Pollution UpDate
12 December 1997
"Pollution UpDate" is a publication dedicated to the reporting of timely environmental news.
Environmental activists with story ideas or comments can e-mail gateway@rayproffitt.org . I'd like to thank the readers of Pollution UpDate for their comments and suggestions, and DEP for giving us plenty to write about.
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ROUTE 220 IMPROVEMENTS PROJECT (I-99) ROUTING ALIGNMENT ALTERNATIVES - SECTION 1 (BALD EAGLE TO PORT MATILDA) HYDROGEOLOGY FOR THE RIDGE WETLANDS AND SEEPS
by David Coleman Moshannon Group, Pa. Sierra Club
The Ridgeside (RT-G) alignment is designed to traverse up and down the ridge to avoid wetlands and seeps that are on the ridgeside. However, the alignment does adversely effect the very environmental resources it is designed to preserve by significantly altering the hydrology that the ridgeside wetlands and seeps depend on.
Groundwater Baseflow, which the ridgeside wetlands and seeps depend on most during periods of little precipitation and drought, will be severely reduced by:
* Draining the groundwater table above the highway cut through exposed saturated bedrock.
* Reducing permeable surface area with pavement and cut slopes, thereby reducing groundwater recharge.
* The removal of groundwater storage volume with the million cubic yards of earth removed associated with the RT-G cuts.
The RT-G alignment will not alter the amount of rainfall on the ridge. However, the alignment will change the way in which that rainfall is used. The highway cut associated with RT-G will force rainfall and groundwater drained from the cut slopes to the surface.
This surface water will not recharge the groundwater aquifer. During drought conditions, the wetlands will not receive the amount of groundwater baseflow that they are accustomed to, and had developed from. The surface water that does reach the wetlands will be laden with road salts, oils and other contaminants from the highway, and will be delivered mostly only during periods of heavy rainfall.
PennDot has countered the delineation of these obvious impacts with skewed and misleading "water budget" computations for the wetlands. PennDot has clearly employed some very shaky, probably intentional, data manipulation to arrive at their preconceived conclusions.
Although receiving the "Record of Decision" from the Federal Highway Administration, PennDot still has not secured the necessary permits for constructing I-99 on Bald Eagle Ridge. The U.S. Corps of Engineers has yet to issue the Section 404 (b) (1) permit for the project. The Corps has made it clear that reinfiltrating these intercepted waters back into the ground is critical to their review of the project impacts and the issuance of a permit. PennDot is proposing a concept plan to reinfiltrate captured waters back into the groundwater aquifer.
The "mitigation" proposed is the construction of a "reinfiltration trench" to reinfiltrate captured waters of the RT-G cuts. This trench would be roughly 10 foot square in cross section and as long as necessary (currently 5000 feet) to reinfiltrate the calculated flowrates from the RT-G cut slopes of exposed bedrock. There are several technical problems with this proposed "concept plan":
* PennDot has not demonstrated that the concept plan is effective or feasible; rather, it has only sized a reinfiltration trench based on inappropriate and misapplied factors.
* PennDot did not employ true maximum discharge rates, safety or replacement factors in the sizing of the necessary reinfiltration trenches. The use of these factors would result in a calculated sizing too large to be considered feasible. This is even true allowing the liberal associated hydraulic conductivity for the reinfiltration trenches utilized by PennDot.
* Recharge, and the resulting Discharge in cut exposed bedrock, varies with precipitation and ET conditions (rates); whereas, the proposed reinfiltration system is designed to receive average rates. The soaking rain events will not have a chance to fill up (charge) the aquifer. Only the amount (PennDot's current estimate of 42 gpm) during the rain event plus the residual discharge after the storm has ended would be reintroduced into groundwater. However, how much residual discharge would there be if the aquifer above the cut is dry (drained) prior to the soaking event?
* The Concept Plan, if implemented, will surely fail to reintroduce the necessary groundwater flow to the South Bald Eagle Creek Headwater Wetland, and will be exceedingly costly.
The RT-G alignment will adversely effect the hydrology of the ridge ecosystem. It is impossible to construct a highway on the side of the ridge without severely impacting everything downgradient. The complex ridge wetland and seep ecosystems cannot be replaced (mitigated). What would be lost with the RT-G cuts is not only a vast groundwater recharge area, but also a large groundwater storage reservoir. The relatively minuscule size of the reinfiltration trenches will not even begin to serve the function of the natural ridge hydrogeology that would be removed.
Please call or write the Corps and state that you do not think that PennDot can adequately protect the wetlands at the base of Bald Eagle Ridge with their reinfiltration concept plan. Tell them that you do not feel it is prudent to waste a 600 to 900 foot swath of forested ridgeside to construct I-99. Tell them that there are better alternatives to RT-G.
U.S. Army Corps of Engineers
CENAB-OP-RX
Post Office Box 1715
Baltimore, MD. 21203-1715
Phone: (410) 962-1843 and 6086
Fax: (410) 962-6024
E-Mail: Brian.Yanchik@nab02.usace.army.mil