1. Decreased velocity
    2. Pollution control/water quality
      1. 7.5 Mined Lands
    3. 7.6 Stormwater Management Near Water Supply Wells
    4. Stormwater infiltration BMPs near water supply wells

Pennsylvania Stormwater Best Management Practices Manual
Chapter 7
Decreased velocity
Increased vegetation density / vegetated swales
Terraced slopes
Rip rap (preferably using carbonate rock)
Pollution control/water quality
Filter berms
Gravel or sand filtration systems
Peat moss or activated carbon filtration
Constructed wetlands (lined)
Increased vegetation density / rain gardens
Rip rap
7.5 Mined Lands
Disturbed lands that have been strip or surface mined, or are underlain by deep mine
excavations, are one of the most difficult areas on which to apply stormwater BMPs. The
drainage of rainfall that has percolated through residual mine wastes on the land surface, or
infiltrated the existing land surface and drained into deep mines and subsequently found its way
to the surface from mine tunnels, has produced one of the most severe water quality conditions in
Pennsylvania. Thousands of miles of streams within the state are devoid of aquatic life because
of the extreme acidity of surface waters that are polluted by abandoned mine discharges. This
condition is considered by most experts to be the single greatest pollution issue in the state,
simply because it has no obvious or easy solution.
Since this acid drainage from abandoned mines begins as rainfall on the surface, the obvious
solution would seem to be to redirect any rainfall away from any surface materials containing
mine wastes, and assure that as little infiltration as possible took place above deep mine layers.
The exclusion of all infiltration BMPs in these areas would negate many of the BMPs described in
Chapter 6, other than the vegetated roof systems and the capture/reuse measures. One
important consideration is that the use of vegetation to remove or change the chemical form of
pollutants in acid mine drainage could also include the pollutant load from new impervious
surfaces where suitable. A great deal of research has been directed toward the use of wetland
systems as passive AMD treatment technologies (PADEP, 2005). These systems form part of a
larger strategy for abandoned mine reclamation (PADEP, 1998) in those watersheds where the
problem is widespread.
All of this very important water quality research does not address the specific problem created by
new development or redevelopment on mined lands. Where the potential exists for runoff from
new development to come into contact with mine wastes, then surface drainage design should
convey runoff to surface swales and channels free of any mine waste residual. If detention basins
are used for rate mitigation, they should be lined if situated on surface mined lands or over deep
mines. Water quality measures will need to rely on intensive maintenance programs for new
development, and control of pollutant application, especially fertilizers, herbicides and pesticides.
If porous pavements are designed, the sub-surface beds must be lined, so that the primary
function will be detention rather than volume reduction by infiltration. Finally, the land
development plan should place special emphasis on protection of existing vegetation and
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Pennsylvania Stormwater Best Management Practices Manual
Chapter 7
restoration of new woodlands, because they offer the best method of healing and restoring these
damaged lands.
Stormwater Management Near Water Supply Wells
Pennsylvania ranks third in the nation for the total number of public water supply wells, and nearly
half of Pennsylvania’s 12 million residents get drinking water directly from ground water sources.
It is critical that stormwater BMPs be designed to remove pollutants from stormwater that is to be
infiltrated in close proximity to public or private water supply wells, and be sufficiently isolated
from ground water supply sources.
Water supply wells in Pennsylvania generally pump water from two types of aquifers,
unconsolidated aquifers and consolidated rock or fractured-bedrock aquifers. Unconsolidated
aquifers are composed of sands, silts and gravel. They are generally unconfined and close to the
surface, have high porosity and a high measure of permeability. Water moves into and through
unconsolidated aquifers readily. These aquifers are generally limited to major stream valleys, the
Atlantic Coastal Plain and the glaciated northeast and northwest regions of the state. Fractured-
bedrock aquifers are the most widespread and commonly exploited aquifers in the state. They
may be bedrock layers composed of sandstone, shale, or carbonate rocks such as limestone and
dolomite but they can also be layered or irregular bodies of crystalline rocks such as gneiss,
schist, granite and diabase. Ground water in bedrock aquifers can occur in either unconfined or
confined conditions. Fractured-bedrock aquifers have low primary porosity and ground water is
mainly stored in openings between rock layers and in fractures throughout the rock. Water moves
into and through these aquifers much more slowly than in unconsolidated aquifers. Exceptions
occur in limestone and dolomite where dissolution of the rock increases the size and frequency of
the fractures and therefore increases secondary porosity and permeability. Some Pennsylvania
public water supply wells in limestone and dolomite aquifers produce larger volumes of water
than do wells in unconsolidated aquifers.
Stormwater infiltration BMPs near water supply wells
Pennsylvania’s Safe Drinking Water Regulations (25 Pa. Code § 109) establish a three-tiered
approach to wellhead protection of public ground water supplies. Zone I is the innermost
protective zone surrounding a well, spring or infiltration gallery that may range from a radius of
100 to 400 feet depending on site-specific source and aquifer characteristics. The water supplier
must own this area or substantially control activities within the zone that could potentially harm
quality or quantity of the source. Zone II is the capture zone that encompasses the portion of the
aquifer through which water is diverted to a well or flows to a spring or infiltration gallery. Zone II
is defined as a one-half mile radius around the source unless a more rigorous hydrogeologic
delineation is performed. Zone III is the area beyond the capture zone that contributes significant
recharge to the aquifer within the capture zone. For more detailed information about protecting
underground drinking water supplies, please refer to the Department’s Source Water Protection
Infiltration BMPs should not be located within Zone I wellhead protection areas. In addition,
extreme caution must be exercised when planning stormwater infiltration BMPs for use in
delineated Zone II areas or for use in areas within one half mile
of public water supply wells. This
is especially important where the water supply wells are in unconsolidated aquifers or bedrock
aquifers of fractured limestone of dolomite. These easily recharged aquifers can become
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