Plan will cause Seven years of noise, dust, truck traffic
HIGHLANDS – The Environmental Protection Agency (EPA) has just released many volumes of reports from the GHD Consulting Engineering firm, detailing their ideas for how to remove the toxic wastes from the North and South Impoundments along the San Jacinto River, known as the Superfund Site.
The report is extremely long and detailed, consisting of 10 volumes of information for the Northern Impound Site, and Two volumes for the Southern Impound Site. In total, there are many thousands of pages with data, drawings, boring logs, and most important a Work Plan on how to remove the waste material, and how it will impact the environment around the communities of Highlands and Channelview.
The engineers have proposed excavation within “cells” on the Northern site, encompassed by sheet piling, and on the Southern site removal without the piling enclosures. The full extent of the work includes driving piles to form five cofferdams, dewatering the soil, excavating the material, and hauling it away to licensed landfills approximately 100 miles away. They envision one year of preparation, five years of excavation, and one year of clean-up and restoration, for a total of seven years of work.
The report emphasizes that it is preliminary in nature, and must be evaluated and refined. It is written by the GHD Environmental Engineering firm, located in Baton Rouge, Louisiana, but reflects input from the EPA, the TCEQ, and the US Army Corps of Engineers. The report says that it will also need the concurrence and coordination with the Port of Houston Authority, Harris County Flood Control District, the TXDOT Texas Department of Transportation, and the Coastal Water Authority. The latter two have work projects in the area that might conflict with the Waste Pits remedial activity, they said.
The conclusions delineated in the report indicate the toxic material is deeper and wider than originally thought, and qualities will be larger and time to remove the material extended over the original schedule. In addition, these factors are expected to increase the costs an unknown amount.
It is expected that the EPA will have to negotiate with the PRP (Potential Responsible Parties) to come to an agreement on the cost of the work which they will be responsible for.
In the narrative accompanying the reports and the Work Plan, the consulting engineers say that the size, location, and required techniques for removal may be beyond reasonable construction parameters, and may in fact not be feasible. They indicate further study is needed in this regard.
Some details from the report emphasize the scope and difficulty of the project. Due to poor soil conditions, the engineers say the steel sheet piling must be 109 feet long in some situations, and have a cross section of a 41” I-beam, or a 5’-6” tubular cross section, and weight hundreds of pounds per foot of length. These structural members are not normally available, and may have to be fabricated overseas. It is obvious that their transportation will be very difficult, too.
The Northern site is about 14 acres, with more than half of it normally under water. The report says that another site of about 10 acres must be located as a staging area, and a gravel road built to access the waste pits site. This gravel road would be in TxDOT right-of-way of I-10, and there is a strong possibility that a new bridge for I-10 will be under construction at the same time, creating possible conflicts for work crews.
The waste material soil must be dewatered prior to excavation the report says, and this will require building a temporary water treatment plant. Its plan is very large, about 75’ x 150’ and consists of either 24 or 16 stages of treatment, depending upon the scheme selected. The Work Plan calls for all materials to be removed that test above 30 ng/kg in toxicity, and this means some of the excavation will be 25 feet or more deep.
Environmental groups including THEA’s Jackie Young Medcalf, have questioned whether the 30 ng/kg criteria is safe enough. She also thinks the plan to use some of the rock material that forms the present “cap” is not a good idea since it may be contaminated. She is also worried about worker safety, and neighborhood safety as the excavation work and transportation present opportunities for escape of toxins. Jackie Young Medcalf also takes issue with the GHS/EPA determination that the waste material can be classified as “non-hazardous industrial waste” allowing it to be handled and removed at lower limits of safety. The material was tested for “ignitability, corrosively, reactivity, and toxicity to arrive at this conclusion, GHD said.
The report points out some of these problems, saying that driving the sheet pilings would be very noisy, cause vibrations, and last for five years. Impact hammers might have to strike the piles 1500 to 2500 times each, the report said. It is expected that the noise would bother nearby residences, and distract drivers on I-10 who were not expecting it. Work would be confined to the November to April calendar months, to avoid floods or hurricanes that might affect the site and release toxic material. In addition, excavation would probably release dust, that must be contained by the contractor with some method.
The material to be removed from the Northern site is now calculated to be 212,000 cubic yards, not 162,000 as originally figured in the ROD, or Record Of Decision of 2017. This would require 15,000 truck loads of material to be hauled away from the site. This means these trucks would enter I-10 at the Monmouth ramp, if TxDOT would allow this. The Southern site would have an additional 26,000 cy of material transported, with 30,000 cy stored on-site for reuse. The Southern Impound site is approximately 20 acres.
The majority of the work would be scheduled from November to April, to avoid the high water periods in the San Jacinto River, and to also avoid the hurricane season. High Water could greatly affect the safety of the site and the exposed material. However, the report notes that the Coastal Water Authority is constructing 10 new gates in the dam at Lake Houston, and this would allow greater discharge rates, and could affect the height of the river in a rainy season. The sheet piling is designed to extend 9 feet above average water level, but the report says it is not known if future water events might exceed this height.
In a word of caution that might be understated, the report concludes for the Northern Impoundment, the following uncertainties:
“Uncertainties… could render the remedial alternative outlined in the ROD technically impractical and not implementable.” These include the following factors:
— Uncertain Depth
— Pile types… are not conventional
— Possible slope failure… releasing toxic material into the river
— Logistics of (pile) transportation
— Inability to remove the piles after completion, leaving an obstruction in the river
— Overtopping (flooding) possible in a storm
— Coastal Water Authority (CWA) water releases at the dam
— Water treat ability, so that it may be returned to the river. At present the treatment is only theoretical
— Trucks entering I-10. May need a TxDOT permit and traffic control if allowed
— Release of greenhouse gases due to heavy truck volume.
In the report, the SSA or Sand Separation Area was found to have toxicity below the allowable levels, and the report recommended that no treatment other than MNR (Monitored natural remediation) be needed for this area.
In the Southern Impoundment, some demolition of existing structure and concrete slabs are required to allow excavation, and sheet piling 55’ long and 180’ long is planned for the western edge of the impoundment site to hold back river water. Criteria for this site is 240 ng/kg, and much of the material is below that criteria, the GHD report said. The plan is to excavate and dewater the areas that tested above that figure, and then backfill and restore the site.
Due to the Pandemic from COVID-19 virus, the EPA has not been able to present this information in a public forum as originally planned. You can read the reports yourself, at https://semspub.epa.gov/src/collection/06/SC32193. The consultant, GHD Environmental Engineers, is continuing to work on the Remedial Design and the next report will be the 90% RD.