My WebLink
|
Help
|
About
|
Sign Out
Home
Search
07/08/2020 P&Z Packet
LinoLakes
>
Advisory Boards & Commissions
>
Planning & Zoning Board
>
Packets
>
2020
>
07/08/2020 P&Z Packet
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
7/9/2021 3:50:09 PM
Creation date
7/2/2020 11:16:31 AM
Metadata
Fields
Template:
P&Z
P&Z Document Type
P&Z Packet
Meeting Date
07/08/2020
P&Z Meeting Type
Regular
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
104
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
View images
View plain text
Ms. Katie Larsen <br />7/012020 <br />Page 3 <br />After the project is completed, the site will include approximately 8.8 acres of new impervious surfaces <br />including the streets, sidewalks, paths, parking lots, and rooftops. Due to poor soils in the south portion of the <br />site and a high groundwater table in the north portion of the site, infiltration is not feasible. <br />Groundwater was encountered at depths ranging from 4 to 19 feet. Topsoil was encountered at to 1 foot. <br />Below the topsoil, soils consist of glacial outwash sands and native clayey glacial till and are classified as <br />hydrologic groups HSG D in the southern portion and HSG C in the north. <br />The applicant used a HydroCAD model based on the Atlas 14, 24-hour storms to design the storm sewer <br />conveyance system and ponds. The site is designed to reduce site runoff rates for the 2-, 10-, and 100- <br />year rainfall events. <br />Pre- and Post- Development Discharge Rates (cfs) <br />Condition <br />2-Year <br />100-Year <br />Pre -Development <br />189 19.2 <br />46.446.7 <br />103.4103.3 <br />Post -Development <br />12 1 9.8 <br />41 732.2 <br />91.Q 87.0 <br />Post -development stormwater discharge rates are less than the pre -development rates. <br />During the public hearing held at the Planning and Zoning Board meeting on February 12, 2020 there were a <br />number of questions regarding the proposed developments' stormwater management plan. Below is a summary <br />of findings and actions to address the questions: <br />The site outlets to two private ditches, one in the northwest, and one to the north. There is also a small <br />area of the site that drains to the south. <br />The proposed project is required to mitigate surface water and address water quality through City, <br />Watershed District and State Rules and Statues. This includes maintaining the existing rate or reducing <br />the rate of runoff from the site, and providing water quality treatment for the proposed <br />development. The project meets the City of Lino Lakes' stormwater management requirements and <br />RCWD rules. RCWD approved a CAPROC on April 8, 2020. <br />o This project is proposing to reduce rates as detailed in the Stormwater Report, and will utilize <br />stormwater ponding for water quality treatment. The stormwater management plan incorporates <br />existing soils and time of concentrations to calculate the needed ponding systems to mitigate <br />the new impervious surfaces. <br />o The surface water from the new impervious surfaces will be accommodated through three new <br />ponds. Pond 200, located in the middle of the site, will pick up surface water from the south <br />portion of the site and direct it towards Pond 100. Pond 100 will pick up surface water from the <br />northwest portion of the site and discharge to the west to an existing private ditch. Pond 400 will <br />receive the remaining surface water and discharge to an existing ditch to the north. <br />o The design includes a standard outlet control structure with pipe outlet. An outlet control <br />structure is a device that holds water back in the proposed pond and then discharges it slowly <br />into the ditch so that the flow to the downstream ditch is less than the existing condition flow <br />into the ditch. <br />Adjacent property owners expressed concerns over the stormwater runoff from the site and the <br />downstream private ditches. Staff had multiple conversations and Zoom meetings with the property <br />owners to better understand their concerns and explain the existing and proposed conditions. This <br />included an onsite evaluation, reviewing topographic data, record plans, survey, and incorporation of the <br />NorthPointe development drainage plan. The downstream systems appear to be working correctly and <br />the NorthPointe development has reduced the surface water flow to the subwatershed in question. We <br />will continue to work the property owners and provide information and findings. <br />0 2019 was a record year for rainwater in Minneapolis -St. Paul area according to the Minnesota <br />DNR Year to Date Precipitation Chart. Soil saturation in the fall of 2019 was similar to a spring <br />snow melt condition where typically the fall is a dryer condition. These conditions have led to <br />standing water due to soil saturation and higher flows in conveyance systems. <br />0 We are working with one of the downstream property owner to complete culvert maintenance <br />on their property. <br />In addition, we are having the developer verify the downstream conditions to confirm their assumptions. <br />Nadeau Acres Engineering Review <br />
The URL can be used to link to this page
Your browser does not support the video tag.