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Improving vegetation establishment practices for SURFACE MINE RECLAMATION

WATERSHED APPROACH to streambank stabilization for erosion and fl ood control

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STAFF

Kenneth M. RaschPresident

Jane RaschVice President

Amy DencklauPublishing Editor

landandwater@frontiernet.net

Martha SteinkampCirculation Manager

lwsub@frontiernet.net

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lwmarketing@frontiernet.net

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lwacct@frontiernet.net

SALES

Gail HenryAccount Executive

gail@landandwater.comphone: 515-227-5042 or

515-576-3191

Shanna EgliAccount Executive

lweditor@frontiernet.net515-576-3191

CONTENTS

4 September/October 2012

Land and Water (ISSN 0192-9453) is published bimonthly by Land and Water, Inc., 320 A. Street, Fort Dodge, IA 50501-9925. Telephone (515)576-3191, Fax (515)576-2606. Land and Water is edited for contractors, engineers,

architects, government officials and those working in the field of natural resource management and restoration from idea stage through project completion and maintenance. Subscription rates for printed copies: One year - $20.00; Two

years - $35.00; Three years - $50.00; Foreign - add $12.00 per year. All non-paid subscriptions are mailed on a rotating basis to receive occasional copies at Fort Dodge, Iowa and at additional mailing offices. No charge for digital version

of the magazine. No part of this publication may be reproduced without the written consent of the publisher. Land and Water assumes no responsibility for statements expressed by contributors. Jeremiah 29:11

DEPARTMENTS 6 Tell It Like It Is 53 Equip-Board 54 Advertiser’s Index

FEATURES

Volume 56, Number 5 September/October 2012

STORMWATER MANAGEMENT 8 Retrofitting a Major Retail Mall for Stormwater Volume Reduction The combined goals of phosphorus reduction and stormwater volume reduction to a nearby lake called for the retrofitting of stormwater BMPs at Maplewood Mall, Minnesota.

by Clifton Aichinger & Erin Anderson Wenz

STREAMBANK STABILIZATION 15 Multi-Objective Stream Stabilization in Fort Branch Creek Severe streambank erosion drove the City of Austin’s Watershed Protection Department to undertake three stream stabilization projects, all located on the same watershed at Fort Branch Creek, Texas.

by Morgan Byars, P.E. & Janna Renfro, P.E.

LAKES & PONDS 21 The Perfect Pond What must come together for a pond to be perfect?

by Bob Lusk

SOIL AMENDMENTS 25 Improving Vegetation Establishment Practices for Surface Mine Reclamation By utilizing a comprehensive approach that encompassed soil science, agronomy, and soil stabilization, vegetation establishment success rates were substantially increased on reclaimed surface mines within the Appalachian Coal Basin. by Brian Free, CPESC

SOIL REINFORCEMENT 29 Los Vaqueros Reservoir Expansion In order to expand the storage capacity of the Los Vaqueros Dam in California, MSE walls were constructed to increase the height of the dam. by Michele Curry

SHORELINE STABILIZATION 33 Liner Repair Using an Engineered Bentonite/ Aggregate Composite When locals at a Minnesota townhome development noticed their lake level dropping, they needed to find a solution for damage to the lake’s HDPE synthetic geomembrane liner. by Kevin VanTuyl & Brent Vatland

WETLANDS RESTORATION 36 Opportunity Ponds Wetlands – Adapting to Revegetation Variables A short growing season, low nutrient soils, and hungry wildlife provided many lessons at a wetland mitigation project in the Rocky Mountains of Montana.

by Leonard Ballek

EROSION CONTROL BMPS 45 Construction Site BMPs Challenging construction sites throughout the United States are requiring the use of a wide variety of BMPs.

by Donald Thieman, CPESC

FLOODPLAIN MANAGEMENT 50 Reaching Across the Aisle for Conservation Douglas County Nevada took up the challenge to develop the Douglas County Conservation Bill in order to maintain, preserve, and protect their community’s floodplain functions.

by Debra Turrieta

You can now read Land and Water Magazine online, visit www.landandwater.com

ABOUT THE COVER

Multi-objective stream stabili-zation project on Fort Branch Creek in Austin, Texas at end o f cons t ruc t i on phase . Mechanically stabilized earth walls with vegetated geogrids and a meandering pi lot channel provide a natural aesthetic and function. The project will provide flood hazard reduction, erosion control and water quality pro-tection. See the full story on page 15.

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15www.landandwater.com

STREAMBANK STABILIZATION

The City of Austin has utilized numer-

ous stream stabilization techniques

over the years, evolving from fl ood-fo-

cused concrete and gabion designs to more

natural channel designs meant to restore

benefi cial stream function. What has be-

come a widely accepted popular standard

of practice is a system that includes natu-

ral limestone boulders for toe protection,

which are locally available, with native

riparian vegetation on the upper banks.

Th e boulder treatment usually extends be-

low the creek bed to the anticipated scour

depth and vegetated area begins above

the bankfull elevation. In many cases the

upper slopes are designed as a mechani-

cally stabilized earth system (MSE) using

geogrid reinforced soil lifts that allow for

vegetation establishment. Th e approach

to channel bed stabilization may include

constructed step-pools or riffl es for grade

control and a pilot channel to allow for

base fl ow that provides aquatic habitat.

Th is approach provides a reliable struc-

tural solution for solving both erosion and

fl ood control problems, while incorporat-

ing natural materials that help restore the

Multi-Objective Stream Stabilization in Fort Branch Creek

Reach 1 one year after construction.

16 September/October 2012

STREAMBANK STABILIZATION

riparian zone to the extent possible in the

urban context. Th e following case study

highlights several projects in the same wa-

tershed to illustrate how these techniques

are used to achieve multiple goals of ero-

sion control, fl ood control and stormwater

water quality protection.

Th e City of Austin’s Watershed Protec-

tion Department is guided by a 2001 City-

wide Watershed Master Plan that provides

unifi ed direction in fulfi lling the depart-

ment’s goal of protecting lives, property,

and the environment by reducing problems

associated with adverse fl ooding, erosion,

and stormwater pollution. A particular fo-

cus is given to solutions that demonstrate

a commitment to environmental responsi-

bility, cost-eff ectiveness, and sustainability.

Th e master plan identifi ed Fort Branch

Creek to be one of its highest priority wa-

tersheds within the city. Fort Branch Creek

drains a 3.5 square mile urban watershed

in East Austin and exhibits multiple char-

acteristics of an impaired stream – heavily

eroded channel and banks, degraded water

quality, and insuffi cient fl ood capacity for

the new fl ow regime.

The watershed experienced nearly full

build out several decades prior to the

implementation of the City’s watershed

protection stormwater management regu-

lations in the early

1980’s. Current reg-

u l a t i on s r equ i re

stream setbacks and

stormwater deten-

t ion to p reven t

potential problems

related to flooding,

erosion and water

quality. The effects

of rapid, uncon-

trolled urbanization

were apparent in the

results of the 2001

Watershed Master

Plan, as Fort Branch

showed some of the

more severe flooding

and erosion prob-

lems within the City.

To begin addressing

these issues, a comprehensive study of the

watershed was conducted by dividing Fort

Branch into eleven distinct geomorphic

reaches and providing detailed analysis of

each segment’s hydrology, hydraulics, geo-

morphology, sediment transport, and

environmental integrity.

To prioritize project areas within the

watershed a quantitative ranking system

was developed to assign problem scores and

a ranking for each stream reach related to

problems associated with fl ooding, erosion

and water quality. Based on the problem

scores, the three highest priority reaches

– Reach 1, Reach 6, and Reach 7 - were

selected to proceed to design and imple-

mentation. Th e primary driving factor for

all of these projects was severe streambank

erosion.

Alternatives for the channel design

where evaluated from a cost-eff ectiveness,

Reach 1 before construction.

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STREAMBANK STABILIZATION

sustainability and environmental impact

perspective. Th e range of solutions evalu-

ated included construction of a concrete-

gabion lined channel, natural boulder-veg-

etated mechanically stabilized earth system

and a non-structural solution of voluntary

home buyouts along the creek. Hydraulic

modeling showed that the concrete channel

was most eff ective at reducing water surface

elevations within the individual project

reaches, but the adverse environmental im-

pacts due to loss of stream habitat and eco-

system services were not acceptable based

on the City’s multi-objective approach to

watershed management. Additionally,

while this approach may reduce fl ooding

and erosion problems at the project loca-

tion, downstream channel reaches may ex-

perience unwanted increases in peak fl ows

and erosion as the energy is translated from

Reach 1 near end of construction.

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STREAMBANK STABILIZATION

18 September/October 2012

one location to another. Th e non-structur-

al home buyouts solution proved to be too

costly and not acceptable from a social per-

spective in that many residents would be

displaced from a well-established residen-

tial neighborhood. Rather selective volun-

tary acquisitions were off ered for owners in

isolated areas with severe fl ooding or ero-

sion and where a structural solution would

not be cost-eff ective for a single residence.

Th e preferred approach was the structural

stabilization using the natural limestone

boulders, vegetated banks, and pool/riffl e

bed forms to mimic natural channel mor-

phology. Not only was this approach less

costly, it provided benefi ts other than sta-

bility and fl ood hazard reduction. Th e fol-

lowing describes the three project areas in

more detail.

Reach 1

Th e fi rst project reach to go forward

was Fort Branch Reach 1 which included

2,200 linear feet of channel confi ned with-

in a 50 foot drainage easement between

backyards of single-family homes that

paralleled the creek. Channel erosion had

resulted in nearly vertical banks 10’ to 18’

high, presenting immanent threat to util-

ity poles, residential structures, fences, and

Left: Reach 7 Phase 1 after construction. Right: Reach 7 Phase 2 during construction.

19www.landandwater.com

STREAMBANK STABILIZATION

resident safety. Numerous yards experi-

enced massive slope failures resulting in the

loss of 10 to 20 feet of land on residential

lots. Near the upstream end of the proj-

ect a wastewater line that crosses the chan-

nel had become exposed by more than 4

feet due to years of channel down cutting.

Additionally most every house along this

reach was located in the in the 100-year

fl oodplain.

Th e fi nal design featured a mechani-

cally stabilized earth system using lime-

stone boulders and mechanically stabilized

earth soil lifts of both sides of the channel

for the entire project length. Th e boulders

measured 1.5’ by 2’ by 3’ and were stacked

two to three rows above grade with six-

inch horizontal off sets. Above the boul-

der toe, 18-inch soil lifts were constructed

with soil retention blanket, biaxial geogrids

and welded wire form facings. Not only

do the wire forms provide structural sup-

port for the soil lift facing, but they also

facilitate construction because each row of

lifts can be assembled in long continuous

spans. Within the geotextile fabric, the

front face of each lift was fi lled with top-

soil and seeded with native plants. Th e soil

lifts are stepped back with 1-foot off sets.

Above the soil lifts, the slope was gently

graded and revegetated with rooted plants

and trees. Geogrids between all layers pro-

vided additional stabilization of the entire

system. For drainage, gravel backfi ll was

used behind the boulders with 12” wide

stripdrains spaced 5’ on centers terminat-

ing at the topsoil layer. Th e ends of the

project key into the natural channel with a

rock riprap transition to stable bank.

Th e channel bottom ranged from 25‘

to 35’ and featured a 10’ wide meandering

pilot channel lined with coir logs. Where

the constructed meander neared the MSE

wall, rock riprap was placed at the base for

additional scour protection. Rock riprap

was used to place four grade controls to

maintain the channel at its equilibrium

slope. Th e eight storm drain outfalls locat-

ed within the project reach were realigned

to discharge at 45-degree angles in the di-

rection of fl ow and were protected with

rock riprap aprons. Th e exposed wastewa-

ter pipe was encased and a large rock riprap

grade control structure was constructed

to protect it from further undermining.

Th roughout the design phase, storm events

continued to wreak rapid havoc on Reach

1 such that an interim 450-foot emergency

project had to be constructed until the fi nal

project could be implemented.

Th e Reach 1 project not only stabi-

lized the channel banks, but also provided

signifi cant fl ood control benefi ts by lower-

ing the 100-year water surface elevation

below the foundation elevation of all but

fi ve homes. Th e total capital cost to imple-

ment this solution was approximately $3.7

million. Today, Reach 1 is well vegetated

and stable. Walking through the reach, it

is barely recognizable as a major CIP fl ood

and erosion control project.

Reach 7

In 2011 the City of Austin began

construction of stream stabilization for

Reach 7 in the lower portion of the water-

shed. Conditions were similar to Reach 1

in that yards, homes fences and utilities

were threatened due to severe and acceler-

ated erosion. This project was constructed

in two phases with each being approxi-

mately 500 feet in stream length. Similar

techniques were used for erosion control,

but a more natural looking type of stone

was utilized as compared to Reach 1. Also

instead of the wire forms used to construct

the soil lifts in Reach 1, temporary forms

were used that were removed upon com-

pletion. In the end this approach leaves

less manmade material in the creek and

R

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STREAMBANK STABILIZATION

20 September/October 2012

provides softer lines for the stabilization

facing. This project required integrating

two storm drain outfalls into the stabiliza-

tion and protecting two exposed wastewa-

ter crossings. At each of these crossings

the wastewater lines were stabilized with

rock grade control structures to prevent

undermining. Because this location is at

the lower end of the watershed and the

channel slope is much flatter, minimal

flood control benefits could be achieved

with this project. As the channel slope

becomes flatter, modifications to channel

geometry have a much smaller effect of

water surface elevation. Additionally, high

sediment loads delivered to the lower

reach would make channel modifications

unsustainable. The Reach 7 project was

designed with in-house engineers and con-

struction crews.

Reach 6

Th e third priority project in Fort

Branch will begin construction in the fall

of 2012 and continue through 2013. Th is

project includes 1,500 linear feet of stream

length using limestone boulder toe me-

chanically stabilized earth stabilization,

rock riprap grade control structures for

erosion control and replacement of a box

culvert with a 90 foot span bridge to reduce

roadway fl ooding. In this project the struc-

tural bank stabilization is limited to one

side of the channel and the opposite bank

is to be inclined to a stable slope and reveg-

etated. Th e fl ood control benefi ts include

nearly a 2-foot reduction in the 100-year

fl oodplain that currently makes local streets

a hazard during high fl ow events. Th e low

bid construction cost for the Reach 6 proj-

ect was approximately $2.5 million.

Summary

Th e Watershed Protection Depart-

ment has developed a multi-objective ap-

proach to watershed management and

stream stabilization that strives to maxi-

mize opportunities to achieve multiple

goals while minimizing adverse impacts

that have been associated with traditional

river engineering practices used in the past.

Focusing on accomplishing multiple goals

allows for better collaboration between

workgroups, better use of resources, and

more economically eff ective and environ-

mentally friendly projects. Although this

approach takes time and planning the ulti-

mate success of this integrated, reach-based

approach proves to be worth the additional

eff ort. L&W

by Morgan Byars, P.E. & Janna Renfro, P.E.

For more information contact Morgan Byars, P.E., Supervising Engineer, morgan.byars@austintexas.gov, (512)974-9790 or Janna Renfro, P.E., En gineer B, janna.ren-fro@austintexas.gov. Th ey are both with the City of Austin Watershed Protection Depart-ment, Sustainable Stormwater Solutions Sec-tion, 505 Barton Springs Road, Austin, Texas 78704.

Acknowledgements: Th e City of Aus-

tin Watershed Protection Department

would like to acknowledge Eric Stewart,

P.E. with HDR Engineering, Inc. in Aus-

tin, Texas for assistance with design of the

Reach 1 and Reach 6 projects.

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