Director's Rule

Title

Conditional Discharge of Contaminated Industrial Stormwater to the Sanitary Sewer Number

DWW-370 Rev. no.

1

Responsibility

Drainage and Wastewater Line of Business Supersedes

N/A Pages

5

General Manager/CEO (interim) signature

/s/ Andrew Lee Approval date

April 8, 2022 Effective date

April 15, 2022

1. PURPOSE

Provide criteria for which Seattle Public Utilities (SPU) will authorize and establish conditions for new discharges of contaminated industrial stormwater to the sanitary sewer. Discharge of contaminated industrial stormwater to the sanitary sewer requires approval by SPU per Seattle Municipal Code and King County Industrial Waste (KCIW) per King County Code.

2. DEFINITIONS

applicant. party seeking approval to discharge contaminated industrial stormwater to the sanitary sewer system.

best management practice (BMP). A schedule of activities, prohibitions of practices, operational and maintenance procedures, structural facilities, or managerial practice or device that, when used singly or in combination, prevents, reduces, or treats contamination of stormwater, prevents or reduces soil erosion, or prevents or reduces other adverse effects of stormwater on receiving waters (SMC 22.801.030.B).

Contaminated Industrial Stormwater (CISW). Stormwater that becomes contaminated with pollutants when it falls on, drains from, runs through, or comes into contact with areas where industrial activity occurs.

industrial activity. Areas where material handling equipment or activities, raw materials, intermediate products, final products, waste materials, byproducts, or industrial machinery are located. Such areas include but are not limited to: material handling sites; refuse sites; sites used for the application or disposal of process wastewater; sites used for the storage and maintenance of material handling equipment; sites used for residual treatment; storage or disposal sites; shipping and receiving areas; manufacturing buildings; material storage areas for raw materials and intermediate and finished products; and areas where industrial activity has taken place in the past and significant materials remain.

King County Industrial Waste Program (KCIW). Program administered by the King County Department of Parks and Natural Resources, Wastewater Treatment Division that regulates and authorizes discharges of industrial wastewater (including contaminated industrial stormwater) to the regional collection system and wastewater treatment plants owned and operated by King County.

sanitary sewer. Publicly owned and maintained sewage system which conveys wastewater, and is not designed to convey drainage water

SPU Discharge Approval. Agreement issued by the Director of SPU and signed by the discharging party that establishes conditions for discharge of Contaminated Industrial Stormwater into the sanitary sewer system and compliance reporting requirements, pursuant to SMC 22.802.030 C and SMC 22.802.030.D.

3. RULE

SPU seeks to minimize any new stormwater discharges into the sanitary sewer. SPU requires dischargers to minimize, modify, and/or mitigate the site conditions, activities, or processes that generate or have the potential to generate contaminated industrial stormwater.

A. SPU Discharge Approval is required to discharge Contaminated Industrial Stormwater (CISW) to the Sanitary Sewer

1) Prior to SPU consideration, the party seeking approval to discharge CISW (the "Applicant") shall first submit an application to KCIW for an industrial wastewater discharge permit along with the initial application requirements in Exhibit A.

2) Following KCIW's forwarding of the permit application to SPU, SPU will review the permit application and proposed BMPs, and will perform a sewer capacity assessment for the SPU Sanitary Sewer to determine if the Applicant's proposed discharge will or will not overburden or otherwise harm the Sanitary Sewer.

3) If SPU determines that: 1) there is sufficient capacity for the Applicant's proposed discharge and 2) the discharge will not otherwise overburden or harm the Sanitary Sewer, SPU will provide the Applicant and KCIW with the conditions of approval. Discharge conditions shall include allowable discharge rate, compliance reporting requirements, and any other conditions as may be required by SPU, in its sole discretion, including but not limited to additional BMPs. When SPU requires engineered controls, the Applicant must then submit to SPU a report and engineering plans stamped by a Washington state (WA) licensed Professional Civil Engineer. See Exhibit B for submittal requirements.

4) If SPU approves the application, report and engineering plans, SPU will provide the Applicant and the KCIW Program with an SPU Discharge Approval that includes conditions of the approval. The Applicant must agree to all terms and conditions by signing the Discharge Approval, implementing all BMPs, other obligations, and satisfying permit conditions before commencing the discharge. If SPU denies the discharge request, SPU will provide KCIW and the Applicant with a letter stating the reasons for such denial. Applicant may request Director's review of a denial by SPU of a discharge request in accordance with Section G. of this Director's Rule.

B. Allowable Discharge Rate

If SPU determines there is sufficient capacity for the Applicant's proposed discharge, SPU will determine the approved discharge rate as either:

1) The Peak Flow Control Standard per SMC 22.805.080.B.4, or

2) A flow control standard based upon assessment of the Sanitary Sewer, as required by SPU in its sole discretion.

C. Additional Permitting

If the discharge is approved by SPU, the Applicant must submit both the SPU Discharge Approval and the KCIW approval to the City of Seattle Department of Construction and Inspections (SDCI) and obtain a side sewer permit for all side sewer work necessary to connect the Contaminated Industrial Stormwater discharge to the Sanitary Sewer. Additional construction permits may be necessary from SDCI to construct source control BMPs, treatment or flow control facilities.

D. Termination

Upon giving 30 days' notice, SPU may require the discharging party to terminate the discharge of Contaminated Industrial Stormwater to the Sanitary Sewer, and SPU may withdraw or terminate the SPU Discharge Approval in its sole discretion, for any reason, including but not limited to violation of any conditions of the SPU Discharge Approval, the KCIW Permit, or the Seattle Municipal Code.

E. Indemnity

As a condition of SPU Discharge Approval, the Applicant must agree to indemnify, hold harmless, and defend the City of Seattle, its officers, elected officials, agents, and employees from and against any and all claims, losses, costs and damages, including without limitation personal injury, death, property damage, loss of use, and attorney's fees, arising out of, relating to, or resulting from the Discharge, except for such damages or other losses caused by or resulting from the sole negligence of the City of Seattle, its agents, or employees.

F. Access to Discharger's Premises and Records

As a condition of SPU's Discharge Approval, the Applicant/Discharger shall, at all reasonable times, allow authorized representatives of SPU to enter that portion of Discharger's premises where a discharge source or flow control facilities are located, and to inspect any records that are required under the terms and conditions of the Discharge Approval.

G. Director's Review for Denial or Termination of Discharge Approval

Applicant or Discharger may request a review of a denial or termination of an SPU Discharge Approval in accordance with the procedures and requirements of SMC 21.16.358 D. Any further appeals shall be in accordance with SMC 21.16.358 F.

4. AUTHORITY/REFERENCES

SMC 22.802.030 B- Permissible Discharges

SMC 21.16.300 Prohibited Discharge of Certain Substances

SMC 21.16.040 A. Wastewater Side Sewer Connections

SMC 22.805.080 Minimum Requirements for Flow Control

SMC 21.16.358 D- Enforcement Actions- Review by Director

SMC 21.16.358 F - Enforcement Actions- Appeal to Superior Court

SMC 22.807.090 Maintenance and Inspections

Exhibit A. Initial application requirements

1) Applicant contact information

2) Preliminary report and accompanying map that shows:

a) Existing site conditions (including address, all buildings, existing drainage, pervious/impervious surfaces, and sewer systems on the property and parcels adjacent to the property)

b) Proposed site conditions

i) Portion of site area proposing stormwater flow control and discharge of contaminated industrial stormwater to the Sanitary Sewer, including identification of areas of industrial activities.

ii) Portion of site area draining to a receiving water body or separated storm drainage system.

iii) Location of proposed on-site contaminated industrial stormwater detention system including:

1) Discharge point of detention system.

2) Overflow discharge location of the detention system discharging to the separated storm drainage system or receiving water body (including any other state or federal authorizations for such discharge).

3) Location of BMPs used to minimize contaminated stormwater discharge area.

c) Calculated discharge rate based on area discharged to the Sanitary Sewer applying the Peak Flow Control Standard per 22.805.080.A.4 for the area proposed to discharge to the Sanitary Sewer or other approved SPU discharge rate.

d) Description of BMPs used on-site to minimize pollutants impacted by stormwater.

e) Other relevant information, as determined by SPU.

Exhibit B. Report and engineering plans submittal requirements (required to be stamped by a WA licensed Professional Civil Engineer)

a) Applicant and engineer contact information

b) Existing site conditions (including all buildings, existing drainage and sewer systems on the property and parcels adjacent to the property).

c) Proposed site plan including

i. Site area subject to flow control/detention and discharging to Sanitary Sewer, including identification of areas of industrial activities.

ii. Location and sizing of Flow Control BMPs (i.e. detention system)

1) Discharge point of detention system

2) Overflow discharge location of the system

iii. Location of any structural BMPs on the site

d) Detailed engineering drawings and associated engineering calculations for the detention system

i. Discharge rate per Seattle Stormwater Manual or approved

ii. Flow control/Detention system sizing

iii. Flow control device (i.e. orifice plate, pump, etc.) sizing

e) Description of how potential overflows from the flow control/detention system will be managed so it does not discharge to the Sanitary Sewer.

f) Other relevant information, as determined by SPU.