Dig a hole in the proposed location,
approximately 12 inches in depth
and four to six inches in diameter. An
auger or posthole digger is the
typical tool of choice
1.
Record measurements. Drop, d, is the
difference between measurements.
Infiltration rate is the drop, d, divided
by the time interval, 1 hour or less. For
the final rate, use the lowest steady
state infiltration rate or the average of
all infiltration rates, whichever is
lower.
Measure the distance from the stick to
the water surface at least every hour for
four hours or until hole is dry. If presoak
drains within 1 hour, measure every 10
minutes or less.
3. 4.
Presoak the hole. Fill with water to
saturate the soil and then let stand
until all the water has drained into
the soil. If presoak drains away
within 1 hour, repeat presoak.
2.
Once the water has drained, refill the
empty hole again with water so that the
water level is about one inch from the
top of the hole. Use a stick to indicate
the location of the starting water level.
Record the time using a watch.
5.
Time
(hours)
Measurement, m
(inches)
Drop, d
(inches)
Infiltration rate, i
(inches/hour)
0.00 --------------------
0.00
This is the approved infiltration test for the Virginia Conservation Assistance Program. Use this method for Rain Gardens, Dry Wells
and any practice without an underdrain. This is a 3-dimensional flow percolation test. Actual vertical infiltration rates may be less.
Divide the final rate by 2 if the failure of the practice will exacerbate existing resource concerns or create new ones. Infiltration rates
should generally be greater than 0.5 inches per hour.
Falling Head Infiltration Test
Virginia Conservation Assistance Program (VCAP) v.2018
Final rate
Mandatory Minimum Infiltration Test Procedure
