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Hyperion Alerts

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1-Mile Outfall Gate Exercise

In advance of the coming wet weather season, in an annual exercise to ensure that the plant's three bypass gates are properly functioning, fully treated and disinfected water from each of the two channels is scheduled to be discharged to the 1-Mile Outfall on Wednesday, November 17, 2021, and Thursday, November 18, 2021 from 5:00am to 1:00pm.

All activities will occur on the premises of the plant and will not produce any additional odors, noise or other negative impacts to the surrounding communities. Because the water will be fully treated, disinfected, and pumped back to the plant for reuse, the LA County Department of Public Health (DPH) will not be closing the beaches. DPH will monitor the bacterial levels in the recreational waters close to the 1-Mile Outfall on November 17th and 18th and report on exceedances of health standards as applicable.

On Thursday, November 18th, one Northbound lane on Vista del Mar Blvd in front of the Plant will be closed during the activity from 5:00 a.m. until 8:00 a.m., which may impact commuter traffic.

Our November 15, 2021 media advisory is available for download at the bottom of this page.

Throughout this exercise, LASAN is in close coordination with county, city, state, federal, regulatory agencies, surrounding communities, and environmental organizations. Because the work is underground and out of view, we will not be inviting anyone to observe the exercise. However, we will share the results of the gate exercise here on our website upon completion.
 

Background

During the exercising of the gates, fully-treated effluent will be discharged into the 1-Mile Outfall and then pumped back into the plant before reaching the ocean. The 1-Mile Outfall is typically used only for excess stormwater, downstream maintenance and/or repairs, or emergency use.

Hyperion One-Mile Outfall Diversion Structure graphic

 

Testing will involve one open cycle and one close cycle for each of the three 1-Mile Outfall gates (North, South and East gates) from the following locations: Local Control Panel in the 1-Mile Vault and Effluent Pumping Plant Flow Control Panel.

Approximately 250,000 gallons of chlorinated secondary effluent from each effluent channel will be discharged to the Diversion Structure/Surge Chamber, which is connected to the 1-Mile Outfall. There are two effluent channels: East and West Channels. Hyperion will install metal plates in the effluent channel upstream and downstream of the 1-Mile Outfall gates to be activated.

Concurrently, LASAN’s Environmental Monitoring Division will use a monitoring vessel to sample and perform analysis of any possible effluent discharge out of the 1-Mile Outfall.

While we do not anticipate that any of the 250,000 gallons of the fully treated secondary effluent to be discharged into the receiving waters, sampling and analyses are not required by our regulatory permit if there is no effluent discharge into the Santa Monica Bay, LASAN will conduct water quality sampling during the 1-Mile gate exercise as a precautionary measure.

LASAN Environmental Monitoring staff will collect surface and depth samples at the end of the outfall, and 50 meters north and south. In addition, out of an abundance of caution, we will conduct bacteriological and total residual chlorine analyses, as well as other chemicals, to confirm that the effluent did not make its way into the Santa Monica Bay. It is not expected that water quality will be impacted by this exercise.

Outcome

On Wednesday and Thursday, November 17 and November 18, tested the east channel and west channel gates for the Hyperion Water Reclamation Plant to ensure that they are properly functioning. It was confirmed through this routine test that the gates were successfully able to open and close without incident.

This exercise involved approximately 500,000 gallons of treated and disinfected wastewater being discharged from the east and west channels to the 1-Mile Outfall. Metal plates were installed near the gates to prevent any discharge into the Outfall. This water was successfully pumped back to the HWRP for reuse and was not released into the ocean.

Being that the water was fully treated, disinfected, pumped back to the plant for reuse, and not released into the ocean, the LA County Department of Public Health (DPH) did not need to close the beaches as no sewage was released.

As required by the plant’s permit and out of an abundance of caution, LASAN used its monitoring vessel to sample ocean water during and after this exercise, and is analyzing the samples for any possible effluent discharge out of the 1-Mile Outfall.

If you have any questions, please contact the LASAN 24-hour Customer Care Center at 800-773-2489. 

LASAN continues to closely coordinate with the DPH and other entities as part of this exercise.

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