Odor Sources

Map of Odor
Milpitas Odor Map

Man made odor sources

  • Newby Island Landfill & Composting operations
  • Santa Clara / San Jose Wastewater Facility AKA Water Pollution Control Plant (WPCP)
  • Zanker Landfill & Composting Facility
  • Zanker Organic Digester Facility (ZWED)

BAAQMD Confirmed Odor Data

Bay Area Air Quality Management District (BAAQMD) data for the Milpitas region in google docs.  This graphs the BAAQMD confirmed odor reports since 2013 to Feb 2015. Confirmed odor reports are odor complaints which are positively confirmed to a given source.  An inspector is dispatched out to meet with the person who is reporting the odor complaint.  The inspector will then trace the odor to its source. If the inspector successfully traces the odor back to the source, it is then listed as confirmed.

BAAQMD has been investigating Milpitas odor complaints for decades. Their 2013-2015 records showed 90% of confirmed complaints are from Newby Island (Composting, Recyclery and Landfill). ZWED (anaerobic digester) and WPCP (aka Sewage Plant) accounts for the remaining 10%. No bay odor were confirmed in this area. Yes – BAAQMD investigates natural odor sources too – it has confirmed bay odor in Dumbarton Bridge area and a lake in Almaden San Jose.

BAAQMD odor Sources
BAAQMD odor Sources

WPCP odor Study

I pasted the following from this doc, 2011, “San Jose/Santa Clara Water Pollution Control Plant Master Plan. Task No 5. Project memorandum No. 5 Odor Treatment Alternatives”. Section 2.2.2 Off-Site Considerations, page 5.

Regional Odor Considerations. As part of ongoing discussions with interested stakeholders, particularly the City of Milpitas, it became apparent that the odor issues in the region were not limited to the WPCP operations. As a result, field investigations were completed in late 2010 to potential sites in the area surrounding the WPCP, which included the following: (1) Newby Island, (2) Zanker Resources; (3) Milpitas Pump Station, and (4) various locations in the City’s sewerage collection system (see summary information in Appendix C). As is the case with the WPCP, all of these operations have implemented odor mitigation measures over the last several years (see details in Appendix C). These efforts have been recognized by the City of Milpitas in their June 2008 Odor Control Action Plan (refer to Section 2.2 in Appendix D).

These field investigations resulted in the following preliminary findings:

Collection System. It appears that operating a fewer number of interceptors along Zanker Road has reduced the septicity of the sewage entering the WPCP. The major source of sulfides appears to be coming from the Santa Clara tie-in at Junction Structure C (high levels of hydrogen sulfide were observed). Caustic soda addition at the current ten locations will continue.

Milpitas Pump Station. The pump station was completely upgraded two years ago. Current design has a covered wetwell which is ventilated, but the air is not treated. Pump station could have been a source of off-site odors prior to this upgrade. However, no obvious odor issues were observed at the time of the site visit to the pump station.

Two force mains pump raw sewage to the Milpitas Structure at the WPCP. There is a surge tower on one of the force mains that is located in the RSM area, but because of its height, difficult to determine if there are odor issues. High localized sulfide levels were measured at the Milpitas Structure (160 ppm of hydrogen sulfide), which also receives supernatant from the storage lagoons.

Zanker Materials Processing Facility. Facility does not handle putrescible waste material because of odor issues. Yard waste was composted on-site for a number of years, but now that is performed at a facility in Gilroy (strongest odors were from composting leaf piles). Eliminating the composting took care of their major odor issues. They currently limit onsite storage of green wastes to three days or less to manage potential odors. No obvious odor issues were observed at the time of the site visit.

Republic Newby Landfill. Major sources of odors are the stockpiled WPCP biosolids, the food/green waste grinding operation, the landfill tipping face and the composting operation. They operate several fogging stations, which utilize an odor neutralizing agent, that are located strategically around the site. The food grinding operation will move to the compost area and will eventually be covered. The tipping face is maintained at less than one acre and is covered up at the end of the day (5 pm). They perform dust suppression on the WPCP biosolids and use best practices when breaking the stored piles. The compost operation, which is located in the western-most area of the site and operates year around, is comprised primarily of green wastes with a small fraction of food wastes (five percent). Odors were very strong off the compost operation.

WPCP Operations. Odors were detected in the Emergency Basin Overflow Structure (EBOS), headworks area (especially at the junction structures), primary clarifiers, dissolved air flotation (DAFT) units, and grease room. All odors measured were low level except for the launder area of the primary clarifiers. No odors were detected at the primary effluent equalization basins, but it was noted that some low levels of odors are sometimes detected when these basins are at their lowest operating levels. Observed the filling operation of the lagoons – localized low level odors. No odors noted around the dredging operation. Observed the filling operation for one of the drying beds – no odors were noticed. Based on the site visit, it appears that off-site odor potential is greatest for primary clarifier launder area (especially during the warmer months) and for the sludge drying operation once the beds are being turned during the summer and early Fall.

Based on these preliminary findings, it was concluded that the primary regional sources of odors in the area are the WPCP facilities and the Newby Island landfill operation. The offsite odors from the WPCP appear to be more seasonal in nature, while the offsite odors from Newby Island appear to be more independent of season, which is consistent with the BAAQMD odor complaint data previously presented. This preliminary investigation confirmed the need to perform a more detailed data collection and dispersion analysis to more accurately develop specific recommendations for long-term odor mitigation measures.

This additional data collection and odor dispersion analysis would be completed as part of regional odor assessment program and would potentially involve all the potential odor site in the area surrounding the plant. The benefits to the WPCP of a more detailed assessment include: (1) providing a more scientific analysis of the WPCP’s contribution to odor in the region; (2) helps to identify the extent of odor control required at each source, and (3) helps to optimize the treatment technologies selected and implemented. This would translate to savings in both capital and O&M costs.

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This site contains information on odor issues in Milpitas.