

1. The minimum pitch of gravity conveyance system piping having a 2-inch inside diameter or less shall be 1/8 inch per foot.

2. The minimum pitch of clearwater gravity conveyance system piping having at least a 3-inch inside diameter or more shall be 1/16 inch per foot.

(f) Branch connections near base of stack. Branch drains from interior clearwater inlets may not connect downstream from the base fitting or fittings of a drain stack within a distance equal to 20 pipe diameters of the building drain.

(g) Detention systems.

1. The storage volume of a dry detention system shall be designed and installed with a drain time of 72 hours after a storm event.

2. Paved surfaces or parking lots serving as detention areas shall be limited to a design depth of 6 inches, unless otherwise limited by local ordinance.

3. By design, ground surface ponding shall drain within 24 hours after a storm event.

4. A subsurface stormwater detention system that has a permanent pool of water shall be designed and installed in a manner that accomplishes vector control.

- See PDF for table

Note: To convert to cubic feet per second (cfs) divide gpm by 448.8.

- See PDF for table

Note: To convert to cubic feet per second (cfs) divide gpm by 448.8.

- See PDF for table

a. Sizing per manufacturer’s specifications.

Note: To convert to cubic feet per second (cfs) divide gpm by 448.8.

- See PDF for table

Note: To convert to cubic feet per second (cfs) divide gpm by 448.8.

- See PDF for table

(7) Other design requirements.

(a) Subsoil drains.

1. A subsoil drain discharging to a plumbing system shall discharge into an area drain, manhole or storm sewer, trapped receptor or a sump with a pump.

2. Where a foundation drain is subject to backwater, the drain shall be protected by a backwater valve or a sump with a pump.

(b) Backwater valve. All backwater valves shall be accessible for maintenance.

1. No storm building sewer or private interceptor main storm sewer may pass through or under a building to serve another building, unless one of the following conditions is met:

a. The storm building sewer or private interceptor main storm sewer serves farm buildings or farm houses, or both, that are located on one property.

b. Where a storm building sewer or private interceptor main storm sewer serves buildings that are located on one property, a document that indicates the piping and distribution arrangement for the property and buildings is recorded with the register of deeds no later than 90 days after installation.

2. The location of storm building drains and building sewers shall comply with ss. SPS 382.30 (11) (d) and 382.40 (8) (b) 7.

(d) Installation requirements.

1. The connection of a stormwater leader discharging to a storm building sewer shall be made at or above the finished grade.

Note: For more information regarding joints and connections, refer to s. SPS 384.40.

1m. If in direct connection and at finished grade, a removable strainer shall protect the inlet. The capacity of the strainer shall be provided in accordance with sub. (9) (b).

2. The elevation of a storm building drain shall comply with s. SPS 382.30 (11) (b) 1.

3. Interior inlets and drains subject to backflow or backwater shall be protected with a check valve or backwater valve.

4. Storm building drains and building sewers shall be installed to comply with s. SPS 382.30 (11) (e).

5. Storm building sewer connections to public sewers shall be in accordance with s. SPS 382.30 (11) (f).

6. Cleanouts for conveyance system piping shall be installed in accordance with s. SPS 382.35.

7. Storm building sewers that receive clearwater and that may be subject to freezing shall be installed in accordance with s. SPS 382.30 (11) (c) 2.

8. Storm building drains, clearwater building drains, and building storm sewers and appurtenances shall be separated from water wells by the applicable separation distances contained in chs. NR 811 and 812, or as otherwise permitted by the department of natural resources.

9. All underground stormwater storage tanks for water reuse shall be separated from sanitary sewers by a minimum of 8 feet.

10.

a. A means to locate buried non-metallic storm building sewers and private interceptor main sewers that discharge to municipal mains shall be provided in accordance with the options under s. SPS 382.30 (11) (h), except as provided in subd. 10. b.