July 17, 2025 Update

Termination of Seal Cove Geotechnical Hazards Area Emergency.

On July 17th, the MWSD Board took action to terminate our Seal Cove Emergency. Since the last significant rain events in March, no further water mainline leaks have developed in Seal Cove. Additionally, San Mateo County has assured MWSD that encroachment permits can be issued in the impacted areas based on a licensed engineer’s inspection, signature, and acknowledgment of potential impacts on the area.
Staff suggested terminating the emergency status due to the reduced land movement and subsequent reduced damage to District assets. Work continues to develop a conceptual design for above ground water service lines, and where necessary, to provide fire flows using above ground water lines for fire protection.

June 12, 2025 Update

 What is the latest MWSD activity in Seal Cove?

MWSD has continued to keep all existing Seal Cove customers connected for both water and sewer services.

MWSD staff continue to assess options for affected Seal Cove infrastructure and associated costs. Continued land movement will require more repairs and replacement of the affected water mains, exceeding the typical repair and replacement lifecycle of these community paid assets.

Proposed solutions to maintain water and sewer services in the hazard area may include abandonment of water mains, meter relocations, and above ground permanent service lines - effectively a main replacement.

Please Remember:

• Check and properly maintain your sewer lateral, shared sewer laterals, sewer sump and grinder pumps.
• Leaks on your private water and sewer laterals may be repaired by a qualified plumber.
• Sewer pump repairs should be completed by the service company (Signa Mechanical) listed on the electrical panels of the pumps.

New Geological Survey Report

MWSD was alerted to a new California Geological Survey report with a proposed revised Alquist-Priolo Earthquake Fault Zone affecting the Seal Cove area. These maps are released under the authority of the Alquist-Priolo Act, a state law designed to reduce the hazard from surface fault rupture during an earthquake.

Seal Cove is one of only two exposed onshore locations of the San Gregorio Fault. The Seal Cove Fault section extends for approximately 4 km from where the fault initially comes onshore in Moss Beach and continues southward along Pillar Point Bluff before heading back offshore south of Pillar Point Harbor. The report states ‘there is also clear evidence of active landsliding located over 100 meters inland from the top of the sea cliff.’

Full report online at www.conservation.ca.gov/cgs/publications/preliminary-releases

San Mateo County Seal Cove Community Meeting
Wednesday, June 11th 5:30-7:30PM
270 Capistrano Road, Half Moon Bay

Supervisor Ray Mueller is hosting a community meeting to address concerns in the Seal Cove area. Representatives from San Mateo County including Planning and Public Works will be in attendance, along with other resources for residents.

San Mateo County & Seal Cove

San Mateo County’s Planning and Building Department establishes land use policies and development regulations that protect public health and safety. This includes oversight of County streets and structures on private property.

In Seal Cove:

The Building Division has been performing visual inspections of impacted properties to determine if and how the use of these homes needs to be restricted.

Public Works personnel have been inspecting road conditions to evaluate the need for any immediate measures that can be taken to maintain the County roads and ensure the continued use by the traveling public.

Updates online at www.smcgov.org/planning/sealcoveinfo

Emergency Contact Numbers

Water Emergencies: Call MWSD at (650) 728-3545
Sewer Emergencies: Call SAM at (650) 726-0124
Dial 911 for life-threatening and safety

April 28, 2025 Update

MWSD Board Action on May 1st

On May 1st, the MWSD Board will consider continuing this District Emergency as declared at our March 27th Board meeting. A District Emergency allows for faster contracting and response to the emerging issues in the Seal Cove area. This emergency also authorizes the District to seek state and federal financial assistance.

We continue our investigations to recommend safe solutions for Seal Cove water and sewer infrastructure.

MWSD is committed to providing continued updates directly to our Seal Cove customers, and during MWSD Board Meetings.

What is the latest MWSD activity in Seal Cove?

Staff have continued active response in the Seal Cove area. This includes responding to and repairing additional leaks of water and sewer infrastructure, as well as continuing evaluation of safe solutions to maintain water and sewer services. Some key updates:

• Everyone remains connected and served by both water and sewer systems.
• On San Lucas Avenue, we have abandoned both our water and sewer mains west of the Del Mar Avenue intersection. We are no longer utilizing these pipes for any water or sewage flows.
• The water main in San Lucas was reconfigured east of the Del Mar intersection. The main now crosses San Lucas, keeps the fire hydrant at the intersection operational, and connects into the water main in Del Mar Avenue.
• We have continued to meet and coordinate with both Coastside Fire Protection District and San Mateo County as we assess our infrastructure in the affected area.
• Our crews have seen increased land movement most recently on La Grande Avenue.
• Water and sewer mains on the western ends of Madrone, La Grande and Los Banos Avenues, as well as the Park Street and Beach Street intersection, are being examined for safer configurations. This may include above ground pipelines, and relocation of water meters for private properties. Above ground pipelines provide increased flexibility and quick visual access, ensuring leaks are less frequent and caught quickly.

Please Remember:

• Check and properly maintain your sewer lateral, shared sewer laterals, sewer sump and grinder pumps.
• Leaks on your private water and sewer laterals may be repaired by a qualified plumber.
• Sewer pump repairs should be completed by the service company (Signa Mechanical) listed on the electrical panels of the pumps.

History of Seal Cove Land Movement

Since the 1960’s there have been numerous, geotechnical studies of the Seal Cove area by San Mateo County, the land use authority for this area.

Study started in the 1960’s, when the U.S. Geological Survey slowed Seal Cove development due to active landsliding and accelerated coastal erosion. In 1971 and 1984 San Mateo County studies confirmed continued instability and geologic hazards. Structural damage due to landslide activity has been documented throughout this time.

San Mateo County

San Mateo County’s Planning and Building Department establishes land use policies and development regulations that protect public health and safety. This includes oversight of County streets and structures on private property.

Emergency Contact Numbers

Water Emergencies: Call MWSD at (650) 728-3545
Sewer Emergencies: Call SAM at (650) 726-0124
Dial 911 for life-threatening and safety