Source: http://www.nctimes.com, September 16, 2011
By: Paul Sisson
Just as long-awaited efforts to clean up the site of former gravel mine in Oceanside got underway last month, heavy earth-moving equipment uncovered two more patches of contaminated soil near where Buena Vista Creek cuts through the land.
Marvin Howell, director of land use planning and permitting for property owner Hanson Aggregates, said Thursday that the soil was contaminated by hydrocarbons, probably from oil or another petroleum-based product used on the 104-acre property during the decades when it was home to an active mining operation.
Howell said the discovery will not halt ongoing reclamation efforts that are reshaping the so-called Quarry Creek property, south of Highway 78 and west of College Boulevard in Oceanside. The plans also include widening the creek.
Hanson has sold development rights for some portions of the property to McMillan Development, which has plans to build about 500 homes on flatter land further away from the creek bed itself. But first Hanson needs to clean up the site, a years-long process overseen by the city of Oceanside.
“We are trucking the soil off site for disposal in a landfill,” Howell said, adding that he did not know exactly how many cubic yards of dirt would have to be removed.
Shelly Hayes Caron, who lives in a historic adobe home just west of the property, said she hopes that the excavation and cleanup goes deep enough.
“We have to do this right, and we hope it has not gotten into the ground water,” Hays Caron said.
Scott Weldon, a supervising environmental health specialist with the county Department of Environmental Health, said most of the contaminated soil surrounds what was a maintenance yard at the old quarry property.
He said that, because the contamination was caused by surface spills of gasoline, diesel fuel and oil, it is not likely that ground water was affected. He said workers will need to keep digging until they have reached ground that is found to contain less than 500 parts hydrocarbons per million.
The site has already had ground water contamination from a total of eight underground storage tanks that were removed in the early 2000s.
At the time, Hanson removed 40,000 cubic yards of soil that was left in large covered piles until the fuel had dissipated enough to be re-used. Weldon said air was also forced into the ground near where the tanks were buried to help reduce contamination to the local water supply.
Weldon said ground water samples have shown the contamination shrinking.
“The levels of contamination in those wells are now extremely low to the point where we can close the case,” Weldon said.
The groundwater remediation efforts were one of the first steps in what is a comprehensive reclamation project for the old quarry. A contractor working for Hanson has now begun final reclamation grading work which Howell said he expects to be finished by the end of the year.
That excites Jim Knowlton, owner of Geopacifica Inc., a local consulting firm hired in 1991 to help coordinate the reclamation effort that is now nearly finished.
Knowlton said it is exciting to see the property finally begin to take shape after years of planning and public debate about how the creek and its surrounding landscape should be reborn.
“They’re finally going forward and the site is going to look great when they’re done,” Knowlton said.
A granite mining operation was active on the site from 1961 to 1995. It was purchased by Hanson Aggregates Pacific Southwest in 1991.
The reclaimation plan calls for workers to widen Buena Vista creek from its present 25 to 50 feet. The new bed will be 150 feet wide with additional banks on either side that will push the project’s total width to 300 feet.
Knowlton said a wider creek bed will provide much more room for native plants and other habitat.
Efforts are also under way to make the creek flow more slowly from east to west. Knowlton said crews are installing a series of very low dams —- called “drop structures” —- in the creek bed to keep water from running too fast and washing out native plants.
“By putting in the drop structures, we basically reduce the energy of the water and that enables the vegetation and trees to grow,” he said.
After widening the creek bed and installing the structures, Hanson is to create new sloped banks that will require moving 280,000 cubic yards of soil from other parts of the site.
The reclamation work also includes removing non-native plants from land just west of El Salto Falls, a natural waterfall on the site’s eastern border right next to the towering retaining wall installed when developers built the Quarry Creek Shopping Center at Marron Road and College Boulevard.
Though the falls will be more visible when non-native plants are removed, the public will still have only one legal view of the falls. That view is possible from the northwestern corner of the shopping center property.
Knowlton said that, when the reclamation project is finished, there will be no immediate public access to the newly-improved creek bed or to the falls.
He said public access to the creek and falls is expected to be part of any development agreement approved by Carlsbad and Oceanside.
Many local environmental groups have asked for the entire valley to be restored to a natural, park-like condition.