april 6, 2016 board meeting packet

Our Mission is to protect, manage and improve the water resources of Capitol Region Watershed District

Regular Meeting of the Capitol Region Watershed District (CRWD) Board Of Managers, for Wednesday, April

6, 2016 6:00 p.m. at the office of the CRWD, 1410 Energy Park Drive, Suite 4, St. Paul, Minnesota.

REGULAR MEETING AGENDA

I. Call to Order of Regular Meeting (President Joe Collins)

A) Attendance

B) Review, Amendments and Approval of the Agenda

II. Public Comment For Items not on the Agenda (Please observe a limit of three minutes per person.)

III. Permit Applications and Program Updates (Permit Process: 1) Staff Review/Recommendation, 2) Applicant Response, 3) Public Comment, and 4)

Board Discussion and Action.)

A) Permit # 11-002 Fairview Ave. Closeout (Hosch) B) Permit # 12-029 Arlington Rice Closeout (Hosch) C) Permit # 13-030 Western U Plaza Amendment (Hosch) D) Permit # 15-011, Ziitel Greenhouse Demo Closeout (Hosch) E) Permit # 15-032 Victoria Park East Trails (Kelley) F) Permit # 16-009 Jackson Street Downtown Improvements (Kelley) G) Permit Program/Rules Update (Kelley)

IV. Special Reports Eustis Street Regional Modeling, Anna Eleria

V. Action Items A) AR: Approve Minutes of the March 16, 2016 Regular Meeting (Sylvander) B) AR: Approve Minutes of the March 25, 2016 Special Meeting (Sylvander) C) AR: Approve Minutes of the March 30, 2016 Board Workshop (Sylvander) D) AR: Approve Comment Letter for West Midway Industrial Area (Zwonitzer) E) AR: Approve Cost Share Grant for Frogtown Farms (Castro)

VI. Unfinished Business A) FI: Snelling Midway Redevelopment Update (Eleria) B) FI: Targeted Watershed Grant Application Update (Zwonitzer) C) FI: Pierce Butler Route Stormwater Basin Update (Kelley/VanPatten) D) FI: Crisis Communication Plan Update (VanPatten)

VII. General Information A) Board Workshop Topics

VIII. Next Meetings

A) Thursday, April 14, 2016 CAC Meeting B) Tuesday, April 19, 2016 Metro MAWD Meeting, 7:00 PM, CRWD Offices C) Wednesday, April 20, 2016 Board Meeting

IX. Adjournment W:\04 Board of Managers\Agendas\2016\March 2, 2016 Agenda Regular Mtg.docx

Materials Enclosed

Our Mission is to protect, manage and improve the water resources of Capitol Region Watershed District.

DATE: March 31, 2016

TO: CRWD Board of Managers

FROM: Elizabeth Hosch

RE: Permit Closeouts

Background

Construction activity is complete for permits #11-002, Fairview Ave., #12-029, Arlington-Rice, and

#15-011, Ziittel Greenhouse Demo.

Issues

Fairview Ave. #11-002

This City of St. Paul street reconstruction project has been completed and the disturbance has been

stabilized. Stormwater treatment accomplished through the use of banked volume credits. Gross

pollutant removal is provided in the form of 9 sumped/snouted manholes that are being maintained by

the City. As a public project, no surety was required.

Arlington-Rice #12-029

This City of St. Paul street reconstruction project has been completed and the disturbance has been

stabilized. Stormwater treatment accomplished through the use of banked volume credits. As a public

project, no surety was required.

Ziittel Greenhouse Demo #15-011

Final inspection has been conducted to confirm final stabilization and construction of this demolition

project. The permit was issued for erosion and sediment control requirements only. As a public project,

no surety was required. The site will be further disturbed and used this coming season as a community

garden, a use that does not trigger CRWD Rules though sediment controls will be employed.

Action Requested

Approve Certificate of Completion for permit #11-002, Fairview Ave.

Approve Certificate of Completion for permit #12-029, Arlington-Rice.

Approve Certificate of Completion for permit #15-011, Ziittel Greenhouse Demo

W:\07 Programs\Permitting\Board Memos\2016-04-06 Permit Closeout Board Memo.docx

April 6, 2016

III. Permit Applications

(A, B, D) Permit Close

Outs (Hosch)

Capitol Region Watershed District Permit 13-030A Western U Plaza

Permit Report 13-030A Board Meeting Date: 04-06-2016

Applicant: Leo Draveling

Sand Construction, LLC

46 4th Street

Saint Paul, MN 55101

STAFF RECOMMENDATION: Approve with 4 Conditions:

1. Provide plans signed by a professional engineer per the Minnesota Board of AELSLAGID. The

Overall Site Plan is not signed and is noted as preliminary.

2. Document that all roof runoff from the Parcel A building is directed to the underground system

as indicated on the drainage area map.

3. Verify and revise, if necessary, the invert elevation of the rock and 48 pipes in HydroCAD.

The pipes are typically set 6 inches above the invert of the rock. Elevations in HydroCAD shall

reflect the as-built survey.

4. Revise the as-built survey and HydroCAD to include the infiltration system outlet structure.

The HydroCAD model shall use the as-built elevations.

Consultant:

Description: Amend existing permit to build out Parcel A

Stormwater Management: Use of banked volume requested, from underground infiltration system on-site

District Rule: C, D, E, F

Disturbed Area: 0.18 Acres

Impervious Area: 0.16 Acres

Permit Location

Aerial Photo

University Ave.

Wes

tern

Ave

.

W:\07 Programs\Permitting\2013\13-030 Western U Plaza\13-030 Permit_Review_04_EMH.doc

Page 1 of 4

Capitol Region Watershed District

Permit Report

CRWD Permit #: 13-030A

Review date: March 21, 2016

Project Name: Western U Plaza Parcel A Amendment

Applicant: Jamie Thelen

Sand Companies

46 E Fourth St.

St. Paul, MN 55101

Purpose: Amendment to Permit 13-030 to include Parcel A in the site plan

and stormwater management design. Overall project has included

demolition of a portion of existing building and addition of parking

structure, apartment complex, and underground infiltration system.

Location: Southeast corn of the intersection of University Avenue West and

Western Avenue.

Applicable Rules: C, D, E and F

Recommendation: Approve with 4 Conditions

EXHIBITS:

1. Western U Plaza Storm Water Management Plan (includes Narrative, Figure 1.1,

HydroCAD model, volume control worksheet), by MSA Professional Services,

dated 8/14/14, recd. 8/15/14.

2. Design Plans (sheets C1, C2, C.3, C4, C5, C6), by Paramount Engineering &

Design, dated 7/16/14, recd. 7/15/14.

3. Letter to CRWD, by Sand Companies, Inc., dated 3/16/16, recd. 3/16/16.

4. ALTA/ACSM Land Title Survey, by Bohlen Surveying & Associates, dated

12/10/15, recd. 3/16/16.

5. Overall Site Plan, by Sand Architects, not dated, recd. 3/16/16.

6. Stormwater Management Plan, by MSA, dated 4/16/15, recd. 3/16/16.

HISTORY & CONSIDERATIONS:


Page 2 of 4

Parcel A was shown on the 2013 plans approved by CRWD as a future building. The

owner now desires to construct the building and use the infiltration system constructed in

2013 to manage stormwater from Parcel A.

RULE C: STORMWATER MANAGEMENT

Standards

Proposed discharge rates for the 2-, 10-, and 100-year events shall not exceed existing rates.

Developments and redevelopments must reduce runoff volumes in the amount equivalent to an inch of runoff from the impervious areas of the site.

Stormwater must be pretreated before discharging to infiltration areas to maintain the long-term viability of the infiltration area.

Developments and redevelopments must incorporate effective non-point source pollution reduction BMPs to achieve 90% total suspended solid

removal.

Findings

1. A hydrograph method based on sound hydrologic theory is used to analyze

runoff for the design or analysis of flows and water levels.

2. Runoff rates for the proposed activity do not exceed existing runoff rates for

the 2-, 10-, and 100-year critical storm events. Stormwater leaving the project

area is discharged into a well-defined receiving channel or pipe and routed to a

public drainage system.

3. Stormwater runoff volume retention is achieved onsite in the amount

equivalent to the runoff generated from 1.1 inch of rainfall over the

impervious surfaces of the development.

a. The total amount of proposed impervious onsite is 54,058 square feet.

This includes approximately 44,791 square feet for the 2013

application and approximately 7,897 square feet for the 2016

Amendment.

b. CRWD amended the volume control rule in 2015. Therefore, the

current volume control standard is different than when the application

was approved in 2013. Volume retention summary:

Permit Application

Volume

Retention

Requirement

(cu. ft.)

Volume

Retention

Provided

(cu. ft.)

2013 Application 4,054

10,366 2016 Amendment 724

Total 4,778

c. Excess volume retention of 5,588 cubic feet remains in the bank

unused.


Page 3 of 4

d. Infiltration volume and facility size has been calculated using the

appropriate hydrological soil group classification and design

infiltration rate.

e. The infiltration area is capable of infiltrating the required volume

within 48 hours.

f. Stormwater runoff is pretreated to remove solids before discharging to

infiltration areas.

4. Alternative compliance sequencing has not been requested.

5. Best management practices achieve 90% total suspended solids removal from

the runoff generated on an annual basis.

6. A recordable executed maintenance agreement has been submitted.

7. Adequate maintenance access is provided for surface and/or underground

system. A site specific plan, schedule, and narrative for maintenance of the

proposed stormwater management practices has been submitted.

RULE D: FLOOD CONTROL

Standards

Compensatory storage shall be provided for fill placed within the 100-year floodplain.

All habitable buildings, roads, and parking structures on or adjacent to a project site shall comply with District freeboard requirements.

Findings

1. There is floodplain on the property according to FEMA.

2. It is not known if the building proposed on Parcel A complies with CRWD

freeboard requirements.

RULE E: WETLAND MANAGEMENT

Standard

Wetlands shall not be drained, filled (wholly or in part), excavated, or have sustaining hydrology impacted such that there will be a decrease in the

inherent (existing) functions and values of the wetland.

A minimum buffer of 25 feet of permanent nonimpacted vegetative ground cover abutting and surrounding a wetland is required.

Findings

1. There are no known wetlands located on the property.

RULE F: EROSION AND SEDIMENT CONTROL

Standards

A plan shall demonstrate that appropriate erosion and sediment control measures protect downstream water bodies from the effects of a land-

disturbing activity.

Erosion Control Plans must adhere to the MPCA Protecting Water Quality in Urban Areas Manual.


Page 4 of 4

Findings

1. Erosion and sediment control measures are consistent with best management

practices, as demonstrated in the MPCA manual Protecting Water Quality in

Urban Areas.

2. Adjacent properties are protected from sediment transport/deposition.

3. Wetlands, waterbodies and water conveyance systems are protected from

erosion/sediment transport/deposition.

4. Project site is greater than 1 acre; an NPDES permit is required. A SWPPP has

been submitted and satisfies NPDES requirements.

RULE G: ILLICIT DISCHARGE AND CONNECTION

Standard

Stormwater management and utility plans shall indicate all existing and proposed connections from developed and undeveloped lands for all water

that drains to the District MS4.

Findings

1. New direct connections or replacement of existing connections are not

proposed.

2. Prohibited discharges are not proposed.


Conditions:

1. Provide plans signed by a professional engineer per the Minnesota Board of

AELSLAGID. The Overall Site Plan is not signed and noted as preliminary.

2. Document that all roof runoff from the Parcel A building is directed to the

underground system as indicated on the drainage area map.

3. Verify and revise, if necessary, the invert elevations of the rock and 48 pipes in

HydroCAD. The pipes are typically set 6 inches above the invert of the rock.

Elevations in HydroCAD shall reflect the as-built survey.

4. Revise as-built survey and HydroCAD to include the infiltration system outlet

structure. The HydroCAD model shall use the as-built elevations.

Capitol Region Watershed District Permit 15-032 Victoria Park Trails East

Permit Report 15-032 Board Meeting Date: 04/06/2016

Applicant: Diane Nordquist

St. Paul Planning and Economic Development

25 W Fourth Street, Suite 1300 CHA

St Paul, MN 55102


1. Provide a copy of the NPDES permit.

Volume Bank Recommendation:

Approve withdrawal of 1,874 cubic feet from the St. Paul Parks and Recreation Volume Reduction

Bank.

Consultant: Eric Klingbeil

TKDA, Inc

444 Cedar Street, Suite 1500

St. Paul, MN 55101-2140

Description: Construction of new trails at Victoria Park

Stormwater Management: Soil amendments to reduce and disconnect runoff, small rock trenches to promote infiltration

excess treatment at filtration basin for Stuart Street, and volume bank credits

District Rule: C, D, F Disturbed Area: 2.25 Acres


Permit Location

Aerial Photo

First Street

Secon

d A

ve

W:\07 Programs\Permitting\2015\15-032 Victoria Park East Trails\15-032 Victoria Park Trail_R2.doc Page 1 of 5


Permit Report

CRWD Permit #: 15-032

Review date: March 22, 2016

Project Name: Victoria Park Trail East Improvements

Applicant: Diane Nordquist

Saint Paul Planning and Economic Development

25 West Fourth Street


651-266-6640

[email protected]

Purpose: Construct and expand walking and biking trails.

Location: Victoria Park, intersection of W. 7th St. and Otto Ave, St. Paul

Applicable Rules: C, D, and F

Recommendation: Approve with 1 Condition

Volume Bank Approve withdrawal of 1,874 cubic feet from the St. Paul Parks

Recommendation: Volume Reduction Bank.

EXHIBITS:

1. 2015 Victoria Park Trail Improvement Memorandum, by TKDA, dated 8/26/15,

recd. 9/1/15.

2. Victoria Park Trail Improvement Plan Set (Sheet C1-C9 and L1-L2), by TKDA,

dated 8/19/15, recd. 3/18/16.

3. NOAA Atlas 14, dated 8/18/15, recd. 9/1/15.

4. HydroCAD Report, by TKDA, dated 3/9/16, recd. 3/18/16.

5. CRWD Permit 11-023 Victoria Park Memorandum, by TKDA, dated 10/8/15,

recd. 9/1/15.

6. Permit 14-022 Victoria Park South Stormwater, by CRWD, dated 9/26/2014,

recd. 9/1/15.

7. Drainage Report Bluff Street Improvements, by TKDA, dated 8/9/2012, recd.

9/1/15.

8. Memo to CRWD, by TKDA, dated 3/18/16, recd. 3/18/16.



Additional work adjacent to the 15-032 application was previously approved under

permits 11-023, 14-022, 15-025, and 15-026.


Standards





removal.

Findings

1. A hydrograph method based on sound hydrologic theory is used to analyze






3. Stormwater runoff volume retention is not achieved onsite in the amount



a. The amount of proposed impervious onsite is 26,136 square feet.

a. Volume retention required:

26,136 ft2 x 1.1 inches x 1 ft/12 inches = 2,396 ft3

Volume

Retention

Required

(cu. ft.)

BMP

Volume

Retention

Provided below

outlet (cu. ft.)

1.1 inch

Runoff

(cu. ft.)

2 inch

Runoff

(cu. ft.)

2,396 Soil Amendment 744 998 1,815

b. Filtration using sand media (55% credit) is proposed due to bedrock

conditions; filtration required:


(2,396 ft3 744 ft3) x 1.82 credit factor = 3,006 ft3

Filtration

Volume

Required

(cu. ft.)

BMP

Filtration

Volume

Provided below

outlet (cu. ft.)

1.1 inch

Runoff

(cu. ft.)

2 inch

Runoff

(cu. ft.)

3,006 Filtration basin 245 (assuming 70 x 7 x 0.5) 312 567

Stuart Street Basin Excess 887 - -

Total 1,132

c. Banking of excess volume retention is not proposed.

d. Infiltration volume and facility sizes have been calculated using the

appropriate hydrological soil group classification and design infiltration

rate.

e. The infiltration areas are capable of infiltrating the required volume

within 48 hours.

f. Stormwater runoff is pretreated to remove solids before discharging to

infiltration areas.

4. Alternative compliance sequencing has been requested due to bedrock and

steep slopes.

a. The applicant partially complied with the volume retention standard.

b. The project does not exceed the cost cap of $18,000

c. The applicant requests withdrawal of 1,874 cubic feet of qualified

banking credits for the balance of the volume retention requirement.

5. Practices do not achieve 90% total suspended solids removal from the runoff

generated on an annual basis.

6. The City of St. Paul has a standing Memorandum of Understanding for

maintenance with CRWD. Adequate maintenance access is provided for the

surface systems.


Standards



Findings

1. There is no floodplain on the property according to FEMA.

2. It is unknown if all habitable buildings, roads, and parking structures on or

adjacent to the project site comply with CRWD freeboard requirements.

However, adequate conveyance has been provided to prevent flooding.



Standard



A minimum buffer of 25 feet of permanent nonimpacted vegetative ground cover abutting and surrounding a wetland is required.

Findings



Standards




Findings



Urban Areas.





been submitted and satisfies NPDES requirements.


Standard



Findings


proposed.

2. Prohibited discharges are proposed.

Recommendation: Approve with 1 Condition

Conditions:



Volume Bank Recommendation:

Approve withdrawal of 1,874 cubic feet from the St. Paul Parks and Recreation

Volume Reduction Bank.

Capitol Region Watershed District Permit 16-009 Jackson Street

Permit Report 16-009 Board Meeting Date: 04-06-2016

Applicant: Kevin Nelson

St. Paul

25 West Fourth Street (900 CHA)

St. Paul, MN 55102


1. Provide a site specific plan, schedule and narrative for maintenance of the proposed stormwater management

practices that includes the following: Items a-c attached

2. Provide plans signed by a professional engineer per the Minnesota Board of AELSLAGID.


4. Revise SWPPP to include the following: Items a-d attached

5. Provide a subwatershed delineation diagram consistent with the drainage area calculations.

6. Revise filtration BMPs: Items a-e attached

Consultant: Chad Setterholm

SEH

3535 Vadnais Center Drive

Vadnais Heights, MN 55110

Description: Reconstruction of Jackson Street and addition of permeable pavement bikeway from 11th to Shepard

Stormwater Management: Permeable asphalt, tree trenches, and stormwater planters

District Rule: C D F Disturbed Area: 6.6 Acres


Permit Location

Aerial Photo

W:\07 Programs\Permitting\2016\16-009 Jackson Street\16-009 Permit_Review_Jackson Street_01fjk.doc

Page 1 of 5


Permit Report

CRWD Permit #: 16-009

Review date: 3/22/16

Project Name: Jackson Street

Applicant: Chad Setterholm, SEH Inc.

3535 Vadnais Center Drive


[email protected]

651-490-2000

Purpose: Street reconstruction and addition of bike trail

Location: Jackson Street between 11th Ave to Shepard Road

Applicable Rules: C, D, and F


EXHIBITS:

1. Stormwater Design Narrative, by SEH Inc., dated 3/16/16, recd. 3/18/16.

2. Site Plan Set, by SEH Inc., dated 3/14/16, recd. 3/18/16.

3. Updated BMP Plan Sheets (Sheets 96, 97, 98, 99, 100, 101, and 103), by SEH

Inc., dated 3/14/16, recd. 3/21/16.


None.


Standards




Page 2 of 5



removal.

Findings

1. A hydrograph method based on sound hydrologic theory is not used to analyze






3. Stormwater runoff volume retention is not achieved onsite in the amount



a. The amount of proposed impervious onsite is 286,957 square feet.

b. Volume retention required:

286,957 ft2 x 1.1 inches x 1 ft/12 inches = 26,304 ft3

Volume

Retention

Required

(cu. ft.)

BMP

Volume

Retention

Provided below

outlet (cu. ft.)

1.1 inch

Runoff

(cu. ft.)

2 inch

Runoff

(cu. ft.)

26,304 None, filtration is proposed.

c. Filtration using sand media (55% credit) is proposed due to poor soils

and site constraints; Filtration required:

26,304 ft3 x 1.82 credit factor = 47,826 ft3

Filtration

Volume

Required

(cu. ft.)

BMP

Filtration

Volume

Provided below

outlet (cu. ft.)

1.1 inch

Runoff

(cu. ft.)

2 inch

Runoff

(cu. ft.)

47,826

Biorention BMP A 439 1,200 2,183

Biorention BMP B 239 2,206 4,010

Biorention BMP C 197 472 857

Biorention BMP D 255 808 1,469

Permeable Pavement 15,297 5,077 9,231

Total 10,361 cf

d. Banking of excess volume retention is not proposed.

e. Filtration volume and facility sizes have not been calculated using the

appropriate hydrological soil group classification and design filtration

rate.

f. It is not known if the filtration areas are capable of filtering the

required volume within 48 hours.


Page 3 of 5

g. Stormwater runoff is pretreated to remove solids before discharging to

filtration areas.

4. Alternative compliance sequencing has been requested.

a. The applicant partially complied with the volume retention standard.

b. The applicant did not partially comply with the volume retention

standard at an offsite location or through the use of qualified banking

credits.

c. The applicant has not submitted money to be contributed to the

Stormwater Impact Fund.

d. The project is linear, and the cost cap has been reached. The cost cap

for this project is set at $168,000 and the applicant proposes $363,280

for stormwater management.

5. Best management practices do not achieve 90% total suspended solids

removal from the runoff generated on an annual basis. The project is linear

and the applicant satisfies the gross pollutant removal requirement.

6. A memorandum of agreement for maintenance of stormwater facilities exists

between the City of St. Paul and the CRWD. Adequate maintenance access is

not provided for the surface system. Maintenance agreement does not include

a site specific plan, schedule, and narrative for maintenance of the proposed

stormwater management practices.


Standards



Findings

1. There is a floodplain on the property according to FEMA.

2. The total floodplain impact is 0 cubic feet.

3. Compensatory storage is not needed.

4. It is not known if all habitable buildings, roads, and parking structures on or

adjacent to the project site comply with CRWD freeboard requirements.

However, adequate conveyance of stormwater has been provided to prevent

flooding.


Standard



A minimum buffer of 25 feet of permanent non-impacted vegetative ground cover abutting and surrounding a wetland is required.


Page 4 of 5

Findings



Standards




Findings



Urban Areas.





been submitted and does not satisfy NPDES requirements.


Standard



Findings


proposed.

2. Prohibited discharges are not proposed.


Conditions:

1. Provide a site specific plan, schedule and narrative for maintenance of the

proposed stormwater management practices that includes the following.

a. Establish a watering plan that extends a minimum of one year after

planting.

b. At a minimum, require annual maintenance of filtration areas to include

trimming vegetation, replacing vegetation where needed, mulch

replacement, and removal of accumulated sediment and debris.

c. At a minimum, require annual maintenance of pervious pavement to

include vacuuming of accumulated sediment and repairs where needed.


Page 5 of 5

2. Provide plans signed by a professional engineer per the Minnesota Board of

AELSLAGID.


4. Revise SWPPP to include the following:

a. Filtration perimeter control and erosion control practices shall remain in

place until the final completion of the project or vegetation has been

established (whichever is later).

b. Installation of filtration practices shall be done during periods of dry

weather and completed before a rainfall event. Placement of engineered

soils shall be on dry native soil only.

c. Engineered soil shall remain uncontaminated (not mixed with other soil)

before and during installation.

d. During construction, stormwater must be routed around filtration areas

until all construction activity has ceased and tributary surfaces are cleaned

of sediment.

5. Provide a subwatershed delineation diagram consistent with the drainage area

calculations.

6. Revise filtration BMPs:

a. Adjust the draintile layout to use the filtration media (at least 18) to

separate the filtration storage volume from the outlet device (i.e. pipe or

draintile). This will increase the available volume retention. See attached

sketches. Previous tree trench cross-sections were acceptable because

water in the void volume below the 18 tree media would infiltrate rather

than be routed downstream.

b. Provide maintenance access to the underdrain system using riser pipes or

other approved practices.

c. Provide invert elevations for the tree trench media, filtration media, and

drain tile that demonstrate the system will have a flat bottom (0% slope) or

add a note to each detail stating the system shall be installed with a flat

bottom (0% slope). This will provide the greatest volume retention.

d. Install curb cuts upstream of all catchbasins to preferentially direct runoff

into the filtration BMPs before discharging to the storm sewer.

e. Demonstrate that the BMPs draw down within 48 hours.

Our Mission is to protect, manage and improve the water resources of Capitol Region Watershed District.

DATE: April 1, 2016 TO: CRWD Board of Managers FROM: Anna Eleria, Planning, Projects and Grants Program Manager RE: Eustis Street Regional Modeling Project

Background Last summer, CRWD, in partnership with City of Lauderdale and Ramsey County, began evaluating opportunities for managing stormwater runoff in a portion of the City of Lauderdale. Originally the focus of the project was to evaluate the feasibility of implementing green infrastructure practices along Eustis Street south of Larpenteur Avenue and within an adjacent County-held drainage easement. Based on further discussions with project partners and the private property owner during this evaluation, localized flooding concerns were raised and the project scope was expanded to a regional analysis of the hydrologic and water quality concerns within approximately 150 acres. It also included identification of potential flood mitigation and water quality improvement solutions in the study area. Update Barr Engineering has completed the enclosed draft Eustis Street Regional Modeling Project Report. They have estimated the 10- and 100-year flow rates and pollutant loading for the subwatershed and the current pollutant removal efficiencies of several dry and wet ponds and evaluated and compared alternatives to mitigate flooding and improve water quality. Staff will present the scope of work and results of the project and seek input on the findings and recommendations from the Board. A hard copy of the draft report is available upon request. Action Requested Accept the Eustis Street Regional Modeling Report enc: Draft Eustis Street Regional Modeling Report W:\06 Projects\Lauderdale\Eustis Street Stormwater Improvement Project\Board Memos\BM Eustis Street Regional Modeling 04-06-16.docx

April 6, 2016 Board Meeting IV. Special Report - Eustis Street

Regional Modeling Project (Eleria)

Technical Report: Eustis Street Regional Modeling

Capitol Region Watershed District Saint Paul, MN Barr Engineering Co. December 2015

DRAFT


BY CAPITOL REGION WATERSHED DISTRICT

Barr Engineering Co.

Lauderdale, Minnesota December 2015

DRAFT

i W:\06 Projects\Lauderdale\Eustis Street Stormwater Improvement Project\Feasibility Study\Report\Third Draft\EustisRegionalModeling_Report_122115.docx


December 2015

Contents 1.0 Background ................................................................................................................................................................................ 1

1.1 Purpose ........................................................................................................................................................................... 1

1.2 Background and Scope ............................................................................................................................................. 1

1.3 Study Area ...................................................................................................................................................................... 3

2.0 Hydraulic and Hydrologic Modeling ................................................................................................................................ 5

2.1 Field survey of stormsewer network .................................................................................................................... 5

2.2 Delineation of Subwatersheds and Field Review ............................................................................................ 5

2.3 Hydrologic Modeling ................................................................................................................................................. 5

2.3.1 Land Use and Imperviousness ............................................................................................................... 5

2.3.2 Soils and Infiltration ................................................................................................................................... 6

2.3.3 Watershed Width and Slope .................................................................................................................. 6

2.3.4 Rainfall ............................................................................................................................................................. 6

2.4 Hydraulic Modeling .................................................................................................................................................... 9

2.4.1 Stormsewer and Stormsewer Inlets ..................................................................................................... 9

2.4.2 Open-channels and Overflow Conduits ............................................................................................ 9

3.0 Water Quality Modeling ......................................................................................................................................................10

3.1 Hydrologic Modeling ...............................................................................................................................................10

3.2 Hydraulic and Particulate Modeling ..................................................................................................................10

4.0 Modeling Results ...................................................................................................................................................................11

4.1 Hydraulic Results .......................................................................................................................................................11

4.2 Water Quality Results ..............................................................................................................................................15

5.0 Potential Watershed Improvements ..............................................................................................................................21

5.1 Flood Mitigation ........................................................................................................................................................21

5.1.1 Earthen Berm in Ravine ..........................................................................................................................23

5.1.2 Expansion of Wet Pond (CB99013) ....................................................................................................24

5.1.3 Expansion of Dry Pond and Sheet Pile Wall (CB99027) .............................................................25

5.1.4 Expansion of Dry Pond and Earthen Berm (CB99027) ...............................................................26

DRAFT

ii W:\06 Projects\Lauderdale\Eustis Street Stormwater Improvement Project\Feasibility Study\Report\Third Draft\EustisRegionalModeling_Report_122115.docx

5.1.5 Expansion of Storage at Confluence (CB99029) ...........................................................................27

5.1.6 Combined Flood Mitigation Alternative ..........................................................................................27

5.2 Water Quality ..............................................................................................................................................................33

5.2.1 Redevelopment of Wet Pond (CB99013) ........................................................................................33

5.2.2 Conversion of Dry Pond to Wet Pond (CB99027) ........................................................................33

5.2.3 Conversion of Dry Pond to Wet Pond with IESF (CB99027) ....................................................34

5.2.4 Residential Rain Gardens .......................................................................................................................35

5.2.5 BMP Cost and Cost-Benefit ..................................................................................................................37

6.0 Recommendation ..................................................................................................................................................................39

7.0 References ................................................................................................................................................................................42

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List of Tables Table 1 Directly connected impervious fraction by surface type and land use.......................................... 7

Table 2 Horton infiltration parameters by hydrologic soil group .................................................................... 7

Table 3 Selected Atlas 14 design event inundation elevations.......................................................................11

Table 4 Comparison of peak outflow rates. ............................................................................................................12

Table 5 Average annual TSS and TP load reduction ...........................................................................................15

Table 6 Storage and peak flow comparison at the proposed earthen berm. ...........................................24

Table 7 Storage and peak flow comparison at the proposed expanded wet pond. ..............................25

Table 8 Storage and peak flow comparison at the proposed expanded dry pond and sheet pile wall. .........................................................................................................................................................................26

Table 9 Storage and peak flow comparison at the proposed expanded dry pond and earthen berm. ......................................................................................................................................................................27

Table 10 Flood mitigation alternative hydraulic summary. .................................................................................29

Table 11 Flood mitigation alternative capital costs and annualized costs. ..................................................32

Table 12 Annual TSS and TP reduction at proposed redeveloped wet pond. ............................................33

Table 13 Annual TSS and TP reduction provided by conversion of dry pond to wet pond. .................34

Table 14 Annual TSS and TP reduction provided by conversion of dry pond to wet pond with IESF and earthen berm. ...................................................................................................................................35

Table 15 Residential rain garden sizing. .....................................................................................................................35

Table 16 Annual water load, TSS, and TP reduction provided by residential rain gardens. ..................35

Table 17 Water quality BMP capital cost, annualized cost, and cost-benefit. .............................................38

Table 18 Proposed alternative capital cost, annualized cost, and cost-benefit. .........................................41

List of Figures Figure 1 Concrete swales located near 1568 Eustis Street (junction of swales, north-west swale,

east-west swale)................................................................................................................................................... 2

Figure 2 Eustis Street study area ..................................................................................................................................... 4

Figure 3 Eustis Street hydrology ..................................................................................................................................... 8

Figure 4 Design event inundation area ......................................................................................................................13

Figure 5 10-year design event pipe capacity ...........................................................................................................14

Figure 6 Areal TSS loading ..............................................................................................................................................16

Figure 7 Areal TP loading ................................................................................................................................................17

Figure 8 Water quality treatment .................................................................................................................................18

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iv W:\06 Projects\Lauderdale\Eustis Street Stormwater Improvement Project\Feasibility Study\Report\Third Draft\EustisRegionalModeling_Report_122115.docx

Figure 9 TSS load reduction............................................................................................................................................19

Figure 10 TP Load reduction .............................................................................................................................................20

Figure 11 Rating curve for combined outflow from the 24-inch and 36-inch outlet pipes at the confluence of the concrete swales. ............................................................................................................22

Figure 12 Existing condition outflow hydrograph from the confluence of the concrete swales...........22

Figure 13 Flood Mitigation Alternative. ........................................................................................................................30

Figure 14 Existing condition compared to combined flood mitigation alternative for 10-year design event. .......................................................................................................................................................31

Figure 15 Existing condition compared to combined flood mitigation alternative for 100-year design event. .......................................................................................................................................................31

Figure 16 Residential Rain Gardens ...............................................................................................................................36

Figure 17 Profile: Dry Pond Expansion and Conversion to Wet Pond..............................................................39

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1.0 Background 1.1 Purpose The purpose of this technical report is to summarize regional modeling efforts to determine the 10- and 100-year flow rates and pollutant loading for the watershed tributary to the concrete swales near 1568 Eustis Street in Lauderdale, Minnesota. 10- and 100-year flows were evaluated by creating a hydraulic and hydrologic model of the 148-acre drainage area to the concrete swales, and localized flooding was evaluated. Additionally, a water quality model of the drainage area was created to assess the total suspended solids (TSS) and total phosphorus (TP) removal efficiency of several dry and wet ponds tributary to the concrete swales.

The developed water quantity and water quality models were used to evaluate the impact of several flood mitigation alternatives and water quality projects throughout the study area. Water quality improvement projects evaluated were targeted at portions of the study area which were identified as having little or no water quality treatment. Flood mitigation alternatives were evaluated with the goal of protecting the apartment complex immediately northeast of the concrete swales during the 10- and 100-year design storm events, and minimizing inundation of the apartment complex parking lot during the 10-year event.

Flood inundation and water quality modeling methodology and modeling results are outlined in Sections 1.0 through 4.0 of this report. Flood mitigation alternatives and water quality improvement projects evaluated are discussed in Section 5.0.

1.2 Background and Scope At the request of City of Lauderdale, Ramsey County, and the property owner of 1568 Eustis Street, Capitol Region Watershed District (CRWD) has determined the capacity and potential flooding concerns of a concrete swale drainage system located in the city of Lauderdale near 1568 Eustis Street (Figure 1). The swale system (Figure 2) consists of two concrete swales which drain to the 36-inch and 24-inch outlet pipes shown in Figure 1. The north-south swale and east-west swale are roughly 125 and 220 feet long, respectively. Both swales are, on average, four feet wide, and have a maximum depth of six to nine inches. The total drainage area to the east-west swale is 129 acres. The drainage area to the north-south swale is 15 acres, and direct drainage area to the confluence of both swales (subwatershed CB99029 in Figure 2) is 4 acres, leading to a total drainage area of 148 acres.

City staff and the landowner (Aspen Waste Management) state that the parking lot adjacent to the concrete swales (shown in Figure 2) frequently floods, requiring tenants of a nearby apartment complex to avoid the low area in the southwest portion of the parking lot during heavy rainfall events (see signage in Figure 1). To evaluate the hydraulic performance of the concrete swale drainage system and assess the extent of localized flooding, a hydraulic and hydrologic model of the total 148-acre drainage area (Figure 2) was created using XP-SWMM version 2014.

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Figure 1 Concrete swales located near 1568 Eustis Street (junction of swales, north-west swale, east-west swale)

The stormsewer network in the 148-acre drainage area to the concrete swale system was digitized from stormsewer alignments and as-builts received from Ramsey County and the Cities of Falcon Heights and Lauderdale. The as-builts and alignments had complete data coverage of Larpenteur Avenue West through the project area, as well as small portions of Eustis Street, Carl Street, Pleasant Street, and Coffman Street. All other stormsewer in the watershed (an estimated 60-70% of stormsewer in the drainage area), was generated from field inspection surveys conducted by CRWD and Barr Engineering Co (Barr) staff. Final stormsewer data, created by combining available data from as-builts and alignments with data collected during field inspection surveys, was used to evaluate the hydraulic performance and flood inundation throughout the 148-acre drainage area.

Additionally, water quality performance of several ponds upstream of the east-west concrete swale was evaluated using the P8 (Program for Predicting Pollution Particle Passage through Pits, Puddles, and Ponds) Urban Catchment Model. Data from the final XP-SWMM model; as well as pond outlet information and bathymetry data from field investigations; and as-builts were used to create device and watershed modeling parameters used in the P8 model. Below is a summary of tasks performed to complete the water quality model and hydraulic and hydrologic analysis of the concrete swale drainage system:

1. Create modeled stormsewer network by combining data from as-builts and alignments with data collected during field survey inspections.

2. Delineate and field-verify subwatersheds to the location of localized flooding and nearby storm sewer inlets.

3. Develop an XP-SWMM model of the study area to assess the hydraulic performance of the concrete swale system and evaluate localized flooding.

4. Develop a P8 model to evaluate TSS and TP loading within the drainage area, as well as assess the TSS and TP removal efficiency of four (4) dry and wet ponds.

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1.3 Study Area The study area includes all potential sources of direct drainage to the concrete swales near 1568 Eustis Street. This area is generally bounded to the North, East, South, and West by Ione Street, North Cleveland Avenue, West Hoyt Avenue, and Eustis Street, respectively. The extent of the 148-acre drainage area, subwatershed divides, and the location of localized flooding is shown in Figure 2.

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FalconHeightsLauderdale

SaintPaul

N Eust

is St

N Raym

ond Av

e

N Hyth

e St

Eustis S

t

W Hoyt Ave

Northrop Ave

VincentAve

Folwell Ave

W Dudley Ave

W Hendon AveComo Ave

N Grantham St

Ione St

N Branston StN Bran

ston St

N Eust

is St

W Buford Ave

Idaho Ave

Fulham

St

N Chel

msford

St

Burton

Ave

Pleasa

nt St N

Carl St

Lake S

t N

Fulham

Ave

Carl St

N Fulh

am St

N Brom

pton S

t

Coffma

n Ave

Larpenteur Ave W LarpenteurAve W127

128

456730456730

CB99022CB99023CB101

CB105BCB99016

CB99014

CB112

AP115 SD132

CB143A

CB143A

SD149

CB99029CB99028

CB99020CB99013

CB99027

CB99007

CB99004

CB99001

SD144A

CB99018SD1552 CB99017

MH1540CB99015

MH118A

MH113A MH123MH128

MH136 MH141 MH147 MH153

CB99002CB99003

CB99006

CBMH102

SD130A

CB99008CB99009

CB99010

CB99012

CB99011

CB99019CB99021CB99024

CB99026CB99025

CB1536

Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX,Getmapping, Aerogrid, IGN, IGP, and the GIS User Community

Barr Footer: ArcGIS 10.3, 2015-12-14 14:21 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 2 - Study Area.mxd User: MBM

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Figure 2EUSTIS STREETSTUDY AREAEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

Municipal BoundarySubwatershed BoundaryStormsewer

Concrete swale system near1568 Eustis Street Lauderdale, MN

Dry pond south ofIdaho Ave (CB99027)

Wet pond eastof Carl St (CB99013)

Wet pond northof Larpenteur (CB99014)

Dry pond northof Folwell Ave (CB99004)

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2.0 Hydraulic and Hydrologic Modeling

2.1 Field survey of stormsewer network As discussed in Section 1.2, the as-builts and alignments from Ramsey County and the Cities of Lauderdale and Falcon Heights covered roughly 30 percent of the total stormsewer located within the 148-acre drainage area. The remaining stormsewer was digitized from field surveys conducted by CRWD and Barr staff (two surveys completed June 25, 2015 and July 1, 2015). During field surveys, staff measured relative depths to inverts and pipe sizes using a laser-sight depth meter, which allowed the survey to be performed without entry into the structures. Relative depths were later compared to LiDAR data at the horizontal location where each data-point was collected to determine the elevation of the pipe inverts. Measured inverts and pipe sizes aligned well with available as-built data. The final modeled stormsewer network (Figure 2) is the combination of as-built and collected field survey data.

2.2 Delineation of Subwatersheds and Field Review Barr delineated subwatersheds throughout the 148-acre drainage area to catch basin clusters and storage areas (low areas, ponds, etc.) using the data sources outlined below:

High resolution (1-meter grid resolution) LiDAR data for Ramsey County collected in 2011.

As-builts of stormsewer received from Ramsey County and the Cities of Falcon Heights and Lauderdale.

Stormsewer data collected during two field surveys conducted by CRWD and Barr staff.

Divides were field-verified during stormsewer field surveys. Figure 2 shows the final subwatershed divides used in XP-SWMM and P8 modeling efforts. A total of 49 subwatersheds were defined within the study area, ranging in area from 0.1 to 13 acres, with an average area of three (3) acres.

2.3 Hydrologic Modeling The XP-SWMM model was developed using similar hydrologic parameters as those used in the 2012 XP-SWMM Trout Brook Interceptor (TBI) model for the CRWD. Calibration parameters used in the TBI 2012 study pertaining to various Horton infiltration parameters and impervious depression storage were not applied to this project area, as drainage to the concrete swale is not ultimately tributary to the TBI. The following sub-sections outline hydrologic modeling methodology and assumptions developed for the XP-SWMM model.

2.3.1 Land Use and Imperviousness The same methodology used in the 2012 XP-SWMM TBI model to define land use and related imperviousness was used in this study to calculate total impervious area, directly connected impervious area, and impervious depression storage for each of the 49 subwatersheds in the study area. A vector-

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based impervious dataset received from CRWD (Figure 3), delineating impervious area surface type, was used to calculate the total impervious area for each subwatershed. To calculate the directly connected impervious area, the impervious dataset was intersected with the 2010 Metropolitan Council land use data (also provided by CRWD). Directly connected impervious fractions for each impervious surface type and land use combination (Table 1) were applied and used to calculate the fraction of total impervious which is directly-connected. Impervious depression storage of 0.06-inches and impervious Mannings roughness of 0.015 was assumed, consistent with the hydrologic parameters used in the 2012 XP-SWMM TBI model.

2.3.2 Soils and Infiltration Soil and infiltration assumptions were designed to match assumptions made for the 2012 XP-SWMM TBI model. The infiltration modeling parameters were based on Horton infiltration, and infiltration modeling parameters for pervious areas were defined by hydrologic soil group (Table 2). Final infiltration parameters were determined by calculating the area of each hydrologic soil group in each subwatershed from a vector-based file received from CRWD (Figure 3).

2.3.3 Watershed Width and Slope Watershed width is a parameter used in XP-SWMM to define subwatershed time of concentration, as described in the SWMM users manual, Storm Water Management Model; Version 4 Users Manual, U.S. EPA 1988. Matching the methodology outlined in the 2012 XP-SWMM TBI model, watershed width was calculated by dividing the area of each subwatershed by the longest flow-path length within the subwatershed (Figure 3). Slope was calculated using the same 30-meter slope grid dataset used in the 2012 XP-SWMM TBI model. The average slope of each subwatershed was calculated from this dataset using zonal average data processing techniques.

2.3.4 Rainfall The Atlas 14 100-year, 24-hour and 10-year, 24-hour events were modeled using the National Resources Conservation Service (NRCS) MSE3 rainfall distribution. Atlas 14 depths were developed from the centroid of the watershed area. The 10- and 100-year cumulative depths modeled were 4.24 and 7.43 inches, respectively.

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Table 1 Directly connected impervious fraction by surface type and land use

Impervious Surface Type

Alley

Parking Lot

Structure Tennis Court

Road Driveway Sidewalk

Directly Connected Impervious Fraction

Land Use Type All All Downtown &

Urban Others All All All

Downtown & Urban

Others

Commercial 100 100 100 80 0 100 100 100 75 Industrial 100 100 100 100 0 100 100 100 100 Institutional 100 100 100 50 0 100 100 100 50 Residential Low Density 100 100 0 0 0 100 100 0 0 Residential High Density 100 100 100 50 0 100 100 100 50 Parks and Open Space 100 100 50 50 0 100 100 25 25 Undeveloped 100 100 100 75 0 100 100 0 0 Water N/A N/A N/A N/A N/A N/A N/A N/A N/A Roads 100 100 100 100 0 100 100 100 100

Table 2 Horton infiltration parameters by hydrologic soil group

Horton Infiltration Parameters Hydrologic Coil Group Description Parameter Unit A B C D Initial Infiltration Rate fo in/hr 5 3 2 1 Saturated Infiltration Rate fc in/hr 0.38 0.23 0.1 0.03 Infiltration Decay Constant k sec-1 0.00115 0.00115 0.00115 0.00115

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Figure 3EUSTIS STREET HYDROLOGYEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

Impervious SurfaceParking LotRoadsStructureAlley

Soil TypeABCDWATERSubwatershed BoundariesLongest Flow Path

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2.4 Hydraulic Modeling Hydrographs generated from hydrologic modeling of subwatersheds within the project area were routed to stormsewer inlets or to the location of flooding via overland conveyances. Where inlet control and stormsewer surcharging were possible; storage, overflow conduits, and hydraulic control structures were included to accurately account for all potential sources of overland flow to the location of flooding.

2.4.1 Stormsewer and Stormsewer Inlets As discussed in Section 2.1, stormsewer throughout the 148-acre drainage area was digitized from as-builts, alignments, and data from two field surveys. To ensure consistency throughout the model, hydraulic parameters were generated based on methodology and data sources outlined in Section 3.3 of the 2012 TBI model report. A typical reinforced concrete pipe (RCP) Mannings roughness value of 0.013 was assumed, and entrance and exit losses assigned to each individual pipe segment were referenced from the Wurbs and James 2002 Water Resources Engineering textbook. Flared end section (FES) inlets were modeled as having grooved ends, projecting from the surrounding surface. Complex riser-outlet structures on two ponds were modeled based on measured dimensions from field surveys and received as-builts. Riser inlets were modeled as a weir and orifice in series. Modeling the outlet in this fashion ensures that weir flow is correctly controlling at low depths over the riser, and orifice flow becomes controlling as depth increases. Weir and orifice discharge coefficients were modeled consistent with the 2012 XP-SWMM TBI model.

2.4.2 Open-channels and Overflow Conduits Open-channels and overflow conduits were modeled within the project area to convey overland flow and surcharged flow from the stormsewer. Road overflows were modeled using one of two typical section geometries (modeled in XP-SWMM as natural sections). One typical road overflow type was based on the dimensions of Larpenteur Avenue West, and one was created to be typical of area-residential roads. Street flow Mannings roughness was assumed to be 0.013. Overland flow is conveyed to wet and dry ponds in several areas via rocky and earthen ditch channels. Ditch channels were modeled as trapezoidal sections in XP-SWMM based on field observation notes related to channel width, typical channel depth, and side-slope. Mannings roughness values applied to ditch channels were based on field notes related to the material composition of the ditch (e.g., large stones and cobbles, weedy earthen channel, etc.). Assumed values were then based on published roughness values listed in Bedient, Huber and Vieux 2008 Hydrology and Floodplain Analysis.

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3.0 Water Quality Modeling 3.1 Hydrologic Modeling Many of the hydrologic parameters used in the P8 sediment transport model were calculated using the same methodology outlined in Section 2.0 (e.g., directly connected impervious fractions, pervious and impervious depression storage, etc.). The only hydrologic parameter calculated that was unique to the P8 water quality model was pervious Curve Number. Because P8 is designed for long-term simulation of sediment transport, hydrologic modeling is simplified by using the SCS Curve Number Method. Curve Numbers for pervious surfaces were taken from the USDAs 1986 Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds. Pervious surfaces were assumed to be grass covered and in good conditions. Pervious Curve Number values were then based on soil type, with values of 39, 61, 74, and 80 being assigned to A, B, C, and D hydrologic soil groups, respectively. Continuous simulation was performed for a period of 30 years (1984 through 2013) using precipitation and daily average temperature data pulled from the Minneapolis-Saint Paul International Airport.

3.2 Hydraulic and Particulate Modeling The XP-SWMM model (discussed in Section 2.0) was used to generate all hydraulic data used in the P8 model. Ponds with simple outlet structures (i.e., flared end sections) were modeled as pond type devices with the outlet pipe diameter matching the size in the existing XP-SWMM model. Ponds with complex-riser outlet structure were modeled as general devices, which allows for the modeling of a user-defined rating curve. Rating curves for general devices were pulled directly from the XP-SWMM model. Because P8 models sediment settling, the bathymetric volume of each pond must be entered into the model to allow for the correct calculation particulate settling and associated pollutant removal. Pond bathymetry of the two wet ponds in the study area were developed from received bathymetric as-builts, or calculated using an average depth measured in the field. Particulate properties (e.g., setline velocity, particle size fractions, event-mean contaminant concentrations, etc.) were assumed to match the NURP 50 percent (NURP50) P8 particle file. NURP50 particulate properties are assumed to be typical of urban stormwater, and are based on data collected under the EPAs Nationwide Urban Runoff Program (NURP, Athayde, 1983).

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4.0 Modeling Results 4.1 Hydraulic Results The extent of localized flooding was evaluated by modeling the Atlas 14 10- and 100-year, 24-hour events using the XP-SWMM model described in Section 2.0. As outlined in Section 2.3.4, the cumulative depths of the 10- and 100-year Atlas 14 design events are 4.24 and 7.43 inches, respectively. Inundation elevations of selected subwatersheds are outlined below in Table 3. Additionally, inundation areas developed from the Atlas 14 design events are shown in Figure 4.

Table 3 Selected Atlas 14 design event inundation elevations

Description

Storage Overflow

Elev.1

Atlas 14 Design Events, Max Elev. (ft)

Subwatershed 10-yr, 24-hr 100-yr, 24-hr CB99013 Wet pond east of Idaho Ave. 941.5 942.1 942.7 CB99027 Dry pond southwest of wet pond. 913.0 914.1 914.9 CB99029 Concrete swales and parking lot. 899.82 899.2 900.9

1 Storage overflow elevations are taken from 2011 Ramsey County LiDAR and have not been ground surveyed 2 The overflow elevation for the concrete swale system is the low elevation along the south retaining wall adjacent to the east-west swale.

As shown in Table 3 and Figure 4, inundation of the parking lot near 1568 Eustis Street occurs during both the 10-year and 100-year, 24-hour events. Flooding of this parking lot has been reported to occur during moderately intense rainfall events, and the model confirms that frequent flooding of the parking lot is likely, given that the model suggests that most of the parking lot area inundates during the 10-year, 24-hour event. Modeling of the 100-year, 24-hour event shows that capacity issues at the concrete swale drainage system shown in Figure 1 may cause the apartment complex to the northeast to be impacted by flood inundation during that rainfall event. Survey of low-entry to the apartment complex should be collected to determine if the apartment is impacted based on the 100-year event MWSE.

The maximum water surface elevation (MWSE) within many storage subwatersheds coincides with the peak inflow rate. This suggests peak inundation elevations are driven by outflow capacity issues. Figure 5 shows where pipe capacity issues exist during the modeled 10-year, 24-hour Atlas 14 event. Pipes displayed in red were found to be under-sized to convey the 10-year design event. In this analysis, a pipe was considered to be undersized if the 10-year elevation at the upstream node was either greater than the upstream node rim elevation or greater than the upstream node overflow elevation (when the upstream node represented a storage area). Capacity issues exist throughout the model area, but are particularly prevalent in the vicinity of the parking lot near 1568 Eustis Street.

In the City of Lauderdales 2008 Surface Water Management Plan (SWMP), peak outflow rates for a 100-year, 24-hour design rainfall event are reported for several large drainage areas within the Cities of Lauderdale and Falcon Heights. Reported peak outflow rates are compared to equivalent subwatersheds from the updated modeling results presented in this technical report below in Table 4.

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Table 4 Comparison of peak outflow rates.

2008 Lauderdale SWMP

2015 Eustis Street Regional Modeling

Precipitation Frequency Estimate TP-40 Atlas 14 100-year, 24-hour cumulative rainfall depth (in)

5.9 7.43

Subwatershed Description Dry pond immediately

northeast of east-west concrete swale

Subwatershed ID SA-3 CB99027 Peak Outflow Rate (cfs) 46 218 Subwatershed Description Outflow from confluence of

concrete swales Subwatershed ID SA-4 CB99029 Peak Outflow Rate (cfs) 95 246

Peak outflow rates reported in this updated modeling effort are much greater than those reported in the 2008 SWMP. A major reason for the difference in peak outflow rates is that the updated modeling presented in this technical report utilized precipitation frequency estimates published in NOAA Atlas 14 Volume 8 (Atlas 14), whereas the 2008 SWMP modeling effort used precipitation frequency estimates published by the U.S. Weather Bureaus Technical Paper No. 40 (TP-40). As shown in Table 4, the cumulative depth of the 100-year, 24-hour Atlas 14 event is about 1.5 inches (~25%) greater than the TP-40 design event. The additional rainfall volume generated by the Atlas 14 rainfall event causes the storage areas summarized in Table 4 to overflow, increasing the peak outflow rate from both areas.

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CB99022CB99023

CB101CB105B

CB99016

CB99014

CB112

AP115 SD132

CB143A

CB143A

SD149

CB99029CB99028

CB99020CB99013

CB99027

CB99007

CB99004

CB99001

SD144A

CB99018SD1552 CB99017

MH1540 CB99015

MH118A

MH113A MH123MH128

MH136 MH141 MH147 MH153

CB99002CB99003

CB99006

CBMH102

SD130A

CB99008CB99009

CB99010

CB99012

CB99011

CB99019CB99021CB99024

CB99026CB99025

CB1536

Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping,Aerogrid, IGN, IGP, and the GIS User Community

Barr Footer: ArcGIS 10.3, 2015-07-27 13:17 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 4 - Inundation Area.mxd User: mbm

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Figure 4DESIGN EVENTINUNDATION AREAEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

10-yr Inundation Area100-yr Inundation AreaSubwatershed BoundariesStormsewer

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Figure 510-YEAR DESIGN EVENTPIPE CAPACITYEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

Pipe Capacity: 10-yr, 24 hrUnder CapacityOver CapacitySubwatershed Boundaries

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4.2 Water Quality Results Annual areal watershed loading of TSS and TP for each subwatershed is shown in Figures 6 and 7, respectively. As can be seen, TSS loading ranges from 15 to over 500 pounds per acre per year (lbs/ac/yr), while TP loading ranges from less than 0.1 to 1.7 lbs/ac/yr. Areal loading rates of TSS and TP follow similar trends, with more-developed areas along Larpenteur Avenue West and Eustis Street producing higher TSS and TP loads than less-developed subwatersheds. As demonstrated in Figure 8, a majority (86 percent) of the subwatershed area is routed through either a wet pond or dry pond, or multiple water quality treatment features in series. A small, highly developed portion of the drainage area located near the intersection of Larpenteur Avenue West and Eustis Street does not receive any water quality treatment.

Average annual percent TSS and TP reduction at four water quality treatment features is shown in Figures 9 and 10, and is summarized below in Table 5. As demonstrated, TSS and TP removal is greater in the wet ponds within the drainage area than within the dry ponds because the constant storage volume within wet ponds (also referred as the dead storage volume) allows for particle settling throughout the course of a runoff event. A small amount of particle settling occurs in the temporarily stored volume within dry ponds during a runoff event, but because stored water volume is filled and completely drained throughout the course of an event, the potential for particle settling is much lower in dry ponds than in wet ponds.

Wet ponds designed to meet NURP design criteria should remove 80 percent of TSS and 60 percent of TP on an average-annual basis. The wet pond in subwatershed CB99014 is close to meeting these design criteria, and thus is likely appropriately-sized for the small drainage area it receives. P8 modeling of the wet pond in subwatershed CB99013 indicates that the pond may be undersized for the large drainage area (114 acres) it receives.

As can be seen in Table 5, wet ponds remove significantly more TSS and TP load than dry ponds. As stormwater moves through the permanent pool of a wet pond, suspended sediment and associated phosphorus settles out of the water column. The same process occurs in dry ponds, but because a stored volume of water only exists in the pond during a portion of the storm event, the potential for particle settling is significantly reduced. The TSS and TP removal performance of the two dry ponds could be improved by altering the outlet configuration to convert these features to wet ponds or by excavating additional storage to create a wet pool. It may similarly be possible to improve the performance of the wet pond in subwatershed CB99013 by altering the outlet to store more water (i.e., increase the ponds permanent pool). If conversion to wet ponds or alteration of outlets is pursued, hydraulic analysis should be performed to insure that maximum water surface elevations do not increase.

Table 5 Average annual TSS and TP load reduction

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Figure 6AREAL TSS LOADINGEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

Watershed TSS Load (lbs/ac/yr)0 - 4040 - 8080 - 120120 - 160160 - 200200 - 240240 - 280280 - 320320 - 360>360Subwatershed Boundaries

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Barr Footer: ArcGIS 10.3, 2015-07-27 13:29 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 7 - TP Load.mxd User: mbm

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Figure 7AREAL TP LOADINGEustis Street Regional ModelingCRWD

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Watershed TP Load (lbs/ac/yr)0 - 0.150.15 - 0.300.30 - 0.450.45 - 0.600.60 - 0.750.75 - 0.900.90 - 1.051.05 -1.201.20 - 1.35>1.35Subwatershed Boundaries

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CB99014

CB99013

CB99027CB99004


Barr Footer: ArcGIS 10.3, 2015-07-27 13:47 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 8 - Tributary to WQ.mxd User: mbm

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Figure 8WATER QUALITY TREATMENTEustis Street Regional ModelingCRWD

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Tributary to WQ FeatureUntreatedTributary to CB99004Tributary to CB99014Tributary to CB99013Tributary to CB99027Subwatershed Boundaries

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CB101

CB99014

CB99013

CB99027CB99004


Barr Footer: ArcGIS 10.3, 2015-07-27 13:44 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 9 - Percent Reduction TSS.mxd User: mbm

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Figure 9TSS LOAD REDUCTIONEustis Street Regional ModelingCRWD

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1 inch = 500 feet

TSS Reduction (%)No Treatment0-10%10-20%20-30%30-40%40-50%50-60%60-70%70-80%>80%Subwatershed Boundaries

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CB99014

CB99013

CB99027CB99004


Barr Footer: ArcGIS 10.3, 2015-07-27 13:49 File: I:\Client\CapitolRegionWD\Projects\23621162 Eustis St Strmwater\Maps\Figures\Figure 10 - Percent Reduction TP.mxd User: mbm

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Figure 10TP LOAD REDUCTIONEustis Street Regional ModelingCRWD

0 250 500 750Feet

1 inch = 500 feet

TP Reduction (%)No Treatment0-10%10-20%20-30%30-40%40-50%50-60%60-70%70-80%>80%Subwatershed Boundaries

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5.0 Potential Watershed Improvements

5.1 Flood Mitigation Based on results from the uncalibrated XP-SWMM model (see Section 4.1), the apartment complex immediately northeast of the concrete swales near 1568 Eustis Street appears to be impacted by flooding during the Atlas 14 100-year, 24-hour design event. As discussed in Section 4.1, survey of low-entry to the apartment complex is required to determine if the apartment is impacted based on the 100-year event. Additionally, modeling in XP-SWMM indicates that parking lot near 1568 Eustis Street is partially inundated during the 10-year and 100-year design events (see Figure 4). To address localized flooding issues in the vicinity of the concrete swales, Barr evaluated several flood mitigation alternatives with the goal of (a) protecting the apartment complex during the 10- and 100-year, 24-hour design events, and (b) protecting the parking lot during the 10-year, 24-hour design event.

A rating curve developed for the combined outflow from the confluence of the concrete swales (Figure 1) is shown in Figure 11. Total outflow from the confluence is the sum of outflow from the 24-inch and 36-inch outlet pipes at Eustis Street, as well as flow which overtops the concrete headwall and flows towards Eustis Street (overflow). In addition to the rating curve, Figure 11 also indicates at what elevation and flow rate the parking lot and apartment complex become potentially impacted, and shows the elevation and flow rate at which flow begins to overtop the headwall. As indicated in Figure 11, to protect the apartment complex, inflow to the confluence of the concrete swales must be restricted to less than 97 cfs. To protect the parking lot, inflow to the confluence must be restricted to less than 70 cfs. The existing conditions outflow hydrographs from the concrete swale system for the 10- and 100-year design events are shown in Figure 12. As shown in Figure 12, to protect the apartment complex during the 100-year design event, peak 100-year outflow must be reduced by 149 cfs (61%), and to protect the parking lot during the 10-year event, peak 10-year outflow must be reduced by 22 cfs (23%).

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Figure 11 Rating curve for combined outflow from the 24-inch and 36-inch outlet pipes at the confluence of the concrete swales.

Figure 12 Existing condition outflow hydrograph from the confluence of the concrete swales.

899.8 ft,99.6 cfs

899.5 ft,96.6 cfs898 ft,

70.7 cfs0

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After evaluating several design alternatives, Barr determined that to meet the stated flood mitigation design goals, several existing storage areas throughout the watershed will need to be significantly expanded to further attenuate flow. Specifically, the proposed flood mitigation alternative requires:

a) construction of an earthen berm in the ravine immediately upstream of the existing wet pond (CB99013);

b) expansion of live storage in the existing wet pond (CB99013);

c) expansion of live storage in the existing dry pond (CB99027); and

d) expansion of live sto

april 6, 2016 board meeting packet

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