Rain, Tides, Will Affect Drainage in City's Point Section

Newport’s department of utilities has issued an alert over extremely high tides expected tonight that could cause tides to discharge onto the street in the city’s Point section.

This morning’s high tide was predicted to be 4.7 feet but at 11:12 a.m., it was recorded at 5.54 feet. Normal high tides are between 3.5 to 4 feet and the next high tide, expected at 10:52 p.m., is expected to be significant.

The drainage system in the Point section, specifically near Second, Bridge, Marsh and Third Streets, is affected during astronomical high tides and there could be tides discharging as a result of the combined high tide and heavy rain earlier Wednesday.

“Overall, the storm drain system in this area is substantial with respect to the size of the storm drains; however, the low elevation of the area will be challenged in large storms and astronomical tides,” the city said in a release.

The drainage system outfall in the area is a 48-inch drain from Bridge Street that discharges into Newport Harbor at Storer park.

Catch basins at the corner of Second and Marsh streets collect runoff into a 12-inch storm drain that flows north to the Bridge Street drain.

Another pair of catch basins at Third and Marsh Streets collect runoff into another 12-inch drain that flows north to the Bridge Street drain.

During severe rainfall events, combined with high tides, the 48 outfall in Storer Park can get submerged.

In 2011, United Water installed tide gates to prevent backflow from tides into the Bridge Street storm drain.

But those gates were installed to prevent the “usual” astronomical high tide of 4.5 feet.

According to a release, The tide gates are hinged at the top and the flapper rests on an angled surface which initially seals under the force of gravity. As the water level from the tide on the downstream side of the gate rises, the hydrostatic pressure provides additional sealing force.

The cost for the installation of the tide gates at the two locations was $81,144.

A third tide gate was originally recommended at Third Street on the north side of Bridge Street but it will not address the ongoing tidal flooding and is no longer recommended.

United Water has a preventative maintenance procedure for the tide gates. Each tide gate is inspected monthly and any maintenance performed at the time of inspection. Additional inspections are performed prior to any predicted significant rain event and astronomical high tides. The inspection involves verifying the flapper is making contact with the sealing surface.

Small accumulation of debris at the hinge point will prevent the flapper from making firm contact providing the seal to prevent tide backflow.

“In summary the storm drain systems in the coastal areas are greatly influenced by the tides,” the release stated. “When we have extremely high astronomical high tides sometimes combined with a storm surge (above 4.5ft), the tides discharge onto the street surface through catch basins at the intersections of Bridge with 2nd and 3rd Streets downstream of the tide gate.”