Managing Visual Impacts on Historic Sites and DistrictsMN State Historic Preservation OfficeReview and Compliance SeminarApril 26, 2011

Panel Members:Mary Ann Heidemann, SHPOMatt Bartus, Pinnacle EngineeringGarneth Peterson, Mn/DOT

Why are Visual Impacts Important?

• Part of the Assessment of Adverse Effect required by the NHPA regs (36 CFR 800.5)

• Visual impacts have the potential to diminish the historic property’s integrity

• Through negative impacts on setting, feeling or association of the historic property

• Property integrity is key to maintaining Register eligibility

Types of Adverse Visual Impact

• Introduction of visual elements outside the period of significance

• Addition of elements that alter the design characteristics of the site

• Overwhelming the historic property in scale, mass or feeling

• Blocking or substantially altering historic vistas or views to or from the property

Examples of Adverse Visual Impact

Defining the Visual Area of Potential Effect

• The visual APE defines an indirect impact

• Different from both the archaeological APE and the direct above-ground APE

• Usually the largest APE in terms of land area

• Can be difficult to define responsibly

• Vague statements are not sufficient

• SHPO will say: “Show Me”

Tools to Define Visual APE & Impacts

• Distance guidelines

• Topo maps

• Google Earth views

• Visual simulations

• Diagrams

• Site photos

Presumed Visual APE from Telecommunications Nationwide PA

Tower Height

Less than 200 feet

200-400 feet

400 feet and above

Visual APE Boundary

Half mile

Three-quarter mile

One and a quarter mile

Other Tools: Photo Simulation

Before: Existing Conditions After: Proposal in Place

Photos as a Tool: Well or Poorly Used

First Submittal Second Submittal

Factors Limiting Visual APE

• Topography

• Foliage

• Intervening buildings

• Sight lines

• Distance

• Explain it to us!

• Document it

Sight Line Limitations

Documentation Standards

36 CFR 800.11

(a) Adequacy of documentation. The agency official shall ensure that a determination, finding or agreement in this subpart is supported by sufficient documentation to enable any reviewing party to understand its basis.

Sometimes Visual Impacts Cannot Be Avoided: Example of Knodt Farm

Univ. of MN’s U-More Wind Turbine and Visual Impact on Knodt FarmsteadAPE for 490’ Wind Turbine Adverse Effect Unavoidable

• Existing agricultural setting remarkably intact

• Open farm fields meant nothing could block the view to the turbine

• University had no practical site alternatives

• Preparation of Minnesota Historical Property Record was used as mitigation for adverse visual effect

Finding Alternatives to Avoid Adverse Visual Impacts

Some Project Examples

From Telecommunication Antennae Projects

• Matt Bartus, Pinnacle Engineering

From the Lyndale Avenue Bridge Project

• Garneth Peterson, Mn/DOT Cultural Resources Unit

Techniques to Avoid Visual Disturbance from Antennae

• Utilize appropriate equipment shape

• Careful placement

– Avoid principle façade, move away from roof edge, hide among existing roof utilities

• Use flush mounts

• Paint color that blends into background

• Employ stealth screening devices

Assessing Visual Impact

• Decoy antennae used for visual assessment

• Integrate with existing building utilities

• At non-prominent location

• Flush mount

• Painted to match

Crane Test for Assessing Visual Impact

Antennae shielded from street view by equipment setback

More setback examples: Salvation Army Building

Penthouse Mounts

Chimney Mounts

Stealth Mounts

Lyndale Bridge Design ProcessGarneth O. Peterson, Mn/DOT CRU

On the boardwalk approaching the bridge from the east

The Original Arch

Early Replacement Options

Elliptical Arch Alternative

Round Arch Concept Design

Concrete textures for Public Advisory Committee and Public Comment

Bridge Arch Designs: Radial and Elliptical

The Final Bridge Design