San Luis Obispo Municipal Code Art. II General Sewer Use Requirements

A. No person shall discharge or cause to be discharged rain, stormwater, surface water, ground water, seepage, roof runoff, street or yard drainage, subsurface drainage, ponds or lawn sprays or uncontaminated water or water added for the purpose of diluting wastes which exceed maximum concentration limitations, as stated in Section 13.08.040, to the publicly owned treatment works.

B. It shall be unlawful to discharge any wastewater, including domestic sewage, and industrial wastewater, petroleum products, or otherwise polluted water, derived from residential dwellings, commercial buildings, industrial and manufacturing facilities, or institutions, to any stormdrain or natural outlet. (Ord. 1598 § 1, 2014)

A. General Prohibitions. No user shall introduce or cause to be introduced into the POTW any pollutant or wastewater which causes pass-through or interference. These general prohibitions apply to all users of the POTW whether or not they are subject to categorical pretreatment standards or any other national, state, or local requirements.

B. Specific Prohibitions. Except as hereinafter provided, no person shall discharge or cause to be discharged any of the following described waters or wastes to any sewers:

1. Any liquid or vapor having a temperature higher than one hundred fifty degrees Fahrenheit (sixty-six degrees Celsius), or which will inhibit biological activity in the treatment plant, resulting in interference, but in no case higher than one hundred four degrees Fahrenheit (forty degrees Celsius) at introduction into the wastewater treatment plant.

2. Any waters or wastes containing non-petroleum-based fats, oils, or grease (FOG), and/or petroleum-based oil and grease such that the discharge results in a stoppage, plugging, breakage, significant obstruction to flow or any other damage to or increased maintenance of sewers or sewerage facilities. No person shall discharge oil and grease which results in pass-through and/or interference.

3. Any liquids, solids or gases which by reason of their nature or quantity are or may be sufficient, either alone or by interaction with other substances, to cause fire or explosion or be injurious in any other way to the POTW and/or cause acute worker health and safety problems to its personnel or to the operation of the system.

4. Any waters or wastes that have a closed cup flashpoint of less than one hundred forty degrees Fahrenheit (sixty degrees Celsius), using the test methods specified in 40 CFR 261.21. Prohibited materials include, but are not limited to, gasoline, kerosene, naphtha, benzene, toluene or xylene.

5. Any solid or viscous substance, including but not limited to unground garbage, feathers, ashes, cinders, sand, polishing compounds, resin beads, metal, glass, straw, rags, spent grains or hops, wood, plastic, mud, shavings or manure which may cause obstruction to the flow in sewers or other interference with the proper operation of the POTW.

6. Any waters or wastes having pH lower than 5.0 or higher than 9.0, or having any other corrosive property capable of causing damage or hazard to structures, equipment or personnel of the POTW.

7. Any water added to a wastewater discharge for the sole purpose of dilution as a means to achieve compliance with any pretreatment standard or local discharge limit.

8. Any waters or wastes including oxygen demanding pollutants (BOD, etc.) at a flow rate and/or concentration which, either singly or by interaction with other pollutants, will cause interference or pass-through.

9. Any average daily flow greater than two percent of the WWTP average daily sewage flow.

10. Any petroleum oil, nonbiodegradable cutting oil, or products of mineral oil origin in amounts that will cause interference or pass-through.

11. Any trucked or hauled pollutants, except at discharge points designated by the director.

12. Any waters or wastes containing any radioactive materials or wastes of such half-life or concentration that they do not comply with regulations issued by appropriate authorities (Sections 30285 and 30287 of the California Code of Regulations).

13. Any infectious wastes.

14. Any medical wastes, except as specifically authorized by the director in an individual wastewater discharge permit or a general permit.

15. Any waters or wastes containing color which is not removed in the ordinary WWTP treatment process.

16. Any noxious or malodorous liquids, gases, solids, or other wastewater which either singly or by interaction with other wastes are sufficient to create a public nuisance or a hazard to life, or to prevent entry into the sewers for maintenance or repair.

17. Any stormwater, surface water, ground water, artesian well water, roof runoff, subsurface drainage, condensate, deionized water, noncontact cooling water, and unpolluted wastewater, unless specifically authorized by the director.

C. Pollutants, substances, or wastewater prohibited by this section shall not be processed or stored in such a manner that they could be discharged to the POTW.

D. Users with the potential to discharge flammable substances may be required to install and maintain an approved combustible gas detection meter.

E. Local Limits.

1. The director is authorized to establish local limits pursuant to 40 CFR 403.5(c).

2. The following pollutant limits are established to protect against pass-through and interference. No person shall discharge wastewater containing in excess of the following:

3. Unless otherwise stated in individual discharge permit, the uniform limits shall apply to all dischargers. Application for contributory limit A or B may be made to the director. The director’s decision shall be the city’s final decision.

4. The above limits apply at the point where the wastewater is discharged to the POTW. All concentrations for metallic substances are for total metal unless indicated otherwise. The director may impose mass limitations in addition or alternative to the concentration-based limitations above.

F. Limitations on wastewater strength in this chapter may be supplemented with more stringent limitations if:

1. The director determines that the limitations listed in this chapter may not be sufficient to protect the operation of the city’s treatment works; or

2. The director determines that the limitations listed in this chapter may not be sufficient to enable the city’s treatment works to comply with water quality standards or effluent limitations specified in the city’s NPDES permit.

G. When the director determines that a user is contributing any of the substances mentioned in subsection A of this section in such amounts as to interfere with the operation of the POTW, the director may:

1. Advise the user of the impact of the contribution on the POTW;

2. Develop effluent limitations for the user to correct;

3. Place limits on rate and time of discharge or requirements for flow regulations and equalization;

4. Require pretreatment of discharge prior to discharge to POTW; and/or

5. Take any other action necessary to eliminate the interference.

H. Where an industrial user utilizes all or a portion of their domestic water supply from a source other than city of San Luis Obispo potable water, the city may require additional laboratory testing of any potential constituents of concern which may be discharged to the POTW. This testing will be performed by a state of California accredited laboratory, at a frequency and length of time determined by the city, at solely the industrial user’s expense.

I. The director may develop best management practices (BMPs) in individual wastewater discharge permits, to implement local limits and the requirements of this chapter.

J. The contents of swimming pools and/or spas (including filter backwash from swimming pools and/or spas) shall only be discharged into the sanitary sewer in the manner specified herein.

1. The water is discharged by pumping and shall not exceed the capacity of the sewer lateral and/or public main.

2. Each swimming pool discharging to a sewer system shall be equipped with an indirect waste connection to preclude any possibility of a backflow of sewage into the swimming pool or piping system.

3. Draining, pools, reservoirs, or tanks with a capacity of five hundred thousand gallons or greater require an approved drainage schedule. This drainage schedule shall be submitted to and approved by the director or designee at least fourteen days prior to starting drainage, to reduce the likelihood of a sanitary sewer overflow or POTW upset. (Ord. 1734 § 8, 2024; Ord. 1598 § 1, 2014)

Industrial users must comply with the categorical pretreatment standards found at 40 CFR Chapter I, Subchapter N, Parts 405 through 471. (Ord. 1734 § 8, 2024; Ord. 1598 § 1, 2014)

The city reserves the right to establish, by ordinance or in individual wastewater discharge permits, more stringent standards or requirements on discharges to the POTW consistent with the purpose of this chapter. (Ord. 1598 § 1, 2014)

No user shall ever increase the use of process water, or in any way attempt to dilute a discharge, as a partial or complete substitute for adequate treatment to achieve compliance with a discharge limitation unless expressly authorized by an applicable pretreatment standard or requirement. The director may impose mass limitations on users who are using dilution to meet applicable pretreatment standards or requirements or in other cases when the imposition of mass limitations is appropriate. (Ord. 1598 § 1, 2014)