HomeMy WebLinkAboutStormwater Mapping Work Plan5/22/12
City of Bozeman
Storm Water Mapping
Work Plan
Background:
On April 9th, 2012 the Bozeman City Commission provided policy direction to proceed with the creation
of a storm water utility to more effectively treat and manage Bozeman’s storm water runoff and
subsequent discharge to local streams and rivers (using water meter size as a method for the initial
charge with a stipulation to re‐assess the situation based on the data collected after a two year period).
This is consistent with the current Facility Plan recommendation to fund the required terms and
conditions of the state‐issued discharge permit. This work plan is intended to provide details with
regard to the overall scope and timing of tasks related to the completion of a comprehensive map and
condition assessment of the entire storm water system.
The existing storm water infrastructure consists of a complex system of outfalls, drainage basins, swales,
chases, roadside ditches, culverts, pipes, catch basins, manholes, detention basins and treatment
systems. To effectively develop an operation and maintenance program for storm water facilities, an
inventory of existing features must be developed and updated on a regular basis as the system is
expanded. This information will form the basis for any plans to address future billing methodology as
well as collection, treatment, discharge and deferred maintenance issues.
We will be using a GIS (Geographical Information System) to manage several aspects of the system. This
technology allows us to efficiently and effectively maintain a variety of information as it relates to the
overall inventory, condition, operation and maintenance of the utility. Some examples of the benefits of
using GIS include (but not limited to):
• Asset Management (i.e., work orders, service requests, recurring scheduled tasks, maintenance
history, staff/equipment/material costs, record keeping, etc.)
• T.V. Inspection Integration (used for examining the overall condition of underground pipes to
prioritize deferred maintenance)
• Access to Data in the Field (critical for locates and responding to emergencies)
• Ties to Other Systems (Sungard – for customer information and GASB34 requirements, etc.)
The City has various records depicting storm water infrastructure throughout the organization.
Information is currently available in the form of individual hard‐copy record drawings for each
subdivision and special improvement district. Some data is also made available on quarter‐section grid
maps.
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There have been at least two previous efforts in creating comprehensive digital storm water data. In
2002 the City contracted for the GPS collection of water, sewer and storm water features (fixed points
only). This project resulted in the identification of 676 manholes and 1,905 inlets. In 2004 the City
contracted for the completion of a Storm Water Master Plan (adopted 2008). Deliverables from the
plan included 1,815 pipe segments (see Appendix A for a map of existing data). These efforts focused
only on hard infrastructure and do not include outfalls, open channels, swales, culverts, chases or
detention facilities. Only 40% of the total number of quarter sections within the city limits were
included in this study, with only 12% of subdivision records and 8% of SID’s represented.
Considerable effort will be required to build a comprehensive map while assessing the condition of the
storm water system. Essentially, all existing data will need to be migrated into a unified system while
existing and future subdivision and SID record drawings must be digitized. Extensive field work will be
necessary to identify and assess the condition of all features. It should be recognized that many
unknowns exist when assessing the condition of both underground and aboveground infrastructure.
Some of the challenges we face are the presence of weeds within detention ponds and roots,
sedimentation and offsets within the underground pipes which could make t.v. inspection very time
consuming (over the past four years, we have spent an average of $7,064.24 per mile to flush, root cut
and t.v. sewer mains [includes staff/equipment/materials]. These operations take approximately 3,490
man hours per year to conduct – it has been suggested that proper inspection of the storm water system
could take twice as long, depending on the variables listed above).
Water quality treatment of known outfalls should be considered as an effective means to mitigate
pollution from storm water runoff. More information is needed to determine the cost/benefit of
mitigating contaminants versus the cost/benefit of t.v. inspection and subsequent pipe
repair/replacement. All of the information we collect will need to be maintained throughout the life of
the utility.
Recommendation:
Section 6.8 of the 2008 Storm Water Facility Plan recommends the following “phased” approach to
developing and maintaining an accurate storm water map and GIS database:
1. Develop Database Maintenance Procedures
2. Fully Incorporate the Grid Maps
3. Add Open Channels
4. Update Poorly Mapped Areas of the Database
5. Incorporate Remaining Documentation‐Based Data
6. Perform Illicit Discharge Detection and Elimination (Outfall) Mapping
The plan also recommends “The City should require that engineers or developers to submit all new storm
water infrastructure information to the City in GIS with coordinates, inverts, and elevations….”(6.7.2).
This requirement is critical to maintaining the data for future use.
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To accomplish these tasks, we have proposed a budget which includes a full‐time GIS Technician as well
as two summer interns to assist in creating and maintaining a variety of data. Performing the work in‐
house is the most cost effective solution for this type of effort and provides unmatched accuracy with
our extensive local knowledge of the system. We will begin with an Outfall Reconnaissance Inventory
(at the direction of the DEQ), which will provide much needed insight into the condition and quality of
locations where storm water discharges to surface waters (see Appendix B for a map of all ten receiving
waters listed in our permit). It is recommended that this process be repeated once during every five
year permit cycle. A complete guide to this process including field data collection forms can be found at
the following link:
http://www.epa.gov/npdes/pubs/idde_chapter‐11.pdf
We will also inventory all existing swales, chases, roadside ditches, culverts, pipes, catch basins,
manholes, detention basins and treatment systems. The inspection will include location, elevation,
type, dimensions, orientation and condition of each structure. The presence and amount of sediment or
groundwater in the chamber bottoms will be noted, and whether it has a formed invert or a sump
bottom. Pipe data will include drop distance from rim to invert, pipe size, shape, material, year
constructed and overall condition. As noted above, we will also begin the t.v. inspection process for all
underground pipes. The inventory will include both public and private systems which are critical in
determining maintenance responsibility and their affect on the system as a whole. We have already met
with MSU and received a copy of their data to incorporate into our GIS.
According to a recently conducted records inventory, we have the following features to be mapped:
Feature Existing To Be Mapped
Pipes 37.7 miles 34.1 miles
Manholes 676 845
Catch Basins 1905 1659
Detention Basins ‐ 317
Swales ‐ 3.2 miles
Outfalls ‐ 724
Chases ‐ ?
Roadside Ditches ‐ ?
Culverts ‐ ?
Treatment Systems ‐ ?
Based on the above information, it will be difficult to estimate the total amount of time necessary to
complete an inventory and assessment of the entire storm water system. Initially, we anticipate at least
three years before we have a solid understanding of what the future ongoing costs for administration,
repair and maintenance are likely to be. Once we begin the process, we will quickly learn more about
the overall scope and time‐frame needed to complete this project. We will provide regular updates on
our progress in hopes of establishing a more solid foundation from which important decisions can be
made.
Report compiled by:
Jon Henderson
GIS Manager
S 19TH AVE
INTERSTATE 90 HWY
FRONTAGE RD
DURS TON RD
COTTONWOOD RD
STUCKY RD
S 3RD AVE
W MAIN ST
W OAK ST
SOURDOUGH RD
N 7TH AVE
DAVIS LN
HUFFINE LN
E VALLEY CENTER RD
W COLLEGE ST
W BABCOCK ST
S 11TH AVE
SPRINGHILL RD
E MAIN ST
BAXTER LN
N ROUSE AVE
B R I D GER DR
HIGHLAND BLVD
OAK ST
E KAGY BLVD
B R I D G E R C A N Y O N RD
W OAK ST
W PEACH ST
GRAF ST
GOLDENSTEIN LN
INTERSTATE 90 HWY
FRONTAGE RD
S 3RD AVE
INTERSTATE 90 HWY
DAVIS LN
BAXTER LN
1 0 10.5 Mile
¯
Legend
!Manholes
#Catch Basins
MS4 Permit Receiving Waters
Major Roads
City Limits
Existing Quarter Section Pages (~2002)
City of Bozeman Storm Water Facility Plan (2008)
*Represents only 40% of the
total number of quarter sections,
12% of the total number of
subdivisions and 8% of the total SID's
Exhibit A
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DURSTON RD
GOOCH HILL RD
STUCKY RD
HUFFINE LN
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W M A I N ST
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W OAK ST N 7TH AVE
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B R I D G E R CANYON RD
W COLLEGE ST
W BABCOCK ST E MAIN ST
W KAGY BLVD
N
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B R I D G ER DR
HIGHLAND BLVD
OAK ST
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INTERSTATE 90 HWY
BAX TER LN
FRONTA
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City of Bozeman MS4 Permit Receiving Waters
2 0 21 Miles
¯
Legend
MS4 Permit Receiving Waters
Major Roads
City Limits
Community Plan Boundary
As of 5/15/12:
21.6 miles of receiving waters
within city limits
54.5 miles of receiving waters
within community plan boundary
Bozeman Creek
Spring Creek
Middle CreekDitch
Mandeville CreekDitch
Farmer's Canal
Bear Creek
East GallatinRiver
Baxter Creek
Maynard BorderDitch
Bridger Creek
East GallatinRiver
Exhibit B