Low Impact Development Manual for Michigan - OSEH - University ...

Additional Maintenance Information for
Infiltration Basins
• Inspect the basin after major storm events and
make sure that runoff drains down within 72
hours. Mosquito’s should not be a problem if the
water drains in 72 hours. Mosquitoes require a
considerably long breeding period with relatively
static water levels.
• Inspect for accumulation of sediment, damage to
outlet control structures, erosion control measures,
signs of water contamination/spills, and slope
stability in the berms.
• Mow only as appropriate for vegetative cover
species.
• Remove accumulated sediment from the sediment
pretreatment device/forebay as needed. Inspect
pretreatment forebay at least one time per year.
• If Infiltration basin bottom becomes clogged, scrape
bottom and remove sediment and restore original
cross section. Properly dispose of sediment.
Additional Maintenance Information for
Dry Wells
• Inspect dry wells at least four times a year, as well
as after every storm exceeding one inch.
• Remove sediment, debris/trash, and any other
waste material from the dry well and dispose of at
a suitable disposal/recycling site and in compliance
with local, state, and federal waste regulations.
• Evaluate the drain-down time of the dry well
to ensure the maximum time of 72 hours is not
being exceeded. If drain down time exceeds the
maximum, drain the dry well via pumping and
clean out perforated piping, if included. If slow
drainage persists, the system may need replacing.
• Regularly clean out gutters and ensure proper
connections to facilitate the effectiveness of the dry
well.
• Replace filter screen that intercepts roof runoff as
necessary.
• If an intermediate sump box exists, clean it out at
least once per year.
Winter Considerations
Most infiltration practices are typically located below
the frost line and continue to function effectively
throughout the winter. It is imperative to prevent salt,
sand, cinder, and any other deicers from clogging the
surface area of infiltration practices by avoiding piling
snow in these areas. Sand and cinder deicers could clog
infiltration devices and soluble deicers such as salt can
damage the health of vegetation.
Cost
The construction cost of many infiltration BMPs can
vary greatly depending on the configuration, location,
site conditions, etc. Following is a summary of both
construction and maintenance costs. This information
should be strictly as guidance. More detailed cost information
should be discerned for the specific site before
assessing the applicability of the BMP.
Dry well* $4-9/ft3
Infiltration basin
Infiltration
trench**
Subsurface
infiltration bed
Construction Costs
Varies depending on
excavation, plantings,
and pipe configuration.
$20-30/ ft3
$13/ ft3
*2003 dollars.
**City of Portland. 2006 dollars.
Maintenance
Costs
5-10% of
capital costs
Disposal costs
5-10% of
capital costs
LID Manual for Michigan – Chapter 7 Page 215