Towar Rain Garden Drains: - Michigan Water Environment Association

12/14/2011 

P a t r i c k E . L i n d e m a n n 

INGHAM COUNTY DRAIN COMMISSIONER 

Towar Rain Garden Drains 

A Low-Impact Urban Retrofit 





Towar Rain Garden Drains: 

A Michigan Urban Retrofit Low Impact Stormwater Management System 

Discussion of the Project, Results of Post Construction Monitoring and Methods Used 

MWEA Watershed Seminar – December 8, 2011 

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Twenty percent of the world’s available 

fresh water is in the Great Lakes 

• “Don’t go to Michigan, that land of ills, the word means ague, 

fever, and chills” 

• Drainage critical to settlement of Michigan – adopted drainage law 

in first State Legislative session in 1838 

• Elected county official in charge of managing drainage 





Towar Rain Garden Drains are in the 

headwaters of the Great Lakes 

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Towar Rain Garden Drains are located in Towar Gardens 

neighborhood, an urbanized area near state capital, Lansing 





Towar Gardens neighborhood: 

• Approximately 200-acre area 

• Over 400 single-family homes & several 

multi-family and commercial 

developments 

• Affordable housing 

• Platted originally in 1920s-1940s 

• 40% Impervious 

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Towar Gardens developed over the years with no organized drainage system 

for collection or conveyance of stormwater which resulted in widespread and 

longstanding flooding 

Flooding along Roadways – Roads in Poor Repair & Impassable at Times 





Flooding in Yards 

Standing water would remain for days 

after 30-minute rainfall or less than 

one-year storms resulting in loss of 

use of private property and unhealthy 

conditions 

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Flooding of Basements - Sump pumps ran constantly in 

many homes & illegal connections to sanitary system 





Why LID for Towar Gardens? 

• Allowed for feasibly overcoming site constraints 

– Flat, low-lying topography with poorly-drained soils 

– Narrow rights-of-way with multiple utility conflicts 

– Rear yards lower than front yards 

– Downstream outlet elevation limitations for gravity flow 

– Lack of available land for detention w/o removing affordable 

housing 

• Cost of conventional system was prohibitive for 400 modest homes 

($20 million vs. $9.8 million) 

• Met NPDES Phase II requirements 

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What are the Towar Rain Garden Drains? 

• 200-acre watershed 

• 10-year pipe design; 100-year detention design 

• 8.25 miles of drain constructed 

– Collection and treatment system: underdrained rain gardens and roadside 

ditches (150 rain gardens/5.6 acres) 

– Conveyance system: roadway concrete drain pipes (none larger than 24”) 





Overall System 

Treatment Train 

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Roadside Rain Gardens 

• Underdrained infiltration bed with amended soil profile overlay 

• Small, most 400 to 4,000 square feet 

• 6” topsoil/compost 

• 6” sand (geotextile fabric separating aggregate) 

• 12” aggregate 

• 12” underdrain (perforated dual wall HDPE, nonwrapped) 

• Overflow weir 





Rear Yard Rain Gardens 

• Underdrained infiltration bed with amended soil 

profile overlay 

• Large, most 0.10 to 0.50 acres 

• 6” topsoil/compost 

6” sand (geotextile fabric separating aggregate) 

• 12” aggregate 

• 12” underdrain on most (perforated dual wall HDPE, 

non-wrapped) 

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Regional Indigenous 

Plants 

• Why are they important? 

• What is different about 

native plants? 

• What's wrong with using 

hybrids? 

• Compromise is sometimes 

necessary. 





Planting 

Design 

Plant Team 

• Wetland Scientist 

• Soil Scientist 

• Arborist 

• Botanist 

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Rain Garden Planting Facts 

• 111 pounds of wildflower 

seeds (95 species) 

• 52,000 perennial forbs (125 

species) 

• 36,000 cubic yards of compost 

• 51,000 cubic yards of topsoil 

Note: 1,100 trees & shrubs (52 

species) 





Project Constructed March 2006 – December 2007 

So what is the difference in Towar Gardens Post-Construction? 

• Before 

– Many complaints of flooding of structures, streets and 

property reported after minor rainfall. 

– Landowner surveys revealed that 64% had drainage problems 

and 13.5% had basement flooding 

• After 

– Put to the Test: No flooding observed, no drainage problems 

or flooding reported. 

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Before 

After 





Before 

After 

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Before 

After 





Before 

After 

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Before 

After 





Before 

After 

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Before 

After 





Before 

After 

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Flooding overwhelms the Sanitary Sewer System 

• The sanitary sewer was the only 

outlet for storm water for many 

homes 

• 46 direct connections were 

eliminated 





Analysis Of Sump Pump And Dehumidifier Operating Costs (Pre & Post Construction) 

Based On Records From Two Flood Prone Homes 

• Pre-construction: homeowners frequently reported 

sump pump use “all the time” 

• Post-construction: homeowners frequently report 

reduction in sump pump use 

• Estimated total annual savings of $350 per home 

• Average annual assessment is $255 per home 

$500.00 

$450.00 

$400.00 

$350.00 

$300.00 

$250.00 

$200.00 

$150.00 

$100.00 

$50.00 

$- 

$218 Savings 

Total Sump 

Pump Annual 

Savings 

$132 Savings 

Total 

Dehumidifier 

Annual Savings 

$350 Savings 

Total Annual 

Savings 

Before Project 

After Project 

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The Goal of LID 

“The goal of Low Impact Development (LID) 

is the cornerstone of stormwater 

management with the goal of mimicking a 

site’s pre-settlement hydrology by using 

design techniques that infiltrate, filter, 

store, evaporate and detain runoff close to 

its source.” 

− SEMCOG LID Manual 

Christopher Columbus Landing in America 





Purpose of testing 

Testing finds answers to specific questions. 

Our questions: 

• Q1: Was LID goal of mimicking pre-settlement hydrology 

accomplished? 

• Q2: What TP, TN and TSS loads do rain gardens remove? 

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Testing balances three elements 

How much is enough? 

• Knowledge 

• Money 

• Time 





Why these parameters? 

TSS,TP,TN 

• Know the watershed 

• Know the pollutant sources 

• Know the receiving waters 

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Four levels of monitoring 

1. Regular schedule for 

inspections 

2. Grab sampling and field 

measurements 

3. Sampling rain events 

4. Simulated events 





1. Observation and Inspection 

• Crew on site at least once a week 

• Logging observations and work performed daily 

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2. Grab Sampling and Field Measurement 

• Take Grab samples 1-2 times per 

year 

• Gather Quanta meter and 

turbidity meter readings 

• Test infiltration rate of rain 

garden 





3. Rain Event 

• Actual Performance 

• Natural hydrologic cycle 

• At mercy of mother nature 

• Common storms, lack uncommon and 

extreme storms 

• Must be always ready to collect and 

process samples. 

4. Simulated Event 

• Idealized 

• Impossible to synthesize full hydrologic 

cycle in field tests 

• Very controlled environment 

• Takes more people and resources and is 

more stressful 

• Able to collect data at very high resolution 

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“It Takes Two to Test” 

Test comparatively: 

• Upstream/Downstream 

• LID/No LID 

• Treated/Untreated 

• Sheet Flow/Stream Flow 





Sampling/Testing Equipment 

• Auto Samplers 

• Flow Meters 

• Depth Meters 

• Data Collectors 

• Quanta 

• Laptop computer 

• Survey equipment 

• Coolers / Ice 

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The Procedures Manual 

• Methods to collect, preserve and 

transport 

• Each Technical Method 

• Step by step instruction guide to run 

each method 





Example Test Procedures 

-- TNT plus Low Range 0.05 - 1.50 mg/L PO 4 -P, Method 10210 (TNT843) 

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Add 2.0 mL of sample to vial 

-- TNTplus Low Range 0.05 - 1.50 mg/L PO 4 -P, Method 10210 (TNT843) 





Insert vial or vials into the DRB200 Reactor 

Close cover and heat for 1 hour at 60° C 


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When the timer expires invert again 2-3 

times and then insert into a 

Spectrophotometer for readings 

Record the readings 






TNT plus methods 

• Expedite the analysis 

• Process 3-5 times faster 

• Contaminate fewer samples 

• Minimize glassware 

• Reduce human errors 

• Tighten QA test results 

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What is a Spectrophotometer? 

• Very precise device. A “Bionic eye” 

• Senses absorption of light frequencies 

• Increased pollutant concentration changes the 

sample color 

• Gives readings as mg/L of pollutant 





Software Used 

• Databases 

• iPhone®/ iPad® data collection 

• GIS Layers 

• Calculation spreadsheets 

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Performance Testing of Flow and Water Quality for Natural and Synthetic Events 

• Sampled 4 months starting in April 2011 

• 20 natural runoff events – three vegetated rain gardens tested 

• For synthetic runoff events – same three rain gardens tested, along 

with turf rain garden and turf ditch. (Nutrients were added to the 

influent water to determine removal efficiency) 

• Data collected with ISCO auto-samplers and ISCO flow meters 

including the following: 

• Flow, Depth, Duration, Volume 

• TSS, TP, TN 





ANALYSIS OF POST CONSTRUCTION RAINFALL BY MONTH 


tested post construction by 

420 rainfall events 

• Eighteen of 45 months had 

above average rainfall (4 

of the 18 were dormant 

months) 

• Three events were 10-year 

or greater (1 of the 3 was 

50-year event) 

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May 13 th , 2011 

One of the Three 10-year or Greater Events 

1.4 

1.2 

1 

0.8 

0.6 

0.4 

0.2 

0 

July 28-29 

Event 

May 13th 

Event 

Growing Season Event – May 13th, 2011 

1:00:00 AM 

4:00:00 AM 

7:00:00 AM 

10:00:00 AM 

1:00:00 PM 

4:00:00 PM 

7:00:00 PM 

10:00:00 PM 

12 hours after 2.32”, 4 hour duration rainfall 

(10-year event) 





Dormant Season Event 

2/27/2009 Growing Season Event 

5/28/2009 

12 hours after snowmelt and 

0.8”, 5 hour duration rainfall (< 2-month event) 

18 hours after 

3.44”, 5 hour duration rainfall (50-year event) 

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Typical Depth and Flow Hydrographs (Vegetated Rain Garden – Natural Events) 

General Results of Natural Event Testing 

• All rain gardens effectively reduced peak discharge, 81% 

average (34% to 100% ) 

• Eight of the twenty events had 100% volume control 

(produced no effluent). 

Volume reduction is function of 

• antecedent conditions 

• site factors 

• storm intensity 

• elevation of overflow weir 





Water Quality 

TSS Removal Efficiency, 4/21/11 Natural Event in Vegetated Rain Garden 

The first flush removal of TSS 

averaged 94%, (80 to 100%) 

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TP Removal Efficiency, 4/21/11 Natural Event in Vegetated Rain Garden 

The first flush removal of TP averaged 71%, (29 to 94%) 






TN Removal Efficiency 6/15/11 Synthetic Event in Vegetated Rain Garden 

The first flush TN removal with synthetic events was as high as 97%. The first 

flush TN removal with natural events averaged 27% (15 to 38%) 

Nutrient Concentration (mg/L) 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

97% 

91% 

100% 

0 10 20 30 40 50 60 70 80 

Inf. TN Conc. 

Time (minutes) 

Eff. TN Conc. 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

TN Reduction 

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Performance Conclusions 

• Treatment effectiveness is primarily a function of infiltration 

– Infiltration capacity and treatment effectiveness highest in 

vegetated rain gardens 

– Infiltration capacity and treatment effectiveness lower in turf rain 

garden 

– Infiltration capacity and treatment effectiveness absent in turf 

ditch 

• Peak flow reduction significant in vegetated rain gardens 

• Treatment capacity drops by 50% or more when mulch and 

deep-rooted native vegetation replaced with turf grass 

• Although not tested, the infiltration data suggest that larger 

turf rain gardens (perhaps 2 to 5 times larger) could remove 

pollutants as well as vegetated rain gardens 

• Turf ditches do little other than convey water 





General Results of Infiltration and Water Quality Testing 

(Rain Gardens were designed to dewater in less than 24 hours. All tests recorded dewatering within 1 hour) 

Vegetated Rain Garden 

Turf Rain Garden 

Turf Ditch 

• High infiltration rate 

• Treated runoff (Tested TSS, 

TP,TN) 

• Low infiltration rate 

• Bypassed most runoff w/o 

treatment (Tested TP, TN) 

• No Infiltration 

• No treatment (Tested TP, TN) 

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Towar Rain Garden Drains Retrofit 

• Eliminates flooding 

• Removes pollutants 

• Reduces volume / peak discharge 

• Lowers cost of drainage 

infrastructure 

• Increases property values 

• Adds aesthetic amenity 

• Creates sense of place 





Given the success of Towar Rain Garden Drains, why not more retrofits like it? 

Challenges of large-scale LISMS 

• Neophobia 

– Public 

– Public officials / Regulatory agencies 

– Engineers 

• “In your face” infrastructure 

– Interaction between public and infrastructure 

– Aesthetics 

• Complexity of design and execution 

– Relative newness and lack design guidance 

– Knowledgeable professionals 

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Rain Gardens require maintenance!! 

• Performance is so good 

because of the hands on 

routine maintenance 

program 





Questions and Answers 

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Towar Rain Garden Drains: - Michigan Water Environment Association

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