ImpactAssessment (PDF)

Rui  Chen  
 

Memorandum

To: Chapel Hill Town Manager
From: Rui Chen
Date: 4/24/2015
Re: Proposed Roberson Square Development

Project Description
Roberson Square is proposed to be a mixed-use development with retail, office and
residential areas. The development plan proposed is to consist of one building with
•

1st floor: Retail

12,000 square feet
Employ 36 persons

•

2nd floor: Office

19,000 square feet
Employ 57 persons

•

3rd – 5th floor: Residential

18 dwelling units
47 residents

The development site is located at a currently vacant lot on the southeast corner of
Roberson Street and Sweet Bay Place. It is within the downtown of Carrboro.
Purpose of Assessment
The following Impact Assessment report details specific areas of concern for
communities when considering a new development: Public Service, Traffic, Water
and Wastewater Service, Stormwater, and Climate Change impact to the
development, the surrounding area, and the Town of Carrboro. The purpose of this
assessment is to evaluate possible impacts that Roberson Square development will
generate, identify their influence on the Town of Carrboro, and provide alternatives to
mitigate adverse effects of this development.
Assessment Procedures
The report evaluates pre-development conditions and post-development conditions
under each impact area. Based on the pre- and post-development comparison, the
report measure whether the project has negative impact on the Town mainly
according to Town standards. In light of the evaluation results, the report identifies
responsibility and possible mitigation measures.

 

1  

Summary of Impacts
Public Service: The parks and recreation facilities on the proposed site do not meet
Carrboro’s standards, and Roberson Square will not create any new deficit of supply.
Carrboro will exceed its standards of schools in some years. The proposed project will
only alter the scenario of high school by exceeding the standards one year earlier.
Current police service supply satisfies both pre- and post-development demand.
Current fire service meets the need of Roberson Square development, but the service
radius fails to cover the entire town.
Traffic: The Roberson Square development will generate new traffic and reduce the
level of service (LOS) at the intersection from F to G during PM Peak hours, but LOS
in AM Peak hours will remain at E, which fails to meet Carrboro standards neither.
The mixed-use development will generate new pedestrians in the intersection and
increase pedestrian-vehicle conflicts and worsen hazardous conditions.
Water and Wastewater: With the additional water demand created by Roberson
Square, the water supply will sustain Carrboro standard especially after the expected
OWASA expansion. Water velocities are not adequate for both pre- and postdevelopment conditions. The project will generate demand of fire flow, which is not
necessary currently. Existing hydrants are able to satisfy the requirement. Roberson
Square will not significantly change the demand of wastewater service, but the peak
day demand exceeds average day capacity already. Also velocity in some pipes of the
wastewater system have exceeded the standards, while the project will deteriorate this
situation
Stormwater: Roberson Square will lower stormwater discharge and pollutant load and
improve stormwater quality, because it reduce the current impervious area.
Climate Change: The construction of Roberson Square will cause 42.3 tons of CO2
emission per year. The building operation will emit an equivalent of 25 million tons
of CO2 a year in terms of global warming potentials. The transportation led by the
development will generate 1,858 tons of CO2 emission per year.
Summary of Mitigation
See next page.
Decision
The proposed Roberson Square development should be approved with specific
conditions to mitigate negative impacts, especially traffic impacts. Overall, this
development will not significantly change current conditions. Approving this impact
may provide opportunities to improve some conditions by public-private cooperation.
The disadvantage of this decision is that Roberson Square alone will not cause server
adverse impacts, but together with adjacent proposed projects that are not assessed in
this report, there might be aggregated negative outcomes for the communities.
For detailed descriptions and outputs for each assessment, please refer to the report
appendices.

 

2  

Impact

Public
Service

Traffic

Water and
Wastewater

Stormwater
Climate
Change

 

Mitigtion

Add facilities (one picnic table and one tennis
court) in Carrboro Town Commons
Provide more capacity of McDougle Middle School
Increase teachers in Town
Use building and occupancy permit for fire safety
Add vehicles for the police station and the fire
station
Build a new fire station in north Carrboro
Add a traffic signal and build crosswalks
Add a right-turn lane and increasing the number of
lanes in the long term
Allocate some office space to parking space
Provide shuttles at PM Peak Hour
Design a car-pool system for employees and
residents in Roberson Square
Widen sidewalks from Roberson Square to bus
stops
Build sheltered bus stops
Improve sharrows
Provide bike parking and way signs to bus stops
Complete the OWASA expansion project
Install Pipe 8 with other materials to increase
velocity
Use water-efficiency facilities
Install a sprinkler system
Improve sewerage maintenance
Increase Mason Farm Treatment Plant capacity
Enlarge wastewater piples
Build an infiltration trench and a grass swale
Use some concrete grid pavement
Build a bioretention (optional)
Use lower CDIR construction materials
Use energy efficient design (solar power system)
Increase nuclear energy

3  

Responsibility
The
Developer
Town

✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓

✓
✓
✓

✓
✓
✓
✓
✓
✓

✓
✓
✓
✓
✓

✓
✓
✓

✓

✓

ROBERSON  SQUARE  DEVELOPMENT  IMPACT  ASSESSMENT   1  
 

Table of Content
 
  Introduction  to  Roberson  Square  Development  ................................................  4  
1.1   Introduction  .......................................................................................................................  5  
1.2   Objectives  of  Impact  Assessment  ...............................................................................  5  
1.3   Project  Description  .........................................................................................................  5  
1.4   Elements  of  Proposed  Project  .....................................................................................  6  
1.5   Environmental  Setting  ...................................................................................................  7  
1.5.1   Location  Map  ..............................................................................................................................  7  
1.5.2   Zoning  ............................................................................................................................................  7  
1.5.3   Surrounding  Land  Uses  .........................................................................................................  7  
1.5.4   Public  Service  Providers  .......................................................................................................  7  
1.6   Site  Analysis  .......................................................................................................................  8  
1.6.1   Existing  uses  ...............................................................................................................................  8  
1.6.2   Demographics  ............................................................................................................................  8  
1.6.3   Topography/Slope  and  Hydrological  Features/Drainage  ......................................  8  
  Public  Services  Impact  Assessment  ........................................................................  9  
2.1   Introduction  ....................................................................................................................  10  
2.2   Parks  and  Recreation  ..................................................................................................  10  
2.2.1   Background  information  ....................................................................................................  10  
2.2.2   Pre-­‐Development  Conditions  ...........................................................................................  10  
2.2.3   Post-­‐Development  Conditions  .........................................................................................  11  
2.2.4   Mitigation  ..................................................................................................................................  11  
2.3   Schools  ..............................................................................................................................  12  
2.3.1   Background  Information  ....................................................................................................  12  
2.3.2   Pre-­‐Development  and  Post-­‐Development  Conditions  ..........................................  12  
2.3.3   Mitigation  ..................................................................................................................................  13  
2.4   Public  Safety  ...................................................................................................................  13  
2.4.1   Background  Information  ....................................................................................................  13  
2.4.2   Pre-­‐Development  Conditions  ...........................................................................................  13  
2.4.3   Post-­‐Development  Conditions  .........................................................................................  14  
2.4.4   Mitigation  ..................................................................................................................................  14  
  Traffic  Impact  Assessment  ......................................................................................  16  
3.1   Introduction  ....................................................................................................................  17  
3.2   Background  Information  ............................................................................................  17  
3.3   Pre-­‐Development  Conditions  ...................................................................................  17  
3.4   Post-­‐Development  Conditions  ..................................................................................  18  
3.5   Hazardous  Conditions  .................................................................................................  20  
3.5.1   Enhancing  Pedestrian  Safety  ............................................................................................  20  
3.5.2   Changing  Lane  Settings  .......................................................................................................  20  
3.5.3   Regulating  the  Development  ............................................................................................  21  
3.5.4   Public  Transit/Alternative  Transportation  ...............................................................  21  
3.6   Conclusion  .......................................................................................................................  22  
  Water  and  Wastewater  Service  Impact  Assessment  .......................................  23  
4.1   Introduction  ....................................................................................................................  24  
4.2   Water  Service  .................................................................................................................  24  
4.2.1   Pre-­‐Development  Demand  ................................................................................................  24  
4.2.2   Post-­‐Development  Demand  ..............................................................................................  25  

2   ROBERSON  SQUARE  DEVELOPMENT  IMPACT  ASSESSMENT  

 
4.2.3   Mitigation  ..................................................................................................................................  25  
4.3   Fire  Flow  ..........................................................................................................................  26  
4.3.1   Pre-­‐Development  Conditions  ...........................................................................................  26  
4.3.2   Post-­‐Development  Conditions  .........................................................................................  26  
4.3.3   Mitigation  ..................................................................................................................................  27  
4.4   Wastewater  .....................................................................................................................  27  
4.4.1   Background  Information  ....................................................................................................  27  
4.4.2   Pre-­‐Development  and  Pro-­‐Development  Conditions  ............................................  27  
4.4.3   Evaluation  of  B&A  Report  ..................................................................................................  28  
4.4.4   Mitigation  ..................................................................................................................................  28  
4.5   Summary  ..........................................................................................................................  28  

  Stormwater  Impact  Assessment  ............................................................................  30  
5.1   Introduction  ....................................................................................................................  31  
5.2   Peak  Discharge  Impacts  ..............................................................................................  31  
5.2.1   Pre-­‐Development  Conditions  ...........................................................................................  31  
5.2.2   Post-­‐Development  Conditions  .........................................................................................  31  
5.2.3   Mitigation  ..................................................................................................................................  32  
5.3   Stormwater  Quality  Impacts  .....................................................................................  33  
5.3.1   Pre-­‐Development  Condition  .............................................................................................  33  
5.3.2   Post-­‐Development  Condition  ...........................................................................................  33  
5.3.3   Issuance  of  Permit  .................................................................................................................  33  
5.3.4   Mitigation  ..................................................................................................................................  34  
5.4   Conclusion  .......................................................................................................................  35  
  Climate  Change  Impact  Assessment  .....................................................................  36  
6.1   Introduction  ....................................................................................................................  37  
6.2   Background  .....................................................................................................................  37  
6.3   Construction  Emissions  ..............................................................................................  38  
6.4   Building  Operation  Emissions  ..................................................................................  38  
6.5   Transportation  Emission  ...........................................................................................  39  
6.6   Mitigation  ........................................................................................................................  39  
  Appendix  ........................................................................................................................  41  
Appendix  I.  Maps  and  Figures  .............................................................................................  42  
Figure  A-­‐1.1  Location  Map  of  Roberson  Square  ......................................................................  42  
Figure  A-­‐1.2  Roberson  Square  Site  Plan  .....................................................................................  43  
Figure  A-­‐1.3  Zoning  Map  of  Roberson  Square  .........................................................................  44  
Figure  A-­‐1.4  Topography  of  Roberson  Square  ........................................................................  45  
Figure  A-­‐1.5  Hydrology  of  Roberson  Square  ............................................................................  46  
Table  A-­‐1.1  Demography  of  Carrboro  .........................................................................................  47  
1.1.1   47  
Table  A-­‐2.1  Park  Classifications  and  Descriptions  .................................................................  47  
Table  A-­‐2.2  Current  Recreation  Facility  Condition  ................................................................  47  
Figure  A-­‐2.1  Parks  for  Roberson  Square  ....................................................................................  49  
Figure  A-­‐2.2  Carrboro  Fire  Station  Service  Area  ....................................................................  50  
Figure  A-­‐3.1  Location  of  Roberson  Square  ................................................................................  51  
Figure  A-­‐3.2  Distribution  of  Roberson  Square  Trip  Generation  ......................................  52  
Figure  A-­‐4.1  Segments  of  OWASA  Water  System  Networks  ..............................................  53  
Figure  A-­‐4.2  Segment  of  OWASA  Wastewater  System  Network  ......................................  53  
Appendix  II.  Methods  ..............................................................................................................  54  
1.  Methods  for  Public  Service  ..........................................................................................................  54  
2.  Methods  for  Traffic  Impact  ..........................................................................................................  54  
3.  Methods  for  Water  and  Wastewater  Service  .......................................................................  54  
4.  Methods  for  Stormwater  Impact  ...............................................................................................  56  

ROBERSON  SQUARE  DEVELOPMENT  IMPACT  ASSESSMENT   3  
 
5.  Methods  for  Climate  Change  Impacts  .....................................................................................  56  
Appendix  III  Traffic  Reports  Generated  by  Synchro  9  ................................................  57  
1.  Current  AM  Peak  Hour  Intersection  Traffic  Report  ..........................................................  57  
2.  Current  PM  Peak  Hour  Intersection  Traffic  Report  ..........................................................  58  
3.  Future  Background  AM  Peak  Hour  Intersection  Traffic  Report  (Two-­‐Year  Growth  
plus  Adjacent  Development)  ...........................................................................................................  59  
4.  Future  Background  PM  Peak  Hour  Intersection  Traffic  Report  (Two-­‐Year  Growth  
plus  Adjacent  Development)  ...........................................................................................................  60  
5.  Post-­‐Development  AM  Peak  Hour  Intersection  Traffic  Report  ....................................  61  
6.  Post-­‐Development  PM  Peak  Hour  Capacity  Report  ..........................................................  62  
7.  Future  Background  PM  Peak  Hour  Traffic  Simulation  Report  .....................................  63  
8.  Post-­‐Development  PM  Peak  Hour  Traffic  Simulation  Report  .......................................  64  

Tables
 
TABLE  1.1  ROBERSON  SQUARE  DEVELOPMENT  DETAILS  
TABLE  1.2  PUBLIC  SERVICE  PROVIDERS  
TABLE  2.1  CARRBORO  STANDARDS  FOR  PARKS  AND  RECREATION  
TABLE  2.2  POST-­‐DEVELOPMENT  RECREATION  FACILITY  NEEDS  
TABLE  2.3  CHANGE  OF  NEEDS  AFTER  ADDING  ONE  INSUFFICIENT  FACILITY  
TABLE  2.4  LEVEL  OF  SERVICE  FOR  SCHOOLS  IN  CARRBORO  
TABLE  2.5  SCHOOL  CONDITIONS  
TABLE  2.6  CURRENT  CONDITIONS  OF  PUBLIC  SAFETY  
TABLE  2.7  POST-­‐DEVELOPMENT  CONDITIONS  OF  PUBLIC  SAFETY  
TABLE  3.1  TRAFFIC  GENERATION  FOR  ROBERSON  SQUARE  
TABLE  4.1WASTEWATER  GENERATION  AND  TREATMENT  PLANT  DEMAND  
TABLE  5.1  PEAK  FLOWS  
TABLE  5.2  TOTAL  RUNOFF  
TABLE  5.3  PEAK  FLOWS  
TABLE  5.4  TOTAL  RUNOFF  
TABLE  5.5  BMP  REDUCTION  AND  COST  
TABLE  5.6  POLLUTANT  REDUCTION  
TABLE  6.1EMISSIONS  FROM  FIVE  MAIN  COMPONENTS  
TABLE  6.2OPERATION  EMISSION  DETAILS  

6  
8  
10  
11  
11  
12  
12  
14  
14  
19  
27  
31  
31  
32  
32  
32  
34  
38  
39  

Figures
 
FIGURE  3.1  BASIC  TRAFFIC  VOLUMES  (2009  AND  2011)  
FIGURE  3.2  TRAFFIC  VOLUMES  OF  ADJACENT  DEVELOPMENTS  
FIGURE  3.3  TRAFFIC  GENERATION  OF  ROBERSON  SQUARE  
FIGURE  3.4  POST-­‐DEVELOPMENT  TRAFFIC  CONDITIONS  

 

18  
18  
19  
20  

4   ROBERSON  SQUARE  DEVELOPMENT  IMPACT  ASSESSMENT  

 
 
 
 
 
 
 
 

Introduction to Roberson Square
Development

ROBERSON  SQUARE  DEVELOPMENT  IMPACT  ASSESSMENT   5  
 

1.1 Introduction
Roberson Square is a new development proposal for the Town of Carrboro. It
will be located at the southeast corner of Roberson Street and Sweet Bay Place. The
developer, Yaggy Corporation, proposes as a mixed-use project, including residential,
retail, and office. This project evokes concerns by the community of Carrboro. People
particularly worry its impact on the parking issue in the Downtown. This document
will provide an overall impact assessment for Roberson Square project in order to
help the public understand this project and make the decision on its approval.

1.2 Objectives of Impact Assessment
The purpose of this assessment for Roberson Square is to evaluate possible
impacts that this development may have on the community of Carrboro in the short
term and in the long term. This document will investigate public service, traffic level
service, water supply and wastewater, stormwater discharge, and climate change
impacts. Understanding these impacts is important to mitigate or avoid adverse effects
of this project. There are four major objectives of this assessment.
Ø Address potential impacts
Ø Identify resource and/or action needed to mitigate adverse impacts
Ø Help the Town, the developer, and residents understand this project
Ø Facilitate communication and negotiation between interest groups
Ø Ensure the development consistent with the community’s comprehensive plan

1.3 Project Description
Roberson Square takes the site of the old Andrews-Riggsbee Hardware Store
in the middle of Carrboro Downtown, adjacent to established residential single-family
neighborhoods (see Figure A-1.11). Roberson Square covers approximately 91,575
square feet within five stories. Yaggy Corporation intends to offer 11 retail stores, 11
office spaces, 18 units of condominiums (including three affordable housing units),
and an underground parking lot (see the site plan in Figure A-1.2). Table 1
summarizes three uses of this building in details. This project is supposed to be started
in 2009 and completed in 2011. It will bring 93 potential employees and 47 potential
residents in total. Yaggy Corporation originally wanted to contain a restaurant in the
rail section. Because of the parking controversy raised by the community, the
restaurant now is excluded from this development. Also, the developer will offer 65
underground parking spaces (29 of them for residents of Roberson Square) and seven
public, on-street parking spaces along Carr Street. In addition, Roberson Square will
have a 10-foot sidewalk on Roberson Street, with five feet of trees, shrubs and grass.
The building’s first two floors will be visible from the sidewalk.
Yaggy Corporation designed Roberson Square with the purpose of meeting
the town of Carrboro’s vision for growth. One purpose of this project is to increase
walkability, bikeability and more public gathering spaces of the town. The
                                                                                                               
1

All figures in Appendix I are numbered as Figure A-Section #.×.