Project: Municipal Utility Upgrades
Phase I Assessment & Design Support
Municipal Utility Upgrades
CRETE principals subcontracted to a civil engineering firm to perform a Phase I environmental site assessment associated with the design of a significant utility and right-of-way enhancement project. The project was for a 2-mile stretch of a commercial business district with stormwater outfall to a salmon-bearing stream. The purpose of the assessment was to determine and map all known and suspected soil and groundwater impacts along the project. Based on the assessment, the following modifications were made to the utility design plan:
- Electric utility vaults were relocated to avoid areas with possible explosive vapors
- Storm drains that intercepted groundwater were backfilled with controlled density fill to avoid creating preferential pathways for contaminated groundwater flow
- Storm drain installation plans were modified to include above-grade welding of HDPE pipe and rolling of the storm drain into the trench to limit dewatering of contaminated groundwater and control unnecessary worker exposure to contaminants
CRETE principals developed specifications in accordance with Washington State Department of Transportation (WSDOT) format related to environmental aspects of the project including soil segregation and stockpiling, construction stormwater and groundwater management, and soil and water treatment or disposal. After award of the construction contract, CRETE principals continued to work on the project to assist with:
- Contained-in determination approaches to manage and sample solvent-impacted soil
- Local sewer company discussions to allow discharge of petroleum- and solvent-impacted groundwater from excavations
Work Performed
- Property assessment due diligence
- Regulatory negotiations - MTCA
- Permitting - construction stormwater, POTW discharge
- Development coordination
- Construction plans and specifications
- Stormwater system design
Value Added
- Relocated utility vaults to allow future utility maintenance without vapor mitigation
- Developed a modified stormwater pipe design and installation technique to minimize site dewatering and water treatment costs and to limit the exposure of workers to hazardous materials
- Modified the stormwater pipe backfill design so that the project did not result in preferential migration of contaminated groundwater