Coastways Reservoir Report

Last Updated: December 5, 2025

Coastways is a private dam located in San Mateo, California, with a primary purpose of water supply for irrigation and domestic use.


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Summary

Completed in 1951, this earth dam stands at a height of 46 feet and has a storage capacity of 100 acre-feet. It is situated on Tr Ano Nuevo Creek, near the Pacific Ocean, making it a crucial water resource in the region.

Managed by the California Department of Water Resources and regulated for safety by the Safety of Dams agency, Coastways is subject to regular inspections to ensure its structural integrity. With a high hazard potential but a current satisfactory condition assessment, the dam plays a vital role in water management in the area. The dam's spillway type, maximum discharge capacity, and other key details are not specified in the available data.

Although there have been no reported modifications or emergency action plans for Coastways, its location and function underscore the importance of sustainable water resource management in the face of climate change and increasing water scarcity. Enthusiasts of water resources and climate adaptation will find Coastways to be a fascinating case study in the intersection of infrastructure, environmental stewardship, and community resilience.

Year Completed

1951

Dam Length

1000

Dam Height

46

River Or Stream

Tr Ano Nuevo Creek

Primary Dam Type

Earth

Surface Area

9

Hydraulic Height

43.6

Drainage Area

0.12

Nid Storage

100

Hazard Potential

High

Nid Height

46
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.