14-05 Letter from MFRA 03-04-2014infra
engmee- ng planning
March 4, 2014
Mr. Todd Gerhardt, City Manager
Mr. Terry Jeffery, Water Resources Coordinator
City of Chanhassen
770 Market Blvd., PO Box 147
Chanhassen, MN 55317
Subject: PPB Holdings, LP
Lyman Boulevard (CSAH 18) Wetland Mitigation Plan
MFRA #19951
Dear Mr. Gerhardt and Mr. Jeffery:
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CITY OF CN 'A "*6SEN
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MAR n 5 ?014
ENGIMEEFWCI DEPT,.
We have reviewed the Lyman Boulevard wetland mitigation plan prepared by SRF Consulting on January 15, 2014. The
following comments should be included in a revised mitigation plan:
1) Wetland 1A should be noted as fully impacted and included in the mitigation plan since the wetland will be drained
with the proposed street and storm sewer improvement project This has been previously discussed at the Technical
Evaluation Panel meeting on February 19, 2014.
a. Action required: Revise the wetland permit to fully impact wetland 3A and include in the mitigation
requirements.
2) The Lyman Boulevard construction documents show a 24" culvert crossing (near plan Station 209 +50) that conveys
water from the north side of Lyman Boulevard to the south side where the PPB Holdings property is located. Public
water that will be conveyed through the 24" culvert will discharge on private property without an easement or a
defined ditch at a minimum 1% slope to convey the water toward Bluff Creek along the south side of Lyman
Boulevard. The construction plans should be revised to connect this flow of water to the Lyman Boulevard storm
sewer system rather than discharging the water on private property. Alternatively, the water could be conveyed in a
pipe to the northwest corner of the PPB Holding property and discharged to the ditch located west of the PPB
Holdings property.
If the current plan were constructed with the 24" culvert in the current location, without a defined ditch, the project
would have a negative impact on the PPB Holdings property and cause potential flooding on the PPB property. There
will potentially be more water discharging through a 24" pipe rather than the existing 18" culvert crossing, as well the
original roadway culvert was only a 15" culvert. The proposed toe of slope elevation is also 0.5 to 1.0 ft. higher than
the existing road toe of slope, this will as well negatively impact the PPB Holdings property with potential flooding in
the area.
a. Action required: Revise the 24" culvert crossing eliminating the discharge of public water on private
property.
Page 2 of 2
3) The mitigation plan does not identify the complete wetland impact area in the area of Wetland #2 for the construction
project. Along the north line of the PPB Holdings property, the impact area aligns with the toe of slope for the
proposed roadway. The impact area needs to be expanded to account for the full area of wetland impact that results
from the grading operations that will occur beyond the toe of slope where a ditch wit[ be needed to convey the water.
A ditch cross section, similar to the ditch shown from 206 +50 and 207 +00, is required to convey the flow to the west
toward Bluff Creek. The current plan does not show the ditch with a minimum 1% ditch slope to convey the water
from the PPB Holdings property to Bluff Creek.
a. Action required: Revise the mitigation plan to show the complete wetland impact area required for
grading to construct at ditch at the toe of slope with a minimum 1% slope. The easement area needs to
be revised to accommodate the grading of the ditch to provide positive drainage from the PPB Holdings
property.
Thank you for the opportunity to comment on the impact/mitigation plan. We look forward to reviewing the revised
plan that addresses our comments.
Sincerely,
Todd Ullom, WDC Mark Anderson, PE LEED AP
Environmental Scientist Director of Commercial Services