HomeMy WebLinkAbout8A - City of Prior Lake Nondegradation Report
MEETING DATE:
AGENDA #:
PREPARED BY:
AGENDA ITEM:
DISCUSSION:
4646 Dakota Street S.E.
Prior Lake, MN 55372-1714
CITY COUNCIL AGENDA REPORT
NOVEMBER 5, 2007
8A
ROSS BINTNER, WATER RESOURCES ENGINEER
HOLD A PUBLIC HEARING AND CONSIDER APPROVAL OF A
RESOLUTION ACCEPTING THE NONDEGRADATION REPORT FOR THE
CITY OF PRIOR LAKE AND AUTHORIZING STAFF TO PREPARE A
RECORD OF DECISION AND SUBMIT THE REPORT TO THE MPCA FOR
REVIEW.
Introduction
The purpose of this agenda item is for the City Council to hold a public
hearing, approve a resolution accepting the nondegradation report, authorize
staff to prepare a record of decision, and authorize staff to submit the report to
the MPCA for review.
Historv
On March 3, 2006 the Minnesota Pollution Control Agency issued a revised
Municipal Separate Storm Sewer System (MS4) permit that requires permit
holders like the City of Prior Lake to complete analysis and planning to comply
with State and Federal Clean Water Laws. In the effort to stay in compliance
with the revised MS4 permit, the City contracted with WSB and Associates, Inc
to conduct a study and prepare a report that meets the requirement set forth
by the MS4 Permit. The 300-page report is available on the City's online
Laserfiche system in the Current Projects folder, entitled Nondegradation
Report. A three-page executive summary is attached.
Current Circumstances
The modeling and analysis conducted by WSB built off the current city
Geographical Information System (GIS). The study makes assessments of
system-wide pollutant flows in stormwater. Three pollutants were tracked in
the study, they include: Phosphorus, Total Suspended Solids (TSS), and
Volume.
Pollutant flow concepts that were emphasized in the study include:
1. Total pollutants outflow from an area depend on concentrations of
pollution in the storm water and total volume of storm water.
2. Urban Best Management Practices (BMPs) are important pollutant
removal tools.
3. Urbanized land has less concentration of pollution than agricultural
land, but higher volume of stormwater due to impervious surfaces.
www.cityofpriorlake.com
Phone 952.447.9800 / Fax 952.447.4245
These three concepts reinforce the need for stormwater management
practices in urban and agricultural application.
1. It is important to prevent small sources of nutrients from getting into the
drainage system such as soil erosion, leaf and grass clippings or
excess lawn fertilizer.
2. Maintenance of pipes and ponds is critical to providing additional
pollutant removal before the water goes into lakes and wetlands.
3. Effective management of peak and total storm flows helps to promote a
stable drainage system downstream of urban areas.
ISSUES:
Although this was a mandated study, it is the hope of staff that both the
analysis itself and the mapping completed as part of the study will provide a
broader base of knowledge for understanding overall water quality in the City
of Prior Lake.
FINANCIAL
IMPACT:
The contract for nondegradation is on a cost-not-to-exceed basis, so there is
no further fiscal impact for the City. The total cost of the report itself was
$35,694. No glaring issues were found with water quality that would require
additional capital investment as a result of this study; however, current
practices related to the MS4 program and maintenance of current
infrastructure do require the continued allocation of significant resources.
ALTERNATIVES:
1. Hold a public hearing, approve a resolution accepting the nondegradation
report and authorize staff to prepare a record of decision and submit the
report to the MPCA for review.
2. Deny this item for a specific reason and provide staff with direction.
3. Table this item until some date in the future.
RECOMMENDED
MOTION:
Alternative #1.
Revi
iL
4646 Dakota Street S.E.
Prior Lake, MN 55372-1714
RESOLUTION 07 -xx
A RESOLUTION ACCEPTING THE NONDEGRADATION REPORT FOR THE CITY OF
PRIOR LAKE AND AUTHORIZING STAFF TO PREPARE A RECORD OF DECISION AND
SUBMIT THE REPORT TO THE MPCA FOR REVIEW.
Motion By:
Second By:
WHEREAS, The City of Prior Lake is required to comply with its Municipal Separate Storm Sewer
Systems (MS4) Permit; and,
WHEREAS, The 2006-2011 MS4 Permit required the City to complete an analysis of its water
quality and plan for the nondegradation of resources; and,
WHEREAS, The report was forwarded to the Prior Lake Spring Lake Watershed District and the
Scott Watershed Management and opened for public comment, and;
WHEREAS, The City of Prior Lake held the required public hearing on November 5 2007; and,
NOW THEREFORE, BE IT HEREBY RESOLVED BY THE CITY COUNCIL OF PRIOR LAKE,
MINNESOTA as follows:
1. The recitals set forth above are incorporated herein.
2. City of Prior Lake Staff is hereby authorized to create a record of decision for any comments
received and submit the Nondegradation report to the MPCA.
PASSED AND ADOPTED THIS 5TH DAY OF NOVEMBER 2007.
YES
NO
Haugen Haugen
Erickson Erickson
Hedberg Hedberg
LeMair LeMair
Millar Millar
Frank Boyles, City Manager
www.cityofpriorlake.com
Phone 952.447.9800 / Fax 952.447.4245
City of Prior Lake
N ondegradation Report
Executive Summary
The Nondegradation Report outlines the results of a Loading Assessment and presents a
nondegradation analysis that was completed for the City of Prior Lake. The City was designated
by the Minnesota Pollution Control Agency (MPCA) as one of the selected Municipal Separate
Storm Sewer Systems (MS4) required to complete a nondegradation analysis as part of the
National Pollutant Discharge Elimination System (NPDES) requirements. Cities are selected for
this requirement based on high population growth from census data taken from 1990 to 2000 and
projected growth as determined by Metropolitan Council and the State Demographer from 2000
to 2020.
The Nondegradation Standard set forth by the MPCA requires the City to evaluate if there has
been an increase in runoff volume, total suspended solids loading, or phosphorus loading as a
result of development that occurred from 1990 to 2003. The City must also determine if there
will be an increase in these parameters as a result of projected development from 2003 to 2030.
If an increase is anticipated in the future, taking into consideration projected stormwater
management requirements for new development, the City must propose a mitigation plan to
reduce volumes of runoff and pollutant loads to the levels estimated for 1990 conditions.
A summary of the results of the loading assessment is outlined below for each parameter:
1990-2003 2003~2030 1990-2030
Land Use
Agricultural or Open Space Land Developed 1,338 ac 5,414 ac 6,752 ac
Annual Total Phosphorus Loadinl!
Projected annual increase in loading as a result of -1631bs 223 Ibs 60lbs
development prior to application of BMPs
TP Removal by new treatment ponds -366 Ibs -1,474Ibs -1,840 Ibs
(60% removal)
TP Reduction through phosphorus fertilizer ban * * *
(10% reduction in residential land use)
TP Reduction through street sweeping * * *
(5% increase in frequency and efficiency)
TP Reduction through infiltration facilities - * *
(required by City beginning in 2007)
Total Phosphorus Removed bv BMPs -366 Ibs -1,474Ibs -1,840Ibs
Net Chan2e in Phosphorus -529 Ibs -1,251Ibs -1,780Ibs
G:IWater Resourcesl06-07 NondegradationlNondeg Exec Summary. doc
1990-2003 2003-2030 199Q..2030
27 tons 223 tons 250 tons
-117 tons -467 tons -584 tons
* * *
* *
-117 tons -467 tons -584 tons
-90 tons -244 tons -334 tons
1990-2003 2003-2030 1990-2030
Annual RunofTVolumes
Projected annual increase in TUnoffvolumes as a result 398 ac-ft 1,882 ac- ft 2,280 ac-ft
of deyelopment prior to application of BMPs
Eyaporation within treatment ponds -120 ac-ft -487 ac-ft -607 ac- ft
(3 feet annually)
Infiltration within treatment ponds -578 ac-ft -2,339 ac-ft -2,917 ac-ft
(0.03 in/hr oyer 240 days)
Infiltration within infiltration features 0 * *
(required by City beginning in 2007)
Runoff Volume Removed by BMPs -698 ac-ft -2,826 ac-ft -3,524 ac-ft
Net Chanl!e in Runoff Volumes -300 ac-ft -944 ac-ft -1,244 ac-ft
Results of the loading assessment indicate that there is no increase in runoff volumes,
phosphorus loads or TSS loads between 1990 and 2030. Therefore, the City meets the
nondegradation standards of the MPCA and no mitigation plan is necessary.
G: I Water Resources 106-07 NondegradationWondeg Exec Summary. doc