VIDEO. From the Sewer Authority Mid-Coastside (SAM) Director’s meeting on Monday, September 12th, 2022 at 7:00pm by Zoom.
SAM Chair, Debbie Ruddock, introduces the agenda item and SAM General Manager, Kishen Prathivadi, reports.
“The purpose of this report is to discuss and authorize General Manager to Issue a Purchase Order to Global Diving & Salvage for repairing the damaged outfall diffusers in the Amount of $132,069.00″
The discharge of treated wastewater from SAM to the Pacific Ocean is through a discharge pipe and a submerged, multi-port diffuser located west of Pilarcitos Creek, approximately 1,900 feet offshore. The discharge pipe lies on ballast rock on the sea floor approximately 37 feet below mean lower low water and is covered with sand much of the year due to seasonal sand drift. The final 238 feet of the outfall is a muti-port diffuser fitted with thirty-five (35) 6” rubber duck bill valves, approximately 7 feet apart, that discharge vertically approximately 2 feet above the ocean floor.
Outfall inspection is carried out every year. The inspection typically includes the following:
Document exterior condition of the diffuser section and ballast rock or sand cover elevations adjacent to the pipe.
Record the condition of the Tideflex diffuser check valves
Confirm effluent flow through each diffuser
Record valve rise elevations referenced to natural bottom
Note any observed damage or anomalies
During the inspection in 2021, the general observation was that there were no significant changes since the prior year inspection. Minor tears along the sides of some of the diffusers did not appear to be growing in size or worsening in any manner.
A recent inspection of the outfall was performed on August 4, 2022. There have been significant changes since the inspection in 2021. Although much of the information remains the same from the previous year’s inspection, it appears that nearly all the diffusers have sustained damage. Diffuser D-33 seems to be of continual concern. Diffuser D-33 was temporarily repaired at the time of inspection in 2021 in an effort to stabilize it. The rebar reinforcements along with the D-33 diffuser could not be found. Only a length of the1/4” polymer line could be seen sticking out of the sand between diffusers 32 and 34. Nearly 40% of the Tideflex diffusers are now showing signs of damage. This is evident in the later half of the outfall in the offshore direction. It is without doubt that diffuser 33 is in need of the most attention. It is buried entirely and most likely bent hard over and in need of replacement.
Therefore, Staff reached out to Global Diving & Salvage for a proposal for diffuser excavation and repair. Global Diving & Salvage submitted a proposal for providing diving services to excavate the area around each of the damaged Tideflex diffusers and remove and replace them. The total cost is not to exceed $132,069.
Sewer Authority Mid-Coastside (SAM) Meetings ~ 2nd & 4th Mondays @ 7:00pm
Watch remotely. Comments and questions by email.
SAM Meeting Videos via Pacific Coast TV
Our regular office hours are 7:00 a.m. through 4:00 p.m., Monday through Friday, excluding holidays.The Authority can be reached 24-hours a day at:
Our Mailing Address is:
Sewer Authority Mid-Coastside
1000 Cabrillo Hwy N.
Half Moon Bay, CA 94019
(650) 726-7833 (fax)
Regular Board Meetings are on the 2nd and 4th Mondays of each month at 7:00pm.
From time to time a meeting date may be changed, cancelled or relocated. Check the posted agenda for any changes to the normal schedule (click on links below).
The Sewer Authority Mid-Coastside (SAM) provides wastewater treatment services and contract collection maintenance services for a population of approximately 27,000 in the following areas:
- City of Half Moon Bay
- El Granada
- Moss Beach
- Princeton by the Sea
Chair, Representing Granada Community Services District
Vice-Chair, Representing the City of Half Moon Bay
Secretary/Treasurer, Representing Montara Water and Sanitary District
Director, Representing the City of Half Moon Bay
Director, Representing Montara Water & Sanitary District
Director, Representing Granada Community Services District