Delaware Dam Safety Program Update May 2008

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Dam Safety Program UpdateMay 2008



Delaware Dam Safety Law

Criteria for regulation: – Public ownership

and – High or significant hazard potential

or – Dam height greater than 25 feet – Maximum storage capacity greater than 50 acre-feet

Exclusions: – Dam height less than 6 feet (even if the storage capacity is

greater than 50 acre-feet)

– Dams with storage capacity less than 15 acre-feet (even if thedam height is greater than 25 feet)

– Dams with low hazard potential – Privately-owned dams



Hazard Potential Classifications

High hazard potential dam shall mean any damwhose failure or mis-operation will cause probable loss of human life

Significant hazard potential dam shall mean anydam whose failure or mis-operation will causepossible loss of human life, economic loss,environmental damage, disruption of lifelinefacilities, or can impact other concerns

Low hazard potential dam shall mean any damwhose failure or mis-operation is unlikely to cause loss of human life but may cause minor economicand/or environmental losses



Update and Verify

Delaware Dam Inventory Verify/update information in

our current dam inventory

Determine list of regulateddams

Perform limited hazardpotential assessment

Create database formanaging dam information

Perform risk-based analysis

for portfolio of dams to helpprioritize rehabilitationneeds



Methodology

Historic Dam Inventories – 1974 State Dam Inventory

– 1981 National Inventory of Dams (NID)

– 1988 DelDOT Ponds & Impoundments – 1999 NID

– 2003 State Inventory Update by UD WRA

Systematic search of: – Current orthophotos (2002)

– USGS topoquad maps

– National Hydrography Dataset waterbodies

– Permitting of dam construction (2002-present)



Results of Initial Search

170 public dams – Located on State, County, or municipal

property 27 federal dams

– Located on federal agency property

126 private dams – Located on private property

323 dams initially identified



Screening of Initial

Results Private and Federal dams excluded – not

regulated Obvious low-hazard public dams excluded –

impoundments in tidal areas, run-of-riverdams

Private NID dams included Dams that appeared to be private/public

included 97 dams to be field reviewed

– 83 public dams – 14 private NID dams



Field Reviews Conducted

June – October 2007



Field Review Results

87 dams field reviewed

– 83 public or public/private

– 4 private NID dams

10 private NID dams not reviewed(yet) due to budget concerns



Preliminary Hazard Class

Determination Dam height

– ¾ of dam height was projected

downstream to map an approximate areaflooded in “sunny day” failure

Structure and infrastructure at risk – Population at risk – 3 people per

residential structure – Critical infrastructure such as roads and

railroads



Hazard Class Results

71 high hazard dams

– 4 private dams

8 significant hazard dams

8 low hazard dams

75 regulated dams

12 non-regulated dams



Risk Assessment Methodology

Used new FEMA tool

Risk factors include: – Hazard class

– Condition of dam – Level of maintenance

– Frequency of inspections

– Likely failure modes

– Historic incidents

– Population at risk

– Life loss potential

Three risk categories created (high, medium, low)



Risk Assessment Results

34 regulated dams in high risk category

32 regulated dams in medium risk category

21 regulated dams in low risk category



32 DNREC-Owned Regulated Dams

25 dams with shared ownership between DFW and DelDOT 3 dams with shared ownership between DPR and DelDOT 4 dams owned by DFW

27 High Hazard dams 5 Significant Hazard dams

13 High Risk dams 10 Medium Risk dams 9 Low Risk dams



Example Inventory Graphics



Dam Safety Regulations

Final draft of regulations completed

Dam Safety RAC meeting to be held

May 21 Draft regulations to be released for

public review and comment

subsequent to RAC meeting Anticipate regulations adopted Fall

2008



DNREC notifiesdam owner

Ownershipacknowledged

to DNREC

DNREC conditionassessment of dam

Dam insatisfactorycondition

Dam inunsatisfactory

condition

DNREC issuesProvisional Certificate

To Impound

Owner permit submittal:$500 Application Fee

Engineer’s Report O&M Plan

EAP

DNREC issuesPermit to Impound

Owner inspections,evaluation and upgrades

to comply with regulations

DNREC notifiesDam owner

Owner respondswith intended action

Permitrequired

Permit notrequired

Processrepairpermit

Repaircomplete

RegulationsPromulgated

Ownershipdisputed

Ownershipinvestigatedby DNREC

Permitting Process for Existing Dams



Ongoing Projects

Evaluation/rehabilitation of state-owneddams:

– Records Pond Dam – Laurel – Chipmans Pond Dam – Laurel

– Haven Lake Dam – Milford

– Silver Lake Dam – Milford – Hearns Pond Dam – Seaford

– Williams Pond Dam - Seaford



Emergency Action Planning

$1 million in DWSC FY08 budget for damsafety emergency planning services

$500,000 in Tier 1 reversion Processing PO’s for remaining $500,000 with

four selected consultants

Anticipate completing 6-8 EAP’s for state-owned dams chosen from Risk Category A

Documents

Delaware Dam Safety Program Update May 2008