City of Lake Forest’s Plan Review Comments for 27W Dated May 25, 2011

 

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TO: Cathy Czerniak

Director of Community Development

FROM: Engineering

DATE: May 25, 2011

SUBJECT: Plan Review Comments for 27 W Onwentsia 

The Engineering Section reviewed the Engineering Plans prepared by Reed Engineering, LLC with the revision date of 3/7/11 for the proposed residence at 27 Onwentsia Road. Along with the plans the Engineering Section reviewed the “Compensatory Storage Calculations” (dated 3/7/11) undertaken by Manhard Engineering. In addition, the Engineering Section reviewed a letter (dated 5/4/11) from Bleck Engineering which was sent to the Building Review Board (BRB). The Engineering Section also reviewed a response from Reed Engineering (dated 5/23/11) to the aforementioned letter from Bleck Engineering.

This memorandum is being written in an effort to clarify the stormwater issues that are being generated by this proposed development. Before doing so it is important to identify the regulatory agencies responsible for reviewing this proposed development as well as the extent of their responsibilities which are noted as follows:

Lake County Stormwater Management Commission (LCSMC) – Responsibility is limited to oversight of impacts to Isolated Wetlands.

United States Army Corps of Engineers (USACOE) – Responsibility is limited to oversight of impacts to “Waters of the United States‟.  In this case it would involve impacts to the East Skokie River.

Federal Emergency Management Agency (FEMA) – Responsible for approving changes to the Regulatory Floodplain

The City of Lake Forest (City) – Certified community which allows oversight of the Watershed Development Ordinance (WDO). In this particular development the City will be reviewing compensatory storage, conveyance and residential flood-proofing requirements as noted in the WDO.

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Comments in regard to Reed Engineering‟s response to the Bleck letter:

1. The City received a letter (dated 5/6/11) from LCSMC stating that “no further action is required by SMC with respect to the isolated wetlands”.  LCSMC also “has no objection with The City of Lake Forest proceeding with permitting with respect to the WDO”.

2. The City concurs with Reed Engineering‟s explanation.  Since the proposed residence is no longer going to be built on fill above the FPE, (FPE: Flood Protection Elevation = Regulatory Floodplain Elevation + 2 ft.), receiving FEMA concurrence that the new residence would be located outside the Regulatory Floodplain is no longer necessary.  Instead the proposed residence would be built on a foundation elevated above the FPE.  The foundation system would be open to allow flood waters to flow in and out of the foundation area during certain flood events. The foundation system would need to be designed to withstand hydrostatic pressures as well as hydrodynamic forces. Construction materials below the FPE must be resistant to flood damage. Electrical, heating, ventilation, plumbing and air conditioning equipment will need to be located above the FPE.  This type of residential construction is allowable in accordance with Art. IV.C.2.f.(1)(b) of the WDO.

3. The proposed site plan includes the installation of a storm sewer that will discharge stormwater from the site into the East Skokie River.  A Wetland Delineation Study will need to be undertaken to determine whether the area that will be disturbed to accommodate the proposed storm sewer is located within a wetland.  The owner will need to acquire a permit or a letter of  “No Objection‟ from the USACOE.  This issue must be addressed prior to the issuance of a permit from the City.

4. The 3-7-11 Compensatory Storage Calculations have been reviewed and approved by the City.  If revisions are being proposed the City must review and approve those revisions before any permits are issued.

5. Additional exhibits depicting the 10 and 100 year flood elevation limits may be provided at the discretion of the owner.

6. The type of vegetation that can tolerate prolonged periods of flooding will be addressed on the Landscape Plan.

7. The BFE for the site is 659.4.

8. The owner must accommodate offsite tributary flows and intends to accomplish that through overland flow routes and storm sewers within the subject property.

9. The engineer noted that there will be access to all areas of the property in order to provide maintenance of the vegetation.

10. The engineer stated that the height of some of the vegetation will reach 7 ft., while the grasses and forbs reach a maximum height of 3-4 ft.

11. The location, size and number of vents within the foundation system will need to meet the applicable provisions of the WDO.

12. The existing storm sewer located on the property is privately owned. (?)

13. Snow removal is the responsibility of the owner.

14. The compatibility of the retaining wall material with the architecture and landscape design is outside the scope of engineering.

15. The design of the retaining wall will need to be sealed by a Professional Structural Engineer.

16. The owner will have to remove any stockpiled material out of the floodway when encountered.

17. The site plans do not show locations of any stockpiles which are not permissible in the floodplain.

The construction of the proposed residence has stormwater drainage issues not only on the entire property, but directly affiliated with the structure itself.  During the review process we need to ensure that not only the site, but the structure meets the provisions of the WDO.  Most notably, Art.IV.C.2.f.(1)(b) of the WDO as mentioned in Comment #2 above.

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About Onwentsia Memorandum

I am a long time LF homeowner who has been witnessing an expansion of standing water each year getting deeper and wider. Each Spring, the next generation of ducks appear to raise their ducklings. But this year is different. Their habitat has been altered.
This entry was posted in All Important Information Found Here, Building Review Board Meetings, Lake Forest Engineering, Letters, Email, Etc., Maps, Site Plans, Engineering Designs, Schematics, etc., Regulatory Agencies, USACOE, FEMA, IL-DNR, LCSMC, City of Lake Forest. Bookmark the permalink.

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