WHAT: Soil and Ground Maintenance Plan
OWNER: Dallas Water Utilities
CONSULTANT: Terracon Consultants Inc.
TIMELINE: July — November 2011
As cities expand their water distribution territories and redevelop existing areas, water utility infrastructure upgrades become a constant need. Often, upgrades occur along corridors adjacent to commercial and industrial areas that have been impacted by petroleum hydrocarbon and other chemical releases, which pose problems to the integrity of the water utility, the safety of consumers, and the safety of the construction workers installing the utilities.
In Dallas, a large amount of aging infrastructure is slated for replacement and/or upgrades over the next several years. But already, Dallas Water Utilities (DWU) is experiencing major delays and cost overruns on projects due to contamination issues being discovered after construction begins.
Although the utility had management procedures in place, they were reactive instead of proactive, says Chad Kopecki, DWU interim program manager. Plus, the procedures weren't very thorough, consisting of a half-page document of directions on how to react to a contamination situation.
To minimize potential contamination problems before projects begin, the utilities department worked with the Dallas Sustainable Development and Construction Department to institute new requirements for installation and upgrades of water utilities.
Additionally, the utilities department created a manual that establishes mandatory yet easy-to-follow procedures; describes appropriate actions to be taken by staff; provides a much higher degree of liability protection not only to utility customers, but also to contractors; and gives the city and the departments an excellent public image — as public agencies in the mode of continual improvement and innovation.
Prior to a few years ago, the water utilities and sustainable development departments largely ignored potential contagion issues and only dealt with upgrading piping, etc., if contamination was discovered during development or construction. Although they have always worked together, they had to step up their collaboration efforts to develop a two-fold strategy that identifies and addresses contaminated properties.
Because each of the two departments caters to its own unique customer base — Sustainable Development customers are property developers while the utility serves water consumers — each took a different approach that complements the other's. Sustainable Development and Construction primarily deals with permitting and code issues on new development and redevelopment of individual properties within city limits. The department established a policy that seeking construction permits to submit information regarding the site's environmental conditions. If the submitted information indicates site soils or groundwater have been contaminated or may be contaminated, the developer is required to conduct soil and/or groundwater sampling to ensure soils and groundwater in the vicinity of the water service lines (i.e., the connection from the water main to the site building) are not impacted.
If contaminated soils or groundwater are identified, the water utility then steps in to require installation of alternate piping, trench construction, or special gaskets for the water service line connecting the site building(s) to the water main, thereby preventing any potential contamination of the water supply to the building(s) and protecting water consumers across the distribution network. It is also important to ensure the trench does not become a pathway of travel for contaminants from one location to another.
Developing a soil and groundwater management plan
Unlike the Sustainable Development and Construction strategy, which addresses single-site developments, the water utility needed a broad-scale approach for the city's entire water distribution system (i.e., the water mains). It needed a comprehensive plan that could easily be used by all staff engineers and subcontractors to protect the public water supply, as well as workers performing upgrades and installations.
The utility contracted Terracon Consultants Inc. to develop a thorough and prescriptive soil and groundwater management plan (SGMP). Terracon's goal was to create a 15- to 20-page plan that would include the necessary technical information, background, and specifications to ensure the safety of the water supply pipelines, while also remaining simple and user-friendly for civil engineers unfamiliar with technical environmental issues.
The utility also chose to use its internal Geographic Information System (GIS) to assist with screening criteria as part of the new procedures. To help project engineers identify potentially contaminated areas during planning stages on all pipeline projects, the following layers are used (see the map on page 30):
- City-permitted monitoring sites
- Voluntary Cleanup Program sites
- Leaking petroleum storage tanks
- Registered dry cleaners
- Areas with a Municipal Setting Designation (MSD; identifies properties with groundwater that's not potable)
Known landfills (existing, closed, permitted, and unpermitted).
The soil and groundwater management plan had to account for contaminants that could come into contact with various types of water piping and associated gaskets. DWU engineers evaluated degradation thresholds (the concentration of a particular contaminant that impairs the proper operation of a particular material, such as a polyvinyl chloride or polyethylene pipe) to determine a conservative approach to protecting the city's pipelines. They used the resulting information to devise a plan that:
- Instructs utility personnel on how to obtain environmental information through available in-house resources, and how to retain a consultant to assist in evaluating the potential for a pipeline right of way to contain contaminated soils and/or groundwater. Procedures include measures to take to obtain available Phase I environmental site assessments that are completed as part of right-of-way acquisitions, and how to conduct regulatory searches or reviews of regulatory files. If issues are identified, the plan provides step-by-step instruction on ordering subsurface investigations to evaluate and characterize contaminated soils and groundwater located within the pipeline right of way.
- Presents protocol for evaluating known contaminant concentrations on a scale of low, high, or unacceptable contaminant conditions, as defined by risk-based protective concentration levels used by the Texas Commission on Environmental Quality. Low and high conditions take into consideration piping and gasket materials requirements for the pipeline, trench design parameters, construction parameters, and waste management requirements. Unacceptable contaminant conditions include the presence of free-phase product within the proposed pipeline corridor. The free-phase product must be removed from utility pipeline corridors or the pipeline must be relocated outside of the free-phase product plume. (For examples, see images on page 31.)
- Details steps to prepare summary documentation of contaminant conditions in the work area, which are then given to contractors to ensure that proper health and safety practices are followed during construction. Procedures for the proper handling of contaminated soil and groundwater during construction activities (i.e., stockpiling and covering contaminated soils on plastic, and containerizing contaminated groundwater) are also included.
Provides information on the training requirements (40-hour OSHA Hazardous Waste Operations training; HAZWOPER) for contractor personnel tasked with excavating contaminated soils and ground-water. Thus, the utility department's bid documents can include requirements for properly trained construction personnel (see image on page 29). Additionally, if contaminated media are known to exist, the contractor is required to provide its own soil and ground-water management plan to ensure that proper handling procedures are followed.
To ensure that the management plan is used by all employees — and isn't just another dust-collecting manual sitting on a shelf — Terracon conducted presentations for both engineers and field staff. The engineering staff presentation included a thorough review of procedures and how the plan should be used in the planning and design of pipelines. The field staff presentation was tailored with information specific to inspections and procedures that staff would be observing in the field during construction.
The manual also includes several case studies and site scenarios to help personnel understand how the document works, and how to proceed under the new procedures. The water utility department plans to update the manual continually over time to keep procedures fresh and accurate.
— Sallman (firstname.lastname@example.org) is a principal with engineering consulting firm Terracon, in their Dallas office.
- WEB EXTRA
To access DWU's soil/groundwater management plan, click here.
|WHY USE A SOIL AND GROUNDWATER MANAGEMENT PLAN?|
A wide variety and mixture of contaminants exist in shallow soils and groundwater along rights of way and major thoroughfares where water utilities are typically located. These contaminants can interact with both water pipes and piping gaskets, degrading or weakening the pipeline materials. Contaminant damage to water piping may cause premature failure of the water piping or gaskets (especially for pressurized piping), resulting in potential unsafe drinking water supply, service interruptions, costly repairs, and untold damage to a department's public image.
Discovering contaminated soils and/or groundwater during the construction phase of utility upgrades typically results in schedule delays and large cost overruns. But by following established procedures to identify contaminated areas during the infrastructure planning stage prior to installation allows for proper planning and cost evaluation of the issues.