&EPA
United States
Environmental Protection
Agency
2014 GREEN INFRASTRUCTURE TECHNICAL ASSISTANCE PROGRAM
Iowa City, IA
Towards a Resilient Future: Restoration of
Ralston Creek within Riverfront Crossings Park
JUNE 2016
EPA 832-R-16-003
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About the Green Infrastructure Technical Assistance Program
Stormwater runoff is a major cause of water pollution in urban areas. When rain falls in undeveloped
areas, soil and plants absorb and filter the water. When rain falls on our roofs, streets, and parking lots,
however, the water cannot soak into the ground. In most urban areas, stormwater is drained through
engineered collection systems and discharged into nearby water bodies. The stormwater carries trash,
bacteria, heavy metals, and other pollutants from the urban landscape, polluting the receiving waters.
Higher flows also can cause erosion and flooding in urban streams, damaging habitat, property, and
infrastructure.
Green infrastructure uses vegetation, soils, and natural processes to manage water and create healthier
urban environments. At the scale of a city or county, green infrastructure refers to the patchwork of
natural areas that provides habitat, flood protection, cleaner air, and cleaner water. At the scale of a
neighborhood or site, green infrastructure refers to stormwater management systems that mimic nature
by soaking up and storing water. Green infrastructure can be a cost-effective approach to improving
water quality and helping communities stretch their infrastructure investments further by providing
multiple environmental, economic, and community benefits. This multibenefit approach creates
sustainable and resilient water infrastructure that supports and revitalizes urban communities.
The U.S. Environmental Protection Agency (EPA) encourages communities to use green infrastructure to
help manage stormwater runoff, reduce sewer overflows, and improve water quality. EPA recognizes
the value of working collaboratively with communities to support broader adoption of green
infrastructure approaches. Technical assistance is a key component to accelerating the implementation
of green infrastructure across the nation and aligns with EPA's commitment to provide community-
focused outreach and support in response to the President's Priority Agenda for Enhancing the Climate
Resilience of America's Natural Resources. Creating more resilient systems will become increasingly
important in the face of a changing climate. As more intense weather events or dwindling water supplies
stress the performance of the nation's water infrastructure, green infrastructure offers an approach to
increase resiliency and adaptability.
For more information, visit http://www.ei3a.aov/areeninfrastructure.
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Acknowledgements
Principal U.S. Environmental Protection Agency Staff
Tamara Mittman
Christopher Kloss
Jamie Piziali
Leah Medley
Community Team
Karen Howard, City of Iowa City
Ben Clark, City of Iowa City
Brenda Nations, City of Iowa City
Mike Moran, City of Iowa City
Zac Hall, City of Iowa City
Doug Boothroy, City of Iowa City
Kris Ackerson, City of Iowa City
Consultant Team
Russ Dudley, Tetra Tech, Inc.
William Musser, Tetra Tech, Inc.
Jonathan Smith, Tetra Tech, Inc.
Martina Frey, Tetra Tech, Inc.
John Kosco, Tetra Tech, Inc.
This report was developed under U.S. Environmental Protection Agency (EPA) Contract No. EP-C-11-009
as part of the 2014 EPA Green Infrastructure Technical Assistance Program.
Cover photo: Southern equalization basin at the decommissioned North Wastewater Treatment Facility.
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Contents
1 Executive Summary 1
2 Introduction 2
2.1 Historical Conditions 3
2.2 Project Overview and Goals 5
2.3 Project Benefits 5
2.3.1 Water Quality Benefits 5
2.3.2 Flood Resiliency Benefits 6
2.3.3 Habitat Benefits 6
2.3.4 Recreational and Educational Benefits 6
2.3.5 Local Redevelopment Benefits 6
3 Design Approach 8
3.1 Hydrology 9
3.2 Soils 14
3.3 Topography 15
3.4 Geomorphology 15
3.5 Habitat and Water Quality 20
4 Conceptual Design 23
4.1 Stream/Wetland Complex 23
4.2 Water Quality Treatment 25
4.3 Typical Restoration Components 27
4.4 Plant Palette 29
4.5 Park Configuration and Connection to Surrounding Redevelopment 33
5 Future Steps 36
6 References 37
Appendix A: Soil Boring Map and Log
Appendix B: Soil Classification Map
Appendix C: Proposed Restoration Area
Appendix D: Draft Grading Plan and Cross Sections
IV
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Figures
Figure 1. Location of the North Wastewater Treatment Plant within Iowa City 3
Figure 2. 2008 Flood Overview—North Wastewater Treatment Facility 4
Figure 3. Riverfront Crossings Conceptual Rendering of the Park District (labels added) 7
Figure 4. Floodplain Site Types 8
Figure 5. Screen Capture Showing the Ralston Creek Watershed 10
Figure 6. Stage-Discharge Relationship for Ralston Creek Determined Using Flows 11
Figure 7. Project Site shown in Zone X on the Johnson County FIRM, Panel 195 14
Figure 8. Channel Pattern of Ralston Creek 16
Figure 9. Bank Stability of Ralston Creek 16
Figure 10. Channel Condition of Ralston Creek 17
Figure 11. Bank Height of Ralston Creek 17
Figure 12. Map of Iowa City (1947) 19
Figure 13. Close-up of Treatment Facility Site (1947) 20
Figure 14. Conceptual Rendering of Restoration Cross Section 23
Figure 15. Proposed Grading for the Restoration Area 24
Figure 16. Site Inundation under Flood Conditions 26
Figure 17. Examples of Design Details and Field Photos of Root Wads Used in Restoration 27
Figure 18. Design Details and Field Photo of Cross Vanes Used in Restoration 28
Figure 19. Design Detail of Double Soil Lift Used in Restoration 29
Figure 20. Design Detail of Imbricated Rip-Rap Used in Restoration 29
Figure 21. Typical Cross Section of Wetland Types 30
Figure 22. Proposed Concept for Riverfront Crossings Park 34
Figure 23. Gravel Wetland Schematic 35
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Tables
Table 1. Ralston Creek Water Surface Elevations 11
Table 2. Difference in Elevation between FIS and StreamStats Flows 12
Table 3. Comparison of Iowa River and Ralston Creek Flood Elevations 12
Table 4. Ground Water Elevations 13
Table 5. Design Elevations for Floodplain Zones 13
Table 6. Ralston Creek Watershed Stream Assessment 18
Table 7. Performance of Stormwater Wetlands 21
Table 8. Wetland Types by Water Depth 30
Table 9. Grasses and Grass-Like Plants 31
Table 10. Flowering Plants 31
Table 11. Tree and Shrubs 33
VI
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I Executive Summary
Like many communities across the country that have established themselves along rivers, Iowa City has
a rich history intricately linked to its water resources. Development has encroached upon the Iowa River
and Ralston Creek to the point at which some areas of their channels have been hardened, straightened,
or even buried. "Sunny-day development" of Iowa City's floodplains has left critical infrastructure
vulnerable to large floods and heavy storm events, which can occur more and more frequently with
climate change affecting weather patterns.
The North Wastewater Treatment Plant, inundated during the flood of 2008, is one example of critical
public infrastructure susceptible to flooding from the Iowa River. Located at the confluence of Ralston
Creek and the Iowa River and immediately upstream of Highway 6, the site of the treatment plant
becomes completely isolated during a 100-year flood event. Rather than continually protecting the
treatment plant from future floods or repairing it after flood damage, Iowa City has decommissioned the
plant and is removing all of the built components from the floodplain. As part of that project, the city
plans to soften the edge along the Iowa River by creating a public park with 5 acres of restored
floodplain and wetland area along Ralston Creek.
Restoring the floodplain and wetland areas on the treatment plant site can benefit water quality, flood
resiliency, urban habitat, recreation, and education, and can serve as a catalyst to encourage additional
economic development in adjacent areas. Creating a viable and sustainable ecosystem that can support
the necessary flora requires a reliable water supply to reestablish wetland conditions. This component
of the project consists of three main objectives:
• To excavate the previously elevated floodplain to connect the restored wetland area to the
ground water table. Since this area is located at the confluence of the Iowa River and Ralston
Creek, connecting it to ground water will provide reliable hydrology for the wetland and mimic
the natural conditions found in stream confluences.
• To restore Ralston Creek's banks. To maximize the potential of the wetland area to improve
water quality, restoration of the creek banks is proposed to allow storm flows from the Ralston
Creek watershed to flow into the wetland area during smaller, more frequent storm events,
enabling physical and chemical processes to reduce sediment and nutrients.
• To stabilize Ralston Creek. Stream restoration structures and emergent plant species will be
incorporated to support long-term stability, habitat creation, and the aesthetics of the project
site. By incorporating natural stream structures, restoration activities along the banks and
floodplain area will be protected until native vegetation can stabilize the site.
The stream and floodplain restoration is one component of a larger proposed park plan, which in turn is
part of a larger redevelopment master plan for downtown Iowa City. Trails and pathways will connect
the restoration site with the remainder of the park and the adjacent proposed mixed-use development
area. City residents and visitors will be able to access the restored area at a variety of points and interact
with ecosystems, plants, and habitats, which will help to instill a strong environmental ethic in frequent
users of the park. The green infrastructure concepts implemented on a large scale in the restored
wetland are easily transferable beyond the site. Smaller stormwater gravel wetlands are proposed as
part of the master redevelopment plan to treat stormwater from impervious areas. The smaller
wetlands, which will treat stormwater instead of storm flows, will perform similar water quality
functions and incorporate similar plants, creating a seamless connection from the restoration project to
the upland mixed-use area.
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2 Introduction
Iowa City's history as the former state capital and home to the University of Iowa is richly intertwined
with the Iowa River. Residential and commercial zones are located on both sides of the river, and the
university's world-renowned hydraulics laboratory is built on the river to enable scientists to draw water
for experiments directly from it. The city's history includes several large floods that have caused
extensive damage to many city and university properties, even with the Coralville Dam controlling much
of the watershed upstream. As the city continues to grow, much of its growth is focused on moving
critical infrastructure out of the floodplain and providing effective management and safe access to the
Iowa River corridor.
One such project is the decommissioning and demolition of the North Wastewater Treatment Plant,
which is located at the confluence of the Iowa River and Ralston Creek and just north of Highway 6 (see
Figure 1). The site is approximately 1 mile south of the University of Iowa campus and downtown Iowa
City and is easily accessible from nearby residential areas. While the majority of the plant's components
have been elevated out of the floodplain, some areas are still inundated during extreme flood events.
One such event occurred in the summer of 2008 and left the facility nearly inoperable. Because of the
increased risk, the plant was decommissioned and Iowa City received funding to demolish its
components in preparation for converting the area into a public park. In addition to removing critical
infrastructure from the floodplain, the proposed park will serve as a focal point and provide river access
for planned redevelopment. Riverfront Crossings, the name of the redevelopment, will convert light
industrial areas to the north and east of the project site into mixed-use residential and commercial
areas, with a connection to the newly created park through the restored riparian wetland and floodplain
areas of Ralston Creek.
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IOWA CITY EPA Gl
RIVERFRONT GROSSING DISTRICT
LOCATION MAP
i^D '9^3 -iTXTf FL-NE iOV 'A. 3C UTH FIPS 1402
N 0 350 700
0 110 220
1,400 2,100 2,800
440 660 880
__ TBPE Firm No. F-3924 www.tetratech.corn
700 N. Saint Mary's Street, Ste. 300
— -— •• San Antonio, Texas 78205
TRA TECH pn 210.226.2922 Fx. 210.226.8497
Figure I. Location of the North Wastewater Treatment Plant within Iowa City.
2.1 Historical Conditions
The Iowa River has served as a major resource for Iowa City commercial and residential areas and the
University of Iowa campus dating back to the 19th century. Several railroad and vehicular bridges have
provided easy access to both sides of the river. A low-head dam located at the Burlington Street Bridge
originally was constructed to provide river water for early experiments at the University of Iowa's C.
Maxwell Stanley Hydraulics Laboratory, one of the nation's oldest hydraulics labs.
Iowa River flows are partially managed by the Coralville Dam located approximately 5 miles upstream of
the city. During the historic Iowa Flood of 2008, the Iowa River crested at 31.53 feet (ft) at Iowa City, 3 ft
above the previous peak set during the disastrous flood of 1993 (Buchmiller and Eash 2010). The
flooding caused significant damage to sections of the city and the university and inundated the North
Wastewater Treatment Plant (Figure 2).
Following the extreme flood event in 2008, Iowa City developed plans to decommission the treatment
facility and direct wastewater to the upgraded South Wastewater Treatment Plant, located
approximately 4 miles downstream. The North Wastewater Treatment Plant is no longer operating and
Iowa City is currently developing plans to demolish the existing buildings on the site.
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Source: Iowa Homeland Security.
Figure 2. 2008 Flood Overview—North Wastewater Treatment Facility.
The floodplain at the confluence of Ralston Creek and the river was modified to accommodate the
construction of the North Wastewater Treatment Plant. Since its construction in the mid-1930s, the
facility has undergone modifications and expansions that have further altered the local landscape. The
treatment plant and construction of Highway 6 along the southern border of the plant have divided and
greatly impacted the natural floodplain.
The historic condition of the floodplain area is unknown, but a review of the So/7 Survey of Johnson
County Iowa indicates that the site consists of Sparta loamy fine sand, typical of stream benches and
uplands (Schermerhorn 1983). That soil type is excessively drained and normally found on shallow
slopes, common with the loess and glacial drift that makes up much of the soil parent material in the
region.
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2.2 Project Overview and Goals
The construction of the North Wastewater Treatment Plant and Highway 6, along with the need to
protect critical infrastructure from flood events, resulted in the modification of Ralston Creek and loss of
its ecosystem diversity. It also disconnected the Ralston Creek and Iowa River floodplains. With the
removal of the buildings and equipment, Iowa City has the opportunity to transition the site back to its
historic, natural condition.
The city intends to convert the treatment facility site into a multiuse public park to increase access to
the Iowa River and provide open, natural space for the benefit of the community. Conversion plans
include designs for a 5-acre portion of the site to reestablish natural floodplain connections and to
promote additional flood mitigation benefits via off-channel constructed wetlands. The purpose of this
project is to produce a concept plan for the restoration of Ralston Creek that improves flow and habitat
conditions and maximizes the treatment of stormwater overflows in constructed wetlands within the
reclaimed floodplain.
To protect critical infrastructure near the treatment facility, Ralston Creek was straightened, hardened,
and essentially forgotten. Riprap lines both banks in some areas and the channel cross-section remains
uniform through much of the study reach. Without restoration of the floodplain, which is significantly
higher than the bed of the creek and disconnected from bankfull flows, adjustments to the channel
pattern or cross-section will have little impact on the health of the ecosystem. Creating a floodplain that
is accessible under frequent flow conditions will help to establish the hydrologic regimes necessary for
healthy stream conditions, to promote aquatic life, and to reconnect nearby residents to a water
resource that has been significantly minimized throughout Iowa City.
2.3.1 Water Quality Benefits
A constructed wetland system located within the Ralston Creek floodplain will accept storm flows from
the creek and provide water quality benefits through longer residence time, resulting in additional
settling, filtering, and plant uptake processes. By primarily treating creek flows that occur during short,
intense storm events, the off-channel wetland can provide water quality benefits and complement the
water quality improvements from site-scale green infrastructure distributed throughout the watershed.
Restoration from a channelized stream reach to a naturalized section can increase travel time, and a
study by Bukaveckas (2007) has shown that slowing water velocities can result in significantly higher
nutrient uptake rates. Cadenasso et al. (2008) offered many options for reducing nitrate yield from
urban areas, noting that the "key ability of new functional interfaces to serve as hot spots for
denitrification in urban watershed[s] is for them to capture nitrate-laden water and hold it long enough
under the anaerobic, high-carbon conditions suitable for denitrification to occur" (Cadenasso et al. 2008,
p. 223). Directing smaller storm flows from Ralston Creek into a constructed wetland area to provide the
necessary conditions and residence time for denitrification could result in a significant reduction in
nutrients reaching the Iowa River.
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2.3.2 Flood Resiliency Benefits
In an attempt to floodproof the North Wastewater Treatment Plant, the wastewater treatment facilities
were elevated to remain outside of the floodplain, creating an island between Ralston Creek and the
Iowa River during flood events. By lowering the elevated area and introducing a tiered approach to the
landscape and plant material, the restored floodplain area will be able to handle larger and longer flood
events that impact the Iowa River.
2.3.3 Habitat Benefits
The riparian areas and channel banks along the river and the creek upstream of the treatment plant are
heavily developed. Little shelter or food supply is available to encourage aquatic animal diversity within
the Iowa River or Ralston Creek corridors throughout Iowa City. Restoring Ralston Creek and the
surrounding floodplain into a riparian wetland area would provide much-needed habitat to sustain a rich
aquatic ecosystem. In a survey of why landowners restore wetlands conducted by Pease et al. (1996),
more than 80 percent of respondents listed providing habitat for wildlife as "extremely important."
2.3.4 Recreational and Educational Benefits
The restoration of Ralston Creek and the associated floodplain at this location creates an opportunity for
area residents and visitors to access the stream. In its current condition, the stream is largely unavailable
due to encroachment of the riparian area by commercial and industrial land uses along with an incised
stream channel. A tiered, or benched, approach to channel restoration that results in a range of
elevations will inspire a variety of habitats as well as multiple vantage and access points to use to
interact with the habitat areas.
2.3.5 Local Redevelopment Benefits
The conversion of the North Wastewater Treatment Plant site to a park and restored floodplain serves
as a critical focal point of a planned Riverfront Crossings redevelopment project (HDR 2013). The park
district, shown conceptually in Figure 3, is central to the walkable, mixed-use redevelopment anticipated
along the Iowa River and Ralston Creek. The proposed park will serve as a public amenity for the
neighboring community and the entire city, but also will inspire green infrastructure and sustainability
themes that can be carried out on a smaller scale in the surrounding residential and commercial areas.
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Source: HDR 2013.
Figure 3. Riverfront Crossings Conceptual Rendering of the Park District (labels added).
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3 Design Approach
The floodplain restoration of the 5-acre portion of the site focuses on reconnecting more frequent storm
flows within Ralston Creek to a larger floodplain area. Plans include a constructed wetland to maximize
the water quality benefits associated with storm flows inundating the larger floodplain area.
The designs for the restored portion of Ralston Creek, the reclaimed floodplain area at the confluence of
the creek and the Iowa River, and the constructed wetland mimic historical conditions at the site or
natural features commonly found in similar environments. The design is intended to improve ecosystem
health at all flow levels by establishing multiple inundation zones, each defined by different flood
events. The different zones allow the design to incorporate a wide variety of plant species, contributing
to the diverse environment necessary for resilience under varying water surface elevations.
Multiple zones located at different elevations are typical of forested floodplains in Iowa. Randall and
Herring (2012) note that "flooding can both enhance and stress a riparian ecosystem" (Randall and
Herring 2012, p. 1). They identify three main floodplain site types as "point bar," "first bottom," and
"second bottom" (see Figure 4). The design of the restored Ralston Creek and reclaimed floodplain
follows these types, with the added curvature of the Ralston Creek pattern establishing the point bar,
the constructed wetland simulating an oxbow feature within the first bottom, and the remnant
treatment facility site elevation serving as the high terrace, or second bottom.
Cut bank
Second bottom
Point bar
First bottom
River channel
Oxbow
Source: Randall and Herring 2012.
Figure 4. Floodplain Site Types.
The hydrology of Ralston Creek serves as the basis for establishing elevations of the floodplain zones.
The creek's watershed (about 9 square miles) is much smaller and more urbanized than the Iowa River
watershed (more than 3,200 square miles at Iowa City), making the creek much more responsive to
smaller but more intense storm events. Targeting the more frequent fluctuations is consistent with
typical design guidance for other green infrastructure, such as the EPA's criteria of retaining the 95th
percentile storm intended to provide significant water quality treatment (USEPA 2009). In this instance,
the smaller storm events are not used to size retention areas but to set the elevation at which storm
flows will access the overbank area, treating nutrients and sediment through physical and chemical
processes that occur in floodplain areas.
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3.1 Hydrology
The restoration site is influenced by flows from Ralston Creek and the Iowa River, both of which have
defined Federal Emergency Management Agency floodplains. The Johnson County Flood Insurance
Study (FIS) indicates that the 100-year flood (the highest elevation that has a 1 percent chance of
occurring annually) for the Iowa River varies from an elevation of 644.6 ft at Highway 6 and increases to
an elevation of 645.5 ft at the railroad crossing located near the northern portion of the treatment
facility site (FEMA 2002). This represents approximately a 1-foot drop in head as the river flows along
the site from north to south, passing under the structures at the railroad, Benton Street, and Highway 6.
Flood elevations of all of the expected storm events vary from about 18 ft to about 26 ft above the
stream bed of the Iowa River. As most of the existing treatment plant site is situated at elevations above
640 ft, most of the site is currently subjected only to the 10-percent chance flood (or 10-year return
frequency) and higher. This is typical of a higher terrace feature. Access to a floodplain between the 1-
and 10-year return intervals is not consistently available throughout the site. Setting the water surface
elevations for lower flood events is important for establishing the correct elevation for the first bottom
zone. During higher flood events, the floodplain in the area is dominated by the Iowa River; however,
during lower flood events, the water surface elevations most likely will differ between the Iowa River
and Ralston Creek.
Randall and Herring (2012) indicate that first bottoms flood every 1-3 years, which is consistent with the
bankfull frequencies commonly used in stream restoration design (Woodyer 1968). Established flood
elevations are not available within the FIS for events below the 10-year return interval. Therefore, to
develop water levels for lower storm events, USGS StreamStats was used to determine flows at the
ungaged Ralston Creek (Eash et al. 2013).1 Figure 5 shows the delineated watershed for Ralston Creek
displayed in the StreamStats program.
1 A USGS stream gage is located along the south branch of Ralston Creek but is not appropriate to use to determine flows at the
treatment facility site.
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2USGS
Iowa Stream Stats
StreamStats Ralston Watershed
above confluence near HWY 1
':.:,-. r:. £!:.•] ;ri CTt.riic..: P
. Parlel Record
Peak Row; Partial Record
Peak and Low Flow Partial Record
"yvv^
**••
!'• ' -iX&.Tk ~s .ci^~™^*l*i^BBPS^!»"KS?l«Sr9'^i«^'*'i)*
Source: USGS StreamStats.
Figure 5. Screen Capture Showing the Ralston Creek Watershed.
While StreamStats can be an effective way to quickly establish flows over a broad range of return
intervals, they still need to be converted to flood elevations. To determine elevations, the city provided
a cross-section of Ralston Creek created from site topography. Manning's equation was used along with
conservative assumptions for energy slope (0.004) and roughness (0.05) to develop a stage-discharge
relationship for Ralston Creek in the area of the treatment facility site, as shown in Figure 6. Flows for
the 2-, 5-, 10-, 25-, and 50-year return intervals were converted to elevations using this relationship, as
shown in Table 1.
Table 2 compares the elevations calculated using the StreamStats flows and the stage-discharge
relationship to the established elevations presented in the FIS (FEMA 2002). While the difference for the
10-year flood is less than one-half of a foot, this difference doubles at the 50-year return interval. The
reliability of this analysis is limited at higher flow events, but it can be used for lower flow events to
establish the first bottom level. For this conceptual design, the top of the bank for the restored Ralston
Creek will be set at 634 ft to fit within the 1-3-year flood frequency typical of Iowa floodplains.
10
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Stage-Discharge Relationship
fi.-M
542
640
If 638
636
633
b.iO
» Stage-Discharge Relationship
Polynomial Trend Line
500 1000 1500 2000 2500 3000
Flow/rate (cfs)
3500
4000
4500
5000
Source: USGS StreamStats.
Figure 6. Stage-Discharge Relationship for Ralston Creek Determined Using Flows.
Table I. Ralston Creek Water Surface Elevations
Frequency (Years)
2
5
10
25
50
Flow (cfs)
558
1,210
1,850
2,830
3,500
Elevation (ft)
634.7
636.7
638.0
639.5
640.6
Source: USGS StreamStats.
Note: cfs = cubic feet per second.
11
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Table 2. Difference in Elevation between FIS and StreamStats Flows
Frequency
(Years)
10
50
Elevation from
FIS (ft)
638.4
641.4
Elevation from
StreamStats (ft)
638.0
640.6
Difference
(ft)
0.4
0.8
Sources: FEMA 2002; USGS StreamStats.
Performing a regression analysis on gage data over a period of 111 years enables a comparison with the
Iowa River water surface elevations. The USGS National Water Information System provided the stage
and discharge data for the Iowa River stream gage at Iowa City. That gage is located eight-tenths of a
mile upstream from the mouth of Ralston Creek. A Log Pearson Type III flood frequency analysis was
performed to determine flowrates for the 2- and 5-year return intervals and a stage-discharge
relationship was developed for the Iowa River gage and used to convert the selected flows to water
surface elevations. To relate the water surface elevations determined at the stream gage to water
surface elevations at the treatment facility site, a consistent conversion factor was applied to the data.
Table 3 shows a comparison between the Iowa River elevations—calculated with the regression analysis
as well as with the 10-year water surface elevation included in the FIS—and the Ralston Creek
elevations. Although the data show minimal difference at the 2-year frequency, the difference varies
significantly at higher flood events.
Table 3. Comparison of Iowa River and Ralston Creek Flood Elevations
Frequency
(Years)
2
5
10
Iowa River
Elevation from
FIS (ft)
639.8
Elevation from
Regression (ft)
634.9
638.9
Ralston Creek
Elevation from
FIS (ft)
638.4
Elevation from
StreamStats (ft)
634.7
636.7
Difference
(ft)
0.2
2.2
1.4
Sources: FEMA 2002; USGS StreamStats.
Establishing an oxbow feature or, in this case, an off-channel constructed wetland, requires tapping into
ground water sources to obtain the hydrologic conditions necessary to support emergent wetland plant
species. Since this project is at a conceptual level, no soil borings or ground water investigations were
conducted. Instead, past soil investigations were used to determine potential ground water levels. A
subsurface investigation was conducted in July 1994 as part of proposed improvements to the
wastewater treatment and collection facilities (Terracon Consultants 1994). Four borings were
conducted within and adjacent to the treatment facility; appendix A provides a map of the boring
locations and the boring logs. Table 4 shows ground water levels for the boring locations.
12
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Table 4. Ground Water Elevations
Boring No.
NP-1
B-5
B-7
B-7A
Description of Location
Northeast corner of site, near east bank of the Iowa
River
East side of site, along west bank of Ralston Creek
Southeast corner of site, along west bank of Ralston
Creek
Southeast corner of site, along east bank of Ralston
Creek
Range of Elevations
Surface
Elevation (ft)
645.1
641.5
641.5
646.4
641.5-646.4
Ground Water
Elevation (ft)
630.1
631.5
633.0
626.4
626.4-633.0
Source'. Terracon Consultants 1994.
The borings conducted in 1994 show a range of ground water levels across the site. Excluding boring 7 A,
which is located on the east side of Ralston Creek and not within the treatment facility site, the values
range from approximately 630 ft at the northeast corner of the site near the Iowa River to 633 ft at the
southeast corner of the site near Ralston Creek. For the purposes of this concept design, a summer
ground water range of 630-633 ft will be used to establish elevations for the constructed wetland.
Revisiting the cross-section showing the typical zones of Iowa floodplains in Figure 4, Table 5 lists the
defining elevations for each level. These elevations will determine the grading within the proposed
5-acre restoration area.
Table 5. Design Elevations for Floodplain Zones
Floodplain Feature
Point Bar
First Bottom
Constructed Wetland
Second Bottom (Higher Terrace)
Elevation (ft)
632-634
634
631
638-640
Existing flood studies and gage analyses were used to establish the design elevations of the floodplain
zones to allow frequent storms to access the overbank areas. Proposed grading changes within the site
make the area more accessible to flood flows and could have an effect on the floodplain surface
elevations. A section of the flood insurance rate map shows that a large portion of the treatment facility
site is located in zone X, surrounded by zone AE (Figure 7). The floodplain model might need to be
altered and resimulated to provide the final floodplain elevations needed for design. The current
floodplain delineation also includes both a floodplain (flood hazard) and a floodway. The proposed
project should not alter the floodway, but rather create a larger floodplain area by removing some of
the fill material at the treatment plant construction site. A more detailed hydraulic modeling analysis of
the Iowa River than was performed as part of the conceptual design should be included in future design
13
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efforts, especially if the park redevelopment results in significant alteration of the berm along the east
bank of the Iowa River.
Source: FEMA 2002.
Figure 7. Project Site shown in Zone X on the Johnson County FIRM, Panel 195
The U.S. Department of Agriculture's Natural Resources Conservation Service (NRCS) provides soil
surveys for Johnson County from 1922 and 1983 (Tharp and Artis 1922; Schermerhorn 1983). Evaluating
both surveys often provides separate information, as older soil surveys often provide a better context
for replicating the historic floodplain conditions and more recent surveys provide data on current
disturbed conditions. In this case, the two soil surveys represent conditions before and after the
construction of the North Wastewater Treatment Plant. According to the 1922 survey, the prevailing soil
types were silt loams of loessial origin. Rolling hills found within the region were forested and the soils
were not high in organic matter. Flatter areas typically consisted of prairies generally well supplied with
humus. Floodplains along rivers often made very fertile agricultural lands, and farmers historically
stripped them of timber and converted them to farmland.
According to the 1922 NRCS soil survey, there was little alluvial land along the course of the Iowa River.
Below Iowa City, however, was approximately 30 square miles of floodplain and terrace. Only occasional
expansions of the narrow floodplain existed above Iowa City, but below the city the valley widened to
2-3 miles and produced tillable bottom land suitable for agriculture (Tharp and Artis 1922).
The 1983 NRCS maps show the site soils as 7, 11B, 41, 163F, and 793. The Iowa River is listed as "W" for
water. The portion of the property where the treatment plant is currently located is completely in the
designation 41, which refers to soil type Sparta—fine sand mixed with loamy fine sand. That soil type
maintains a depth to the high water table of at least 6 ft or more below the surface. Sparta is an
extremely well-drained soil type and is designated as hydrologic soil group A (Schermerhorn 1983).
14
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The 11B area contains soil type Colo—frequently flooded soil and is found at the location of Ralston
Creek. This soil type consists primarily of silty clay loam with a high water table typically found between
1 -3 ft below the surface. Colo is subjected to occasional flooding and is poorly drained, designated as
hydrologic soil group B/D. Appendix B provides a map of the soil types found in that area.
Soils with hydrologic groups of A and B and high water tables are not hydric or conducive to wetland
formation without connecting to the reliable hydrologic conditions needed to create a saturated or
inundated condition that promotes anaerobic conditions during the wet season. However, these soils
can support vibrant forested areas that accept overbank riverine flooding. Creating off-channel wetland
systems in this area requires a connection to the ground water level to establish the necessary
hydrologic conditions. This process is similar to the forming of oxbow lakes from remnant channel
sections that are closely tied to the ground water level. In natural environments, oxbow lakes often
transition to wetland areas through the accumulation of sediment and wetland seed banks during
overbank flood flows.
3.3 Topography
The confluence of the Iowa River and Ralston Creek is near the portion of the state where the riverine
system transitions from riparian conditions to the north, characterized by steeper bluffs cut by the river
and little adjacent floodplain, to conditions further south, characterized by broader expanses of
floodplain as large as 2-3 miles wide. The restoration system proposed in this conceptual design would
transition to overbank systems that follow the concept of providing for multiple hydrological conditions
and habitats to match the overall transition to wider floodplains typical of southern Iowa.
3.4 Geomorphology
Geomorphological field assessments were not conducted as part of this conceptual-level design. To
develop an understanding of geomorphologic conditions, historic maps and an external stream
assessment were examined.
The Iowa Department of Natural Resources recently conducted a watershedwide assessment of Ralston
Creek, producing several informative maps that document current stream conditions (IDNR 2014).
Figure 8 through Figure 11 show some of the stream parameters IDNR evaluated: channel pattern, bank
stability, channel condition, and bank height. Table 6 includes a comparison of the parameters between
the section of Ralston Creek along the treatment facility site and the dominating condition of the
Ralston Creek watershed.
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Ralston Crvi'k Urban Stream Assessment
linv.i Cily, Johnson County, lovvj
Channel Pattern
Source: IDNR2014.
Figure 8. Channel Pattern of Ralston Creek.
Ralston Creek Urban Mn-am As
Iowa City, Johnson County, Iowa
Bank Stability
Source: IDNR 2014.
Figure 9. Bank Stability of Ralston Creek.
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Ralston Creek Urban Stream
Iowa C'ily, Johnson County, l
Channel Condition
Source: IDNR2014.
Figure 10. Channel Condition of Ralston Creek.
Ralston Creek Urban Stream Assessment
Iowa City, Johnson C'ounty, Iowa
Bank
Source: IDNR 2014.
Figure I I. Bank Height of Ralston Creek.
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Table 6. Ralston Creek Watershed Stream Assessment
Stream Parameter
Channel Pattern
Bank Stability
Channel Condition
Bank Height
Condition at Treatment Facility Site
Meandering, straight
Moderate erosion, minor erosion
Past channel alteration
6-10 ft
Dominating Condition in Watershed
Straight
Stable
Natural channel
3-6 ft, 6-10 ft
Source: IDNR 2014.
Stable and natural channels dominate the overall condition of Ralston Creek. In contrast, the section of
Ralston Creek bordering the treatment facility site is disconnected from the floodplain, altered, and
showing erosion. The figures from the IDNR assessment show a more comprehensive view of Ralston
Creek. Even though much of Ralston Creek is considered to be a natural channel condition, high banks
and erosion are still present in these sections. The assessment indicates that Ralston Creek could be
evolving as a result of changes in hydrology within the watershed. Restoration of this section of Ralston
Creek to preexisting natural conditions found upstream could serve as a guide for future restoration
upstream if instabilities continue.
The IDNR assessment validates the opportunity for channel restoration along the selected reach of
Ralston Creek. As discussed in section 3.1, Hydrology, Iowa floodplains typically include a point bar that
extends towards a first bottom. Establishing the appropriate connection to the first bottom is critical to
restoring a natural channel condition. Even with that connection, however, creating a point bar feature
is not possible in a straightened stream channel. An investigation into previous conditions can help to
establish the appropriate curvature required to initiate the creation of point bar features. Figure 12
shows a map of Iowa City that the City Engineer's Office prepared in 1947. A close-up of the treatment
facility site shows the historic pattern of Ralston Creek (Figure 13). Mimicking those conditions leads to
the establishment of a meandering channel with a radius of curvature in the bends of approximately 230
ft (Iowa City Engineer's Office 1947).
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Source: Iowa City Engineer's Office 1947.
Figure 12. Map of Iowa City (1947).
19
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Source: Iowa City Engineer's Office 1947.
Figure I 3. Close-up of Treatment Facility Site (1947).
3.5 Habitat and Water Quality
Wetlands can be used to treat stormwater flows and as a green infrastructure approach to improve
water quality (Miller 2007; USEPA 1999). Stormwater runoff is a major source of pollutants to our
waterways and has been shown to transport pesticides, oils, heavy metals, nutrients, and other
pollutants (Lenhart and Hunt 2011). Constructed wetlands provide many environmental benefits. They
enhance water quality by mitigating peaks in flow, replenishing ground water, reducing channel erosion,
using vegetation to reduce pollution, and providing wildlife habitat (SMRC 2014; USEPA 1995; USEPA
1999).
The effectiveness of stormwater wetlands in pollutant removal is dependent on establishing proper
hydrology, appropriate flow paths, wetland system type, and loading rates. Stormwater wetlands
achieve pollutant removal through physical (e.g., sedimentation, filtration), chemical (e.g., precipitation,
adsorption to sediments), and biological (e.g., plant and bacterial uptake) mechanisms (USEPA 1996). In
Storm Water Technology Fact Sheet: Storm Water Wetlands, EPA indicates significant long-term removal
rates for many key pollutants found in urban environments (Table 7) (USEPA 1999).
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Table 7. Performance of Stormwater Wetlands
Pollutant
Total Suspended Solids
Total Phosphorus
Total Nitrogen
Organic Carbon
Petroleum Hydrocarbons
Cadmium
Copper
Lead
Zinc
Bacteria
Removal Rate
67%
49%
28%
34%
87%
36%
41%
62%
45%
77%
Source: Modified from USEPA 1999.
A recent study of stormwater wetlands in North Carolina found significant reductions in peak flows and
runoff volumes by 80 percent and 54 percent, respectively. In addition, pollutant load reductions were
significant—total Kjeldahl nitrogen: 35 percent; nitrate/nitrite (NO2+3): 41 percent; ammonium (NH4-N):
42 percent; total nitrogen (TN): 36 percent; total phosphorus (TP): 47 percent; organophosphate OP:
61 percent; and total suspended solids (TSS): 49 percent (Lenhart and Hunt 2011). The International
Stormwater BMP Database is a compilation of BMP effectiveness measures from various designs
throughout the world. According to the July 2012 update, when looking at wetland basins and channels,
median removal of pollutants comparing inflow to outflow included TSS: 20.0-20.4 milligrams per liter
(mg/L) inflow and 9.06-14.3 mg/L outflow; TP: 0.13-0.15 mg/L inflow and 0.08-0.14 mg/L outflow; and
TN: 1.14-1.59 mg/L inflow and 1.19-1.33 mg/L outflow (Leisenberg 2012).
Although the types and effectiveness of constructed wetland systems vary, a common factor in the
success of all wetland systems is the presence of proper hydrology. The dominant soils in the treatment
facility site are well draining and not conducive to establishing the anaerobic conditions necessary to
support wetland vegetation. In many constructed wetlands, a natural or synthetic liner is installed to
prevent water from draining through the soil media and ultimately establishing a hydric soil community.
The success of constructed wetlands with liners is dependent on a reliable water supply that can provide
the proper hydrology. In the case of constructed wetlands for wastewater treatment, effluent
discharges can reliably provide that supply. In the case of stormwater treatment, the wetland system
rely on the dynamic nature of storm events. In both cases, proper sizing of the wetland to match the
incoming load is critical to the success of the system.
Alternatively, a constructed wetland also can tie into the ground water supply to provide the necessary
hydrology. Ground water can provide a reliable source of water for wetland systems, even in well-
drained soils, and is not dependent on loading variations. Ground water levels do fluctuate, which can
lead to large-scale changes in plant communities, but effects can be mitigated by providing a diversity of
plants at a variety of elevations throughout the wetland area. A thorough understanding of the local
ground water table is needed to successfully establish wetland plant communities, ensuring that they
21
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can access the ground water supply at the correct times throughout the year. The fluctuation of the
ground water table will ultimately define the final grading plan, and the correct ground elevations will
support establishment of a strong wetland plant community.
The diversity of plants and elevations also supports a range of habitats and promotes use by a variety of
wildlife. Wetlands can provide food sources, access to water, and refuge from predators and
environmental conditions. They are among the most biologically productive ecosystems in the world. Up
to one-half of North American bird species nest or feed in wetlands and, although wetlands make up
only about 5 percent of the land surface in the continental United States, about 31 percent of the plant
species found in wetlands (USEPA 2001a). Research has shown that constructed wetlands support high
levels of biodiversity among phytoplankton, zooplankton, benthic macroinvertebrates, fish, and birds
(Shaharuddin et al. 2011). Additionally, a national survey conducted by Pease et al. (1996) found that
85 percent of landowners believe that providing habitat for wildlife is an extremely important reason for
restoring wetlands. Bordered by the Iowa River on the west, Highway 6 on the south, and existing and
proposed development areas on the north and east, the treatment facility site can become an important
urban oasis for wildlife.
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4 Conceptual Design
The approach to the conceptual design of the Iowa City restoration site was to re-create the historic
floodplain conditions and establish an off-channel wetland to maximize water quality treatment during
frequent storm events. This approach requires the establishment of multiple elevations that replicate
the functionality of typical floodplain systems in the region, while stabilizing entry and exit points for
flows from both Ralston Creek and the Iowa River. Ultimately, the functionality of the flood flow and
water quality components of the site should seamlessly integrate with the other proposed modifications
and amenities of the park site to encourage public interaction and environmental education in all
portions of the reclaimed treatment facility site. Figure 14 shows a cross section of the proposed
restoration design for Ralston Creek and the off-channel wetland area.
10-YR FLOOD
(RALSTON CREEK)
2 YR FLOOD
(RALSTON CREEK)
Source: Tetra Tech.
Figure 14. Conceptual Rendering of Restoration Cross Section.
4.1 Stream/Wetland Complex
To develop a restored stream/wetland complex that returns natural functionality to this site, a 5-acre
parcel was selected that begins near the abandoned railroad crossing of Ralston Creek and gradually
expands to include the area between the Iowa River and Ralston Creek on the south side of the site,
ending near the Highway 6 embankment. Appendix C provides an outline of the proposed restoration
area. The primary floodplain and wetland restoration components of the project will be located within
this area, although grading could extend beyond the boundary to tie into existing grades or other park
features. Appendix D provides conceptual grading plans of the site (including cross sections); Figure 15
also provides a view of the grading in this area.
The restoration of Ralston Creek into a natural channel with a stable stream-floodplain connection
requires adjustment of the channel cross section and pattern further to the west. The top elevation of
the banks is generally set at 634 ft to provide overbank flows under the 1-2-year flood frequency. A
bench will be graded into the east bank of the creek at that elevation until it matches the existing left
bank. The grading will reduce stresses along the existing left bank, which the city does not currently
control. A radius of curvature of approximately 230 ft—estimated from historical maps of the area to
match preexisting conditions—is used to pull the channel away from the existing left bank and push it
back to reconnect with the existing channel location slightly upstream of the culvert under Highway 6.
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Source: Tetra Tech
Figure 15. Proposed Grading for the Restoration Area.
Reestablishing sinuosity within this section of the complex will help to naturally create point bars in the
meander bends connecting the stream bed to the first bottom, or primary bench. Creating the point bars
is important to manage sediment within this reach and to encourage habitat diversity in the channel.
Point bars and channel sinuosity also can have an effect on local variations in water surface elevation for
various flood events, adjusting specific locations of overbank flows.
The ground water-supplied wetland area is established by using the existing topography to simulate an
oxbow lake configuration. Significant excavation is necessary to establish the approximately 631-ft
elevation required to access the ground water table. Locating the wetland area at the site of the existing
equalization pond (elevation of approximately 638 ft) minimizes this excavation. Typically, oxbow lakes
form from remnant channel sections of large meanders that are cut off from the main channel; to
simulate this formation, a high terrace will be left between Ralston Creek and the created wetland. The
high terrace is the second bottom and is located at an elevation of approximately 638 ft to adhere to the
secondary level found in Iowa floodplains. The terrace is a typical feature of stream corridors
throughout this region.
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The high terrace serves multiple functions. Primarily, it helps to ensure that park users access the newly
established floodplain and wetland area only at specific locations. Intentional access points along the
high terrace help protect the sensitive wetland ecosystem, promote safety, and provide multiple
viewpoints for park users. From a geomorphic perspective, the significant modifications to the channel
pattern and overbank floodplain proposed in this concept design can alter the creek's capacity to
transport sediment. Loads from upstream could dynamically adjust water surface elevations and
overbank flow locations. Maintaining the high terrace helps to ensure that overbank flows primarily
follow designed entrance and exit points into and out of the wetland area. The entry and exit points can
be reinforced to provide long-term stability of the system. The high terrace also creates a higher
established bank on the outside bend of the restored stream channel, helping to maintain natural flow
conditions within Ralston Creek. Finally, the high terrace allows a wider variation of plant material
within the area such as less flood-resistant plants.
To promote more access to the wetland and floodplain areas during lower storm events, the conceptual
design includes lower portions of the west bank of Ralston Creek in areas where there is a remnant
channel. The lower areas, located at approximately 633 ft, would be accessed during the 1-year flood
event or perhaps even more frequently. These areas should be graded appropriately to maintain a
positive drainage from the entrance to the exit to facilitate a natural flow-through system following the
direction of the riparian corridor.
Water surface elevations of the 2-year flood frequency for the Iowa River are similar to those
established for Ralston Creek. Currently, a berm along the east bank of the Iowa River prevents the
flows from accessing this area, and it is not until nearly the 10-year flood event that the Iowa River
directly inundates portions of this site. The concept plan proposes lowering the elevations only slightly,
to an elevation of approximately 636 ft, which is more closely tied to the 5-year flood event. No other
major changes to the berm are proposed in this project as a way to reduce grading and cut on the site
and to minimize any impacts to the Iowa River floodway. Coordinating with other proposed park uses
could adjust the ultimate grading and elevations within the area.
This proposed design requires a significant amount of cut and, ultimately, removal of material from the
site to match the multiple design elevations. Initial estimates indicate a net cut of more than 64,000
cubic yards of material.
By not connecting the Iowa River and Ralston Creek at lower flow events, the full wetland and floodplain
area is available to treat smaller storm events from the Ralston Creek watershed. With an overbank
connection to Ralston Creek near the mouth, this area can assist in removing sediment, nutrients, and
other pollutants before they enter the Iowa River. Stormwater flows up to the 2-year event will enter
only from Ralston Creek,2 and the proposed high terrace and additional site grading will result in longer
flow paths and residence times within the system.
1 Flood events higher than the 2-year event will begin to experience backwater effects from the Iowa River.
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While the ultimate size of the wetland portion depends on available ground water hydrology, a
minimum of one-half acre of permanent wetland area located at an elevation of 631 ft is proposed. This
permanent wetland area could expand to 1 acre depending on ground water and overbank flow
availability. Significant water quality improvements are not limited to the permanent wetland area. As
the water surface elevation increases, flows access larger portions of the site, which causes filtering and
uptake processes to occur. Figure 16 shows the inundation of the site under flood conditions. The
permanent wetland area under normal flow conditions (631 ft, shown in blue) is approximately one-half
acre. As the water surface elevation increases to 634 ft (between the 1- and 2-year events), flows
inundate more than 1 acre of the site. At 634 ft, flood flows access nearly 4 acres of the restored site.
Under current conditions, the banks of Ralston Creek at that elevation would still confine the flows;
however, under restored conditions, there is the possibility for greater water quality benefits through
physical, biological, and chemical processes.
•-*.1
'
.
Source: Tetra Tech
Figure 16. Site Inundation under Flood Conditions.
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4.3 Typical Restoration Components
Typical restoration features that would be beneficial in the design of a stormwater wetland and for
improving the bank and meander pattern of Ralston Creek include root wads, cross vanes, vegetated soil
lifts, and imbricated streambed material.
Root wad structures can help to stabilize banks and provide in-stream habitat among the root branches
for fish and invertebrates. Figure 17 shows typical examples of how a root wad can help stabilize the
edge of a streambank.
Plant and Seed
Cable with a min. of 3
wraps and two cable
c|pmps
Live cuttings and/or
live clumps
Rock Bolster
Option A Excavate for Rock Bolster
Anchor with Rock Bolster and Stone toe.
Anchor with Soil Anchors and Stone toe.
Plant and Seed
Footer Log
Plant and Seed
Footer Log
Backfill
Excavate to seat
Rock Bolster
Rock and fill
as needed.
Rock Bolster
Rock and fill
as needed.
Sources: USEPA 2001b; NRCS 2008.
Figure 17. Examples of Design Details and Field Photos of Root Wads Used in Restoration.
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Cross vanes or J-hook vanes can help to stabilize a channel and to channel flow away from banks to
prevent erosion. Figure 18 shows a typical detail of cross vanes and J-hook vanes, as well as a photo of a
cross vane in practice.
So/7 lifts can help to stabilize a bank and to tie it in to a more gradual slope. Figure 19 shows a typical
detail of a soil lift.
Imbricated rip-rap can help to stabilize a bank and prevent erosion. Figure 20 shows a typical detail of
imbricated rip-rap.
Key into bank for
a minimum length
equal to bank
height Vegetate
Key excavation with
ive cuttings/clumps
before backfill.
Place live cuttings
and live clumps in
excavated bank area
before rock and
backfill.
Stream Bank
Hook Vane Plan
Sources: NRCS 2006, 2007.
Figure 18. Design Details and Field Photo of Cross Vanes Used in Restoration.
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ECM (REFER
TO DETAIL)
1.0' (MIN.) SETBACK
TIE INTO EXISTING BANK
'AS PER ECU DETAIL
J LENGTH IS A
MINIMUM OF
3' INTO EX. BANK
DOUBLE LAYER SOIL LIFT CROSS SECTION
Source: WSSC 2013.
Figure 19. Design Detail of Double Soil Lift Used in Restoration.
2:1 SLOPE
BASE FLOW W.S. ELEV.
STREAM INVERT
TOP OF BANK
FILTER CLOTH
PROFILE
Source: M-NCPPC 2014.
Figure 20. Design Detail of Imbricated Rip-Rap Used in Restoration.
4.4 Plant Palette
In this region of Iowa, native stream/wetland systems contain a variety of species with a significant
adapted variation to perennial or periodic inundation. The tolerance of those species would sort out
along the hydrologic gradient based on the frequency and duration with which the areas become
inundated or saturated. Wetlands often are categorized based on the typical water depth during the
growing season and the vegetative community, as described in Table 8 (Shaw and Fredine 1956). The
proposed restoration of the wetland involves connection to the ground water table to maintain wetland
hydrology; no open water wetland areas are proposed. Instead, the proposed wetland area will be
planted with a marsh vegetative community and transition gradually to wet meadow and upland plants.
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(see Figure 21). The delineation between these vegetative communities will depend on hydrology and
other environmental factors, and will likely adjust as the proposed restoration stabilizes. Similar
plantings will be established along the restored Ralston Creek, with an emphasis on wet meadow plants.
Table 8. Wetland Types by Water Depth
Wetland Type
Wet Meadow
Marsh
Open Water
Water Depth
No standing water, soils
saturated
Up to 3 ft
3-10 ft
Vegetative Community
Grasses, sedges, rushes, various broad-leaved plants
Grasses, bulrushes, spikerushes, cattails, reeds,
pondweeds, waterlilies
Pondweeds, coontail, watermilfoils, waterlilies
Source: Shaw and Fredine 1956.
Marsh
Open Water
Source: Arbuckle and Pease 1999.
Figure 21. Typical Cross Section of Wetland Types.
The following criteria were assessed in selecting the palette of plant species:
• Mimic a typical floodplain wetland with vegetation native to Iowa.
• Require as little maintenance as possible during the species establishment period.
• Contain advantageous seed dispersal and germination traits so that natural regeneration occurs
and the system is sustained.
• Resist varied hydrologic conditions to enable adaptive management and to increase survivability
under natural stabilization processes.
• Be readily available at nurseries and in stock in sizes that make sense for initial planting.
• Create an environment for diverse wildlife.
• Result in an environmental restoration project that is aesthetically pleasing to the public.
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The palette of plant species includes grasses and grass-like plants (Table 9), flowering plants (Table 10),
and trees and shrubs (Table 11) and was created to meet the desired criteria and is based on each
species' suitability for each of the wetland types proposed for the project. The conceptual grading plans
will create a tiered approach with opportunities for differing hydrologic flood regimes so that the system
will stabilize and adjust its native composition, as any natural system does with time.
Table 9. Grasses and Grass-Like Plants
Grasses and Grass-Like Plants
Species
Common Name
Big Bluestem
Bluejoint
Sedges
Spike Rushes
Virginia Wild Rye
Mana Grass
Rushes
Cutgrasses
Common Reed
Fowl Blue Grass
Bulrushes
Dark Green Bulrush
Wool Grass
Prairie Cordgrass
Broadleaf Cattail
Scientific Name
Andropogon gerardii
Calamagrostis canadensis
Carex spp.
Eleocharis spp.
Elymus virginicus
Glyceria spp.
Juncus spp.
Leersia spp.
Phragmites australis
Poo palusths
Schoenoplectus spp.
Scirpus atrovirens
Scirpus cyperinus
Spa rt in a pectinate
Typha latifolia
Upland Prairie
X
X
X
Wetland Type
Wet Meadow
X
X
X
X
X
X
X
X
X
X
X
X
Marsh
X
X
X
X
X
X
X
X
X
Table 10. Flowering Plants
Flowering Plants
Species
Common Name
Nodding Onion
Canada Anemone
Milkweeds
Sticktight
False Aster
Buttonbush
Flat Topped Aster
Rattlesnake Master
Bonset
Scientific Name
Alii urn cernuum
Anemone canadensis
Asclepias spp.
Bidens spp.
Boltonia asteroides
Cephalanthus occidentalis
Doellingeria umbellata
Eryngium yuccifolium
Eupatorium perfoliatum
Upland Prairie
X
X
X
X
X
X
Wetland Type
Wet Meadow
X
X
X
X
X
X
X
X
X
Marsh
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Flowering Plants
Species
Common Name
Joe Pye Weed
Sneezeweed
Sawtooth Sunflower
Cow Parsnip
Rose Mallow
Great St. John's Wort
Blue Flag Iris
Prairie Blazingstar
Great Blue Lobelia
Monkey Flower
White Water Lily
Smartweed
Pondweed
Mountain Mint
Sweet Blackeyed Susan
Water Dock
Arrowhead
Cup Plant
Goldenrod
Aster
Blue Vervain
Ironweed
Golden Alexander
Scientific Name
Eutrochium spp.
Helenium autumnale
Helianthus grosseserratus
Heracleum maximum
Hibiscus laevis
Hypehcum ascyron
Iris virginica
Liatris pycnostachya
Lobelia siphilitica
Mimulus spp.
Nymphaea odorata
Persicaria spp.
Potamogeton spp.
Pycnanthemum spp.
Rudbeckia subtomentosa
Rumex britannica
Sagittaria spp.
Silphium perfoliatum
Solidago spp.
Symphyotrichum spp.
Verbena hastata
Vernonia gigantea
Zizia aurea
Upland Prairie
X
X
X
X
X
X
X
X
X
X
X
X
Wetland Type
Wet Meadow
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Marsh
X
X
X
X
X
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Table I I. Tree and Shrubs
Trees and Shrubs
Species
Common Name
Red Maple
Silver Maple
Speckled Alder
Ohio Buckeye
Birch
Pecan
Shell-Bark Hickory
Dogwood
Black Walnut
Eastern Red Cedar
American Sycamore
Quaking Aspen
Black Cherry
Swamp White Oak
Burr Oak
Pin Oak
Black Elder
Scientific Name
Acer rubrum
Acer saccharin urn
Alnus incana
Aesculus glabra
Betula spp.
Carya illinoinensis
Carya laciniosa
Corn us spp.
Juglans nigra
Juniperus virginiana
Platan us occidentalis
Populus tremuloides
Prunus serotina
Quercus bi color
Quercus macrocarpa
Quercus palustris
Sambucus nigra
Upland Prairie
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Wetland Type
Wet Meadow
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Marsh
A combination of grading, planting, and natural regeneration will be used to establish the vegetation,
which will require proper site preparation, installation, and maintenance. With the goal of establishing
the wetland vegetation as soon as possible, it is recommended that primarily rapidly growing species
such as grasses, sedges, cattails, and maples be used, with a smaller proportion of slower growing
plants. This combination provides diversity and promotes important wildlife habitat value. Quickly
establishing desirable vegetation also reduces the opportunity for nuisance and invasive plants to take
over the freshly disturbed and planted wetland and floodplain areas.
4.5 Park Configuration and Connection to Surrounding Redevelopment
Restoration of Ralston Creek and the adjacent floodplain is part of a larger effort to establish a multiuse
public park at the site of the former North Wastewater Treatment Plant. The park, currently in the
conceptual design phase, will consist of many different design elements and will encourage a wide range
of residential users. Figure 22 shows a section of the proposed park that features the connection
between the restoration area and the surrounding area.
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^R ;
Source: RDG 2015.
Figure 22. Proposed Concept for Riverfront Crossings Park.
A frequent comment at public outreach events for the park project is the desire to obtain better public
access to the water. Accordingly, a trail system is proposed that takes advantage of multiple viewpoints
over the Iowa River, Ralston Creek, and the restored wetland area. The trail system will bridge high
points and include lower sections that will allow users to explore the wetland. Although the main
entrances to the proposed park will be located at the north end, away from the restoration area, low-
water crossings of Ralston Creek using natural rock boulders are included in the conceptual stream
restoration design to allow more informal access points from the anticipated mixed-use area to the east
of the creek. Residents and visitors will be able to access the proposed park from the planned
redevelopment area through a path that will travel through the restored floodplain area and across the
low-water crossing, providing a direct connection to the restored area.
34
-------
The water quality components of the wetland also could extend to the surrounding redevelopment
areas, expanding Iowa City's connection to this restoration. The Downtown and Riverfront Crossings
Master Plan proposes wide promenades leading towards the park and ending at Ralston Creek (HDR
2013). Constructed stormwater gravel wetlands, as shown in Figure 23 , can be very effective at
reducing nutrients and sediment (Ballestero et al. 2012). While the water quality treatment processes
associated with the restored wetland require a larger area and reliable ground water supply,
constructed stormwater gravel wetlands can be installed in much smaller areas with only stormwater
runoff as a water source. It will be easy to integrate these facilities into the redeveloped promenade
areas to treat stormwater from neighboring buildings and impervious surfaces before discharging it to
Ralston Creek. The selection of plant species for the stormwater gravel wetlands can match the
plantings planned for the restored wetland to provide an additional visual connection between the two
areas.
IT WETLAND
SOIL
24'SUBSURFACE
GRAVEL
(3/4-CRUSHED
STONE)
SUBSURFACE DRAIN
(6" PERFORATED PIPE)
OUTLET PIPE
(ELEVATED PIPE
8- BELOW WETLAND SURFACE
TO ENSURE THAT SOIL IS
CONTINUOUSLY SATURATED)
Source: CRWA 2009.
Figure 23. Gravel Wetland Schematic.
35
-------
5 Future Steps
Iowa City is preparing for the demolition of the North Wastewater Treatment Plan facilities and has
developed concepts for the development of the Riverfront Crossings Park. The city has performed park
planning in conjunction with this stream and wetland restoration conceptual design to integrate the
restoration components and necessary grading into the overall park plan. Both the park plan and the
restoration plan will need to advance through more detailed design phases to develop construction
plans. Since the restoration plan affects a regulated waterway, environmental permitting also will be
required before construction can begin.
The redevelopment planning should include the extension of the green infrastructure concepts
implemented in the wetland to the surrounding planned mixed-use development early on in the
planning process. Designing the stormwater gravel wetlands along with the promenade and other
necessary infrastructure will maximize the effectiveness and ease-of-implementation of these green
infrastructure approaches.
36
-------
6 References
Arbuckle, K., and J.L Pease. 1999. Managing Iowa Habitats: Restoring Iowa Wetlands. Pm-1351h.
Iowa State University Extension, Ames, IA.
Ballestero, T., R. Roseen, J. Houle, A. Watts, and T. Puls. 2012. Subsurface Gravel Wetlands for the
Treatment of Stormwater. Paper presented at NJASLA 2012 Annual Meeting and Expo,
January 29-31, 2012, Atlantic City, NJ.
Buchmiller, R.C., and D.A. Eash. 2010. Floods of May and June in Iowa. Open-File Report 2010-1096.
U.S. Geological Survey, Reston, VA.
Bukaveckas, P.A. 2007. Effects of channel restoration on water velocity, transient storage, and nutrient
uptake in a channelized stream. Environmental Science & Technology. 41(5):1570-1576.
Cadenasso, M.L, ST. Pickett, P.M. Groffman, LE. Band, G.S. Brush, M.F. Galvin, J.M. Grove, G. Hagar,
V. Marshall, B.P. McGrath, J.P. O'Neil-Dunne, W.P. Stack, and A.R. Troy. 2008. Exchanges across
land-water-scape boundaries in urban systems. Annals of the New York Academy of Sciences.
1134:213-232.
CRWA (Charles River Watershed Association). 2009. Constructed Stormwater Gravel Wetland. Low
Impact Best Management Practice Information Sheet. Charles River Watershed Association,
Weston, MA. Accessed October 31, 2012.
www.crwa.ora/proiects/stormwater/stormwaterBMPs.html.
Eash, D.A., K.K. Barnes, and A.G. Veilleux. 2013. Methods for Estimating Annual Exceedance-Probability
Discharges for Streams in Iowa, Based on Data Through Water Year 2010. Scientific
Investigations Report 2013-5086. U.S. Geological Survey, Reston, VA.
FEMA (Federal Emergency Management Agency). 2002. Flood Insurance Study Johnson County, Iowa and
Incorporated Areas. Flood Insurance Study Number 19103CVOOOA. Revised February 16, 2007.
Federal Emergency Management Agency, Washington, DC.
HDR (HDR Engineering, Inc.). 2013. Downtown & Riverfront Crossings Master Plan. Prepared for Iowa
City, Iowa, by HDR Engineering, Inc.
Iowa City Engineer's Office. 1947. Iowa City, 1947 [map]. Scale 1" = 800'. University of Iowa Libraries
Map Collection. Posted April 10, 2013. Accessed October 15, 2014.
http://diaital.lib.uiowa.edu/cdm/sinaleitem/collection/sheetmaps/id/84/rec/155.
IDNR (Iowa Department of Natural Resources). 2014. Ralston Creek Urban Stream Assessment.
Leisenberg, M., J. Clary, and P. Hobson. 2012. International Stormwater Best Management Practices
(BMP) Database Pollutant Category Summary Statistical Addendum: TSS, Bacteria, Nutrients,
and Metals. Accessed October 15, 2014.
http://www.bmpdatabase.ora/Docs/2012%20Water%20Qualitv%20Analysis%20Addendum/BM
P%20Database%20Categorical SummaryAddendumReport Final.pdf.
Lenhart, H.A., and W.F. Hunt III. 2011. Evaluating four storm-water performance metrics with a North
Carolina coastal plain storm-water wetland. Journal of Environmental Engineering.
137(2):155-162.
M-NCPPC (Maryland-National Capital Parks and Planning Commission). 2014. Imbricated Rip-rap Detail.
Standard construction details. Maryland-National Capital Parks and Planning Commission,
Riverdale, MD.
37
-------
Miller, J. 2007. Constructed Wetland Technology Assessment and Design Guidance. Iowa Department of
Natural Resources.
NRCS (National Resources Conservation Service). 2006. Small Cross Vane. Conceptual plan.
U.S. Department of Agriculture, Natural Resources Conservation Service, Washington, DC.
NRCS (National Resources Conservation Service). 2007. Hook Vane. Conceptual Plan. U.S. Department of
Agriculture, Natural Resources Conservation Service, Washington, DC.
NRCS (National Resources Conservation Service). 2008. Rootwad in Low Bank. Conceptual plan.
U.S. Department of Agriculture, Natural Resources Conservation Service, Washington, DC.
Pease, J.L., M.L Rankin, J. Verdon, and R. Reisz. 1996. Why Landowners Restore Wetlands: A National
Survey. Iowa State University, Ames, IA.
Randall, J.A., and J. Herring. 2012. Management ofFloodplain Forests. Iowa State University Forestry
Extension, Ames, IA.
Schermerhorn, E.J. 1983. So/7 Survey of Johnson County Iowa. U.S. Department of Agriculture, Soil
Conservation Service, Washington, DC.
Shaharuddin, S., A.A. Ghani, N.A. Zakaria, and M. Mansor. 2011. Biodiversity in Stormwater Constructed
Wetlands: Case Study of USM Wetland. In Proceedings from 3rd International Conference on
Managing Rivers in the 21st Century, Malaysia, December 6-9, 2012, pp. 313-324.
Shaw, S.P., and C.G. Fredine. 1956. Wetlands of the United States—Their Extent and Their Value To
Waterfowl and Other Wildlife. Circular 39. Northern Prairie Wildlife Research Center Online,
U.S. Department of the Interior, Washington, DC.
https://www.fws.aov/wetlands/Documents/Wetlands-of-the-United-States-Their-Extent-and-
Their-Value-to-Waterfowl-and-Other-Wildlife.pdf (Version 05JAN99).
SMRC (Stormwater Manager's Resource Center). 2014. Stormwater Management Fact Sheet:
Stormwater Wetland. Stormwater Manager's Resource Center. Accessed October 31, 2014.
http://www.stormwatercenter.net/.
Terracon Consultants. 1994. Phase II Subsurface Exploration. Letter to Stanley Consultants regarding
subsurface exploration for proposed wastewater facility improvements. October 6, 1994. 137 p.
Tharp, W.E., and G.H. Artis. 1922. Soil Survey of Johnson County Iowa. U.S. Department of Agriculture,
Bureau of Soils, Washington, DC.
USEPA (U.S. Environmental Protection Agency). 1995. Economic Benefits of Runoff Control.
EPA 841-S-95-002. U.S. Environmental Protection Agency, Office of Wetlands, Oceans, and
Watersheds, Washington, DC.
USEPA (U.S. Environmental Protection Agency). 1996. Protecting Natural Wetlands: A Guide to
Stormwater Best Management Practices. EPA-843-B-96-001. U.S. Environmental Protection
Agency, Office of Water, Washington, DC.
USEPA (U.S. Environmental Protection Agency). 1999. Storm Water Technology Fact Sheet: Storm Water
Wetlands. EPA 832-F-99-025. U.S. Environmental Protection Agency, Office of Water,
Washington, DC.
USEPA (U.S. Environmental Protection Agency). 2001a. Functions and Values of Wetlands.
EPA 843-F-01-002c. U.S. Environmental Protection Agency, Office of Wetlands, Oceans, and
Watersheds, Washington, DC.
38
-------
USEPA (U.S. Environmental Protection Agency). 2001b. The Narrows Stream Bank Restoration and
Protection Project. 319 grant success stories. U.S. Environmental Protection Agency, Region 3,
Gettysburg, PA.
USEPA (U.S. Environmental Protection Agency). 2009. Technical Guidance on Implementing the
Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy
Independence and Security Act. EPA841-B-09-001. U.S. Environmental Protection Agency,
Washington, DC.
USGS (U.S. Geological Survey). 2014. StreamStats. Accessed September 28, 2014.
http://water.usgs.gov/osw/streamstats/.
Woodyer, K.D. 1968. Bankfull frequency in rivers. Journal of Hydrology 6(2):114-142.
WSSC (Washington Suburban Sanitary Commission). 2013. Standard Stream Restoration Details.
Washington Suburban Sanitary Commission, Washington, DC.
39
-------
Appendix A: Soil Boring Map and Logs
-------
rt/ 4\
/.EGE/VD
S.APPROXIMATE BORING LOCATION
.APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06095646
.APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06865076
.APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06875041
.APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06945060
.APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06885023
^ .APPROXIMATE BORING LOCATION TERRACON PROJ. NO. 06955103
BASE DRAWING A 2012 AERIAL FROM JOHNSON COUNTY, IOWA GIS
THIS DRAWING IS INTENDED FOR GENERAL LOCATION
PURPOSES ONLY
1
APPROXIMATE DRAWING SCALE
Project No.
P06140170
Project Mngr
TWS
Drawn By:
PC
File Name:
P06140170-01.dwg
Layout Name:
PROPOSED BORING
IFerracon
Consulting Engineers and Scientists
2640 12TH STREET SW CEDAR RAPIDS, IOWA 52404
PH. (319)366-8321
FAX. (319) 366-0032
PROPOSED BORING LOCATION PLAN
EXHIBIT*
IOWA RIVER IMPROVEMENTS PROJECT
MCLAUGHLIN WHITEWATER DESIGN GROUP
IOWA RIVER BETWEEN BENTON ST AND HIGHWAY 6
IOWA CITY, IOWA
A-X.1
-------
LOG OF BORING NO. NP-1 Page i of i
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
A A A
1
4
DESCRIPTION
Approx. Surface Elev.: 645.1ft.
0 5 >LEAN CLAY TRACE , — 644r6-
\ ORGANICS, Dark Brown /
FIL SANDY LEAN CLAY AND
CLAYEY FINE SAND. Brown
6.5 638.6
VERY SANDY LEAN CLAY.
Brown, Stiff
14.5 630.6
2
FINE TO MEDIUM SAND,
TRACE GRAVEL. Brown,
Medium Dense
20 625.1
BOTTOM OF BORING
ARCHITECT/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PHASE II - FACILITY IMPROVEMENTS
*
LL
•W
I
EL
LU
O
1 f\
10
-
1 j
-
—
-
USCS SYMBOL
sc
CL
CL
SP
SP/
sw
SAMPLES
NUMBER
1
2
3
4
UJ
fl_
t-
PA
SS
PA
SS
PA
SS
PA
SS
RECOVERY
13
15
18
18
*
u.
I-O
6
8
13
15
TESTS
MOISTURE, '/.
14.4
16.3
20.0
440
15.1
i—
H
cn
HI
Q
ceu
QQ-
o
UJ
zx
Hl-
U.CO
OLU
cjceu.
ZHOJ
ncno.
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES Calibrated Hand Peratrometer*
BETWEEN SOIL AND ROCK TYPES: IH-SITU, THE TRANSITION MAY BE GRADUAL. CHE 1*0 Lb. Auto. SPT Hammer**
WATER LEVEL OBSERVATIONS
WL
WL
WL
¥ is' ws? C»rr-
IIEfTJ
WCl (2> 15' (6/29/94)
Dear
BORING STARTED 6-27-94
(BORING COMPLETED 6-27-94
RIG #14 FOREMAN GAE
APPROVED TTW JOB# 06945060 ,
-------
LOG OF BORING NO. 5 Page l of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
A A A
•. JH A
A A A
•- A A
<'/^/
' / ~J
// Y
-*i ",•
-•- •/•
^ v.
Ifci",
•***.
JV
DESCRIPTION
Approx. Surface Elev.: 641.5ft.
1 5 STT,TY CLAY, Dark Brown fi/(o
VERY SANDY SILTY CLAYT
Brown Gray, Soft
9 632.5
FINE TO MEDIUM SAND. g
TRACE SILT, Brown, Loose
12 629.5
FINE TO COARSE SAND. WITH
GRAVEL. TRACE SILT &
CLAY, Brown, Very Loose to
Medium Dense
j,t ouy.j
Continued Next Page
ARCHITECr/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PROPOSED FACILITY IMPROVEMENTS
LL
X
Q.
LJ
a
5-
1 1\
IU
-
—
15
-
-
-
*> c
23
ir\
JU
USCS SYMBOL
CL/
MI
SP
sw
sw
sw
sw
SAMPLES
NUMBER
1
2
3
4
5
6
Ul
D.
1-
HS
SS
HS
SS
HS
SS
HS
SS
HS
SS
HS
SS
HS
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN- SITU, THE TRANSITION HAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
WL
WL
WL
g 10' ws ? 7.5. AB
llEITi
WCI IT 48 HR AB
Dcon
RECOVERY
14
10
4
12
6
10
ZL.
I-CO
CDO
it m
3
4
3
11
H
15
TESTS
MOISTURE, y.
19.7
13.8
11.7
18.8
11.7
15.9
H
O>
Ul
a
ceo
ao.
o
LJ
21
HI-
LL (3
OUJ
HI-W
*1000
Calibrated Hand Penetrometer*
CHE HO Lb. Auto. SPT Hammer**
BORING STARTED 12-15-93
BORING COMPLETED 12-15-93
1110 NO. 37 FOREMAN REF
APPROVED DEW JOB* 06935119^
-------
LOG OF BORING NO. 5 Page 2 of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
1
fc^jjj
DESCRIPTION
FTNF. TO MEDIUM SAND.
TRACE STLT & GRAVEL.
Gray, Medium Dense
37 604.5
COARSE SAND & GRAVEL,
40 Gray, Very Dense 6Q, 5
BOTTOM OF BORING
N. END OF PLANT; W. SIDE OF
RALSTON CREEK:
ARCHITECT/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PROPOSED FACILITY IMPROVEMENTS
LL
I
Q.
LU
a
-
USCS SYMBOL
SP
SP
SAMPLES
NUMBER
7
8
LU
Q.
j-
ss
HS
SS
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN-SITU, THE TRANSITION HAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
WL
WL
WL
2 10> ws I 7.5' AB •« r
Uf^.ffm
nerr;
WCI 11' 48 HR AB
aeon
RECOVERY
13
12
*
zu.
i \
1— U)
0-3
CTCO
* -J
25
55
TESTS
MOISTURE, •/.
16.3
8.0
H
to
UJ
a
QQ-
D
LU
Ml-
Lc tfl
OUJ
CJCtiU-
zi-cn
^ to a.
Calibrated Hand Penetrometer*
CHE HO Lb. Auto. SPT Hamner**
BORING STARTED 12-15-93
BORING COMPLETED 12-15-93
WG NO. 37 FOREMAN R£F
APPROVED DEW JOB* 06935119 A
-------
LOG OF BORING NO. 7 Page j of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
A A J
i A ft
A A i
\ A J*
///
^
*2
DESCRIPTION
Approx. Surface Elev.: 641,5ft.
! 5 STI7.TY n.AY, TRACE SAND. ^n
2 5 \ Dark lirown / ^39
~^\SANDY LEAN CJLAX, Brown (~
FINE TO MEDIUM SAND.
TRACE SILT. Brown, Very
Loose
9 ? 632.5
STLTY CLAY. TRACE SAND &
1 1 5 OR PANICS. Gray, Very Soft 63Q
FINE TO MEDIUM SANDT
TRACE SILT. Brown, Loose
15.5 626
STLTY CLAY. TRACE SAND.
WITH SAND LAYERS, Grav.
19.5 S°ft 622
FINE TO MEDIUM SAND,
21.5 TRACE SILT. Grav 620
MEDIUM TO COARSE RAND.
TRACE SILT. GRAVEL &
COBBLES. Brown, Medium
Dense
Continued Next Page
ARCHITECr/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PROPOSED FACILITY IMPROVEMENTS
L.
X
p,
UJ
a
—
10 —
—
15
-
20
-
—
-
"1 €
—
-
—
USCS SYMBOL
SP
MT
SP
/1V
L/IV
SP
SP
SP
SAMPLES
NUMBER
1
2
3
T A
5
6
Ul
CL
1-
HS
SS
HS
SS
HS
SS
HS
EC
^
HS
SS
HS
SS
HS
THE STRATIFICATION HUES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN -SITU, THE TRANSITION MAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
WL
WL
WL
i 8.5' WDl • L
Hens
WCI (8> 8' 48 HR AB
Dcon
RECOVERY
16
17
14
O
16
8
Zli.
1 X
i-cn
CL3
too
* CD
3
1
9
1 A
13
11
TESTS
MOISTURE, y.
3.2
30.4
20.0
9J 4
15 4
20.0
13.5
H
cn
UJ
a
0:0
Od-
Cl
UJ
Hh-
•Z-Z
OUJ
Z3WO.
*500
Calibrated Hand Penetrometer*
CHE 140 Lb. Auto. SPT Hammer**
BORING STARTED 12-15-93
BORING COMPLETED 12-15-93
MG NO. 37 FOREMAN REF
APPROVED DEW JOB* 06935119 J
-------
LOG OF BORING NO. 7 Page 2 of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
-fci-V
•¥••'.'
•¥*•"•'
•**••'•'
•**••',•
I
h_" •*
' w' H
DESCRIPTION
FINE TO COARSE_SAND
TRACE SILT. GRAVE
COBBLES, Brown, Mec
Dense
37.5
38.5 LIMESTONE COBBLES
^ FINE TO COARSE SAND
LJ&
ium
TRACE SILT & GRAVEL.
WITH LIMESTONE
1 FRAGMENTS, Brown,
Dense
Very
604
603
601.5
BOTTOM OF BORING
S. END OF PLANT; W. SIDE OF
RALSTON CREEK
ARCHITECT/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PROPOSED FACILITY IMPROVEMENTS
H
LJ_
X
i—
Q_
LU
O
1 <
JO
40 —
USCS SYMBOL
SP
SP
SAMPLES
NUMBER
7
8
LJ
Q.
>-
t-
ss
HS
SS
o;
LU
O
CJ
LU
8
12
K
1 X
I-CO
coo
*» _J
» 03
10
63
TESTS
MOISTURE, •/.
17.3
8.5
i—
H
CO
LU
Q
arcj
OQ.
a
LU
HI—
U.CD
zz
OLU
CJCdLL
Zl— CO
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES Calibrated Hand Penetroroeter*
BETWEEN SOIL AND ROCK TYPES: IN-SITU, THE TRANSITION MAY BE GRADUAL. CHE 140 Lb. Auto. SPT Hammer**
WATER LEVEL OBSERVATIONS
WL I
WL
WL
2 gp5' WD X
WCI @ 8* 48 HR AB
Iferracor
BORING STARTED 12-15-93
(BORING COMPLETED 12-15-93
WG NO. 37 FOREMAN REp
APPROVED DEW JOB* 06935119 „
-------
LOG OF BORING NO. 7A Page , of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
I
\
"£i*i
flfr,": •'
i;S
ss
J,<
DESCRIPTION
Approx. Surface Elev.: 646.4ft.
FILL, SANDY LEAN CLAY. Dark
Brown
7.5
SANDY L
and Brown
EAN CLAY. Brc
Medium to Soft
19.5
FINE TO COARSE SAND,
TRACE GRAVEL ANC
Gray, Brown, Loose to 1
Continued Next Pa
638.9
>wn,
626.9
i SILT,
}ense
ge
ARCHITECT/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PHASE II - FACILITY IMPROVEMENTS
LL.
X
Q.
LU
a
5-
10-
—
15-
—
20-
j
-
25-
—
30-
—
USCS SYMBOL
CL
CL
SP
SP
SP
SAMPLES
NUMBER
1
2
3
4
5
6
LU
a.
i-
HS
SS
HS
SS
HS
SS
HS
SS
WB
SS
WB
SS
WB
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN-SITU, THE TRANSITION HAY 8E GRADUAL.
WATER LEVEL OBSERVATIONS
WL
WL
WL
§ 20' WD
?
llerracon
RECOVERY
14
14
16
16
12
18
*
i-
u.
HO
com
5
6
3
9
9
47
TESTS
MOISTURE, *
19.8
26.9
29.4
19.0
22.5
18.0
H
CO
UJ
Q
ctro
QD.
a
LU
HJ-
LJ.CD
•Z.-Z.
pLU
OCeU-
ZIWQ.
Calibrated Hard Penetrometer*
CHE 140 Lb. Auto. SPT Hammer**
BORING STARTED 7 _ g _ 94
BORING COMPLETED 7 _ g _ 9 4
RIG #14 FOREMAN GAE
APPROVED TTW JOB# 06945060 A
-------
LOG OF BORING NO. 7A Page 2 of 2
OWNER/CLIENT
CITY OF IOWA CITY
SITE WASTE WATER TREATMENT PLANT
IOWA CITY, IOWA
GRAPHIC LOG
^. '-^
^.''•f
"^•'•^
i_: '-•
•— -•
5*-!?
Ij^-%
>!•!•£
^ !>•
•— -^
^- !*
=
•*•= •"-'"-
!
1
DESCRIPTION
FINE TO COARSE SAND
TRACE GRAVEL AND SILT,
Gray, Brown, Medium Dense
45
FINE TO COARSE SAND
WITH
ato LIMESTONE FRAGMENTS.
4fl \ Gray, Dense
\***H1GHLY WEAlHbREL
\ LIMESTONE, Brown
1
)
i
601.4
599.9
598.4
Refusal @ 48'.
BOTTOM OF BORING
*** Classification estimated from
disturbed samples. Core samples
and petrographic analysis may
reveal other rock types.
ARCHTTECT/ENGINEER
STANLEY CONSULTANTS, INC.
PROJECT
PHASE II - FACILITY IMPROVEMENTS
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THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES Calibrated Hand Penetrometer*
BETWEEN SOIL AND ROCK TYPES: IN-SITU, THE TRANSITION KAY BE GRADUAL. CHE HO Lb. Auto. SPT Hafrmer**
WATER LEVEL OBSERVATIONS
WL
WL
WL
§20' WD *
llbrracar
BORING STARTED 7-6-94
1 BORING COMPLETED 7 _ fi _ 94
RIG #14 IOREMAN GAE
APPROVED TTW JOB# 06945060 ^
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Appendix B: Soil Classification Map
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Project No.: 1QO-FFX-P140150
Cariography By. RM
1
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Appendix C: Proposed Restoration Area
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Appendix D: Draft Grading Plan and Cross Sections
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CROSS SECTION A - A'
500YR FLOOD
(2007
100YR
(2007 FIS)
50YR FLOOD
(2007 FIS)
10YR FLOOD
1+00
2+00
3+00
4+00
H h
5YR FLOOD
(IOWA
ANALYSIS)
2YR FLOOD
(IOWA RIVER
REGRESSION ANALYSIS)
H h
0+0°
1+00
2+00
3+00
5+00
4+00
6+00
H h
H h
5+00
7+00
6+00
H h
7+00
8+00
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SAN I 11 AKYI
: SIZE AND
UNKNOWN
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12+00
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PROPOSED
WETLAND
CROSS SECTION B - B'
500YR FLOOD
(2007 FIS)
100YR FLOOD
(2007 FIS)
5+00
6+00
FLOOD
(2007 FIS)
10YR FLOOD
0+00
1+00 2+00
,_|D|_D _ DT| _
FIBER OPTIC
3+00 4+00
SANITARY SEWER
S|ZE AND DEPTH
50YR FLOOD
-(RALSTON CREEK FIS)
50YR FLOOD
.(STREAM STATS)
25YR FLOOD
-(STREAM STATS)
10YR FLOOD
(STREAM STATS)
SYR FLOOD
(STREAM STATS)
2YR FLOOD
(STREAM STATS)
PROPOSED
CROSS SECTION C - C' WETLAND
500YR FLOOD
(2007 FIS)
100YR
(2007 FIS)
50YR FLOOD
(2007
(2007 FIS)
SYR FLOOD
(IOWA RIVER REGRESSION
ANALYSIS)
2YR FLOOD
(IOWA RIVER
REGRESSION ANALYSIS)
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H h
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H h
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FIBER OPTl
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H h
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10+00
SANITARY SEWER ->
SIZE; AND DEffTFT :
UNKNOWN
H h
11+00
13+00
H h
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-62\
13+00
50YR FLOOD
(RALSTON CREEK FIS)
50YR FLOOD
. (STREAM STATS)
25YR FLOOD
• (STREAM
FLOOD
(STREAM STATS)
(STREAM STATS)
FLOOD
(STREAM STATS)
50YR FLOOD
(RALSTON Cl
50YR FLOOD
. (STREAM STATS)
25YR FLOOD
(STREAM STATS)
IOYRFLOOD
(STREAM STATS)
5YR FLOOD
(STREAM STATS)
2YR FLOOD
(STREAM STATS)
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