Operations and Maintenance Plan 2025 Non-SIU Pretreatment GP Appendix A.pdf

Holly Hill Resource Recovery Facility, Holly Hill Lane, Greenwich, CT

Sanitary Sewer Discharge Operations and Maintenance Plan

Compliance measures associated with requirements of the General Pretreatment Permit for Non- Significant Industrial User Discharges to Publicly Owned Treatment Works (Non-SIU GP)

Plan Date: 02/28/2026

Plan Revision Dates (minimum every 5 years):

Description of Wastewater Treatment Equipment and Discharge Flows

The wastewater treatment equipment (WTE) consists of catch basins and an oil/water separator receiving wastewater from the tipping floor facility. This facility consists of an enclosed two-story building and associated access drives constructed for receiving municipal solid waste (MSW) from incoming MSW collection contractors. The upper floor of the building has a concrete pad for the deposit of solid waste and an access opening to allow movement by mechanical loaders of the trash by gravity into rolloffs positioned directly beneath the opening.

When the rolloffs are filled, they are covered and removed from the site for off-site disposal of the

MSW.

Access to the tipping floor is by traversing a bituminous paved drive and entry pad to the doors by trash hauling trucks. Once inside the building, the trucks drop their loads onto the floor for transfer into the lower level rolloffs.

A consequence of trash delivery is that some trash is crushed by truck wheels and residue is transferred to the exterior access pavement. This residue is exposed to rainfall/runoff during precipitation events. Runoff is collected by catch basins that discharge to the Town of Greenwich sewerage system rather than discharge it to a nearby watercourse. An oil/water separator is located under the building apron that received wastewater before an overflow discharge to the pond and a second oil/water separator in series just prior to the connection with the sanitary sewer line. The overflow discharge to the pond has no signs of ever having operated and was put in place in the event of an extreme rainfall event to avoid overloading the downstream system.

During tipping floor operations, the concrete surface is washed down daily to minimize residue being carried out onto the apron. This washwater flows down to an oil/water separator inside the building prior to discharging to the sanitary sewer.

It is estimated that a maximum of 17,000 gallons of water discharges to the sanitary sewer system from the stormwater runoff, and it is estimated that 500 gallons of water discharges to the sanitary sewer system from the tipping floor washwater. The tipping floor washwater is a relatively constant daily input, but the stormwater discharge only occurs when a storm event generates enough runoff to enter the catch basin system. The reported discharge is based on the impervious area of pavement contributing to the catch basins and the amount of rainfall as reported in a Town of Greenwich weather station.

Sanitary Sewer Discharge O&M Plan 1 Owner/Manager - Town of Greenwich Holly Hill Resource Recovery Facility, Holly Hill Lane, Greenwich, CT Osprey Environmental Engineering

Description of Wastewater Treatment Operations and Management

The system is entirely gravity fed with no power inputs. Therefore no effects are experienced during power outages. No operational valves are present so a system operations plan is no required. Flows from the Tipping House are from a garden hose used to wash off the floor at the end of the work day. Flows from the exterior system are generated by rainfall runoff and there are no operational controls to be managed. The site is fenced in and gates are locked when facility staff are not present.

No moving parts are present so a spare parts inventory is not present. No flow meters are present, nor are any chemical feed systems.

In order to address impacts to the downstream Greenwich Wastewater Treatment Facility (WWTF), management procedures have been developed and are implemented to remove contaminants at the source. These include:

1. Managing catch basin sumps by vacuum pumping the contents for off-site disposal. This is done on a quarterly basis or more frequently as required through a visual inspection of sumps.

2. Maintaining/cleaning pavement surfaces with the use of a street sweeper to collect solids from the pavement for off-site disposal. This is done weekly or more frequently as required.

3. Any solids still remaining after the above management provisions are further treated by processing discharges through an oil/water separator

4. Clean out of oil/water separators - Per the previous DEEP discharge permits the 2,000 gallon tank is pumped out annually and the 1,500 gallon and 500 gallon oil/water separators are cleaned out on a quarterly basis.

In accordance with previous permits held for this discharge, a sample is collected from the stormwater runoff discharge emanating from the oil/water separator just prior to the connection with the sanitary sewer. The interior oil/water separator associated with the tipping floor has not been sampled in the past and it is not proposed to do so under this permit registration.

Operator Staffing and Training:

System operations are conducted by the site supervisor and consist of periodically assessing the catch basins for sum sediment levels and unusual conditions. The supervisor also schedules the tank cleanout procedures by an outside contractor.

Records & Record Keeping:

A monthly record is prepared, recording analytical data with a reference table of permit limits as well as the maximum flow from the exterior collection system as generated by daily rainfall records. This record is compiled and a copy is submitted to the Greenwich Sewer Division for reference and filing.

System Diagram:

A system diagram is appended to this plan.

Sanitary Sewer Discharge O&M Plan 2 Owner/Manager - Town of Greenwich Holly Hill Resource Recovery Facility, Holly Hill Lane, Greenwich, CT Osprey Environmental Engineering