Engineer’s Report February 20, 2019

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Normandale Lake Water Quality Improvement Project:

We are continuing to track the progress of the lake drawdown and depth of frozen sediment. The graph

below shows the lake levels throughout the fall/winter drawdown. As shown, the lake level has periodically

rebounded in response to rainfall and/or snowmelt conditions. The most significant rebound occurred in

late-December when the Twin Cities experienced a winter storm that brought snow and rain (about 1.5

inches of total precipitation). Temperatures fell dramatically at the end of the storm period (20 to 40

degrees), resulting in a “flash freeze” of standing water in many low-lying areas (including much of the

surface of Normandale Lake).

As of February 11, 2019 the top 15-24 inches of sediment across Normandale Lake is frozen (see figure

below).

Graph showing lake levels in Normandale Lake throughout fall/winter drawdown, which have periodically rebounded

resulting from rainfall and snowmelt events.

Results from recent field visit indicate depth of frozen sediment ranges from 15 to 24 inches across the lakebed.

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Normandale Lake Water Quality Improvement Project (continued):

Refilling of the lake will begin at the end of February. Rachel Contracting plans to install the stop logs in

the new bypass manhole structure in the upcoming weeks. Once installed, lake levels will begin to

rebound as flow in Nine Mile Creek increases from spring rainfalls and snowmelt. The original 18-inch

bypass pipe will remain open, or partially open, throughout the lake refill period to maintain some flow

in the creek downstream of Normandale Lake. We anticipate that the lake will refill by April, but the

rate of refill will be dependent on precipitation and snowmelt timing.

The District is planning to conduct an alum treatment of the lake in spring 2019. We have prepared a

Request for Quotes (RFQ), which will be sent to up to three contractors. We plan to have quotes

submitted back to the District by March 14, 2019. The alum treatment will likely occur between mid-

April and mid-May.

Barr and District staff participated in a conference call with Dr. Przemek Bajer and Jordan Wein from

Carp Solutions regarding recommended next steps for potential carp management in Normandale

Lake. Results from the fish survey conducted by Riley Purgatory Bluff Creek Watershed District staff in

summer 2018 indicated that the amount of carp in Normandale Lake is over the carp management

biomass threshold of 100 kg/ha. Dr. Bajer recommended conducting another fish survey (including carp

and native fish) in 2019 to understand the fish community post-drawdown. He also recommended

considering installing trackers in a select number of carp to help understand the movement patterns of

the carp for potential future management/removal efforts. District staff will be in contact with RPBCWD

regarding a 2019 fish survey and has requested a cost estimate from Carp Solutions for carp tracking

services.

Aerial view of the northwest (inlet) side of Normandale

Lake (February 13, 2019). Aerial view of the central and east side of Normandale

Lake (February 13, 2019).

Edina Stream Stabilization Project: Phase II of the project reached substantial completion at the end

of October. The substantial completion deadline was December 31st, so the project was completed

ahead of schedule.

For both Phase I and Phase II, some portions of the project were constructed on private property. Work

continued in January to establish the limits of permanent easements on the private properties to secure

a means for the District to complete maintenance as needed.

Bush Lake Outlet Project: No new activities.

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Lake Cornelia and Lake Edina Use Attainability Analysis (UAA): Barr is wrapping up the Use

Attainability Analyses (UAAs) for North and South Lake Cornelia and Lake Edina. In recent weeks Barr

staff have been using the in-lake water quality models to estimate the anticipated improvement in lake

water quality resulting from various watershed BMPs and in-lake management activities (e.g., curly-leaf

pondweed management, alum treatment). As part of the analysis, we have developed a conceptual-

level design for an innovative spent lime and crushed lime up-flow treatment system to remove

dissolved phosphorus from stormwater before it is discharged to Lake Cornelia. Spent lime

(precipitated calcium carbonate) is a byproduct of the drinking water treatment process; in recent years

Barr has been experimenting with using this byproduct to remove phosphorus from stormwater.

We anticipate completing the draft UAA report by early-March.

Pentagon Park Stormwater Management (in partnership with the cities of Edina and

Bloomington): No new activities.

Nine Mile Creek Watershed District 60th Anniversary Story Map: The design team met to formulate

the content outline for the Story Map. Elements such as overarching messaging themes, the District

beginnings and key events such as the 1987 super-storm were discussed and a preliminary

“storyboard” of the map was created. Design team members (District and Barr staff) are now tasked

with developing portions of the Story Map further, including locating content such as project data and

photos or noting the need of an interview with a particular person from the District’s past or present.

A draft of the Story Map will be developed in late-March as content continues to be generate and

arranged. The roll-out of the Story Map is planned for June in advance of the 60th anniversary

celebration.

Results of “storyboard” brainstorming session with District staff.

District Office (Discovery Point): No new activities. The Discovery Point Restoration is now stable for

the winter. The entire Discovery Point site will continue to be managed for invasive species throughout

the spring as the fall seedings become established. Additional plant installations will take place in the

spring of 2019; another volunteer event will be scheduled as the growing season approaches.

Regional Stormwater Volume Reduction Opportunity Study: No new activities.

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Wetland Conservation Act (WCA) and NMCWD Wetland Rule Administration:

• Submitted WCA 2018 annual reporting form to BWSR.

• Met with Lauren Foley to discuss wetland work and provide WCA information.

• Reviewed 2018 Braemar Golf Course monitoring report for the executive course and

driving range wetland replacement site. Provided report to TEP members and sent

comments to TEP members, applicant, and applicant’s agent.

• Provided comments on site status of Braemar Golf Course redevelopment wetland

replacement site to TEP members, applicant, and applicant’s agent.

• Reviewed and discussed wetland issues related to France Ave Trail in Bloomington and

participated in TEP meeting.

• Reviewed desktop information for 5617 Rowland Road in Minnetonka.

• Provided WCA information regarding Nine Mile Village dredging inquiry.

• Determined source of WCA escrow ledger for audit and respond to questions.

Status of Permitted Construction Projects: Barr staff completed the monthly inspections of

permitted sites between February 4 through 8, 2019. An abbreviated version of the monthly inspection

report is provided for the Managers review. Of the 89 sites inspected, 7 of the sites required corrective

action or follow-up. The full inspection report is available upon request.