AES 2015 Lined Coal Combustion Residuals Staging Project
Guayama, Puerto Rico | 2015 – 2024
Scope of Services
- Design and Permitting
- Construction Management
- Construction Quality Assurance
- Certification of Construction
The sacrificial layer included a warning layer consisting of dye in the top foot so that AES Staging Area equipment operators could readily identify penetration into the layer and cease excavation to protect the separation and drainage layers from equipment and excavation damage.
Oasis Consulting Services was retained by AES Puerto Rico, LP (AES) for the 2015 Lined CCR Staging Project in Guayama, Puerto Rico.
The purpose of the project was to design and install controls for the containment of the existing on-site coal ash staging area. The site consisted of an approximate 5-acre footprint with a conveyor system splitting the area into 2 approximate 2.5-acre sub areas.
Oasis was responsible for providing engineering, design and permitting, construction management, construction quality assurance, and certification of the completed construction.
The project was constructed in two phases so that approximately 2.5 acres of the staging area was fully developed while the remaining 2.5 acres was used to store interim coal ash. Following completion of the liner system installation in Phase 1, the coal ash material was relocated from the Phase 2 area to the Phase 1 area. Oasis developed a construction level design and specifications, as well as obtained the applicable federal, state, and local permits necessary to complete the work. In addition, Oasis developed a CQA/CQC plan for installation of the layers in the staging area containment construction and appurtenant structures. Oasis also prepared as-built drawings, and provided the supporting CQA/CQC certification report.
Oasis was responsible for installing perimeter erosion and sediment controls and/or run-on diversion features as required by the facility’s existing Storm Water Pollution Prevention Plan, and the Contractor’s Erosion & Sediment Control Plans. Oasis also installed a separation layer (“Liner System”) over the entire 5.0+/- acre coal ash Staging Area consisting of a heavy duty geosynthetic clay liner (GCL) overlain by 60 mil HDPE and geocomposite.
The project included the following:
A Geotextile Cushion Layer – 5.0+/- acres of 12-oz./SY geocomposite cushion layer was installed immediately over the 60-mil HDPE geomembrane per manufacturer’s requirements and project specifications.
A Drainage Layer – This layer consisted of a 12-inch layer (approximately 10,000 c.y.) of drainage media capable of providing >1.0 x 10-3 cm/sec in-place hydraulic conductivity, or an approved equivalent which was chemically compatible with coal ash. Oasis was responsible for providing test data to demonstrate both chemical compatibility with coal ash, and the ability to meet hydraulic conductivity specifications.
A Subsurface Drainage System – Oasis installed a 10-oz./SY geotextile and #57 stone wrapped, SCH 80 perforated PVC gravity collection piping system (or equivalent) to collect and manage subsurface water within the infiltration layer.
A Sacrificial Layer – At Oasis’s recommendation, AES agreed with installing a 3-foot minimum thick sacrificial layer immediately over the geotextile and underlying drainage layer.
A Geotextile Filter Layer – Oasis installed a second layer of 12-oz./SY non-woven geotextile fabric above the drainage layer (approx. 5.0+/- acres) to prevent infiltration of fines from the sacrificial layer into the drainage layer.
Surface Water Run-On/Run-Off Controls – Oasis was also responsible for collecting and conveying stormwater runoff via ditches, pumps, etc. from the project site to the adjacent coal pile runoff pond during and throughout the construction period, and also installed associated permanent stormwater run-on/run-off controls as specified in the engineering design drawings.