ITEM 4.2_attachmentReview No. 1
11H
And�erson
ENGINEERING REVIEW
Residential Subdivision
for the City of Otsego
by
Hakanson Anderson
Submitted to: Honorable Mayor and City Council
cc: Lori Johnson, Administrator
Tami Loff, City Clerk
Dan Licht, City Planner
Andy MacArthur, City Attorney
Joe Jablonski, Lennar
Robert Molstad, PE, Sathre-Berquist, Inc.
Reviewed by: Ronald J. Wagner, P.E.
Brent M. Larson, P.E.
Date: March 3, 2016
Proposed
Development: The Lahn Property
Street Location A portion of Section 1, T120, R23. 247+ Acres, N of the Crow
of Property: River and on either side of CSAH 36 (Rawlings Avenue NE).
Applicant: Joe Jablonski
Developer: Lennar
16305 36th Ave. N
Suite 600
Plymouth, MN 55446
Owners of Record: Lennar
Purpose: The Lahn Property is a proposed 346 single family residential
homes, on 247+ acres in the City of Otsego, Wright County,
Minnesota. The proposed development will be served with
municipal water, sanitary sewer, storm sewer, and public streets
typical of an urban setting.
Jurisdictional Agencies: City of Otsego, Wright County, Minnesota Department of
(but not limited to) Health, Minnesota Department of Natural Resources, Minnesota
Pollution Control Agency, Wright Soil and Water Conservation
District.
Permits Required: NPDES, Minnesota Department of Health (water),
(but not limited to) Minnesota Pollution Control Agency (sanitary sewer), and Wright
County
TABLE OF CONTENTS
INFORMATION AVAILABLE
EXISTING CONDITIONS
SUBDIVISION CONFIGURATION, LOT SIZE, DENSITY
STREETS
PRELIMINARY PLAT
TRAFFIC/ACCESS ISSUE
WETLANDS
SURFACE WATER MANAGEMENT
SANITARY SEWER COLLECTION SYSTEM
WATER DISTRIBUTION SYSTEM
ENVIRONMENTAL
OTHER CONSIDERATIONS
SUMMARY AND/OR RECOMMENDATION
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INFORMATION AVAILABLE
ALTA/NSPS Land Title Survey, 2/15/16, by Sathre-Berquist, Inc.
Preliminary Plat of The Lahn Property, 2/15/16, by Sathre-Berquist, Inc.
The Lahn Property EAW
Additional Information
Minnesota Rules, Chapter 4410 — EAW Requirement
City of Otsego Engineering Manual
City of Otsego Zoning and Subdivision Ordinances
National Wetland Inventory Map
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EXISTING CONDITIONS
Existing zoning classifications for land in and abutting the subdivision shall be shown on
the plan. (21-6-2.B.2.) Missing all.
2. Location, size, and elevations of existing storm sewer and culverts, or any other
underground facility within 150 feet of the proposed plat, shall be shown on the plan.
(21-6-2.B.5.) Missing River Place 2"a/3rd Improvements.
3. Boundary lines of adjoining unsubdivided and subdivided land, identified by name and
ownership, shall be shown within 150 feet of the plat. (21-6-2.B.6.) Missing all.
4. Existing 100 -year flood elevations shall be shown on the plan. (21-6-2.B.9.) Shoreland
District must be shown.
5. Provide a legend. Existing well and septic systems within 150' of the preliminary plat
must be shown. Parcels IV Exception Tract 1 and 2 and form yard south of CSAH 36.
6. Section corners and section lines shall be clearly depicted and labeled on the plan. (21-6-
2.A.2.)
7. Revise to Randolf Avenue NE to Randolph Ave NE on all sheets.
The limits of the Shoreland Overlay District shall be shown on the plan.
SUBDIVISION CONFIGURATION, LOT SIZE, DENSITY
Blocks shall be less than 1,200 feet in length. (21-7-3.13) Road 13 as wells as a couple of
block lengths along Road 1 slightly exceeds this. We recommend allowing these
deviations due to topography considerations.
2. Principal building setbacks on Lot 104 and 153 are compromised by wetland setbacks.
3. The purpose and ownership for Outlook K is unclear.
STREETS
Temporary cul-de-sacs shall have a minimum 40' radius and bituminous curb.
PRELIMINARY PLAT
1. Section corners and section lines shall be clearly depicted and labeled on the plan. (21-6-
2.A.2.) Completed.
2. Location, dimensions, and purpose of all proposed easements shall be shown on the plan.
(21-6-2.C.5.) Completed — Temporary construction easement per Document No. 838577
Should be removed.
3. The ROW shall be rounded at intersections parallel to back of curb. (111. 13.)
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4. Normal water elevations and 100 -year peak elevations have been labeled for all ponding
areas, including wetlands, however, 2 -year and 10 -year peak elevations shall be labeled
for each of the stormwater ponds. (Appendix C.6.0.13.)
5. Lots abutting collector streets shall have an additional 10' of width or depth to be
overlaid with a drainage & utility easement for a landscape bufferyard. (20-16-7-D)
6. Lot 72 through 82 Outlot I must encompass all of Pond IW.
7. Outlot 14 must be dedicated to City.
8. Legend must include wetland restoration, wetland, principal builder setbacks, wetland fill
and wetland buffer.
TRAFFIC/ACCESS ISSUE
1. Proposed intersection spacing along Randolph Ave. NE and within the development is
appropriate.
2. Proposed access locations on CSAH 36 appear adequate pending approval of Wright
County Highway Department considering the size of the development north and south of
CSAH 36. An Intersection Control Evaluation (I.C.E.) may be requested by the County
for the Randolph intersection. At a minimum, we would require expansion or pavement
width of CSAH 36 to accommodate dedicated left hand turns. The addition of bypass
waves at Road 7/CSAH6 intersection appears adequate.
WETLANDS
1. Wetlands C, D, E, and F are proposed to be disturbed wetland. Avoidance of wetlands
must be attempted. If wetlands must be disturbed or filled they must be mitigated as per
WCA requirements. (20-16-9.E.2.)
2. A protective buffer of natural vegetation at least 20' wide from the delineated edge shall
surround all wetlands. A principal building setback of 40' from the delineated edge of all
wetlands or 20' from the protective buffer easement, whichever is greater, shall be
provided (20-16-9.E.). Remove protective buffer, setback, and restoration from CSAH
36 right-of-way and wetland DW near the eastern plat boundary and wetland DW near
the intersection of CSAH 36 and Road 1. We recommend renaming one of the wetlands
DW to something unique.
SURFACE WATER MANAGEMENT
1. The Normal, 2 yr, 10 yr, and 100 yr water elevation shall be depicted on the plans for
each basin (Appendix C.6.013). The 10 yr calculations are missing from the stormwater
report and plans.
2. A portion of the North Area discharges to the existing Riverplace Pond 3. We have
reviewed the Stormwater report for Riverplace and this model do NOT account for the
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runoff from this new development. Table 4.8 of the Lennar/Lahn property report
indicates that the pond was remodeled to establish a new HWL elevation (which is lower
than the original proposed HWL, 883.61 vs 884.0, based on new Atlas 14 rainfalls but we
cannot find this model in the report. The Riverplace (RP) Pond 3 calculations shall be
included to show that this additional drainage can be accommodated. (The attached
shows a 61.2 acres "Pond 3 Subarea" from the RP report but the NURP Design for Pond
3 only indicates 26.1 acres flowing to it.)
2. Per City requirements, the post -development runoff rates for both the north and south
areas are less than the pre -development rates though Table 4.3 and 4.4 discharge rates are
lower that we would expect (for both pre and post conditions) due to the off-site
discharges being routed through Links.
3. The hydraulic soils groups indicated are HSG Type C north of CSAH 36 and Type B
south of CSAH 36, which agrees with the NRCS Soils report and soil boring for the site,
therefore both areas require infiltration per the NPDES permit. The calculations
supporting Table 4.5 "Summary of Infiltration Volumes" is required. The models do not
indicate the infiltration ring in any of the ponds and no separate calculations can be
found.
4. The report summarizes the dead storage volumes required for the North and South areas
(per City requirements) in Table 4.2. Looking at the individual pond models for the 2.5"
rain event it appears that some of these ponds have flow out during this event (and
apparently not do to the infiltration ring below the NWL but through the weirs/outlet).
The NURP volume requirements are for each storm water pond and cannot be averaged
over the entire site. Wetlands do not provide/require dead storage as they are not to be
used as treatment. Using them for rate control is acceptable.
SANITARY SEWER COLLECTION SYSTEM
1. The trunk sanitary sewer along Randolph Avenue NE Trunk has sufficient depth and size
to service the area north of the Lahn property and further north. No additional depth or
pipe size is necessary with this development to service areas beyond the project
boundary.
WATER DISTRIBUTION SYSTEM
1. Midblock valve Road 1 between Road 4 and Road 3, and additional valves needed Road
1/Road 9, Road 10/Road 9, Road 13/Road 12.
2. Hydrant at end of lines for flushing and testing purposes end Road 12, Road 5, Road 7
and Road 3, intersection of Road I I/Road 5.
3. Hydrant Coverage appears adequate except in 4 areas, Lot 22, Lot 61, Lot 222, and Lot
281.
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ENVIRONMENTAL
1. The Environmental Assessment Worksheet has been completed. It has been published in
the EQB Monitor and Council has approved.
OTHER CONSIDERATIONS
1. Benchmarks shall be shown on each sheet (see page 7 Section II1.14 of Engineering
Manual).
2. Consideration is needed regarding who owns and will maintain the trails.
SUMMARY AND/OR RECOMMENDATION
We recommend approval contingent on the above comments being addressed.
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