Residential Development Assessment

Challenge & Solution

Prior to purchase and development of a former electric company site located in Elizabeth Township, Pennsylvania, the private owner contracted an engineering firm to prepare all necessary reports and designs required for submittal of a subdivision Preliminary Application to the Township.

The primary firm was interested in aligning with small multi-disciplined firms to complete this fast-track project. Rhea was selected to join the design team to provide services in the areas of environmental assessment, right-of-way and deed research, cultural resources, erosion and stormwater control design, NPDES application, site layout design, and construction technical support.

Project Description & Highlights

The residential development is a 265-acre site located in Elizabeth Township, Pennsylvania. This site had been intended for residential development for over 30 years, but poor economic conditions in the region had halted the development. Recent transportation projects near the site have renewed interest in this R2-zoned property. Four hundred lots, each with an average size of 0.5 acre, were developed on the property.

Initially, Rhea performed the Phase I Environmental Site Assessment and Cultural Resource Study. Rhea also performed deed research and investigated the right-of-way requirements for the site and surrounding properties. Rhea’s civil site design for the project included developing the road layout, site grading design, sanitary sewer design, and storm sewer design. Rhea also designed the erosion and sediment control, stormwater management systems, and submitted the General NPDES Stormwater permit application for the project.

Performing the civil design for the residential development site was an engineering challenge due to the steep terrain and numerous gas service and transmission lines crossing the site. 

Because of our extensive civil design expertise, Rhea developed a vertical layout design that both minimized and balanced cut and fill, the most critical cost issues for a developer. In addition, the General NPDES permit application was accepted after minor comments. 

After Remedial Action Topographic Survey

Challenge & Solution

A building in North Carolina was formerly used as a power substation from the 1930s until 1942, when the federal government purchased the facility. In the mid-1960s, the government converted the building into a maintenance facility.

In 1999, the building was demolished. Contaminants identified on the site included total petroleum hydrocarbons (TPH), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and pesticides. Prior removal actions were completed by 2008, when it was decided to institute Land Use Controls (LUCs) for the remainder of the contamination. A topographic survey was required to verify the remedial objectives had been met and to provide a basis for cut and fill calculations for the design of a new access road around the LUC area.

Project Description & Highlights

At the conclusion of all intrusive remediation actions, Rhea created the LUC document for the site. This LUC document was created to define remediation activity areas and document relevant details of the LUC area. Included within this task was the design of the relocated access road that currently passes through the LUC area.

A topographic survey of the existing ground surface confirmed that the soil cap remedial alternative covered the LUC area to the specified thickness, and provided the existing site grades and features that facilitated cut/fill calculations for the new access road design.

The topographic survey was instrumental in identifying a low-lying area that historically collected pools of runoff during storms. Evidence of previous erosion events at the former access road prompted the inclusion of appropriate stormwater drainage within the design to protect the new road.

The results of the topographic survey confirmed to the Client that the remedial action met the regulations of governing agencies. The survey also provided a basis for a cost-effective design and construction of the relocated access road. 

Airport Improvement Project

Challenge & Solution

A West Virginia airport proposed an improved Runway Safety Area for one of its runways. The current safety area is 400 feet wide and 250 feet long. It is being extended 750 feet to meet Federal Aviation Administration (FAA) requirements and to create a safety area that is 400 feet wide and 1,000 feet long.

This expansion will require approximately 250,000 cubic yards of structural fill borrow for the proposed embankment. The borrow site was thought to be the location of a strip-mining operation.

Project Description & Highlights

Rhea served as the subcontractor for the geotechnical investigation on this project. A review of an in-house soils survey, geotechnical, geologic, and mining literature of the project area as well as plans, reports, and additional literature of the site was completed prior to field reconnaissance. The field work involved evaluating the condition of existing pavements, the proximity of existing structures, site drainage, evidence of groundwater, exposed mine spoils, fill, soil and rock, evidence of mine subsidence, and/ or other site conditions that could affect the proposed construction.

Rhea finalized the client’s Subsurface Exploration and Testing Program (SE&TP) based on the results of the review and field reconnaissance. The SE&TP consisted of 20 test borings totaling approximately 536 linear feet of drilling. Rhea provided a full-time boring inspector during drilling, who logged the test borings, observed that drilling was performed in accordance with specifications, and coordinated with airport personnel. Rhea also provided a part-time drilling inspection supervisor to oversee the drilling program and to modify the drilling program to reflect subsurface conditions encountered.

Rhea performed laboratory testing on soil samples to determine physical properties. The analyses evaluated potential impacts of the site subsurface conditions encountered on the proposed construction. Also, a Test Boring Location Plan, Engineers Field Boring Logs, geotechnical cross sections, and a Geotechnical Investigation Report were prepared.

Rhea’s in-depth understanding of our region’s potential geotechnical problem areas – for this project, the presence of colluvial soil beneath the planned embankment – led to experienced based slope stability analyses and recommendations including 2H:1V slopes, 10-foot wide toe benches, and six-foot wide bonding benches for stability. 

Pedestrian Bridge Investigation

Challenge & Solution

A park in Allegheny County, PA was in need of improvements for the safety of its visitors and natural habitat. Currently, a pedestrian footpath and Frisbee-golf course circle through the park surrounding the lake; however, the path along the southeastern portion of the lake crosses a known wetland and frequently floods. This flooding forces pedestrians to exit the designated path into the wetland area, disturbing the native plant and animal habitats.

Rhea was chosen to investigate the park’s conditions, propose a mitigation plan, and secure a permit for the construction of a bridge to avoid future disturbances.

Project Description & Highlights

The local government and architect proposed the construction of a small pedestrian bridge that would span the wetland area, eliminating disturbance to the surrounding area. Rhea was contracted to perform a wetland delineation study to determine the extent of wetlands present at the proposed construction site.

In order to obtain approval for the bridge construction, Rhea was required to complete the wetland construction permitting process through the Pennsylvania Department of Environmental Protection (PADEP). This process involved further evaluation of existing wetlands, the completion of a Pennsylvania Natural Diversity Inventory (PNDI) search, and the completion and submittal of PADEP-issued permit (BDWM-General Permit-7 for Minor Road Crossings), which involved a site-specific Wetland Mitigation Plan and Erosion and Sediment Control Plan.

Rhea also collected soil borings as part of a geotechnical evaluation to determine soil properties at the proposed bridge foundation locations.

During this project, Rhea followed the PADEP wetland construction permitting process. Although the bridge construction has not yet taken place, Rhea was able to complete all required permitting in a timely manner, allowing this project to progress according to schedule. 

Phase 2 Archaeological Investigation

Challenge & Solution

The federal government recently completed the Grays Landing Lock and Dam that raised the pool elevation of the Monongahela River fifteen feet within the Lower Georges Creek watershed. Prior to the pool change, many cultural resource sites were investigated, excavated, and catalogued. However, the site (36FA434) remained unresolved.

Rhea was contracted to complete a Phase 2 Archaeological Investigation of the site to determine the National Register of Historic Places (NRHP) eligibility. This fast-paced project required the completion of the fieldwork within 2.5 months.

Project Description & Highlights

Located within the flood plain of the Lower Georges Creek Watershed, Site 36FA434 was a historic property that was thought to contain a single family house of D. Hough, a 19th century New Geneva mill owner. The site now resides within the flood pool of Grays Landing Lock and Dam.

Rhea performed approximately 100 one-foot by one-foot shovel test holes across the site along a 10-meter grid pattern to obtain an overall layout of the site. 50 one-foot by one-meter square pits were dug within areas of interest discovered within the shovel pit holes. Areas of interest generally consisted of structure foundations of the house and any related out buildings. Both the shovel pits and meter squares were dug in 10-cm lifts and ended 10 cm into undisturbed natural soils. All soils were screened using a 1/4-inch screen size to locate any artifacts uncovered during the excavations. All subsurface features and artifacts were photographed in accordance with the Pennsylvania Bureau for Historic Preservation Guidelines for Archaeological Investigations.

Artifacts generally consisted of ceramics, glass, rusted metal objects, and other objects. At the conclusion of the fieldwork, all artifacts were cleaned, classified, and tabulated by count and percentage and attributed to their respective soil horizon.

A report presenting the data encountered along with the NRHP eligibility was submitted to the federal government. No further archaeological research was recommended.

Rhea quickly responded to this aggressively paced schedule by coordinating with the field crews, clearing subcontractor, and the property owner so that the field work at the site commenced the same week the Task Order was signed.

UXO Clearance

Challenge & Solution

As mandated by the United States Environmental Protection Agency and supported by state environmental departments, the US military is now limited in the creation of new artillery practice ranges.

This situation poses a significant problem to Mission Sustainment for preparing/training of US troops and development/implementation of new weaponry. As a result, historic range rehabilitation has become a focal point for the military. Unfortunately, many of the historic ranges —  used during the 1940s through 1950s — are unfit for use in their current states due to lack information regarding their prior usage.

Project Description & Highlights

Rhea was contracted by the federal government to perform range clearance for a historical area at a facility in Virginia. The site served as an historic loading and impact area during the 1940s and 1950s, with the adjacent range serving as an aircraft rocket range. Prior usage likely included recoilless rifle ammunition, aircraft rockets, mortars, artillery, rifle grenades and shoulder-launched multipurpose assault weapons.

With no known history of range clearance, it was assumed that sensitive unexploded ordnance (UXO) and materials potentially presenting an explosive hazard (MPPEH) existed in the area.

Rhea employed 19 UXO technicians, qualified per the Department of Defense Safety Explosive Board Technical Paper Number 18, and oversaw the surface clearance of the area. On-site activities included limited vegetation removal in order to access and effectively remove munitions debris (MD) and range debris (RD), clearance of said MD and RD, and blown in place events to effectively render MPPEH and other unsafe RD inert and safe to move.

Close coordination occurred with multiple parties, including Rhea and its government subcontractors.  Rhea cleared over 420 acres for re-use and recycled roughly 90,000 pounds of ferrous material.

Rhea finished under budget and months ahead of schedule.

Installation Restoration Optimization

Challenge & Solution

Two groundwater treatment plants were installed at federal government sites to treat contamination including volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs).  The removal efficiency of the groundwater treatment plants became asymptotic, but the levels of the chemical constituents were still above the federal and state criteria. Because of our closure experience, Rhea was retained to review the plume delineations and develop an optimization plan for the continued use of the groundwater treatment plants, which actively treat the 590 acre site.

Rhea also performed an investigation to locate additional VOC sources of groundwater contamination at the site.  Highly variable contamination levels of PCA and PCE in some of the site recovery wells indicated a potential source area in the vadose zone that becomes saturated during periods of high groundwater.  The goal of the investigation was to improve the subsurface contamination capture, thereby reducing operational time to closure.

Project Description & Highlights

At one site, Rhea determined the groundwater and geology had not been fully characterized for optimal groundwater treatment.  Further, six of the 15 recovery wells had not been properly maintained. At several of the wells, a substantial silt build up was encounteredrather than removing the silt, the pumps had been raised to a higher elevation. Thus, the pump screen had been raised out of the impacted groundwater zone.

Rhea prepared a Work Plan (WP), to better define the vertical and lateral extent of the plume and to optimize the contaminated groundwater recovery.  This project is currently underway, and preliminary sampling has shown that the contaminant plume has migrated beyond the existing remedial system capture zone in some locations.

At the second site, once an Explosive Safety Submission Report was prepared by Rhea, a geophysical survey was performed at the site to assess the possible presence of buried metallic objects. The results indicated several concentrated areas of buried metal.  After preparing a UXO WP and an overall WP, including a Quality Control Plan (QCP), the investigation was performed to delineate the contamination.

After completing the field work, a summary report was prepared with recommendations to accelerate the time for groundwater remediation and cost estimates for each recommendation. The cost savings was estimated to approach $30 million. 

Groundwater Sampling & Analysis

Challenge & Solution

In an effort to achieve groundwater protection standards (GPS) and system closeout, the federal government selected Rhea to monitor, and operate and maintain two closed landfills in Virginia.

Field services include the semi-annual collection of groundwater samples from approximately twenty locations using low flow purging methods; methane monitoring; inspection of cover surfaces, surface water controls, and on-site structures; and grounds maintenance (mowing and cover repairs) at the facilities.  HRC® injections are also conducted at the landfills (i.e., reductive dechlorination of organic contamination exceeding GPS levels) as a barrier treatment to minimize the potential for impacted groundwater to migrate off site.

Project Description & Highlights

The groundwater monitoring program generally includes volatile organic compounds, semivolatile organic compounds, metals, pesticides/ polychlorinated biphenyls, herbicides, and dioxins, but has also included the collection and analysis of total organic carbon, sulfate, volatile fatty acids, and CENSUS DNA samples to aid in the evaluation of the corrective action plan at the site.

Rhea validates the analytical data after each groundwater sampling event.  To minimize the level of effort required for data validation, samples received semi-annually by the analytical laboratory are divided into a maximum of two Sample Delivery Groups (SDGs) at each landfill.  Following validation, the specialist prepares summaries and updates the Electronic Data Deliverable.

Groundwater monitoring reports are submitted to the Virginia Department of Environmental Quality (VDEQ) in accordance with the existing landfill permits.  To date, Rhea has authored or co-authored over 20 major deliverables for these landfills, including numerous remedial measures reports and revisions to the corrective action plan for one of the landfills.

Rhea has provided the federal government with fundamentally sound, cost-effective field services at the landfill facilities since 2006. In 2011, Rhea successfully completed the field work on schedule in the midst of a major revision to one of the landfill permits.

Our knowledge of the old permit, flexibility, and strong relationship with the federal government and the facilities’ personnel allowed us to quickly incorporate changes into the program prior to the finalization of the new permit. 

POL Operations & Maintenance

Challenge & Solution

Rhea was contracted to operate, maintain, and optimize eight petroleum remediation sites at a federal government facility in North Carolina.  These sites had not been optimized nor moved toward closure. Rhea was tasked to do both.

Project Description & Highlights

Since taking over the systems in June 2009, Rhea has made major changes to most of the systems’ operation.  These changes were made in order to prevent frequent system shutdowns and to remediate the contaminated areas.

Many of these systems were constructed in the mid 90s and had remediated part (or all) of the site.  Rhea suggested pursuing No Further Action on one site that showed no contamination.  Rhea has also shutdown wells and parts of an air sparge system where the groundwater was below the remediation standard for more than four quarters. This approach allowed the system to better concentrate on the contaminant “hot spots.”

Communication with the team members is absolutely crucial during O&M activities.  Rhea submits daily reports to the Client and local supervisors. Monthly O&M reports are written to summarize the month’s data that was collected and to make suggestions for operational changes.  These reports are forwarded to the Client and local supervisors.

Rhea prepares Annual Monitoring Reports (AMRs) for each system to summarize the year’s activities and determine the remediation efficiency and progress of the remediation efforts. These reports are submitted to the federal government and other supervising agencies. The AMRs also discuss possible alternatives to the current remediation efforts and identify if site closure should be pursued.

Through excellent operators and constant system optimization, Rhea has increased system operating efficiencies and moved some sites very close to closure. 

Vapor Intrusion Mitigation Design, Installation & Operations

Challenge & Solution

Rhea was contracted to design, install, monitor, and operate a vapor intrusion mitigation (VIM) system at a federal government facility in North Carolina. The facility contains a former fuel farm site that is being remediated. Air sparging and biosparging remediation activities related to the former fuel farm resulted in hydrocarbon vapors seeping into a building at the government facility.

Rhea was contracted to monitor the vapors and provide a remedial solution to both remove vapors from the building and prevent their continued intrusion.

Project Description & Highlights

The goal of this project is to reduce vapor levels within the building to levels below maximum limits approved by base industrial hygiene personnel and/ or the Environmental Management Department (EMD).

Rhea monitored the hydrocarbon vapors surrounding the building as well as potential “hot spots” inside the building.  Based on our knowledge of the site coupled with gauging and free phase product thickness determinations within the area, Rhea provided a design for a vapor intrusion mitigation (VIM) system to recover hydrocarbon vapors within the slab and below grade to prevent vapors from entering the building on site.

Rhea installed a network of vapor extraction points surrounding the building.  These vents were fitted with high efficiency radon fans which created a significant vacuum source which served to draw vapors from beneath the building and actively prevent their intrusion into the breathing zone.

Several of the vent borings were installed at depths that not only removed vapors from below the building but are actively aiding in the further remediation of the former fuel farm area.  In addition, Rhea sealed potential migration points within the building.

Within one week of the VIM system start up, hydrocarbon vapor levels inside the building decreased to below maximum limits approved by the federal government’s industrial hygiene personnel. 

VIM systems are relatively inexpensive and easy to maintain, thus the installation of a VIM system will save our client money by allowing for continued use of the building. 


North Carolina