In an effort to rid Palo Alto's Matadero Creek of the last vestiges of a diesel fuel spill that has contaminated the waterway since early May, experts plan to dig up the soil next to the creek bed to extract pollutants that might still be trapped.
The May 6 spill, which originated from a generator facility at the Veterans Affairs Palo Alto Health Care System's Palo Alto campus, has been a bit more persistent and far-reaching than originally thought. Experts had said it would soon dissipate and its chemicals would break down naturally in sunlight. Some pockets still remain, with contamination well over recommended limits from regulators.
The California Department of Fish and Wildlife, which is monitoring the spill, now expects it will take months before the fuel will naturally disappear. Multiple agencies involved in the cleanup are exploring alternatives to the booms and absorbent pads that have contained and soaked up much of the contamination, according to a joint update issued Thursday by the city and the VA.
The tillage and extraction proposal, the latest idea, would dig up the soil adjacent to the creek bed "to maximize extraction of any remaining pollutants while focusing on preserving the ecosystem to further reduce all affected areas," the update states. The Department of Fish and Wildlife will be meeting with industry consultants next week to determine a plan that would carry out the soil disturbance in a safe manner, the update said.
The spill occurred after a failed sensor in a generator plant pump at the VA hospital campus caused the fuel to enter a nearby storm drain flowing into the creek.
Alerted by concerned residents who took their own water samples after learning of the spill, the VA's consultants tested additional locations farther downstream near and below the Bol Park Path and footbridge. In late May and earlier this month, subsequent testing showed the pollutants had spread farther downstream and two new containment booms were added closer to the footbridge, the city and VA said in a June 4 update.
In one of four remaining hot spots, the fuel was at one point nearly 297 times the water quality freshwater habitat standard of 640 micrograms per liter as set by the San Francisco Regional Quality Control Board. The area is between the seventh and eighth containment booms. These two containment devices are located halfway between where the spill originally occurred and the Bol Park path, a map shows. Another location upstream of the outflow pipe at its highest level was 56 times the standard.
The VA-hired experts anticipate the amount of diesel to continue to decrease due to water movement in the creek, the booms being in place that are absorbing any remaining fuel and the natural degradation of the fuel as it is broken down by sunlight, according to the June 24 update. So far, the pollutants along most of the testing spots have dissipated and are no longer being detected in multiple sampling locations — except in four spots roughly halfway between the original spill site and the Bol Path footbridge.
In two of these last four locations, the highest concentration of fuel is currently 5,700 micrograms per liter or 8.9 times the water quality habitat standard and 1,500 micrograms per liter or 2.3 times the standard. The highest amount is in a shallow, divided part of the creek and the second highest is between the sixth and seventh boom, according to the VA consultants' most recent data.
The water-sample consultants suspect low-sunlight conditions and creek bank vegetation might have trapped fuel and are causing the elevated levels. The data shows the boom system is working well, since this section is the only area now out of the recommended Quality Control Board limits, according to the June 24 update.
The Palo Alto Fire Department continues to consider the incident as stable at this time, the city noted. Representatives from the Department of Fish and Wildlife, the VA, the Palo Alto Fire Department Hazmat Bureau and the Santa Clara Valley Water District board of directors, in addition to city stormwater staff and remediation scientist/water sample consultants, are working collaboratively to solve the problem, according to the update. They plan to issue new public updates as testing and remediation continue.
"fuel" - Google News
June 25, 2021 at 11:33PM
https://ift.tt/2SXzwox
To control diesel fuel spill, city plans to dig up Matadero Creek bank - Palo Alto Online
"fuel" - Google News
https://ift.tt/2WjmVcZ
Bagikan Berita Ini
0 Response to "To control diesel fuel spill, city plans to dig up Matadero Creek bank - Palo Alto Online"
Post a Comment