This week’s Kona low storm was anticipated to be the first big rain in Lahaina since the wildfire that destroyed the heart of the historic town and left toxic ash and chemicals at risk of being washed into the ocean.

But as of Thursday evening, not enough rain had fallen in West Maui to trigger a citizen science group to take planned water quality measurements following what scientists are calling “the first flush.”

“We may sample tomorrow or maybe after the next storm,” said Liz Yannell, program manager with Hui o ka Wai Ola, a community group dedicated to measuring and sharing the status of Maui’s ocean water.

Meanwhile, the U.S. Environmental Protection Agency announced Thursday that it completed its Phase 1 work as part of the federal response to the wildfires in Lahaina and Upcountry Maui.

In addition to hazardous-materials removal work, the EPA applied the soil stabilizer Soiltac to properties in an effort to prevent ash from spreading into the air or running off into streams and the ocean.

Even so, officials were worried about this week’s Kona low storm and its potential to produce heavy rain and excessive muddy runoff, this time likely laced with a toxic mix of ash, metals and chemicals from the Aug. 8 wildfire that killed at least 100 people and destroyed over 2,000 structures.

Two years ago a powerful Kona low storm pounded the entire state and left many shores brown with runoff for days.

In advance of this storm, Maui County mobilized crews to set up a number of erosion control measures aimed at trapping ash, debris and potential contaminants to keep them from entering the area’s storm drains.

On Thursday the county declared their efforts successful, adding that crews and contractors were cleaning up debris and making adjustments in anticipation of further rain.

Even before the Kona low was in the forecast, fears of heavy rain and runoff helped to trigger plans for a $40 million “emergency stormwater capture system” designed to reduce the environmental impact from silt, ash and other disaster debris entering storm drainage systems.

Announced a week and a half ago, the project, which includes design, construction management and continued management of the system through 2024, would be funded through the Federal Highway Administration’s Emergency Relief program.

The area to be covered by the stormwater capture system includes the entire length of Front Street, Hono­apiilani Highway between its southern connection with Front Street and Wahikuli Wayside Park, and stormwater inlets in Leialii Hawaiian Home Land, Kapunakea, Mala, the Puunoa Beach area, Lahaina town, Luna­ville and Wainee.

State Transportation Department spokesperson Russell Pang said crews already completed street sweeping and continue to do drain and pipe cleaning. Additionally, erosion control measures have been installed around all inlets in the Lahaina town area to help the discharge of debris into the ocean.

Additional erosion control measures are being installed this week along Honoapiilani Highway and Front Street, he said, with the estimated completion of inlet controls in mid-January.

“The only element of the stormwater capture system that is in design is the catchment and pollutant removal systems,” Pang said.

Sean Swift is part of a University of Hawaii at Manoa research team that was deployed to Maui this week to collect water quality and coral reef data in anticipation of the first big rain.

Swift, however, described the rain on Wednesday and Thursday as generally “on-and-off again” and “spotty.” Kahoma Stream, which runs through town near Mala Ramp, was running at a lower level than it was three weeks ago when the team deployed 20 sensors across West Maui.

The National Weather Service forecast for Lahaina calls for diminishing chances of rain through the weekend.

Funded by a $200,000 National Science Foundation rapid-response grant, the UH team is planning multiple sampling campaigns over the wet season in an effort to document reef health and contaminant loads, with the collection of samples every few hours over multiple days.

The team, led by Andrea Kealoha of UH Manoa’s Department of Oceanography, had been gearing up for the first big rain of the year, when much of the burned soil, ash, metals and contaminants are expected to reach the ocean and have the biggest impact on the reefs.

Swift said the team decided to take measurements anyway through the weekend.

“We’ll be back if it rains again,” he said.

As for as hazardous- materials removal is concerned, the EPA and its contractors, with help from the U.S. Coast Guard, were on the job since Aug 17, completing the removal of the materials from 1,374 residential and 74 commercial properties, the agency said.

The EPA said it also:

>> Shipped 13 containers containing hazardous materials off Maui for safe disposal.

>> Removed batteries from 94 electric and hybrid vehicles and decommissioned 274 power walls in homes and businesses. Two containers with more than 30 tons of decommissioned battery material were shipped off the island.

>> Set up five air- monitoring stations to provide continuous data on fine particulate matter at EPA’s AirNow website, allowing the state to monitor air quality and advise residents.

The EPA said it also deferred 73 residential and 100 commercial properties to the U.S. Army Corps of Engineers for hazardous-materials removal because physical conditions prevented safe access to the properties.

While the mission to remove hazardous material is finished, the EPA’s work will continue on Maui by helping the county’s Department of Water Supply and Environmental Management to address water infrastructure damaged by the fires, among other things.